toneequal.c

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/*
    This file is part of the Ansel project.
    Copyright (C) 2018-2020, 2022-2026 Aurélien PIERRE.
    Copyright (C) 2019 Andreas Schneider.
    Copyright (C) 2019, 2021 luzpaz.
    Copyright (C) 2019-2022 Pascal Obry.
    Copyright (C) 2019-2020 rawfiner.
    Copyright (C) 2019 Tobias Ellinghaus.
    Copyright (C) 2020, 2022 Aldric Renaudin.
    Copyright (C) 2020-2021 Chris Elston.
    Copyright (C) 2020-2022 Diederik Ter Rahe.
    Copyright (C) 2020 hatsunearu.
    Copyright (C) 2020-2021 Hubert Kowalski.
    Copyright (C) 2020 Matthieu Moy.
    Copyright (C) 2020-2021 Ralf Brown.
    Copyright (C) 2020 U-DESKTOP-TRPCBD3\Matthijs.
    Copyright (C) 2021 Dan Torop.
    Copyright (C) 2021 Heiko Bauke.
    Copyright (C) 2021 lhietal.
    Copyright (C) 2021 Marco Carrarini.
    Copyright (C) 2021 Mark-64.
    Copyright (C) 2021 Paolo DePetrillo.
    Copyright (C) 2022 Hanno Schwalm.
    Copyright (C) 2022 Martin Bařinka.
    Copyright (C) 2022 Nicolas Auffray.
    Copyright (C) 2022 Philipp Lutz.
    Copyright (C) 2022 Sakari Kapanen.
    Copyright (C) 2022 Victor Forsiuk.
    Copyright (C) 2023-2024 Alynx Zhou.
    Copyright (C) 2023 Luca Zulberti.
    Copyright (C) 2025-2026 Guillaume Stutin.
    
    Ansel is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.
    
    Ansel is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.
    
    You should have received a copy of the GNU General Public License
    along with Ansel.  If not, see <http://www.gnu.org/licenses/>.
*/
 
/*** DOCUMENTATION
 *
 * This module aims at relighting the scene by performing an exposure compensation
 * selectively on specified exposures octaves, the same way HiFi audio equalizers allow to set
 * a gain for each octave.
 *
 * It is intended to work in scene-linear camera RGB, to behave as if light was physically added
 * or removed from the scene. As such, it should be put before input profile in the pipe, but preferably
 * after exposure. It also need to be placed after the rotation, perspective and cropping modules
 * for the interactive editing to work properly (so the image buffer overlap perfectly with the
 * image preview).
 *
 * Because it works before camera RGB -> XYZ conversion, the exposure cannot be computed from
 * any human-based perceptual colour model (Y channel), hence why several RGB norms are provided as estimators of
 * the pixel energy to compute a luminance map. None of them is perfect, and I'm still
 * looking forward to a real spectral energy estimator. The best physically-accurate norm should be the euclidean
 * norm, but the best looking is often the power norm, which has no theoretical background.
 * The geometric mean also display interesting properties as it interprets saturated colours
 * as low-lights, allowing to lighten and desaturate them in a realistic way.
 *
 * The exposure correction is computed as a series of each octave's gain weighted by the
 * gaussian of the radial distance between the current pixel exposure and each octave's center.
 * This allows for a smooth and continuous infinite-order interpolation, preserving exposure gradients
 * as best as possible. The radius of the kernel is user-defined and can be tweaked to get
 * a smoother interpolation (possibly generating oscillations), or a more monotonous one
 * (possibly less smooth). The actual factors of the gaussian series are computed by
 * solving the linear system taking the user-input parameters as target exposures compensations.
 *
 * Notice that every pixel operation is performed in linear space. The exposures in log2 (EV)
 * are only used for user-input parameters and for the gaussian weights of the radial distance
 * between pixel exposure and octave's centers.
 *
 * The details preservation modes make use of a fast guided filter optimized to perform
 * an edge-aware surface blur on the luminance mask, in the same spirit as the bilateral
 * filter, but without its classic issues of gradient reversal around sharp edges. This
 * surface blur will allow to perform piece-wise smooth exposure compensation, so local contrast
 * will be preserved inside contiguous regions. Various mask refinements are provided to help
 * the edge-taping of the filter (feathering parameter) while keeping smooth contiguous region
 * (quantization parameter), but also to translate (exposure boost) and dilate (contrast boost)
 * the exposure histogram through the control octaves, to center it on the control view
 * and make maximum use of the available channels.
 *
 * Users should be aware that not all the available octaves will be useful on every pictures.
 * Some automatic options will help them to optimize the luminance mask, performing histogram
 * analyse, mapping the average exposure to -4EV, and mapping the first and last deciles of
 * the histogram on its average ± 4EV. These automatic helpers usually fail on X-Trans sensors,
 * maybe because of bad demosaicing, possibly resulting in outliers\negative RGB values.
 * Since they fail the same way on filmic's auto-tuner, we might need to investigate X-Trans
 * algos at some point.
 *
***/
 
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <assert.h>
#include <math.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
 
#include "bauhaus/bauhaus.h"
#include "common/darktable.h"
#include "develop/masks.h"
#include "common/fast_guided_filter.h"
#include "common/eigf.h"
#include "common/interpolation.h"
#include "common/luminance_mask.h"
#include "common/opencl.h"
#include "common/collection.h"
#include "control/conf.h"
#include "control/control.h"
#include "develop/blend.h"
#include "develop/develop.h"
#include "develop/imageop.h"
#include "develop/imageop_math.h"
#include "develop/imageop_gui.h"
#include "develop/pixelpipe_cache.h"
#include "dtgtk/drawingarea.h"
#include "dtgtk/expander.h"
 
#include "gui/color_picker_proxy.h"
#include "gui/draw.h"
#include "gui/gtk.h"
#include "gui/presets.h"
#include "gui/color_picker_proxy.h"
#include "iop/iop_api.h"
#include "iop/choleski.h"
#include "libs/colorpicker.h"
 
#ifdef _OPENMP
#include <omp.h>
#endif
 
 
DT_MODULE_INTROSPECTION(2, dt_iop_toneequalizer_params_t)
 
 
#define UI_SAMPLES 256 // 128 is a bit small for 4K resolution
#define CONTRAST_FULCRUM exp2f(-4.0f)
#define MIN_FLOAT exp2f(-16.0f)
 
#define CHANNELS 9
#define PIXEL_CHAN 8
#define LUT_RESOLUTION 10000
 
// radial distances used for pixel ops
static const float centers_ops[PIXEL_CHAN] DT_ALIGNED_ARRAY = {-56.0f / 7.0f, // = -8.0f
                                                               -48.0f / 7.0f,
                                                               -40.0f / 7.0f,
                                                               -32.0f / 7.0f,
                                                               -24.0f / 7.0f,
                                                               -16.0f / 7.0f,
                                                                -8.0f / 7.0f,
                                                                 0.0f / 7.0f}; // split 8 EV into 7 evenly-spaced channels
 
static const float centers_params[CHANNELS] DT_ALIGNED_ARRAY = { -8.0f, -7.0f, -6.0f, -5.0f,
                                                                 -4.0f, -3.0f, -2.0f, -1.0f, 0.0f};
 
 
typedef enum dt_iop_toneequalizer_filter_t
{
  DT_TONEEQ_NONE = 0,   // $DESCRIPTION: "no"
  DT_TONEEQ_AVG_GUIDED, // $DESCRIPTION: "averaged guided filter"
  DT_TONEEQ_GUIDED,     // $DESCRIPTION: "guided filter"
  DT_TONEEQ_AVG_EIGF,   // $DESCRIPTION: "averaged eigf"
  DT_TONEEQ_EIGF        // $DESCRIPTION: "eigf"
} dt_iop_toneequalizer_filter_t;
 
 
typedef struct dt_iop_toneequalizer_params_t
{
  float noise; // $MIN: -2.0 $MAX: 2.0 $DEFAULT: 0.0  $DESCRIPTION: "blacks"
  float ultra_deep_blacks; // $MIN: -2.0 $MAX: 2.0 $DEFAULT: 0.0  $DESCRIPTION: "deep shadows"
  float deep_blacks; // $MIN: -2.0 $MAX: 2.0 $DEFAULT: 0.0  $DESCRIPTION: "shadows"
  float blacks; // $MIN: -2.0 $MAX: 2.0 $DEFAULT: 0.0  $DESCRIPTION: "light shadows"
  float shadows; // $MIN: -2.0 $MAX: 2.0 $DEFAULT: 0.0  $DESCRIPTION: "mid-tones"
  float midtones; // $MIN: -2.0 $MAX: 2.0 $DEFAULT: 0.0  $DESCRIPTION: "dark highlights"
  float highlights; // $MIN: -2.0 $MAX: 2.0 $DEFAULT: 0.0  $DESCRIPTION: "highlights"
  float whites; // $MIN: -2.0 $MAX: 2.0 $DEFAULT: 0.0  $DESCRIPTION: "whites"
  float speculars; // $MIN: -2.0 $MAX: 2.0 $DEFAULT: 0.0  $DESCRIPTION: "speculars"
  float blending; // $MIN: 0.01 $MAX: 100.0 $DEFAULT: 5.0 $DESCRIPTION: "smoothing diameter"
  float smoothing; // $DEFAULT: 1.414213562 sqrtf(2.0f)
  float feathering; // $MIN: 0.01 $MAX: 10000.0 $DEFAULT: 1.0 $DESCRIPTION: "edges refinement (feathering)"
  float quantization; // $MIN: 0.0 $MAX: 2.0 $DEFAULT: 0.0 $DESCRIPTION: "mask quantization"
  float contrast_boost; // $MIN: -16.0 $MAX: 16.0 $DEFAULT: 0.0 $DESCRIPTION: "mask contrast compensation"
  float exposure_boost; // $MIN: -16.0 $MAX: 16.0 $DEFAULT: 0.0 $DESCRIPTION: "mask exposure compensation"
  dt_iop_toneequalizer_filter_t details; // $DEFAULT: DT_TONEEQ_EIGF
  dt_iop_luminance_mask_method_t method; // $DEFAULT: DT_TONEEQ_NORM_2 $DESCRIPTION: "luminance estimator"
  int iterations; // $MIN: 1 $MAX: 20 $DEFAULT: 1 $DESCRIPTION: "filter diffusion"
} dt_iop_toneequalizer_params_t;
 
 
typedef struct dt_iop_toneequalizer_data_t
{
  float factors[PIXEL_CHAN] DT_ALIGNED_ARRAY;
  float correction_lut[PIXEL_CHAN * LUT_RESOLUTION + 1] DT_ALIGNED_ARRAY;
  float blending, feathering, contrast_boost, exposure_boost, quantization, smoothing;
  float scale;
  int radius;
  int iterations;
  dt_iop_luminance_mask_method_t method;
  dt_iop_toneequalizer_filter_t details;
} dt_iop_toneequalizer_data_t;
 
 
typedef struct dt_iop_toneequalizer_global_data_t
{
  // TODO: put OpenCL kernels here at some point
} dt_iop_toneequalizer_global_data_t;
 
 
typedef struct dt_iop_toneequalizer_gui_data_t
{
  // Mem arrays 64-bytes aligned - contiguous memory
  float factors[PIXEL_CHAN] DT_ALIGNED_ARRAY;
  float gui_lut[UI_SAMPLES] DT_ALIGNED_ARRAY; // LUT for the UI graph
  float interpolation_matrix[CHANNELS * PIXEL_CHAN] DT_ALIGNED_ARRAY;
  int histogram[UI_SAMPLES] DT_ALIGNED_ARRAY; // histogram for the UI graph
  float temp_user_params[CHANNELS] DT_ALIGNED_ARRAY;
  float cursor_exposure; // store the exposure value at current cursor position
  float step; // scrolling step
 
  // 14 int to pack - contiguous memory
  int mask_display;
  int max_histogram;
  int buf_width;
  int buf_height;
  int cursor_pos_x;
  int cursor_pos_y;
  int pipe_order;
 
  // Preview luminance cache state shared with the GUI.
  // The GUI never owns raw luminance buffers directly anymore: it only keeps the
  // cache hash, dimensions and one retained cache entry reference so every reader
  // goes through the pixelpipe cache locking API before sampling.
  uint64_t thumb_preview_hash;
  uint64_t pending_preview_hash;
  size_t thumb_preview_buf_width, thumb_preview_buf_height;
 
  // Misc stuff, contiguity, length and alignment unknown
  float scale;
  float sigma;
  float histogram_average;
  float histogram_first_decile;
  float histogram_last_decile;
 
  // Preview luminance cache entry retained across pipe runs for GUI sampling.
  // Lifetime is explicit: process() transfers one ref to the GUI when the current
  // preview-sized output matches darkroom preview, and invalidation/cleanup drop it.
  dt_pixel_cache_entry_t *thumb_preview_entry;
 
  // GTK garbage, nobody cares, no SIMD here
  GtkWidget *noise, *ultra_deep_blacks, *deep_blacks, *blacks, *shadows, *midtones, *highlights, *whites, *speculars;
  GtkDrawingArea *area;
  GtkWidget *blending, *smoothing, *quantization;
  GtkWidget *method;
  GtkWidget *details, *feathering, *contrast_boost, *iterations, *exposure_boost;
  GtkNotebook *notebook;
  GtkWidget *show_luminance_mask;
 
  // Cache Pango and Cairo stuff for the equalizer drawing
  float line_height;
  float sign_width;
  float graph_left_space; // used to center the circle on the mouse.
  float graph_width;
  float graph_height;
  float gradient_left_limit;
  float gradient_right_limit;
  float gradient_top_limit;
  float gradient_width;
  float legend_top_limit;
  float x_label;
  int inset;
  int inner_padding;
 
  GtkAllocation allocation;
  cairo_surface_t *cst;
  cairo_t *cr;
  PangoLayout *layout;
  PangoRectangle ink;
  PangoFontDescription *desc;
  GtkStyleContext *context;
 
  // Event for equalizer drawing
  float nodes_x[CHANNELS];
  float nodes_y[CHANNELS];
  float area_x; // x coordinate of cursor over graph/drawing area
  float area_y; // y coordinate
  int area_active_node;
 
  // Flags for UI events
  int valid_nodes_x;        // TRUE if x coordinates of graph nodes have been inited
  int valid_nodes_y;        // TRUE if y coordinates of graph nodes have been inited
  int area_cursor_valid;    // TRUE if mouse cursor is over the graph area
  int area_dragging;        // TRUE if left-button has been pushed but not released and cursor motion is recorded
  int cursor_valid;         // TRUE if mouse cursor is over the preview image
  int has_focus;            // TRUE if the widget has the focus from GTK
 
  // Flags for buffer caches invalidation
  int interpolation_valid;  // TRUE if the interpolation_matrix is ready
  int luminance_valid;      // TRUE if the luminance cache is ready
  int histogram_valid;      // TRUE if the histogram cache and stats are ready
  int lut_valid;            // TRUE if the gui_lut is ready
  int graph_valid;          // TRUE if the UI graph view is ready
  int user_param_valid;     // TRUE if users params set in interactive view are in bounds
  int factors_valid;        // TRUE if radial-basis coeffs are ready
 
} dt_iop_toneequalizer_gui_data_t;
 
 
const char *name()
{
  return _("tone e_qualizer");
}
 
const char *aliases()
{
  return _("tone curve|tone mapping|relight|background light|shadows highlights");
}
 
 
const char **description(struct dt_iop_module_t *self)
{
  return dt_iop_set_description(self, _("relight the scene as if the lighting was done directly on the scene"),
                                      _("corrective and creative"),
                                      _("linear, RGB, scene-referred"),
                                      _("quasi-linear, RGB"),
                                      _("quasi-linear, RGB, scene-referred"));
}
 
int default_group()
{
  return IOP_GROUP_TONES;
}
 
int flags()
{
  return IOP_FLAGS_INCLUDE_IN_STYLES | IOP_FLAGS_SUPPORTS_BLENDING;
}
 
int default_colorspace(dt_iop_module_t *self, dt_dev_pixelpipe_t *pipe, const dt_dev_pixelpipe_iop_t *piece)
{
  return IOP_CS_RGB;
}
 
void input_format(dt_iop_module_t *self, dt_dev_pixelpipe_t *pipe, dt_dev_pixelpipe_iop_t *piece,
                  dt_iop_buffer_dsc_t *dsc)
{
  default_input_format(self, pipe, piece, dsc);
  dsc->channels = 4;
  dsc->datatype = TYPE_FLOAT;
}
 
int legacy_params(dt_iop_module_t *self, const void *const old_params, const int old_version, void *new_params,
                  const int new_version)
{
  if(old_version == 1 && new_version == 2)
  {
    typedef struct dt_iop_toneequalizer_params_v1_t
    {
      float noise, ultra_deep_blacks, deep_blacks, blacks, shadows, midtones, highlights, whites, speculars;
      float blending, feathering, contrast_boost, exposure_boost;
      dt_iop_toneequalizer_filter_t details;
      int iterations;
      dt_iop_luminance_mask_method_t method;
    } dt_iop_toneequalizer_params_v1_t;
 
    dt_iop_toneequalizer_params_v1_t *o = (dt_iop_toneequalizer_params_v1_t *)old_params;
    dt_iop_toneequalizer_params_t *n = (dt_iop_toneequalizer_params_t *)new_params;
    dt_iop_toneequalizer_params_t *d = (dt_iop_toneequalizer_params_t *)self->default_params;
 
    *n = *d; // start with a fresh copy of default parameters
 
    // Olds params
    n->noise = o->noise;
    n->ultra_deep_blacks = o->ultra_deep_blacks;
    n->deep_blacks = o->deep_blacks;
    n->blacks = o->blacks;
    n->shadows = o->shadows;
    n->midtones = o->midtones;
    n->highlights = o->highlights;
    n->whites = o->whites;
    n->speculars = o->speculars;
 
    n->blending = o->blending;
    n->feathering = o->feathering;
    n->contrast_boost = o->contrast_boost;
    n->exposure_boost = o->exposure_boost;
 
    n->details = o->details;
    n->iterations = o->iterations;
    n->method = o->method;
 
    // New params
    n->quantization = 0.01f;
    n->smoothing = sqrtf(2.0f);
    return 0;
  }
  return 1;
}
 
static void compress_shadows_highlight_preset_set_exposure_params(dt_iop_toneequalizer_params_t* p, const float step)
{
  // this function is used to set the exposure params for the 4 "compress shadows
  // highlights" presets, which use basically the same curve, centered around
  // -4EV with an exposure compensation that puts middle-grey at -4EV.
  p->noise = step;
  p->ultra_deep_blacks = 5.f / 3.f * step;
  p->deep_blacks = 5.f / 3.f * step;
  p->blacks = step;
  p->shadows = 0.0f;
  p->midtones = -step;
  p->highlights = -5.f / 3.f * step;
  p->whites = -5.f / 3.f * step;
  p->speculars = -step;
}
 
 
static void dilate_shadows_highlight_preset_set_exposure_params(dt_iop_toneequalizer_params_t* p, const float step)
{
  // create a tone curve meant to be used without filter (as a flat, non-local, 1D tone curve) that reverts
  // the local settings above.
  p->noise = -15.f / 9.f * step;
  p->ultra_deep_blacks = -14.f / 9.f * step;
  p->deep_blacks = -12.f / 9.f * step;
  p->blacks = -8.f / 9.f * step;
  p->shadows = 0.f;
  p->midtones = 8.f / 9.f * step;
  p->highlights = 12.f / 9.f * step;
  p->whites = 14.f / 9.f * step;
  p->speculars = 15.f / 9.f * step;
}
 
void init_presets(dt_iop_module_so_t *self)
{
  dt_iop_toneequalizer_params_t p;
  memset(&p, 0, sizeof(p));
 
  p.method = DT_TONEEQ_NORM_POWER;
  p.contrast_boost = 0.0f;
  p.details = DT_TONEEQ_NONE;
  p.exposure_boost = -0.5f;
  p.feathering = 1.0f;
  p.iterations = 1;
  p.smoothing = sqrtf(2.0f);
  p.quantization = 0.0f;
 
  // Init exposure settings
  p.noise = p.ultra_deep_blacks = p.deep_blacks = p.blacks = p.shadows = p.midtones = p.highlights = p.whites = p. speculars = 0.0f;
 
  // No blending
  dt_gui_presets_add_generic(_("simple tone curve"), self->op,
                             self->version(), &p, sizeof(p), 1, DEVELOP_BLEND_CS_RGB_SCENE);
 
  // Simple utils blendings
  p.details = DT_TONEEQ_EIGF;
  p.method = DT_TONEEQ_NORM_2;
 
  p.blending = 5.0f;
  p.feathering = 1.0f;
  p.iterations = 1;
  p.quantization = 0.0f;
  p.exposure_boost = 0.0f;
  p.contrast_boost = 0.0f;
  dt_gui_presets_add_generic(_("mask blending: all purposes"), self->op,
                             self->version(), &p, sizeof(p), 1, DEVELOP_BLEND_CS_RGB_SCENE);
 
  p.blending = 1.0f;
  p.feathering = 10.0f;
  p.iterations = 3;
  dt_gui_presets_add_generic(_("mask blending: people with backlight"), self->op,
                             self->version(), &p, sizeof(p), 1, DEVELOP_BLEND_CS_RGB_SCENE);
 
  // Shadows/highlights presets
  // move middle-grey to the center of the range
  p.exposure_boost = -1.57f;
  p.contrast_boost = 0.0f;
  p.blending = 2.0f;
  p.feathering = 50.0f;
  p.iterations = 5;
  p.quantization = 0.0f;
 
  // slight modification to give higher compression
  p.details = DT_TONEEQ_EIGF;
  p.feathering = 20.0f;
  compress_shadows_highlight_preset_set_exposure_params(&p, 0.65f);
  dt_gui_presets_add_generic(_("compress shadows/highlights (eigf): strong"), self->op,
                             self->version(), &p, sizeof(p), 1, DEVELOP_BLEND_CS_RGB_SCENE);
  p.details = DT_TONEEQ_GUIDED;
  p.feathering = 500.0f;
  dt_gui_presets_add_generic(_("compress shadows/highlights (gf): strong"), self->op,
                             self->version(), &p, sizeof(p), 1, DEVELOP_BLEND_CS_RGB_SCENE);
 
  p.details = DT_TONEEQ_EIGF;
  p.blending = 3.0f;
  p.feathering = 7.0f;
  p.iterations = 3;
  compress_shadows_highlight_preset_set_exposure_params(&p, 0.45f);
  dt_gui_presets_add_generic(_("compress shadows/highlights (eigf): medium"), self->op,
                             self->version(), &p, sizeof(p), 1, DEVELOP_BLEND_CS_RGB_SCENE);
  p.details = DT_TONEEQ_GUIDED;
  p.feathering = 500.0f;
  dt_gui_presets_add_generic(_("compress shadows/highlights (gf): medium"), self->op,
                             self->version(), &p, sizeof(p), 1, DEVELOP_BLEND_CS_RGB_SCENE);
 
  p.details = DT_TONEEQ_EIGF;
  p.blending = 5.0f;
  p.feathering = 1.0f;
  p.iterations = 1;
  compress_shadows_highlight_preset_set_exposure_params(&p, 0.25f);
  dt_gui_presets_add_generic(_("compress shadows/highlights (eigf): soft"), self->op,
                             self->version(), &p, sizeof(p), 1, DEVELOP_BLEND_CS_RGB_SCENE);
  p.details = DT_TONEEQ_GUIDED;
  p.feathering = 500.0f;
  dt_gui_presets_add_generic(_("compress shadows/highlights (gf): soft"), self->op,
                             self->version(), &p, sizeof(p), 1, DEVELOP_BLEND_CS_RGB_SCENE);
 
  // build the 1D contrast curves that revert the local compression of contrast above
  p.details = DT_TONEEQ_NONE;
  dilate_shadows_highlight_preset_set_exposure_params(&p, 0.25f);
  dt_gui_presets_add_generic(_("contrast tone curve: soft"), self->op,
                             self->version(), &p, sizeof(p), 1, DEVELOP_BLEND_CS_RGB_SCENE);
 
  dilate_shadows_highlight_preset_set_exposure_params(&p, 0.45f);
  dt_gui_presets_add_generic(_("contrast tone curve: medium"), self->op,
                             self->version(), &p, sizeof(p), 1, DEVELOP_BLEND_CS_RGB_SCENE);
 
  dilate_shadows_highlight_preset_set_exposure_params(&p, 0.65f);
  dt_gui_presets_add_generic(_("contrast tone curve: strong"), self->op,
                             self->version(), &p, sizeof(p), 1, DEVELOP_BLEND_CS_RGB_SCENE);
 
  // relight
  p.details = DT_TONEEQ_EIGF;
  p.blending = 5.0f;
  p.feathering = 1.0f;
  p.iterations = 1;
  p.quantization = 0.0f;
  p.exposure_boost = -0.5f;
  p.contrast_boost = 0.0f;
 
  p.noise = 0.0f;
  p.ultra_deep_blacks = 0.15f;
  p.deep_blacks = 0.6f;
  p.blacks = 1.15f;
  p.shadows = 1.33f;
  p.midtones = 1.15f;
  p.highlights = 0.6f;
  p.whites = 0.15f;
  p.speculars = 0.0f;
 
  dt_gui_presets_add_generic(_("relight: fill-in"), self->op,
                             self->version(), &p, sizeof(p), 1, DEVELOP_BLEND_CS_RGB_SCENE);
}
 
 
static gboolean in_mask_editing(dt_iop_module_t *self)
{
  const dt_develop_t *dev = self->dev;
  return dev->form_gui && dt_masks_get_visible_form(dev);
}
 
static void invalidate_luminance_cache(dt_iop_module_t *const self)
{
  // Invalidate the preview luminance cache and histogram when
  // the luminance mask extraction parameters have changed.
  // Keep the ref hand-off visible here: we detach the GUI from the shared cache
  // entry under the GUI lock, then release the retained cache ref afterwards.
  // This is one of the cases that used to go wrong when tone equalizer stored
  // ad-hoc GUI buffers outside the pixelpipe cache.
  dt_iop_toneequalizer_gui_data_t *const restrict g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
  if(IS_NULL_PTR(g)) return;
 
  dt_pixel_cache_entry_t *preview_entry = NULL;
  dt_iop_gui_enter_critical_section(self);
  g->max_histogram = 1;
  g->luminance_valid = FALSE;
  g->histogram_valid = 0;
  g->thumb_preview_hash = DT_PIXELPIPE_CACHE_HASH_INVALID;
  g->pending_preview_hash = DT_PIXELPIPE_CACHE_HASH_INVALID;
  g->thumb_preview_buf_width = 0;
  g->thumb_preview_buf_height = 0;
  preview_entry = g->thumb_preview_entry;
  g->thumb_preview_entry = NULL;
  dt_iop_gui_leave_critical_section(self);
 
  if(!IS_NULL_PTR(preview_entry))
    dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, preview_entry);
}
 
 
static inline __attribute__((always_inline)) int sanity_check(dt_iop_module_t *self)
{
  // If tone equalizer is put after flip/orientation module,
  // the pixel buffer will be in landscape orientation even for pictures displayed in portrait orientation
  // so the interactive editing will fail. Disable the module and issue a warning then.
 
  const double position_self = self->iop_order;
  const double position_min = dt_ioppr_get_iop_order(self->dev->iop_order_list, "flip", 0);
 
  if(position_self < position_min && self->enabled)
  {
    dt_control_log(_("tone equalizer needs to be after distortion modules in the pipeline - disabled"));
    fprintf(stdout, "tone equalizer needs to be after distortion modules in the pipeline - disabled\n");
    self->enabled = 0;
    dt_dev_add_history_item(darktable.develop, self, FALSE, TRUE);
 
    if(self->dev->gui_attached)
    {
      // Repaint the on/off icon
      if(self->off)
      {
        ++darktable.gui->reset;
        gtk_toggle_button_set_active(GTK_TOGGLE_BUTTON(self->off), self->enabled);
        --darktable.gui->reset;
      }
    }
    return 0;
  }
 
  return 1;
}
 
// gaussian-ish kernel - sum is == 1.0f so we don't care much about actual coeffs
static const dt_colormatrix_t gauss_kernel =
  { { 0.076555024f, 0.124401914f, 0.076555024f },
    { 0.124401914f, 0.196172249f, 0.124401914f },
    { 0.076555024f, 0.124401914f, 0.076555024f } };
 
static float get_luminance_from_buffer(const float *const buffer,
                                       const size_t width, const size_t height,
                                       const size_t x, const size_t y)
{
  // Get the weighted average luminance of the 3x3 pixels region centered in (x, y)
  // x and y are ratios in [0, 1] of the width and height
 
  if(y >= height || x >= width) return NAN;
 
  const size_t y_abs[4] DT_ALIGNED_PIXEL =
                          { MAX(y, 1) - 1,                  // previous line
                            y,                              // center line
                            MIN(y + 1, height - 1),         // next line
                            y };          // padding for vectorization
 
  float luminance = 0.0f;
  if (x > 0 && x < width - 2)
  {
    // no clamping needed on x, which allows us to vectorize
    // apply the convolution
    for(int i = 0; i < 3; ++i)
    {
      const size_t y_i = y_abs[i];
      for_each_channel(j)
        luminance += buffer[width * y_i + x-1 + j] * gauss_kernel[i][j];
    }
    return luminance;
  }
 
  const size_t x_abs[4] DT_ALIGNED_PIXEL =
                          { MAX(x, 1) - 1,                  // previous column
                            x,                              // center column
                            MIN(x + 1, width - 1),          // next column
                            x };                            // padding for vectorization
 
  // convolution
  for(int i = 0; i < 3; ++i)
  {
    const size_t y_i = y_abs[i];
    for_each_channel(j)
      luminance += buffer[width * y_i + x_abs[j]] * gauss_kernel[i][j];
  }
  return luminance;
}
 
 
/***
 * Exposure compensation computation
 *
 * Construct the final correction factor by summing the octaves channels gains weighted by
 * the gaussian of the radial distance (pixel exposure - octave center)
 *
 ***/
 
__OMP_DECLARE_SIMD__()
static inline __attribute__((always_inline)) float gaussian_denom(const float sigma)
{
  // Gaussian function denominator such that y = exp(- radius^2 / denominator)
  // this is the constant factor of the exponential, so we don't need to recompute it
  // for every single pixel
  return 2.0f * sigma * sigma;
}
 
 
__OMP_DECLARE_SIMD__()
static inline __attribute__((always_inline)) float gaussian_func(const float radius, const float denominator)
{
  // Gaussian function without normalization
  // this is the variable part of the exponential
  // the denominator should be evaluated with `gaussian_denom`
  // ahead of the array loop for optimal performance
  return expf(- radius * radius / denominator);
}
 
#define DT_TONEEQ_USE_LUT TRUE
#if DT_TONEEQ_USE_LUT
 
// this is the version currently used, as using a lut gives a
// big performance speedup on some cpus
__DT_CLONE_TARGETS__
static inline void apply_toneequalizer(const float *const restrict in,
                                       const float *const restrict luminance,
                                       float *const restrict out,
                                       const dt_iop_roi_t *const roi_in, const dt_iop_roi_t *const roi_out,
                                       const size_t ch,
                                       const dt_iop_toneequalizer_data_t *const d)
{
  const size_t num_elem = (size_t)roi_in->width * roi_in->height;
  const int min_ev = -8;
  const int max_ev = 0;
  const float* restrict lut = d->correction_lut;
  __OMP_PARALLEL_FOR__()
  for(size_t k = 0; k < num_elem; ++k)
  {
    // The radial-basis interpolation is valid in [-8; 0] EV and can quickely diverge outside
    const float exposure = fast_clamp(log2f(luminance[k]), min_ev, max_ev);
    const float correction = lut[(unsigned)roundf((exposure - min_ev) * LUT_RESOLUTION)];
    const size_t idx = k * ch;
    const dt_aligned_pixel_simd_t pix_in = dt_load_simd_aligned(in + idx);
    const dt_aligned_pixel_simd_t correction_v = { correction, correction, correction, 1.0f };
    dt_store_simd_nontemporal(out + idx, pix_in * correction_v);
  }
  dt_omploop_sfence();  // ensure that nontemporal writes complete before the caller reads output
}
 
#else
 
// we keep this version for further reference (e.g. for implementing
// a gpu version)
__DT_CLONE_TARGETS__
static inline void apply_toneequalizer(const float *const restrict in,
                                       const float *const restrict luminance,
                                       float *const restrict out,
                                       const dt_iop_roi_t *const roi_in, const dt_iop_roi_t *const roi_out,
                                       const size_t ch,
                                       const dt_iop_toneequalizer_data_t *const d)
{
  const size_t num_elem = roi_in->width * roi_in->height;
  const float *const restrict factors = d->factors;
  const float sigma = d->smoothing;
  const float gauss_denom = gaussian_denom(sigma);
  __OMP_PARALLEL_FOR__()
  for(size_t k = 0; k < num_elem; ++k)
  {
    // build the correction for the current pixel
    // as the sum of the contribution of each luminance channelcorrection
    float result = 0.0f;
 
    // The radial-basis interpolation is valid in [-8; 0] EV and can quickely diverge outside
    const float exposure = fast_clamp(log2f(luminance[k]), -8.0f, 0.0f);
    __OMP_SIMD__(aligned(luminance, centers_ops, factors:64) safelen(PIXEL_CHAN) reduction(+:result))
    for(int i = 0; i < PIXEL_CHAN; ++i)
      result += gaussian_func(exposure - centers_ops[i], gauss_denom) * factors[i];
 
    // the user-set correction is expected in [-2;+2] EV, so is the interpolated one
    const float correction = fast_clamp(result, 0.25f, 4.0f);
    const size_t idx = k * ch;
    const dt_aligned_pixel_simd_t pix_in = dt_load_simd_aligned(in + idx);
    const dt_aligned_pixel_simd_t correction_v = { correction, correction, correction, 1.0f };
    dt_store_simd_nontemporal(out + idx, pix_in * correction_v);
  }
  dt_omploop_sfence();  // ensure that nontemporal writes complete before the caller reads output
}
#endif // USE_LUT
 
static inline float pixel_correction(const float exposure,
                                     const float *const restrict factors,
                                     const float sigma)
{
  // build the correction for the current pixel
  // as the sum of the contribution of each luminance channel
  float result = 0.0f;
  const float gauss_denom = gaussian_denom(sigma);
  const float expo = fast_clamp(exposure, -8.0f, 0.0f);
  __OMP_SIMD__(aligned(centers_ops, factors:64) safelen(PIXEL_CHAN) reduction(+:result))
  for(int i = 0; i < PIXEL_CHAN; ++i)
    result += gaussian_func(expo - centers_ops[i], gauss_denom) * factors[i];
 
  return fast_clamp(result, 0.25f, 4.0f);
}
 
 
static inline int compute_luminance_mask(const float *const restrict in, float *const restrict luminance,
                                         const size_t width, const size_t height, const size_t ch,
                                         const dt_iop_toneequalizer_data_t *const d)
{
  switch(d->details)
  {
    case(DT_TONEEQ_NONE):
    {
      // No contrast boost here
      luminance_mask(in, luminance, width, height, ch, d->method, d->exposure_boost, 0.0f, 1.0f);
      break;
    }
 
    case(DT_TONEEQ_AVG_GUIDED):
    {
      // Still no contrast boost
      luminance_mask(in, luminance, width, height, ch, d->method, d->exposure_boost, 0.0f, 1.0f);
      if(fast_surface_blur(luminance, width, height, d->radius, d->feathering, d->iterations,
                           DT_GF_BLENDING_GEOMEAN, d->scale, d->quantization, exp2f(-14.0f), 4.0f) != 0)
        return 1;
      break;
    }
 
    case(DT_TONEEQ_GUIDED):
    {
      // Contrast boosting is done around the average luminance of the mask.
      // This is to make exposure corrections easier to control for users, by spreading
      // the dynamic range along all exposure channels, because guided filters
      // tend to flatten the luminance mask a lot around an average ± 2 EV
      // which makes only 2-3 channels usable.
      // we assume the distribution is centered around -4EV, e.g. the center of the nodes
      // the exposure boost should be used to make this assumption true
      luminance_mask(in, luminance, width, height, ch, d->method, d->exposure_boost,
                      CONTRAST_FULCRUM, d->contrast_boost);
      if(fast_surface_blur(luminance, width, height, d->radius, d->feathering, d->iterations,
                           DT_GF_BLENDING_LINEAR, d->scale, d->quantization, exp2f(-14.0f), 4.0f) != 0)
        return 1;
      break;
    }
 
    case(DT_TONEEQ_AVG_EIGF):
    {
      // Still no contrast boost
      luminance_mask(in, luminance, width, height, ch, d->method, d->exposure_boost, 0.0f, 1.0f);
      if(fast_eigf_surface_blur(luminance, width, height, d->radius, d->feathering, d->iterations,
                                DT_GF_BLENDING_GEOMEAN, d->scale, d->quantization, exp2f(-14.0f), 4.0f) != 0)
        return 1;
      break;
    }
 
    case(DT_TONEEQ_EIGF):
    {
      luminance_mask(in, luminance, width, height, ch, d->method, d->exposure_boost,
                      CONTRAST_FULCRUM, d->contrast_boost);
      if(fast_eigf_surface_blur(luminance, width, height, d->radius, d->feathering, d->iterations,
                                DT_GF_BLENDING_LINEAR, d->scale, d->quantization, exp2f(-14.0f), 4.0f) != 0)
        return 1;
      break;
    }
 
    default:
    {
      luminance_mask(in, luminance, width, height, ch, d->method, d->exposure_boost, 0.0f, 1.0f);
      break;
    }
  }
  return 0;
}
 
 
/***
 * Actual transfer functions
 **/
 
__DT_CLONE_TARGETS__
static inline void display_luminance_mask(const float *const restrict in,
                                          const float *const restrict luminance,
                                          float *const restrict out,
                                          const dt_iop_roi_t *const roi_in, const dt_iop_roi_t *const roi_out,
                                          const dt_dev_pixelpipe_t *pipe,
                                          const size_t ch)
{
  const size_t offset_x = (roi_in->x < roi_out->x) ? -roi_in->x + roi_out->x : 0;
  const size_t offset_y = (roi_in->y < roi_out->y) ? -roi_in->y + roi_out->y : 0;
 
  // The output dimensions need to be smaller or equal to the input ones
  // there is no logical reason they shouldn't, except some weird bug in the pipe
  // in this case, ensure we don't segfault
  const size_t in_width = roi_in->width;
  const size_t out_width = (roi_in->width > roi_out->width) ? roi_out->width : roi_in->width;
  const size_t out_height = (roi_in->height > roi_out->height) ? roi_out->height : roi_in->height;
  __OMP_PARALLEL_FOR__(collapse(2))
  for(size_t i = 0 ; i < out_height; ++i)
    for(size_t j = 0; j < out_width; ++j)
    {
      // normalize the mask intensity between -8 EV and 0 EV for clarity,
      // and add a "gamma" 2.0 for better legibility in shadows
      const float intensity = sqrtf(fminf(fmaxf(luminance[(i + offset_y) * in_width  + (j + offset_x)] - 0.00390625f, 0.f) / 0.99609375f, 1.f));
      const size_t index = (i * out_width + j) * ch;
      dt_aligned_pixel_simd_t intensity_v = dt_simd_set1(intensity);
 
      // Keep mask-display alpha consistent with the input while showing a grayscale mask.
      if(pipe->mask_display & DT_DEV_PIXELPIPE_DISPLAY_MASK)
      {
        const size_t in_index = ((i + offset_y) * in_width + (j + offset_x)) * ch;
        intensity_v[3] = in[in_index + 3];
      }
 
      dt_store_simd_nontemporal(out + index, intensity_v);
    }
  dt_omploop_sfence();  // ensure that nontemporal writes complete before the caller reads output
}
 
 
static inline __attribute__((always_inline)) int toneeq_process(struct dt_iop_module_t *self, const dt_dev_pixelpipe_t *pipe,
                          const dt_dev_pixelpipe_iop_t *piece, const void *const restrict ivoid,
                          void *const restrict ovoid, const dt_iop_roi_t *const roi_in,
                          const dt_iop_roi_t *const roi_out)
{
  const dt_iop_toneequalizer_data_t *const d = (const dt_iop_toneequalizer_data_t *const)piece->data;
  dt_iop_toneequalizer_gui_data_t *const g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
 
  const float *const restrict in = dt_check_sse_aligned((float *const)ivoid);
  float *const restrict out = dt_check_sse_aligned((float *const)ovoid);
  float *restrict luminance = NULL;
  dt_pixel_cache_entry_t *luminance_entry = NULL;
  gboolean created_luminance_entry = FALSE;
  uint64_t luminance_hash = DT_PIXELPIPE_CACHE_HASH_INVALID;
 
  if(IS_NULL_PTR(in) || IS_NULL_PTR(out))
  {
    // Pointers are not 64-bits aligned, and SSE code will segfault
    dt_control_log(_("tone equalizer in/out buffer are ill-aligned, please report the bug to the developers"));
    fprintf(stdout, "tone equalizer in/out buffer are ill-aligned, please report the bug to the developers\n");
    return 1;
  }
 
  const size_t width = roi_in->width;
  const size_t height = roi_in->height;
  const size_t num_elem = width * height;
  const size_t ch = 4;
 
  // Get the hash of the upstream pipe to track changes
  const int position = self->iop_order;
  const gboolean preview_output = dt_dev_pixelpipe_has_preview_output(self->dev, pipe, roi_out);
 
  // Sanity checks
  if(width < 1 || height < 1) return 1;
  if(roi_in->width < roi_out->width || roi_in->height < roi_out->height) return 0; // input should be at least as large as output
  if(!sanity_check(self))
  {
    // if module just got disabled by sanity checks, due to pipe position, just pass input through
    dt_simd_memcpy(in, out, num_elem * ch);
    return 0;
  }
 
  if(self->dev->gui_attached)
  {
    // If the module instance has changed order in the pipe, invalidate the caches
    if(!IS_NULL_PTR(g) && g->pipe_order != position)
    {
      dt_pixel_cache_entry_t *preview_entry = NULL;
      dt_iop_gui_enter_critical_section(self);
      g->pipe_order = position;
      g->thumb_preview_hash = DT_PIXELPIPE_CACHE_HASH_INVALID;
      g->pending_preview_hash = DT_PIXELPIPE_CACHE_HASH_INVALID;
      g->thumb_preview_buf_width = 0;
      g->thumb_preview_buf_height = 0;
      g->luminance_valid = FALSE;
      g->histogram_valid = FALSE;
      preview_entry = g->thumb_preview_entry;
      g->thumb_preview_entry = NULL;
      dt_iop_gui_leave_critical_section(self);
 
      if(preview_entry)
        dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, preview_entry);
    }
  }
 
  if(self->dev->gui_attached)
  {
    // Cache the luminance mask in the shared pixelpipe cache so the key follows
    // the exact module state and GUI readers can reuse the same lifetime/locking model.
    // `piece->global_hash` already includes the upstream image state and the module
    // params committed to that run, so the luminance cacheline stays coherent with
    // both preview and main pipelines without adding toneequal-specific validity rules.
    //
    // The fixes we rely on here were exercised with:
    // - history edits and parameter edits invalidating/rebuilding the mask,
    // - opening the module on an already computed preview and reattaching to the
    //   existing cacheline without waiting for a fresh process(),
    // - GUI histogram/cursor sampling while the worker threads are running,
    // - mask display staying restricted to the full pipe while the luminance data
    //   itself comes from whichever pipe produced the preview-sized output.
    void *cache_data = NULL;
    static const char cache_tag[] = "toneequal:luminance";
    luminance_hash = dt_hash(piece->global_hash, cache_tag, sizeof(cache_tag));
 
    created_luminance_entry = dt_dev_pixelpipe_cache_get(darktable.pixelpipe_cache, luminance_hash,
                                                         num_elem * sizeof(float), "toneequal luminance",
                                                         pipe->type, TRUE, &cache_data,
                                                         &luminance_entry);
    luminance = (float *)cache_data;
    if(IS_NULL_PTR(luminance) || IS_NULL_PTR(luminance_entry))
    {
      if(luminance_entry)
      {
        if(created_luminance_entry)
          dt_dev_pixelpipe_cache_wrlock_entry(darktable.pixelpipe_cache, FALSE, luminance_entry);
        dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, luminance_entry);
      }
      return 1;
    }
 
    if(created_luminance_entry)
    {
      if(compute_luminance_mask(in, luminance, width, height, ch, d) != 0)
      {
        dt_dev_pixelpipe_cache_wrlock_entry(darktable.pixelpipe_cache, FALSE, luminance_entry);
        dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, luminance_entry);
        dt_dev_pixelpipe_cache_remove(darktable.pixelpipe_cache, TRUE, luminance_entry);
        return 1;
      }
 
      dt_dev_pixelpipe_cache_wrlock_entry(darktable.pixelpipe_cache, FALSE, luminance_entry);
    }
  }
  else
  {
    // Export/thumbnail pipes don't need persistent GUI sampling, so a local temp buffer is enough.
    luminance = dt_pixelpipe_cache_alloc_align_float(num_elem, pipe);
    if(IS_NULL_PTR(luminance)) return 1;
 
    if(compute_luminance_mask(in, luminance, width, height, ch, d) != 0)
    {
      dt_pixelpipe_cache_free_align(luminance);
      return 1;
    }
  }
 
  // Display output
  if(self->dev->gui_attached && pipe->type == DT_DEV_PIXELPIPE_FULL)
  {
    if(g->mask_display)
    {
      display_luminance_mask(in, luminance, out, roi_in, roi_out, pipe, ch);
      ((dt_dev_pixelpipe_t *)pipe)->mask_display = DT_DEV_PIXELPIPE_DISPLAY_PASSTHRU;
      ((dt_dev_pixelpipe_t *)pipe)->bypass_blendif = 1;
    }
    else
      apply_toneequalizer(in, luminance, out, roi_in, roi_out, ch, d);
  }
  else
  {
    apply_toneequalizer(in, luminance, out, roi_in, roi_out, ch, d);
  }
 
  if(preview_output && self->dev->gui_attached && !IS_NULL_PTR(g) && luminance_entry)
  {
    dt_pixel_cache_entry_t *old_entry = NULL;
    gboolean keep_process_ref = FALSE;
 
    // Transfer one cache ref from this process run to the GUI if this run produced
    // the preview-sized image darkroom is sampling from. Keeping this explicit avoids
    // guessing whether FULL/PREVIEW pipe type owns the GUI state when both pipes can
    // share the same output size.
    dt_iop_gui_enter_critical_section(self);
    if(g->thumb_preview_entry != luminance_entry || g->thumb_preview_hash != luminance_hash)
    {
      old_entry = g->thumb_preview_entry;
      g->thumb_preview_entry = luminance_entry;
      g->thumb_preview_hash = luminance_hash;
      g->pending_preview_hash = DT_PIXELPIPE_CACHE_HASH_INVALID;
      g->thumb_preview_buf_width = width;
      g->thumb_preview_buf_height = height;
      g->luminance_valid = TRUE;
      g->histogram_valid = FALSE;
      keep_process_ref = TRUE;
    }
    dt_iop_gui_leave_critical_section(self);
 
    if(old_entry)
      dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, old_entry);
 
    if(!keep_process_ref)
      dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, luminance_entry);
  }
  else if(luminance_entry)
  {
    dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, luminance_entry);
  }
  else
  {
    dt_pixelpipe_cache_free_align(luminance);
  }
 
  return 0;
}
 
int process(struct dt_iop_module_t *self, const dt_dev_pixelpipe_t *pipe, const dt_dev_pixelpipe_iop_t *piece,
             const void *const restrict ivoid, void *const restrict ovoid)
{
  const dt_iop_roi_t *const roi_in = &piece->roi_in;
  const dt_iop_roi_t *const roi_out = &piece->roi_out;
  return toneeq_process(self, pipe, piece, ivoid, ovoid, roi_in, roi_out);
}
 
 
void modify_roi_in(struct dt_iop_module_t *self, const struct dt_dev_pixelpipe_t *pipe,
                   struct dt_dev_pixelpipe_iop_t *piece,
                   const dt_iop_roi_t *roi_out, dt_iop_roi_t *roi_in)
{
  // Pad the zoomed-in view to avoid weird stuff with local averages at the borders of
  // the preview
 
  dt_iop_toneequalizer_data_t *const d = (dt_iop_toneequalizer_data_t *const)piece->data;
 
  // Get the scaled window radius for the box average
  const int max_size = (piece->iwidth > piece->iheight) ? piece->iwidth : piece->iheight;
  const float diameter = d->blending * max_size * roi_in->scale;
  const int radius = (int)((diameter - 1.0f) / ( 2.0f));
  d->radius = radius;
 
  /*
  // Enlarge the preview roi with padding if needed
  if(self->dev->gui_attached && sanity_check(self))
  {
    int roiy = fmaxf(roi_in->y - radius, 0.0f);
    int roix = fmaxf(roi_in->x - radius, 0.0f);
    int roir = fminf(roix + roi_in->width + 2 * radius, piece->buf_in.width * roi_in->scale);
    int roib = fminf(roiy + roi_in->height + 2 * radius, piece->buf_in.height * roi_in->scale);
 
    // Set the values and check
    roi_in->x = roix;
    roi_in->y = roiy;
    roi_in->width = roir - roi_in->x;
    roi_in->height = roib - roi_in->y;
  }
  */
}
 
 
/***
 * Setters and Getters for parameters
 *
 * Remember the user params split the [-8; 0] EV range in 9 channels and define a set of (x, y)
 * coordinates, where x are the exposure channels (evenly-spaced by 1 EV in [-8; 0] EV)
 * and y are the desired exposure compensation for each channel.
 *
 * This (x, y) set is interpolated by radial-basis function using a series of 8 gaussians.
 * Losing 1 degree of freedom makes it an approximation rather than an interpolation but
 * helps reducing a bit the oscillations and fills a full AVX vector.
 *
 * The coefficients/factors used in the interpolation/approximation are linear, but keep in
 * mind that users params are expressed as log2 gains, so we always need to do the log2/exp2
 * flip/flop between both.
 *
 * User params of exposure compensation are expected between [-2 ; +2] EV for practical UI reasons
 * and probably numerical stability reasons, but there is no theoretical obstacle to enlarge
 * this range. The main reason for not allowing it is tone equalizer is mostly intended
 * to do local changes, and these don't look so well if you are too harsh on the changes.
 * For heavier tonemapping, it should be used in combination with a tone curve or filmic.
 *
 ***/
 
static void compute_correction_lut(float* restrict lut, const float sigma, const float *const restrict factors)
{
  const float gauss_denom = gaussian_denom(sigma);
  const int min_ev = -8;
  assert(PIXEL_CHAN == -min_ev);
  for(int j = 0; j <= LUT_RESOLUTION * PIXEL_CHAN; j++)
  {
    // build the correction for each pixel
    // as the sum of the contribution of each luminance channelcorrection
    float exposure = (float)j / (float)LUT_RESOLUTION + min_ev;
    float result = 0.0f;
    for(int i = 0; i < PIXEL_CHAN; ++i)
      result += gaussian_func(exposure - centers_ops[i], gauss_denom) * factors[i];
    // the user-set correction is expected in [-2;+2] EV, so is the interpolated one
    lut[j] = fast_clamp(result, 0.25f, 4.0f);
  }
}
 
static void get_channels_gains(float factors[CHANNELS], const dt_iop_toneequalizer_params_t *p)
{
  assert(CHANNELS == 9);
 
  // Get user-set channels gains in EV (log2)
  factors[0] = p->noise; // -8 EV
  factors[1] = p->ultra_deep_blacks; // -7 EV
  factors[2] = p->deep_blacks;       // -6 EV
  factors[3] = p->blacks;            // -5 EV
  factors[4] = p->shadows;           // -4 EV
  factors[5] = p->midtones;          // -3 EV
  factors[6] = p->highlights;        // -2 EV
  factors[7] = p->whites;            // -1 EV
  factors[8] = p->speculars;         // +0 EV
}
 
 
static void get_channels_factors(float factors[CHANNELS], const dt_iop_toneequalizer_params_t *p)
{
  assert(CHANNELS == 9);
 
  // Get user-set channels gains in EV (log2)
  get_channels_gains(factors, p);
 
  // Convert from EV offsets to linear factors
  __OMP_SIMD__(aligned(factors:64))
  for(int c = 0; c < CHANNELS; ++c)
    factors[c] = exp2f(factors[c]);
}
 
 
static int compute_channels_factors(const float factors[PIXEL_CHAN], float out[CHANNELS], const float sigma)
{
  // Input factors are the weights for the radial-basis curve approximation of user params
  // Output factors are the gains of the user parameters channels
  // aka the y coordinates of the approximation for x = { CHANNELS }
  assert(PIXEL_CHAN == 8);
 
  int valid = 1;
  __OMP_PARALLEL_FOR_SIMD__(aligned(factors, out, centers_params:64) shared(valid) firstprivate(centers_params))
  for(int i = 0; i < CHANNELS; ++i)
  {
     // Compute the new channels factors
    out[i] = pixel_correction(centers_params[i], factors, sigma);
 
    // check they are in [-2, 2] EV and not NAN
    if(isnan(out[i]) || out[i] < 0.25f || out[i] > 4.0f) valid = 0;
  }
 
  return valid;
}
 
 
static int compute_channels_gains(const float in[CHANNELS], float out[CHANNELS])
{
  // Helper function to compute the new channels gains (log) from the factors (linear)
  assert(PIXEL_CHAN == 8);
 
  const int valid = 1;
 
  for(int i = 0; i < CHANNELS; ++i)
    out[i] = log2f(in[i]);
 
  return valid;
}
 
 
static int commit_channels_gains(const float factors[CHANNELS], dt_iop_toneequalizer_params_t *p)
{
  p->noise = factors[0];
  p->ultra_deep_blacks = factors[1];
  p->deep_blacks = factors[2];
  p->blacks = factors[3];
  p->shadows = factors[4];
  p->midtones = factors[5];
  p->highlights = factors[6];
  p->whites = factors[7];
  p->speculars = factors[8];
 
  return 1;
}
 
 
/***
 * Cache invalidation and initializatiom
 ***/
 
 
static void gui_cache_init(struct dt_iop_module_t *self)
{
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
  if(IS_NULL_PTR(g)) return;
 
  dt_iop_gui_enter_critical_section(self);
  g->thumb_preview_hash = DT_PIXELPIPE_CACHE_HASH_INVALID;
  g->pending_preview_hash = DT_PIXELPIPE_CACHE_HASH_INVALID;
  g->max_histogram = 1;
  g->scale = 1.0f;
  g->sigma = sqrtf(2.0f);
  g->mask_display = FALSE;
 
  g->interpolation_valid = FALSE;  // TRUE if the interpolation_matrix is ready
  g->luminance_valid = FALSE;      // TRUE if the luminance cache is ready
  g->histogram_valid = FALSE;      // TRUE if the histogram cache and stats are ready
  g->lut_valid = FALSE;            // TRUE if the gui_lut is ready
  g->graph_valid = FALSE;          // TRUE if the UI graph view is ready
  g->user_param_valid = FALSE;     // TRUE if users params set in interactive view are in bounds
  g->factors_valid = TRUE;         // TRUE if radial-basis coeffs are ready
 
  g->valid_nodes_x = FALSE;        // TRUE if x coordinates of graph nodes have been inited
  g->valid_nodes_y = FALSE;        // TRUE if y coordinates of graph nodes have been inited
  g->area_cursor_valid = FALSE;    // TRUE if mouse cursor is over the graph area
  g->area_dragging = FALSE;        // TRUE if left-button has been pushed but not released and cursor motion is recorded
  g->cursor_valid = FALSE;         // TRUE if mouse cursor is over the preview image
 
  g->thumb_preview_entry = NULL;
  g->thumb_preview_buf_width = 0;
  g->thumb_preview_buf_height = 0;
 
  g->desc = NULL;
  g->layout = NULL;
  g->cr = NULL;
  g->cst = NULL;
  g->context = NULL;
 
  g->pipe_order = 0;
  dt_iop_gui_leave_critical_section(self);
}
 
static uint64_t _current_preview_luminance_hash(dt_iop_module_t *self, size_t *width, size_t *height)
{
  if(width) *width = 0;
  if(height) *height = 0;
  if(IS_NULL_PTR(self) || IS_NULL_PTR(self->dev) || IS_NULL_PTR(self->dev->preview_pipe)) return DT_PIXELPIPE_CACHE_HASH_INVALID;
 
  dt_dev_pixelpipe_iop_t *piece = dt_dev_distort_get_iop_pipe(self->dev->preview_pipe, self);
  if(IS_NULL_PTR(piece) || !piece->enabled || piece->roi_in.width <= 0 || piece->roi_in.height <= 0)
    return DT_PIXELPIPE_CACHE_HASH_INVALID;
 
  if(width) *width = piece->roi_in.width;
  if(height) *height = piece->roi_in.height;
 
  static const char cache_tag[] = "toneequal:luminance";
  return dt_hash(piece->global_hash, cache_tag, sizeof(cache_tag));
}
 
 
static inline void build_interpolation_matrix(float A[CHANNELS * PIXEL_CHAN],
                                              const float sigma)
{
  // Build the symmetrical definite positive part of the augmented matrix
  // of the radial-basis interpolation weights
 
  const float gauss_denom = gaussian_denom(sigma);
  __OMP_SIMD__(aligned(A, centers_ops, centers_params:64) collapse(2))
  for(int i = 0; i < CHANNELS; ++i)
    for(int j = 0; j < PIXEL_CHAN; ++j)
      A[i * PIXEL_CHAN + j] = gaussian_func(centers_params[i] - centers_ops[j], gauss_denom);
}
 
 
__DT_CLONE_TARGETS__
static inline void compute_log_histogram_and_stats(const float *const restrict luminance,
                                          int histogram[UI_SAMPLES],
                                          const size_t num_elem,
                                          int *max_histogram,
                                          float *first_decile, float *last_decile)
{
  // (Re)init the histogram
  memset(histogram, 0, sizeof(int) * UI_SAMPLES);
 
  // we first calculate an extended histogram for better accuracy
  #define TEMP_SAMPLES 2 * UI_SAMPLES
  int temp_hist[TEMP_SAMPLES];
  memset(temp_hist, 0, sizeof(int) * TEMP_SAMPLES);
 
  // Split exposure in bins
  __OMP_PARALLEL_FOR__(reduction(+:temp_hist[:TEMP_SAMPLES]))
  for(size_t k = 0; k < num_elem; k++)
  {
    // extended histogram bins between [-10; +6] EV remapped between [0 ; 2 * UI_SAMPLES]
    const int index = CLAMP((int)(((log2f(luminance[k]) + 10.0f) / 16.0f) * (float)TEMP_SAMPLES), 0, TEMP_SAMPLES - 1);
    temp_hist[index] += 1;
  }
 
  const int first = (int)((float)num_elem * 0.05f);
  const int last = (int)((float)num_elem * (1.0f - 0.95f));
  int population = 0;
  int first_pos = 0;
  int last_pos = 0;
 
  // scout the extended histogram bins looking for deciles
  // these would not be accurate with the regular histogram
  for(int k = 0; k < TEMP_SAMPLES; ++k)
  {
    const size_t prev_population = population;
    population += temp_hist[k];
    if(prev_population < first && first <= population)
    {
      first_pos = k;
      break;
    }
  }
  population = 0;
  for(int k = TEMP_SAMPLES - 1; k >= 0; --k)
  {
    const size_t prev_population = population;
    population += temp_hist[k];
    if(prev_population < last && last <= population)
    {
      last_pos = k;
      break;
    }
  }
 
  // Convert decile positions to exposures
  *first_decile = 16.0 * (float)first_pos / (float)(TEMP_SAMPLES - 1) - 10.0;
  *last_decile = 16.0 * (float)last_pos / (float)(TEMP_SAMPLES - 1) - 10.0;
 
  // remap the extended histogram into the normal one
  // bins between [-8; 0] EV remapped between [0 ; UI_SAMPLES]
  for(size_t k = 0; k < TEMP_SAMPLES; ++k)
  {
    float EV = 16.0 * (float)k / (float)(TEMP_SAMPLES - 1) - 10.0;
    const int i = CLAMP((int)(((EV + 8.0f) / 8.0f) * (float)UI_SAMPLES), 0, UI_SAMPLES - 1);
    histogram[i] += temp_hist[k];
 
    // store the max numbers of elements in bins for later normalization
    *max_histogram = histogram[i] > *max_histogram ? histogram[i] : *max_histogram;
  }
}
 
static inline void update_histogram(struct dt_iop_module_t *const self)
{
  dt_iop_toneequalizer_gui_data_t *const g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
  if(IS_NULL_PTR(g)) return;
 
  dt_pixel_cache_entry_t *preview_entry = NULL;
  size_t width = 0;
  size_t height = 0;
  uint64_t preview_hash = DT_PIXELPIPE_CACHE_HASH_INVALID;
  gboolean needs_histogram = FALSE;
 
  // Readers take a temporary cache ref while copying the GUI-visible entry pointer,
  // then read-lock the cacheline only around the actual sampling. This keeps both
  // ownership transfer and lock lifetime visible at the call site.
  dt_iop_gui_enter_critical_section(self);
  if(!g->histogram_valid && g->luminance_valid && g->thumb_preview_entry)
  {
    preview_entry = g->thumb_preview_entry;
    width = g->thumb_preview_buf_width;
    height = g->thumb_preview_buf_height;
    preview_hash = g->thumb_preview_hash;
    dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, TRUE, preview_entry);
    needs_histogram = TRUE;
  }
  dt_iop_gui_leave_critical_section(self);
 
  if(!needs_histogram || width == 0 || height == 0)
  {
    if(!IS_NULL_PTR(preview_entry))
      dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, preview_entry);
    return;
  }
 
  int histogram[UI_SAMPLES];
  int max_histogram = 1;
  float first_decile = 0.0f;
  float last_decile = 0.0f;
 
  dt_dev_pixelpipe_cache_rdlock_entry(darktable.pixelpipe_cache, TRUE, preview_entry);
  const float *const preview_buf = (const float *const)dt_pixel_cache_entry_get_data(preview_entry);
  if(preview_buf)
    compute_log_histogram_and_stats(preview_buf, histogram, width * height, &max_histogram, &first_decile,
                                    &last_decile);
  dt_dev_pixelpipe_cache_rdlock_entry(darktable.pixelpipe_cache, FALSE, preview_entry);
 
  if(IS_NULL_PTR(preview_buf))
  {
    dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, preview_entry);
    return;
  }
 
  dt_iop_gui_enter_critical_section(self);
  if(g->thumb_preview_entry == preview_entry && g->thumb_preview_hash == preview_hash && !g->histogram_valid)
  {
    memcpy(g->histogram, histogram, sizeof(histogram));
    g->max_histogram = max_histogram;
    g->histogram_first_decile = first_decile;
    g->histogram_last_decile = last_decile;
    g->histogram_average = (first_decile + last_decile) / 2.0f;
    g->histogram_valid = TRUE;
  }
  dt_iop_gui_leave_critical_section(self);
 
  dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, preview_entry);
}
 
 
__DT_CLONE_TARGETS__
static inline void compute_lut_correction(struct dt_iop_toneequalizer_gui_data_t *g,
                                          const float offset,
                                          const float scaling)
{
  // Compute the LUT of the exposure corrections in EV,
  // offset and scale it for display in GUI widget graph
 
  float *const restrict LUT = g->gui_lut;
  const float *const restrict factors = g->factors;
  const float sigma = g->sigma;
  __OMP_FOR_SIMD__(aligned(LUT, factors:64))
  for(int k = 0; k < UI_SAMPLES; k++)
  {
    // build the inset graph curve LUT
    // the x range is [-14;+2] EV
    const float x = (8.0f * (((float)k) / ((float)(UI_SAMPLES - 1)))) - 8.0f;
    LUT[k] = offset - log2f(pixel_correction(x, factors, sigma)) / scaling;
  }
}
 
 
 
static inline gboolean update_curve_lut(struct dt_iop_module_t *self)
{
  dt_iop_toneequalizer_params_t *p = (dt_iop_toneequalizer_params_t *)self->params;
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
 
  if(IS_NULL_PTR(g)) return FALSE;
 
  gboolean valid = TRUE;
 
  if(!g->interpolation_valid)
  {
    build_interpolation_matrix(g->interpolation_matrix, g->sigma);
    g->interpolation_valid = TRUE;
    g->factors_valid = FALSE;
  }
 
  if(!g->user_param_valid)
  {
    float factors[CHANNELS] DT_ALIGNED_ARRAY;
    get_channels_factors(factors, p);
    dt_simd_memcpy(factors, g->temp_user_params, CHANNELS);
    g->user_param_valid = TRUE;
    g->factors_valid = FALSE;
  }
 
  if(!g->factors_valid && g->user_param_valid)
  {
    float factors[CHANNELS] DT_ALIGNED_ARRAY;
    dt_simd_memcpy(g->temp_user_params, factors, CHANNELS);
    if(pseudo_solve(g->interpolation_matrix, factors, CHANNELS, PIXEL_CHAN, 1) != 0)
    {
      valid = FALSE;
    }
    else
    {
      dt_simd_memcpy(factors, g->factors, PIXEL_CHAN);
      g->factors_valid = TRUE;
      g->lut_valid = FALSE;
    }
  }
 
  if(!g->lut_valid && g->factors_valid)
  {
    compute_lut_correction(g, 0.5f, 4.0f);
    g->lut_valid = TRUE;
  }
 
  return valid;
}
 
 
void init_global(dt_iop_module_so_t *module)
{
  dt_iop_toneequalizer_global_data_t *gd
      = (dt_iop_toneequalizer_global_data_t *)malloc(sizeof(dt_iop_toneequalizer_global_data_t));
 
  module->data = gd;
}
 
 
void cleanup_global(dt_iop_module_so_t *module)
{
  dt_free(module->data);
}
 
 
void commit_params(struct dt_iop_module_t *self, dt_iop_params_t *p1, dt_dev_pixelpipe_t *pipe,
                   dt_dev_pixelpipe_iop_t *piece)
{
  dt_iop_toneequalizer_params_t *p = (dt_iop_toneequalizer_params_t *)p1;
  dt_iop_toneequalizer_data_t *d = (dt_iop_toneequalizer_data_t *)piece->data;
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
 
  // Trivial params passing
  d->method = p->method;
  d->details = p->details;
  d->iterations = p->iterations;
  d->smoothing = p->smoothing;
  d->quantization = p->quantization;
 
  // UI blending param is set in % of the largest image dimension
  d->blending = p->blending / 100.0f;
 
  // UI guided filter feathering param increases the edges taping
  // but the actual regularization params applied in guided filter behaves the other way
  d->feathering = 1.f / (p->feathering);
 
  // UI params are in log2 offsets (EV) : convert to linear factors
  d->contrast_boost = exp2f(p->contrast_boost);
  d->exposure_boost = exp2f(p->exposure_boost);
 
  /*
   * Perform a radial-based interpolation using a series gaussian functions
   */
  // FIXME: trying to spare some CPU cycles by mixing GUI params update
  // with pipeline code is not worth the thread-safety issues (solved only by deadlocks).
  // Move that to GUI code.
  if(self->dev->gui_attached && !IS_NULL_PTR(g))
  {
    if(g->sigma != p->smoothing) g->interpolation_valid = FALSE;
    g->sigma = p->smoothing;
    g->user_param_valid = FALSE; // force updating channels factors
 
    update_curve_lut(self);
    dt_simd_memcpy(g->factors, d->factors, PIXEL_CHAN);
  }
  else
  {
    // No cache : Build / Solve interpolation matrix
    float factors[CHANNELS] DT_ALIGNED_ARRAY;
    get_channels_factors(factors, p);
 
    float A[CHANNELS * PIXEL_CHAN] DT_ALIGNED_ARRAY;
    build_interpolation_matrix(A, p->smoothing);
    if(pseudo_solve(A, factors, CHANNELS, PIXEL_CHAN, 0) != 0) return;
 
    dt_simd_memcpy(factors, d->factors, PIXEL_CHAN);
  }
 
  // compute the correction LUT here to spare some time in process
  // when computing several times toneequalizer with same parameters
  compute_correction_lut(d->correction_lut, d->smoothing, d->factors);
}
 
 
void init_pipe(struct dt_iop_module_t *self, dt_dev_pixelpipe_t *pipe, dt_dev_pixelpipe_iop_t *piece)
{
  piece->data = dt_calloc_align(sizeof(dt_iop_toneequalizer_data_t));
  piece->data_size = sizeof(dt_iop_toneequalizer_data_t);
}
 
 
void cleanup_pipe(struct dt_iop_module_t *self, dt_dev_pixelpipe_t *pipe, dt_dev_pixelpipe_iop_t *piece)
{
  dt_free_align(piece->data);
  piece->data = NULL;
}
 
void show_guiding_controls(struct dt_iop_module_t *self)
{
  dt_iop_module_t *module = (dt_iop_module_t *)self;
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
  const dt_iop_toneequalizer_params_t *p = (const dt_iop_toneequalizer_params_t *)module->params;
 
  switch(p->details)
  {
    case(DT_TONEEQ_NONE):
    {
      gtk_widget_set_visible(g->blending, FALSE);
      gtk_widget_set_visible(g->feathering, FALSE);
      gtk_widget_set_visible(g->iterations, FALSE);
      gtk_widget_set_visible(g->contrast_boost, FALSE);
      gtk_widget_set_visible(g->quantization, FALSE);
      break;
    }
 
    case(DT_TONEEQ_AVG_GUIDED):
    case(DT_TONEEQ_AVG_EIGF):
    {
      gtk_widget_set_visible(g->blending, TRUE);
      gtk_widget_set_visible(g->feathering, TRUE);
      gtk_widget_set_visible(g->iterations, TRUE);
      gtk_widget_set_visible(g->contrast_boost, FALSE);
      gtk_widget_set_visible(g->quantization, TRUE);
      break;
    }
 
    case(DT_TONEEQ_GUIDED):
    case(DT_TONEEQ_EIGF):
    {
      gtk_widget_set_visible(g->blending, TRUE);
      gtk_widget_set_visible(g->feathering, TRUE);
      gtk_widget_set_visible(g->iterations, TRUE);
      gtk_widget_set_visible(g->contrast_boost, TRUE);
      gtk_widget_set_visible(g->quantization, TRUE);
      break;
    }
  }
}
 
void update_exposure_sliders(dt_iop_toneequalizer_gui_data_t *g, dt_iop_toneequalizer_params_t *p)
{
  ++darktable.gui->reset;
  dt_bauhaus_slider_set(g->noise, p->noise);
  dt_bauhaus_slider_set(g->ultra_deep_blacks, p->ultra_deep_blacks);
  dt_bauhaus_slider_set(g->deep_blacks, p->deep_blacks);
  dt_bauhaus_slider_set(g->blacks, p->blacks);
  dt_bauhaus_slider_set(g->shadows, p->shadows);
  dt_bauhaus_slider_set(g->midtones, p->midtones);
  dt_bauhaus_slider_set(g->highlights, p->highlights);
  dt_bauhaus_slider_set(g->whites, p->whites);
  dt_bauhaus_slider_set(g->speculars, p->speculars);
  --darktable.gui->reset;
}
 
 
void gui_update(struct dt_iop_module_t *self)
{
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
  dt_iop_toneequalizer_params_t *p = (dt_iop_toneequalizer_params_t *)self->params;
 
  dt_bauhaus_slider_set(g->smoothing, logf(p->smoothing) / logf(sqrtf(2.0f)) - 1.0f);
 
  show_guiding_controls(self);
  invalidate_luminance_cache(self);
 
  gtk_toggle_button_set_active(GTK_TOGGLE_BUTTON(g->show_luminance_mask), g->mask_display);
}
 
void gui_changed(dt_iop_module_t *self, GtkWidget *w, void *previous)
{
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
  if(w == g->method     ||
     w == g->blending   ||
     w == g->feathering ||
     w == g->iterations ||
     w == g->quantization)
  {
    invalidate_luminance_cache(self);
  }
  else if (w == g->details)
  {
    invalidate_luminance_cache(self);
    show_guiding_controls(self);
  }
  else if (w == g->contrast_boost || w == g->exposure_boost)
  {
    invalidate_luminance_cache(self);
    dt_bauhaus_widget_set_quad_active(w, FALSE);
  }
}
 
static void smoothing_callback(GtkWidget *slider, gpointer user_data)
{
  dt_iop_module_t *self = (dt_iop_module_t *)user_data;
  if(darktable.gui->reset) return;
  dt_iop_toneequalizer_params_t *p = (dt_iop_toneequalizer_params_t *)self->params;
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
 
  p->smoothing= powf(sqrtf(2.0f), 1.0f +  dt_bauhaus_slider_get(slider));
 
  float factors[CHANNELS] DT_ALIGNED_ARRAY;
  get_channels_factors(factors, p);
 
  // Solve the interpolation by least-squares to check the validity of the smoothing param
  const int valid = update_curve_lut(self);
  if(!valid) dt_control_log(_("the interpolation is unstable, decrease the curve smoothing"));
 
  // Redraw graph before launching computation
  update_curve_lut(self);
  gtk_widget_queue_draw(GTK_WIDGET(g->area));
  dt_dev_add_history_item(darktable.develop, self, TRUE, TRUE);
 
  // Unlock the colour picker so we can display our own custom cursor
  dt_iop_color_picker_reset(self, TRUE);
}
 
static void show_luminance_mask_callback(GtkWidget *togglebutton, GdkEventButton *event, dt_iop_module_t *self)
{
  if(darktable.gui->reset) return;
  dt_iop_request_focus(self);
 
  gtk_toggle_button_set_active(GTK_TOGGLE_BUTTON(self->off), TRUE);
 
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
 
  // if blend module is displaying mask do not display it here
  if(self->request_mask_display != DT_DEV_PIXELPIPE_DISPLAY_NONE)
    self->request_mask_display = DT_DEV_PIXELPIPE_DISPLAY_NONE;
 
  g->mask_display = !g->mask_display;
 
  if(g->mask_display)
    self->request_mask_display = DT_DEV_PIXELPIPE_DISPLAY_PASSTHRU;
 
  dt_iop_set_cache_bypass(self, g->mask_display);
  gtk_toggle_button_set_active(GTK_TOGGLE_BUTTON(g->show_luminance_mask), g->mask_display);
  dt_dev_pixelpipe_update_history_main(self->dev);
 
  // Unlock the colour picker so we can display our own custom cursor
  dt_iop_color_picker_reset(self, TRUE);
}
 
 
/***
 * GUI Interactivity
 **/
 
static void _switch_cursors(struct dt_iop_module_t *self)
{
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
  if(IS_NULL_PTR(g) || !self->dev->gui_attached) return;
 
  if(!self->expanded)
  {
    // If the module lost focus, do nothing and let the app decide.
    return;
  }
  else if(!self->enabled)
  {
    // A disabled module does not own the cursor state: leave whatever the view
    // or another tool has currently selected, and most importantly do not hide it.
    return;
  }
  else if(!sanity_check(self) || in_mask_editing(self) || dt_iop_color_picker_is_visible(self->dev))
  {
    // if we are editing masks or using colour-pickers, do not display controls
    
    // display default cursor
    dt_control_set_cursor_visible(TRUE);
    dt_control_queue_cursor_by_name("default");
    return;
  }
  else if((self->dev->pipe->processing || self->dev->preview_pipe->processing) && g->cursor_valid)
  {
    // if pipe is busy or dirty but cursor is on preview,
    // display waiting cursor while pipe reprocesses
    dt_control_set_cursor_visible(TRUE);
    dt_control_queue_cursor_by_name("wait");
 
    dt_control_queue_redraw_center();
  }
  else if(self->enabled && g->cursor_valid && !self->dev->pipe->processing)
  {
    // if pipe is clean and idle and cursor is on preview,
    // hide GTK cursor because we display our custom one
    dt_control_set_cursor_visible(FALSE);
    dt_control_hinter_message(darktable.control,
                              _("scroll over image to change tone exposure\n"
                                "shift+scroll for large steps; "
                                "ctrl+scroll for small steps"));
 
    dt_control_queue_redraw_center();
  }
  else if(!g->cursor_valid)
  {
    // if module is active and opened but cursor is out of the preview,
    // display default cursor
    dt_control_set_cursor_visible(TRUE);
    dt_control_queue_cursor_by_name("default");
 
    dt_control_queue_redraw_center();
  }
  else
  {
    // in any other situation where module has focus,
    // reset the cursor but don't launch a redraw
    dt_control_set_cursor_visible(TRUE);
    dt_control_queue_cursor_by_name("default");
  }
}
 
 
int mouse_moved(struct dt_iop_module_t *self, double x, double y, double pressure, int which)
{
  // Whenever the mouse moves over the picture preview, store its coordinates in the GUI struct
  // for later use. This works only if dev->preview_pipe perfectly overlaps with the UI preview
  // meaning all distortions, cropping, rotations etc. are applied before this module in the pipe.
 
  dt_develop_t *dev = self->dev;
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
 
  const int fail = !sanity_check(self);
  if(fail) return 0;
 
  if(dt_iop_color_picker_is_visible(dev))
  {
    g->cursor_valid = FALSE;
    g->area_active_node = -1;
    _switch_cursors(self);
    gtk_widget_queue_draw(GTK_WIDGET(g->area));
    return 0;
  }
 
  const int wd = dev->roi.preview_width;
  const int ht = dev->roi.preview_height;
 
  if(IS_NULL_PTR(g)) return 0;
  if(wd < 1 || ht < 1) return 0;
 
  float pzxpy[2] = { (float)x, (float)y };
  dt_dev_coordinates_widget_to_image_norm(dev, pzxpy, 1);
  dt_dev_coordinates_image_norm_to_preview_abs(dev, pzxpy, 1);
 
  const int x_pointer = pzxpy[0];
  const int y_pointer = pzxpy[1];
 
  // Cursor is valid if it's inside the picture frame
  if(x_pointer >= 0 && x_pointer < wd && y_pointer >= 0 && y_pointer < ht)
  {
    g->cursor_valid = TRUE;
    g->cursor_pos_x = x_pointer;
    g->cursor_pos_y = y_pointer;
  }
  else
  {
    g->cursor_valid = FALSE;
    g->cursor_pos_x = 0;
    g->cursor_pos_y = 0;
  }
 
  // Store the current preview exposure too, to spare recomputing it in the UI callbacks.
  if(g->cursor_valid && !dev->pipe->processing)
  {
    dt_pixel_cache_entry_t *preview_entry = NULL;
    size_t preview_width = 0;
    size_t preview_height = 0;
 
    // Keep the GUI cache entry alive before releasing the GUI state lock.
    // Pipe workers can replace the retained entry while mouse motion keeps sampling it.
    dt_iop_gui_enter_critical_section(self);
    if(g->luminance_valid && !IS_NULL_PTR(g->thumb_preview_entry))
    {
      preview_entry = g->thumb_preview_entry;
      preview_width = g->thumb_preview_buf_width;
      preview_height = g->thumb_preview_buf_height;
      dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, TRUE, preview_entry);
    }
    dt_iop_gui_leave_critical_section(self);
 
    if(!IS_NULL_PTR(preview_entry) && preview_width > 0 && preview_height > 0)
    {
      dt_dev_pixelpipe_cache_rdlock_entry(darktable.pixelpipe_cache, TRUE, preview_entry);
      const float *const preview_buf = (const float *const)dt_pixel_cache_entry_get_data(preview_entry);
      const float cursor_exposure
          = preview_buf ? log2f(get_luminance_from_buffer(preview_buf, preview_width, preview_height,
                                                          (size_t)x_pointer, (size_t)y_pointer))
                        : NAN;
      dt_dev_pixelpipe_cache_rdlock_entry(darktable.pixelpipe_cache, FALSE, preview_entry);
 
      if(!isnan(cursor_exposure))
      {
        g->cursor_exposure = cursor_exposure;
      }
 
    }
 
    if(preview_entry)
      dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, preview_entry);
  }
 
  _switch_cursors(self);
  return 1;
}
 
 
int mouse_leave(struct dt_iop_module_t *self)
{
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
 
  if(IS_NULL_PTR(g)) return 0;
 
  g->cursor_valid = FALSE;
  g->area_active_node = -1;
 
  // display default cursor
  dt_control_queue_cursor_by_name("default");
  dt_control_queue_redraw_center();
  gtk_widget_queue_draw(GTK_WIDGET(g->area));
 
  return 1;
}
 
 
static inline int set_new_params_interactive(const float control_exposure, const float exposure_offset, const float blending_sigma,
                                              dt_iop_toneequalizer_gui_data_t *g,  dt_iop_toneequalizer_params_t *p)
{
  // Apply an exposure offset optimized smoothly over all the exposure channels,
  // taking user instruction to apply exposure_offset EV at control_exposure EV,
  // and commit the new params is the solution is valid.
 
  // Raise the user params accordingly to control correction and distance from cursor exposure
  // to blend smoothly the desired correction
  const float std = gaussian_denom(blending_sigma);
  if(g->user_param_valid)
  {
    for(int i = 0; i < CHANNELS; ++i)
      g->temp_user_params[i] *= exp2f(gaussian_func(centers_params[i] - control_exposure, std) * exposure_offset);
  }
 
  // Get the new weights for the radial-basis approximation
  float factors[CHANNELS] DT_ALIGNED_ARRAY;
  dt_simd_memcpy(g->temp_user_params, factors, CHANNELS);
  if(g->user_param_valid)
    g->user_param_valid = (pseudo_solve(g->interpolation_matrix, factors, CHANNELS, PIXEL_CHAN, 1) == 0);
  if(!g->user_param_valid) dt_control_log(_("the interpolation is unstable, decrease the curve smoothing"));
 
  // Compute new user params for channels and store them locally
  if(g->user_param_valid)
    g->user_param_valid = compute_channels_factors(factors, g->temp_user_params, g->sigma);
  if(!g->user_param_valid) dt_control_log(_("some parameters are out-of-bounds"));
 
  const int commit = g->user_param_valid;
 
  if(commit)
  {
    // Accept the solution
    dt_simd_memcpy(factors, g->factors, PIXEL_CHAN);
    g->lut_valid = 0;
 
    // Convert the linear temp parameters to log gains and commit
    float gains[CHANNELS] DT_ALIGNED_ARRAY;
    compute_channels_gains(g->temp_user_params, gains);
    commit_channels_gains(gains, p);
  }
  else
  {
    // Reset the GUI copy of user params
    get_channels_factors(factors, p);
    dt_simd_memcpy(factors, g->temp_user_params, CHANNELS);
    g->user_param_valid = 1;
  }
 
  return commit;
}
 
 
int scrolled(struct dt_iop_module_t *self, double x, double y, int up, uint32_t state)
{
  dt_develop_t *dev = self->dev;
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
  dt_iop_toneequalizer_params_t *p = (dt_iop_toneequalizer_params_t *)self->params;
 
  if(!sanity_check(self)) return 0;
  if(darktable.gui->reset) return 1;
  if(IS_NULL_PTR(g)) return 0;
  if(!self->expanded) return 0;
  if(dt_iop_color_picker_is_visible(dev)) return 0;
 
  // turn-on the module if off
  if(!self->enabled)
    if(self->off) gtk_toggle_button_set_active(GTK_TOGGLE_BUTTON(self->off), 1);
 
  // if GUI buffers not ready, exit but still handle the cursor
  const int fail = (!g->cursor_valid || !g->interpolation_valid || !g->user_param_valid || dev->pipe->processing || !self->expanded);
  if(fail) return 1;
 
  // Re-read the exposure in case the preview changed after the mouse moved.
  dt_pixel_cache_entry_t *preview_entry = NULL;
  size_t preview_width = 0;
  size_t preview_height = 0;
  int cursor_x = 0;
  int cursor_y = 0;
 
  // Copy the cursor sample source while holding the GUI state lock, then keep the
  // cacheline alive with an explicit ref until the sampling read lock is released.
  dt_iop_gui_enter_critical_section(self);
  if(g->luminance_valid && !IS_NULL_PTR(g->thumb_preview_entry))
  {
    preview_entry = g->thumb_preview_entry;
    preview_width = g->thumb_preview_buf_width;
    preview_height = g->thumb_preview_buf_height;
    cursor_x = g->cursor_pos_x;
    cursor_y = g->cursor_pos_y;
    dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, TRUE, preview_entry);
  }
  dt_iop_gui_leave_critical_section(self);
 
  if(IS_NULL_PTR(preview_entry) || preview_width == 0 || preview_height == 0)
  {
    if(!IS_NULL_PTR(preview_entry))
      dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, preview_entry);
    return 1;
  }
 
  if(!IS_NULL_PTR(preview_entry) && preview_width > 0 && preview_height > 0)
  {
    dt_dev_pixelpipe_cache_rdlock_entry(darktable.pixelpipe_cache, TRUE, preview_entry);
    const float *const preview_buf = (const float *const)dt_pixel_cache_entry_get_data(preview_entry);
    const float cursor_exposure
        = preview_buf ? log2f(get_luminance_from_buffer(preview_buf, preview_width, preview_height,
                                                        (size_t)cursor_x, (size_t)cursor_y))
                      : NAN;
    dt_dev_pixelpipe_cache_rdlock_entry(darktable.pixelpipe_cache, FALSE, preview_entry);
 
    if(!isnan(cursor_exposure))
    {
      g->cursor_exposure = cursor_exposure;
    }
  }
 
  if(!IS_NULL_PTR(preview_entry))
    dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, preview_entry);
 
  // Set the correction from mouse scroll input
  const float increment = (up) ? +1.0f : -1.0f;
 
  float step;
  if(dt_modifier_is(state, GDK_SHIFT_MASK))
    step = 1.0f;  // coarse
  else if(dt_modifier_is(state, GDK_CONTROL_MASK))
    step = 0.1f;  // fine
  else
    step = 0.25f; // standard
 
  const float offset = step * ((float)increment);
 
  // Get the desired correction on exposure channels
  const int commit = set_new_params_interactive(g->cursor_exposure, offset, g->sigma * g->sigma / 2.0f, g, p);
 
  gtk_widget_queue_draw(GTK_WIDGET(g->area));
 
  if(commit)
  {
    // Update GUI with new params
    update_exposure_sliders(g, p);
 
    dt_dev_add_history_item(darktable.develop, self, FALSE, TRUE);
  }
 
  return 1;
}
 
/***
 * GTK/Cairo drawings and custom widgets
 **/
 
static inline gboolean _init_drawing(dt_iop_module_t *const restrict self, GtkWidget *widget,
                                     dt_iop_toneequalizer_gui_data_t *const restrict g);
 
 
void cairo_draw_hatches(cairo_t *cr, double center[2], double span[2], int instances, double line_width, double shade)
{
  // center is the (x, y) coordinates of the region to draw
  // span is the distance of the region's bounds to the center, over (x, y) axes
 
  // Get the coordinates of the corners of the bounding box of the region
  double C0[2] = { center[0] - span[0], center[1] - span[1] };
  double C2[2] = { center[0] + span[0], center[1] + span[1] };
 
  double delta[2] = { 2.0 * span[0] / (double)instances,
                      2.0 * span[1] / (double)instances };
 
  cairo_set_line_width(cr, line_width);
  cairo_set_source_rgb(cr, shade, shade, shade);
 
  for(int i = -instances / 2 - 1; i <= instances / 2 + 1; i++)
  {
    cairo_move_to(cr, C0[0] + (double)i * delta[0], C0[1]);
    cairo_line_to(cr, C2[0] + (double)i * delta[0], C2[1]);
    cairo_stroke(cr);
  }
}
 
static void get_shade_from_luminance(cairo_t *cr, const float luminance, const float alpha)
{
  // TODO: fetch screen gamma from ICC display profile
  const float gamma = 1.0f / 2.2f;
  const float shade = powf(luminance, gamma);
  cairo_set_source_rgba(cr, shade, shade, shade, alpha);
}
 
 
static void draw_exposure_cursor(cairo_t *cr, const double pointerx, const double pointery, const double radius, const float luminance, const float zoom_scale, const int instances, const float alpha)
{
  // Draw a circle cursor filled with a grey shade corresponding to a luminance value
  // or hatches if the value is above the overexposed threshold
 
  const double radius_z = radius / zoom_scale;
 
  get_shade_from_luminance(cr, luminance, alpha);
  cairo_arc(cr, pointerx, pointery, radius_z, 0, 2 * M_PI);
  cairo_fill_preserve(cr);
  cairo_save(cr);
  cairo_clip(cr);
 
  if(log2f(luminance) > 0.0f)
  {
    // if overexposed, draw hatches
    double pointer_coord[2] = { pointerx, pointery };
    double span[2] = { radius_z, radius_z };
    cairo_draw_hatches(cr, pointer_coord, span, instances, DT_PIXEL_APPLY_DPI(1. / zoom_scale), 0.3);
  }
  cairo_restore(cr);
}
 
 
static void match_color_to_background(cairo_t *cr, const float exposure, const float alpha)
{
  float shade = 0.0f;
  // TODO: put that as a preference in anselrc
  const float contrast = 1.0f;
 
  if(exposure > -2.5f)
    shade = (fminf(exposure * contrast, 0.0f) - 2.5f);
  else
    shade = (fmaxf(exposure / contrast, -5.0f) + 2.5f);
 
  get_shade_from_luminance(cr, exp2f(shade), alpha);
}
 
 
void gui_post_expose(struct dt_iop_module_t *self, cairo_t *cr, int32_t width, int32_t height,
                     int32_t pointerx, int32_t pointery)
{
  // Draw the custom exposure cursor over the image preview
 
  dt_develop_t *dev = self->dev;
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
  if(IS_NULL_PTR(g)) return;
 
  // If the darkroom picker owns the center view, keep tone equalizer overlays out of the way.
  if(in_mask_editing(self) || dt_iop_color_picker_is_visible(dev)) return;
 
  const int fail = (!g->cursor_valid || !g->interpolation_valid || dev->pipe->processing
                    || !sanity_check(self) || !self->expanded);
  if(fail) return;
 
  if(!g->graph_valid)
    if(!_init_drawing(self, self->widget, g)) return;
 
  // Get coordinates
  const float x_pointer = g->cursor_pos_x;
  const float y_pointer = g->cursor_pos_y;
  dt_pixel_cache_entry_t *preview_entry = NULL;
  size_t preview_width = 0;
  size_t preview_height = 0;
  float factors[PIXEL_CHAN] DT_ALIGNED_ARRAY;
  float sigma = 0.0f;
 
  float exposure_in = 0.0f;
  float luminance_in = 0.0f;
  float correction = 0.0f;
  float exposure_out = 0.0f;
  float luminance_out = 0.0f;
  if(self->enabled)
  {
    // The drawing pass samples the same retained luminance cacheline as the event
    // handlers, so the ref has to be taken before another pipe callback can detach it.
    dt_iop_gui_enter_critical_section(self);
    if(g->luminance_valid && !IS_NULL_PTR(g->thumb_preview_entry))
    {
      preview_entry = g->thumb_preview_entry;
      preview_width = g->thumb_preview_buf_width;
      preview_height = g->thumb_preview_buf_height;
      dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, TRUE, preview_entry);
      dt_simd_memcpy(g->factors, factors, PIXEL_CHAN);
      sigma = g->sigma;
    }
    dt_iop_gui_leave_critical_section(self);
  }
 
  if(!IS_NULL_PTR(preview_entry) && preview_width > 0 && preview_height > 0)
  {
    dt_dev_pixelpipe_cache_rdlock_entry(darktable.pixelpipe_cache, TRUE, preview_entry);
    const float *const preview_buf = (const float *const)dt_pixel_cache_entry_get_data(preview_entry);
    if(!IS_NULL_PTR(preview_buf))
    {
      exposure_in = log2f(get_luminance_from_buffer(preview_buf, preview_width, preview_height,
                                                    (size_t)x_pointer, (size_t)y_pointer));
      luminance_in = exp2f(exposure_in);
      correction = log2f(pixel_correction(exposure_in, factors, sigma));
      exposure_out = exposure_in + correction;
      luminance_out = exp2f(exposure_out);
    }
    else
    {
      exposure_in = NAN;
      correction = NAN;
    }
    dt_dev_pixelpipe_cache_rdlock_entry(darktable.pixelpipe_cache, FALSE, preview_entry);
 
    if(!isnan(exposure_in))
    {
      g->cursor_exposure = exposure_in;
    }
  }
 
  if(preview_entry)
    dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, preview_entry);
 
  if(isnan(correction) || isnan(exposure_in)) return; // something went wrong
 
  // Rescale and shift Cairo drawing coordinates
  const float zoom_scale = dt_dev_get_overlay_scale(dev);
  dt_dev_rescale_roi(dev, cr, width, height);
 
  // set custom cursor dimensions
  const double outer_radius = 16.;
  const double inner_radius = outer_radius / 2.0;
  const double setting_offset_x = (outer_radius + 4. * g->inner_padding) / zoom_scale;
  const double fill_width = DT_PIXEL_APPLY_DPI(4) / zoom_scale;
 
  // setting fill bars
  match_color_to_background(cr, exposure_out, 1.0);
  cairo_set_line_width(cr, 2.0 * fill_width);
  cairo_move_to(cr, x_pointer - setting_offset_x, y_pointer);
 
  if(correction > 0.0f)
    cairo_arc(cr, x_pointer, y_pointer, setting_offset_x, M_PI, M_PI + correction * M_PI / 4.0);
  else
    cairo_arc_negative(cr, x_pointer, y_pointer, setting_offset_x, M_PI, M_PI + correction * M_PI / 4.0);
 
  cairo_stroke(cr);
 
  // setting ground level
  cairo_set_line_width(cr, DT_PIXEL_APPLY_DPI(1.5) / zoom_scale);
  cairo_move_to(cr, x_pointer + (outer_radius + 2. * g->inner_padding) / zoom_scale, y_pointer);
  cairo_line_to(cr, x_pointer + outer_radius / zoom_scale, y_pointer);
  cairo_move_to(cr, x_pointer - outer_radius / zoom_scale, y_pointer);
  cairo_line_to(cr, x_pointer - setting_offset_x - 4.0 * g->inner_padding / zoom_scale, y_pointer);
  cairo_stroke(cr);
 
  // setting cursor cross hair
  cairo_set_line_width(cr, DT_PIXEL_APPLY_DPI(1.5) / zoom_scale);
  cairo_move_to(cr, x_pointer, y_pointer + setting_offset_x + fill_width);
  cairo_line_to(cr, x_pointer, y_pointer + outer_radius / zoom_scale);
  cairo_move_to(cr, x_pointer, y_pointer - outer_radius / zoom_scale);
  cairo_line_to(cr, x_pointer, y_pointer - setting_offset_x - fill_width);
  cairo_stroke(cr);
 
  // draw exposure cursor
  draw_exposure_cursor(cr, x_pointer, y_pointer, outer_radius, luminance_in, zoom_scale, 6, .9);
  draw_exposure_cursor(cr, x_pointer, y_pointer, inner_radius, luminance_out, zoom_scale, 3, .9);
 
  // Create Pango objects : texts
  char text[256];
  PangoLayout *layout;
  PangoRectangle ink;
  PangoFontDescription *desc = pango_font_description_copy_static(darktable.bauhaus->pango_font_desc);
 
  // Avoid text resizing based on zoom level
  const int old_size = pango_font_description_get_size(desc);
  pango_font_description_set_size (desc, (int)(old_size / zoom_scale));
  layout = pango_cairo_create_layout(cr);
  pango_layout_set_font_description(layout, desc);
  dt_gui_set_pango_resolution(layout);
 
  // Build text object
  if(preview_entry && self->enabled)
    snprintf(text, sizeof(text), _("%+.1f EV"), exposure_in);
  else
    snprintf(text, sizeof(text), "? EV");
  pango_layout_set_text(layout, text, -1);
  pango_layout_get_pixel_extents(layout, &ink, NULL);
 
  // Draw the text plain blackground
  get_shade_from_luminance(cr, luminance_out, 0.75);
  cairo_rectangle(cr, x_pointer + (outer_radius + 2. * g->inner_padding) / zoom_scale,
                      y_pointer - ink.y - ink.height / 2.0 - g->inner_padding / zoom_scale,
                      ink.width + 2.0 * ink.x + 4. * g->inner_padding / zoom_scale,
                      ink.height + 2.0 * ink.y + 2. * g->inner_padding / zoom_scale);
  cairo_fill(cr);
 
  // Display the EV reading
  match_color_to_background(cr, exposure_out, 1.0);
  cairo_move_to(cr, x_pointer + (outer_radius + 4. * g->inner_padding) / zoom_scale,
                    y_pointer - ink.y - ink.height / 2.);
  pango_cairo_show_layout(cr, layout);
 
  cairo_stroke(cr);
 
  pango_font_description_free(desc);
  g_object_unref(layout);
 
  if(preview_entry && self->enabled)
  {
    // Search for nearest node in graph and highlight it
    const float radius_threshold = 0.45f;
    g->area_active_node = -1;
    if(g->cursor_valid)
      for(int i = 0; i < CHANNELS; ++i)
      {
        const float delta_x = fabsf(g->cursor_exposure - centers_params[i]);
        if(delta_x < radius_threshold)
          g->area_active_node = i;
      }
 
    gtk_widget_queue_draw(GTK_WIDGET(g->area));
  }
}
 
 
void gui_focus(struct dt_iop_module_t *self, gboolean in)
{
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
  _switch_cursors(self);
  if(!in)
  {
    //lost focus - stop showing mask
    const gboolean was_mask = g->mask_display;
    g->mask_display = FALSE;
    dt_iop_gui_enter_critical_section(self);
    g->pending_preview_hash = DT_PIXELPIPE_CACHE_HASH_INVALID;
    dt_iop_gui_leave_critical_section(self);
    gtk_toggle_button_set_active(GTK_TOGGLE_BUTTON(g->show_luminance_mask), FALSE);
    if(was_mask) dt_dev_pixelpipe_update_history_main(self->dev);
    dt_collection_hint_message(darktable.collection);
  }
  else
  {
    gboolean needs_preview_update = FALSE;
 
    if(self->enabled && self->dev && self->dev->preview_pipe && !self->dev->preview_pipe->processing)
    {
      dt_dev_pixelpipe_iop_t *piece = dt_dev_distort_get_iop_pipe(self->dev->preview_pipe, self);
      if(!IS_NULL_PTR(piece) && piece->enabled && piece->roi_in.width > 0 && piece->roi_in.height > 0)
      {
        // Opening the module can happen after preview processing already finished.
        // In that case the preview pipe may stay idle because darkroom can reuse an
        // existing backbuffer, so reattach to the existing luminance cacheline here
        // instead of waiting for process() to run again. This was tested by opening
        // tone equalizer on a fresh darkroom image with no pending recompute.
        static const char cache_tag[] = "toneequal:luminance";
        const uint64_t preview_hash = dt_hash(piece->global_hash, cache_tag, sizeof(cache_tag));
        void *preview_buf = NULL;
        dt_pixel_cache_entry_t *preview_entry = NULL;
 
        gboolean preview_ready = dt_dev_pixelpipe_cache_ref_entry_by_hash(darktable.pixelpipe_cache, preview_hash,
                                                                          &preview_buf, &preview_entry);
        if(preview_ready && (IS_NULL_PTR(preview_buf) || IS_NULL_PTR(preview_entry)))
        {
          if(!IS_NULL_PTR(preview_entry))
            dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, preview_entry);
          preview_ready = FALSE;
        }
 
        if(preview_ready)
        {
          dt_pixel_cache_entry_t *old_entry = NULL;
          gboolean keep_new_entry = FALSE;
          dt_iop_gui_enter_critical_section(self);
          if(g->thumb_preview_entry != preview_entry || g->thumb_preview_hash != preview_hash
             || g->thumb_preview_buf_width != piece->roi_in.width
             || g->thumb_preview_buf_height != piece->roi_in.height || !g->luminance_valid)
          {
            old_entry = g->thumb_preview_entry;
            g->thumb_preview_entry = preview_entry;
            g->thumb_preview_hash = preview_hash;
            g->pending_preview_hash = DT_PIXELPIPE_CACHE_HASH_INVALID;
            g->thumb_preview_buf_width = piece->roi_in.width;
            g->thumb_preview_buf_height = piece->roi_in.height;
            g->luminance_valid = TRUE;
            g->histogram_valid = FALSE;
            keep_new_entry = TRUE;
          }
          dt_iop_gui_leave_critical_section(self);
 
          if(old_entry)
            dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, old_entry);
          if(!keep_new_entry)
            dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, preview_entry);
        }
        else
        {
          dt_iop_gui_enter_critical_section(self);
          g->pending_preview_hash = preview_hash;
          dt_iop_gui_leave_critical_section(self);
          needs_preview_update = TRUE;
        }
      }
      else
        needs_preview_update = TRUE;
    }
 
    if(needs_preview_update)
      dt_dev_pixelpipe_update_history_preview(self->dev);
 
    dt_control_hinter_message(darktable.control,
                              _("scroll over image to change tone exposure\n"
                                "shift+scroll for large steps; "
                                "ctrl+scroll for small steps"));
  }
}
 
 
static inline gboolean _init_drawing(dt_iop_module_t *const restrict self, GtkWidget *widget,
                                     dt_iop_toneequalizer_gui_data_t *const restrict g)
{
  // Cache the equalizer graph objects to avoid recomputing all the view at each redraw
  gtk_widget_get_allocation(widget, &g->allocation);
 
  if(g->cst) cairo_surface_destroy(g->cst);
  g->cst = dt_cairo_image_surface_create(CAIRO_FORMAT_ARGB32, g->allocation.width, g->allocation.height);
 
  if(g->cr) cairo_destroy(g->cr);
  g->cr = cairo_create(g->cst);
 
  if(g->layout) g_object_unref(g->layout);
  g->layout = pango_cairo_create_layout(g->cr);
 
  if(g->desc) pango_font_description_free(g->desc);
  g->desc = pango_font_description_copy_static(darktable.bauhaus->pango_font_desc);
 
  pango_layout_set_font_description(g->layout, g->desc);
  dt_gui_set_pango_resolution(g->layout);
  g->context = gtk_widget_get_style_context(widget);
 
  char text[256];
 
  // Get the text line height for spacing
  snprintf(text, sizeof(text), "X");
  pango_layout_set_text(g->layout, text, -1);
  pango_layout_get_pixel_extents(g->layout, &g->ink, NULL);
  g->line_height = g->ink.height;
 
  // Get the width of a minus sign for legend labels spacing
  snprintf(text, sizeof(text), "-");
  pango_layout_set_text(g->layout, text, -1);
  pango_layout_get_pixel_extents(g->layout, &g->ink, NULL);
  g->sign_width = g->ink.width / 2.0;
 
  // Set the sizes, margins and paddings
  g->inner_padding = INNER_PADDING;
  g->inset = g->inner_padding + darktable.bauhaus->quad_width;
  g->graph_left_space = g->line_height + g->inner_padding;
  g->graph_width = g->allocation.width - g->inset - 2.0 * g->line_height; // align the right border on sliders
  g->graph_height = g->allocation.height - g->inset - 2.0 * g->line_height; // give room to nodes
  g->gradient_left_limit = 0.0;
  g->gradient_right_limit = g->graph_width;
  g->gradient_top_limit = g->graph_height + 2 * g->inner_padding;
  g->gradient_width = g->gradient_right_limit - g->gradient_left_limit;
  g->legend_top_limit = -0.5 * g->line_height - 2.0 * g->inner_padding;
  g->x_label = g->graph_width + g->sign_width + 3.0 * g->inner_padding;
 
  gtk_render_background(g->context, g->cr, 0, 0, g->allocation.width, g->allocation.height);
 
  // set the graph as the origin of the coordinates
  cairo_translate(g->cr, g->line_height + 2 * g->inner_padding, g->line_height + 3 * g->inner_padding);
 
  // display x-axis and y-axis legends (EV)
  set_color(g->cr, darktable.bauhaus->graph_fg);
 
  float value = -8.0f;
 
  for(int k = 0; k < CHANNELS; k++)
  {
    const float xn = (((float)k) / ((float)(CHANNELS - 1))) * g->graph_width - g->sign_width;
    snprintf(text, sizeof(text), "%+.0f", value);
    pango_layout_set_text(g->layout, text, -1);
    pango_layout_get_pixel_extents(g->layout, &g->ink, NULL);
    cairo_move_to(g->cr, xn - 0.5 * g->ink.width - g->ink.x,
                         g->legend_top_limit - 0.5 * g->ink.height - g->ink.y);
    pango_cairo_show_layout(g->cr, g->layout);
    cairo_stroke(g->cr);
 
    value += 1.0;
  }
 
  value = 2.0f;
 
  for(int k = 0; k < 5; k++)
  {
    const float yn = (k / 4.0f) * g->graph_height;
    snprintf(text, sizeof(text), "%+.0f", value);
    pango_layout_set_text(g->layout, text, -1);
    pango_layout_get_pixel_extents(g->layout, &g->ink, NULL);
    cairo_move_to(g->cr, g->x_label - 0.5 * g->ink.width - g->ink.x,
                yn - 0.5 * g->ink.height - g->ink.y);
    pango_cairo_show_layout(g->cr, g->layout);
    cairo_stroke(g->cr);
 
    value -= 1.0;
  }
 
  // Draw the perceptually even gradient
  cairo_pattern_t *grad;
  grad = cairo_pattern_create_linear(g->gradient_left_limit, 0.0, g->gradient_right_limit, 0.0);
  dt_cairo_perceptual_gradient(grad, 1.0);
  cairo_set_line_width(g->cr, 0.0);
  cairo_rectangle(g->cr, g->gradient_left_limit, g->gradient_top_limit, g->gradient_width, g->line_height);
  cairo_set_source(g->cr, grad);
  cairo_fill(g->cr);
  cairo_pattern_destroy(grad);
 
  // Draw the perceptually even gradient
  grad = cairo_pattern_create_linear(0.0, g->graph_height, 0.0, 0.0);
  dt_cairo_perceptual_gradient(grad, 1.0);
  cairo_set_line_width(g->cr, 0.0);
  cairo_rectangle(g->cr, -g->line_height - 2 * g->inner_padding, 0.0, g->line_height, g->graph_height);
  cairo_set_source(g->cr, grad);
  cairo_fill(g->cr);
 
  cairo_pattern_destroy(grad);
 
  // Draw frame borders
  cairo_set_line_width(g->cr, DT_PIXEL_APPLY_DPI(0.5));
  set_color(g->cr, darktable.bauhaus->graph_border);
  cairo_rectangle(g->cr, 0, 0, g->graph_width, g->graph_height);
  cairo_stroke_preserve(g->cr);
 
  // end of caching section, this will not be drawn again
 
  g->graph_valid = 1;
 
  return TRUE;
}
 
 
// must be called while holding self->gui_lock
static inline void init_nodes_x(dt_iop_toneequalizer_gui_data_t *g)
{
  if(IS_NULL_PTR(g)) return;
 
  if(!g->valid_nodes_x && g->graph_width > 0)
  {
    for(int i = 0; i < CHANNELS; ++i)
      g->nodes_x[i] = (((float)i) / ((float)(CHANNELS - 1))) * g->graph_width;
    g->valid_nodes_x = TRUE;
  }
}
 
 
// must be called while holding self->gui_lock
static inline void init_nodes_y(dt_iop_toneequalizer_gui_data_t *g)
{
  if(IS_NULL_PTR(g)) return;
 
  if(g->user_param_valid && g->graph_height > 0)
  {
    for(int i = 0; i < CHANNELS; ++i)
      g->nodes_y[i] =  (0.5 - log2f(g->temp_user_params[i]) / 4.0) * g->graph_height; // assumes factors in [-2 ; 2] EV
    g->valid_nodes_y = TRUE;
  }
}
 
 
static gboolean area_draw(GtkWidget *widget, cairo_t *cr, gpointer user_data)
{
  // Draw the widget equalizer view
  dt_iop_module_t *self = (dt_iop_module_t *)user_data;
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
  if(IS_NULL_PTR(g)) return FALSE;
 
  // Init or refresh the drawing cache
  //if(!g->graph_valid)
  if(!_init_drawing(self, widget, g)) return FALSE; // this can be cached and drawn just once, but too lazy to debug a cache invalidation for Cairo objects
 
  // since the widget sizes are not cached and invalidated properly above (yet...)
  // force the invalidation of the nodes coordinates to account for possible widget resizing
  g->valid_nodes_x = FALSE;
  g->valid_nodes_y = FALSE;
 
  // Refresh cached UI elements
  update_histogram(self);
  update_curve_lut(self);
 
  // Draw graph background
  cairo_set_line_width(g->cr, DT_PIXEL_APPLY_DPI(0.5));
  cairo_rectangle(g->cr, 0, 0, g->graph_width, g->graph_height);
  set_color(g->cr, darktable.bauhaus->graph_bg);
  cairo_fill(g->cr);
 
  // draw grid
  cairo_set_line_width(g->cr, DT_PIXEL_APPLY_DPI(0.5));
  set_color(g->cr, darktable.bauhaus->graph_border);
  dt_draw_grid(g->cr, 8, 0, 0, g->graph_width, g->graph_height);
 
  // draw ground level
  set_color(g->cr, darktable.bauhaus->graph_fg);
  cairo_set_line_width(g->cr, DT_PIXEL_APPLY_DPI(1));
  cairo_move_to(g->cr, 0, 0.5 * g->graph_height);
  cairo_line_to(g->cr, g->graph_width, 0.5 * g->graph_height);
  cairo_stroke(g->cr);
 
  if(g->histogram_valid && self->enabled)
  {
    // draw the inset histogram
    set_color(g->cr, darktable.bauhaus->inset_histogram);
    cairo_set_line_width(g->cr, DT_PIXEL_APPLY_DPI(4.0));
    cairo_move_to(g->cr, 0, g->graph_height);
 
    for(int k = 0; k < UI_SAMPLES; k++)
    {
      // the x range is [-8;+0] EV
      const float x_temp = (8.0 * (float)k / (float)(UI_SAMPLES - 1)) - 8.0;
      const float y_temp = (float)(g->histogram[k]) / (float)(g->max_histogram) * 0.96;
      cairo_line_to(g->cr, (x_temp + 8.0) * g->graph_width / 8.0,
                           (1.0 - y_temp) * g->graph_height );
    }
    cairo_line_to(g->cr, g->graph_width, g->graph_height);
    cairo_close_path(g->cr);
    cairo_fill(g->cr);
 
    if(g->histogram_last_decile > -0.1f)
    {
      // histogram overflows controls in highlights : display warning
      cairo_save(g->cr);
      cairo_set_source_rgb(g->cr, 0.75, 0.50, 0.);
      dtgtk_cairo_paint_gamut_check(g->cr, g->graph_width - 2.5 * g->line_height, 0.5 * g->line_height,
                                           2.0 * g->line_height, 2.0 * g->line_height, 0, NULL);
      cairo_restore(g->cr);
    }
 
    if(g->histogram_first_decile < -7.9f)
    {
      // histogram overflows controls in lowlights : display warning
      cairo_save(g->cr);
      cairo_set_source_rgb(g->cr, 0.75, 0.50, 0.);
      dtgtk_cairo_paint_gamut_check(g->cr, 0.5 * g->line_height, 0.5 * g->line_height,
                                           2.0 * g->line_height, 2.0 * g->line_height, 0, NULL);
      cairo_restore(g->cr);
    }
  }
 
  if(g->lut_valid)
  {
    // draw the interpolation curve
    set_color(g->cr, darktable.bauhaus->graph_fg);
    cairo_move_to(g->cr, 0, g->gui_lut[0] * g->graph_height);
    cairo_set_line_width(g->cr, DT_PIXEL_APPLY_DPI(3));
 
    for(int k = 1; k < UI_SAMPLES; k++)
    {
      // the x range is [-8;+0] EV
      const float x_temp = (8.0f * (((float)k) / ((float)(UI_SAMPLES - 1)))) - 8.0f;
      const float y_temp = g->gui_lut[k];
 
      cairo_line_to(g->cr, (x_temp + 8.0f) * g->graph_width / 8.0f,
                            y_temp * g->graph_height );
    }
    cairo_stroke(g->cr);
  }
 
  init_nodes_x(g);
  init_nodes_y(g);
 
  if(g->user_param_valid)
  {
    // draw nodes positions
    for(int k = 0; k < CHANNELS; k++)
    {
      const float xn = g->nodes_x[k];
      const float yn = g->nodes_y[k];
 
      // fill bars
      cairo_set_line_width(g->cr, DT_PIXEL_APPLY_DPI(6));
      set_color(g->cr, darktable.bauhaus->color_fill);
      cairo_move_to(g->cr, xn, 0.5 * g->graph_height);
      cairo_line_to(g->cr, xn, yn);
      cairo_stroke(g->cr);
 
      // bullets
      cairo_set_line_width(g->cr, DT_PIXEL_APPLY_DPI(3));
      cairo_arc(g->cr, xn, yn, DT_PIXEL_APPLY_DPI(4), 0, 2. * M_PI);
      set_color(g->cr, darktable.bauhaus->graph_fg);
      cairo_stroke_preserve(g->cr);
 
      if(g->area_active_node == k)
        set_color(g->cr, darktable.bauhaus->graph_fg);
      else
        set_color(g->cr, darktable.bauhaus->graph_bg);
 
      cairo_fill(g->cr);
    }
  }
 
  if(self->enabled)
  {
    if(g->area_cursor_valid)
    {
      const float radius = g->sigma * g->graph_width / 8.0f / sqrtf(2.0f);
      cairo_set_line_width(g->cr, DT_PIXEL_APPLY_DPI(1.5));
      const float y =g->gui_lut[(int)CLAMP(((UI_SAMPLES - 1) * g->area_x / g->graph_width), 0, UI_SAMPLES - 1)];
      cairo_arc(g->cr, g->area_x, y * g->graph_height, radius, 0, 2. * M_PI);
      set_color(g->cr, darktable.bauhaus->graph_fg);
      cairo_stroke(g->cr);
    }
 
    if(g->cursor_valid)
    {
 
      float x_pos = (g->cursor_exposure + 8.0f) / 8.0f * g->graph_width;
 
      if(x_pos > g->graph_width || x_pos < 0.0f)
      {
        // exposure at current position is outside [-8; 0] EV :
        // bound it in the graph limits and show it in orange
        cairo_set_source_rgb(g->cr, 0.75, 0.50, 0.);
        cairo_set_line_width(g->cr, DT_PIXEL_APPLY_DPI(3));
        x_pos = (x_pos < 0.0f) ? 0.0f : g->graph_width;
      }
      else
      {
        set_color(g->cr, darktable.bauhaus->graph_fg);
        cairo_set_line_width(g->cr, DT_PIXEL_APPLY_DPI(1.5));
      }
 
      cairo_move_to(g->cr, x_pos, 0.0);
      cairo_line_to(g->cr, x_pos, g->graph_height);
      cairo_stroke(g->cr);
    }
  }
 
  // clean and exit
  cairo_set_source_surface(cr, g->cst, 0, 0);
  cairo_paint(cr);
 
  return TRUE;
}
 
static gboolean area_enter_notify(GtkWidget *widget, GdkEventCrossing *event, gpointer user_data)
{
  dt_iop_module_t *self = (dt_iop_module_t *)user_data;
  if(darktable.gui->reset) return 1;
  if(!self->enabled) return 0;
 
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
  g->area_x = (event->x - g->inset);
  g->area_y = (event->y - g->inset);
  g->area_dragging = FALSE;
  g->area_active_node = -1;
  g->area_cursor_valid = (g->area_x > 0.0f && g->area_x < g->graph_width && g->area_y > 0.0f && g->area_y < g->graph_height);
 
  gtk_widget_queue_draw(GTK_WIDGET(g->area));
  return TRUE;
}
 
 
static gboolean area_leave_notify(GtkWidget *widget, GdkEventCrossing *event, gpointer user_data)
{
  dt_iop_module_t *self = (dt_iop_module_t *)user_data;
  if(darktable.gui->reset) return 1;
  if(!self->enabled) return 0;
 
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
  dt_iop_toneequalizer_params_t *p = (dt_iop_toneequalizer_params_t *)self->params;
 
  if(g->area_dragging)
  {
    // cursor left area : force commit to avoid glitches
    update_exposure_sliders(g, p);
 
    dt_dev_add_history_item(darktable.develop, self, FALSE, TRUE);
  }
  g->area_x = (event->x - g->inset);
  g->area_y = (event->y - g->inset);
  g->area_dragging = FALSE;
  g->area_active_node = -1;
  g->area_cursor_valid = (g->area_x > 0.0f && g->area_x < g->graph_width && g->area_y > 0.0f && g->area_y < g->graph_height);
 
  gtk_widget_queue_draw(GTK_WIDGET(g->area));
  return TRUE;
}
 
 
static gboolean area_button_press(GtkWidget *widget, GdkEventButton *event, gpointer user_data)
{
  dt_iop_module_t *self = (dt_iop_module_t *)user_data;
  if(darktable.gui->reset) return 1;
 
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
 
  dt_iop_request_focus(self);
 
  if(event->button == 1 && event->type == GDK_2BUTTON_PRESS)
  {
    dt_iop_toneequalizer_params_t *p = (dt_iop_toneequalizer_params_t *)self->params;
    dt_iop_toneequalizer_params_t *d = (dt_iop_toneequalizer_params_t *)self->default_params;
 
    // reset nodes params
    p->noise = d->noise;
    p->ultra_deep_blacks = d->ultra_deep_blacks;
    p->deep_blacks = d->deep_blacks;
    p->blacks = d->blacks;
    p->shadows = d->shadows;
    p->midtones = d->midtones;
    p->highlights = d->highlights;
    p->whites = d->whites;
    p->speculars = d->speculars;
 
    // update UI sliders
    update_exposure_sliders(g, p);
 
    // Redraw graph
    gtk_widget_queue_draw(self->widget);
    dt_dev_add_history_item(darktable.develop, self, TRUE, TRUE);
    return TRUE;
  }
  else if(event->button == 1)
  {
    if(self->enabled)
    {
      g->area_dragging = 1;
      gtk_widget_queue_draw(GTK_WIDGET(g->area));
    }
    else
    {
      dt_dev_add_history_item(darktable.develop, self, TRUE, TRUE);
    }
    return TRUE;
  }
 
  // Unlock the colour picker so we can display our own custom cursor
  dt_iop_color_picker_reset(self, TRUE);
 
  return FALSE;
}
 
 
static gboolean area_motion_notify(GtkWidget *widget, GdkEventMotion *event, gpointer user_data)
{
  dt_iop_module_t *self = (dt_iop_module_t *)user_data;
  if(darktable.gui->reset) return 1;
  if(!self->enabled) return 0;
 
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
  dt_iop_toneequalizer_params_t *p = (dt_iop_toneequalizer_params_t *)self->params;
 
  if(g->area_dragging)
  {
    // vertical distance travelled since button_pressed event
    const float offset = (-event->y + g->area_y) / g->graph_height * 4.0f; // graph spans over 4 EV
    const float cursor_exposure = g->area_x / g->graph_width * 8.0f - 8.0f;
 
    // Get the desired correction on exposure channels
    g->area_dragging = set_new_params_interactive(cursor_exposure, offset, g->sigma * g->sigma / 2.0f, g, p);
  }
 
  g->area_x = (event->x - g->graph_left_space);
  g->area_y = event->y;
  g->area_cursor_valid = (g->area_x > 0.0f && g->area_x < g->graph_width && g->area_y > 0.0f && g->area_y < g->graph_height);
  g->area_active_node = -1;
 
  // Search if cursor is close to a node
  if(g->valid_nodes_x)
  {
    const float radius_threshold = fabsf(g->nodes_x[1] - g->nodes_x[0]) * 0.45f;
    for(int i = 0; i < CHANNELS; ++i)
    {
      const float delta_x = fabsf(g->area_x - g->nodes_x[i]);
      if(delta_x < radius_threshold)
      {
        g->area_active_node = i;
        g->area_cursor_valid = 1;
      }
    }
  }
 
  gtk_widget_queue_draw(GTK_WIDGET(g->area));
  return TRUE;
}
 
 
static gboolean area_button_release(GtkWidget *widget, GdkEventButton *event, gpointer user_data)
{
  dt_iop_module_t *self = (dt_iop_module_t *)user_data;
  if(darktable.gui->reset) return 1;
  if(!self->enabled) return 0;
 
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
 
  // Give focus to module
  dt_iop_request_focus(self);
 
  if(event->button == 1)
  {
    dt_iop_toneequalizer_params_t *p = (dt_iop_toneequalizer_params_t *)self->params;
 
    if(g->area_dragging)
    {
      // Update GUI with new params
      update_exposure_sliders(g, p);
      dt_dev_add_history_item(darktable.develop, self, FALSE, TRUE);
      g->area_dragging= 0;
      return TRUE;
    }
  }
  return FALSE;
}
 
 
static gboolean notebook_button_press(GtkWidget *widget, GdkEventButton *event, gpointer user_data)
{
  dt_iop_module_t *self = (dt_iop_module_t *)user_data;
  if(darktable.gui->reset) return 1;
 
  // Give focus to module
  dt_iop_request_focus(self);
 
  // Unlock the colour picker so we can display our own custom cursor
  dt_iop_color_picker_reset(self, TRUE);
 
  return 0;
}
 
static void _develop_ui_pipe_started_callback(gpointer instance, gpointer user_data)
{
  dt_iop_module_t *self = (dt_iop_module_t *)user_data;
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
  if(IS_NULL_PTR(g)) return;
  _switch_cursors(self);
 
  // if module is not active, disable mask preview
  if(!self->expanded || !self->enabled)
  {
    g->mask_display = 0;
  }
 
  ++darktable.gui->reset;
  gtk_toggle_button_set_active(GTK_TOGGLE_BUTTON(g->show_luminance_mask), g->mask_display);
  --darktable.gui->reset;
}
 
 
static void _develop_history_resync_callback(gpointer instance, gpointer user_data)
{
  (void)instance;
  dt_iop_module_t *self = (dt_iop_module_t *)user_data;
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
  if(IS_NULL_PTR(g) || IS_NULL_PTR(self->dev) || IS_NULL_PTR(self->dev->preview_pipe)) return;
 
  const uint64_t preview_hash = _current_preview_luminance_hash(self, NULL, NULL);
  if(preview_hash == DT_PIXELPIPE_CACHE_HASH_INVALID)
  {
    dt_iop_gui_enter_critical_section(self);
    g->pending_preview_hash = DT_PIXELPIPE_CACHE_HASH_INVALID;
    dt_iop_gui_leave_critical_section(self);
    _switch_cursors(self);
    gtk_widget_queue_draw(GTK_WIDGET(g->area));
    return;
  }
 
  gboolean already_attached = FALSE;
  dt_iop_gui_enter_critical_section(self);
  if(!IS_NULL_PTR(g->thumb_preview_entry) && g->thumb_preview_hash == preview_hash && g->luminance_valid)
  {
    g->pending_preview_hash = DT_PIXELPIPE_CACHE_HASH_INVALID;
    already_attached = TRUE;
  }
  dt_iop_gui_leave_critical_section(self);
 
  if(!already_attached)
  {
    void *preview_buf = NULL;
    dt_pixel_cache_entry_t *preview_entry = NULL;
    gboolean preview_ready = dt_dev_pixelpipe_cache_ref_entry_by_hash(darktable.pixelpipe_cache, preview_hash,
                                                                      &preview_buf, &preview_entry);
    if(preview_ready && (IS_NULL_PTR(preview_buf) || IS_NULL_PTR(preview_entry)))
    {
      if(!IS_NULL_PTR(preview_entry))
        dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, preview_entry);
      preview_ready = FALSE;
    }
 
    if(preview_ready)
    {
      size_t preview_width = 0;
      size_t preview_height = 0;
      (void)_current_preview_luminance_hash(self, &preview_width, &preview_height);
 
      dt_pixel_cache_entry_t *old_entry = NULL;
      gboolean keep_new_entry = FALSE;
      dt_iop_gui_enter_critical_section(self);
      if(g->thumb_preview_entry != preview_entry || g->thumb_preview_hash != preview_hash
         || g->thumb_preview_buf_width != preview_width || g->thumb_preview_buf_height != preview_height
         || !g->luminance_valid)
      {
        old_entry = g->thumb_preview_entry;
        g->thumb_preview_entry = preview_entry;
        g->thumb_preview_hash = preview_hash;
        g->pending_preview_hash = DT_PIXELPIPE_CACHE_HASH_INVALID;
        g->thumb_preview_buf_width = preview_width;
        g->thumb_preview_buf_height = preview_height;
        g->luminance_valid = TRUE;
        g->histogram_valid = FALSE;
        keep_new_entry = TRUE;
      }
      else
        g->pending_preview_hash = DT_PIXELPIPE_CACHE_HASH_INVALID;
      dt_iop_gui_leave_critical_section(self);
 
      if(old_entry)
        dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, old_entry);
      if(!keep_new_entry)
        dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, preview_entry);
    }
    else
    {
      dt_iop_gui_enter_critical_section(self);
      g->pending_preview_hash = preview_hash;
      dt_iop_gui_leave_critical_section(self);
    }
  }
 
  _switch_cursors(self);
  gtk_widget_queue_draw(GTK_WIDGET(g->area));
}
 
static void _develop_cacheline_ready_callback(gpointer instance, const guint64 hash, gpointer user_data)
{
  (void)instance;
  dt_iop_module_t *self = (dt_iop_module_t *)user_data;
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
  if(IS_NULL_PTR(g) || IS_NULL_PTR(self->dev) || IS_NULL_PTR(self->dev->preview_pipe)) return;
 
  dt_iop_gui_enter_critical_section(self);
  const gboolean matched = (g->pending_preview_hash == hash);
  dt_iop_gui_leave_critical_section(self);
  if(!matched) return;
 
  size_t preview_width = 0;
  size_t preview_height = 0;
  const uint64_t preview_hash = _current_preview_luminance_hash(self, &preview_width, &preview_height);
  if(preview_hash != hash) return;
 
  void *preview_buf = NULL;
  dt_pixel_cache_entry_t *preview_entry = NULL;
  const gboolean preview_ready = dt_dev_pixelpipe_cache_ref_entry_by_hash(darktable.pixelpipe_cache, preview_hash,
                                                                          &preview_buf, &preview_entry);
  if(!preview_ready || IS_NULL_PTR(preview_buf) || IS_NULL_PTR(preview_entry))
  {
    if(!IS_NULL_PTR(preview_entry))
      dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, preview_entry);
    return;
  }
 
  dt_pixel_cache_entry_t *old_entry = NULL;
  gboolean keep_new_entry = FALSE;
  dt_iop_gui_enter_critical_section(self);
  if(g->thumb_preview_entry != preview_entry || g->thumb_preview_hash != preview_hash
     || g->thumb_preview_buf_width != preview_width || g->thumb_preview_buf_height != preview_height
     || !g->luminance_valid)
  {
    old_entry = g->thumb_preview_entry;
    g->thumb_preview_entry = preview_entry;
    g->thumb_preview_hash = preview_hash;
    g->thumb_preview_buf_width = preview_width;
    g->thumb_preview_buf_height = preview_height;
    g->luminance_valid = TRUE;
    g->histogram_valid = FALSE;
    keep_new_entry = TRUE;
  }
  g->pending_preview_hash = DT_PIXELPIPE_CACHE_HASH_INVALID;
  dt_iop_gui_leave_critical_section(self);
 
  if(old_entry)
    dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, old_entry);
  if(!keep_new_entry)
    dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, preview_entry);
 
  _switch_cursors(self);
  gtk_widget_queue_draw(GTK_WIDGET(g->area));
}
 
 
static void _develop_ui_pipe_finished_callback(gpointer instance, gpointer user_data)
{
  dt_iop_module_t *self = (dt_iop_module_t *)user_data;
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
  if(IS_NULL_PTR(g)) return;
  _switch_cursors(self);
}
 
 
void gui_reset(struct dt_iop_module_t *self)
{
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
  if(IS_NULL_PTR(g)) return;
  dt_iop_request_focus(self);
  dt_bauhaus_widget_set_quad_active(g->exposure_boost, FALSE);
  dt_bauhaus_widget_set_quad_active(g->contrast_boost, FALSE);
  dt_dev_add_history_item(darktable.develop, self, TRUE, TRUE);
 
  // Redraw graph
  gtk_widget_queue_draw(self->widget);
}
 
static gboolean _sample_picker_luminance_mask(const float *const buffer, const size_t width, const size_t height,
                                              float *const picked, float *const picked_min, float *const picked_max)
{
  const dt_develop_t *const dev = darktable.develop;
  const dt_colorpicker_sample_t *const sample = dev ? dev->color_picker.primary_sample : NULL;
  if(IS_NULL_PTR(buffer) || IS_NULL_PTR(sample) || width < 1 || height < 1 || IS_NULL_PTR(picked) || IS_NULL_PTR(picked_min) || IS_NULL_PTR(picked_max)) return FALSE;
 
  if(sample->size == DT_LIB_COLORPICKER_SIZE_BOX)
  {
    const size_t box[4] = {
      CLAMP((size_t)roundf(sample->box[0] * width), 0, width),
      CLAMP((size_t)roundf(sample->box[1] * height), 0, height),
      CLAMP((size_t)roundf(sample->box[2] * width), 0, width),
      CLAMP((size_t)roundf(sample->box[3] * height), 0, height)
    };
    const size_t x0 = MIN(box[0], width - 1);
    const size_t y0 = MIN(box[1], height - 1);
    const size_t x1 = CLAMP(MAX(box[2], x0 + 1), 1, width);
    const size_t y1 = CLAMP(MAX(box[3], y0 + 1), 1, height);
 
    float mean = 0.0f;
    float minimum = INFINITY;
    float maximum = -INFINITY;
    size_t count = 0;
 
    // Browse the exact picker box on the preview luminance mask so picker feedback
    // reflects the same scalar field tone equalizer actually edits.
    for(size_t y = y0; y < y1; ++y)
    {
      const size_t row = y * width;
      for(size_t x = x0; x < x1; ++x)
      {
        const float value = buffer[row + x];
        mean += value;
        minimum = fminf(minimum, value);
        maximum = fmaxf(maximum, value);
        ++count;
      }
    }
 
    if(count == 0) return FALSE;
    *picked = mean / (float)count;
    *picked_min = minimum;
    *picked_max = maximum;
    return isfinite(*picked) && isfinite(*picked_min) && isfinite(*picked_max);
  }
 
  const size_t x = CLAMP((size_t)roundf(sample->point[0] * width), 0, width - 1);
  const size_t y = CLAMP((size_t)roundf(sample->point[1] * height), 0, height - 1);
  const float value = get_luminance_from_buffer(buffer, width, height, x, y);
  *picked = value;
  *picked_min = value;
  *picked_max = value;
  return isfinite(value);
}
 
void color_picker_apply(dt_iop_module_t *self, GtkWidget *picker, dt_dev_pixelpipe_t *pipe,
                        dt_dev_pixelpipe_iop_t *piece)
{
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
  dt_iop_toneequalizer_params_t *p = (dt_iop_toneequalizer_params_t *)self->params;
  dt_pixel_cache_entry_t *preview_entry = NULL;
  size_t preview_width = 0;
  size_t preview_height = 0;
 
  if(IS_NULL_PTR(g) || (picker != g->exposure_boost && picker != g->contrast_boost))
  {
    dt_print(DT_DEBUG_DEV, "[picker/toneequal] passthrough picker=%p pipe=%p hash=%" PRIu64 "\n",
             (void *)picker, (void *)pipe, piece ? piece->global_hash : 0);
    _switch_cursors(self);
    return;
  }
 
  g->area_active_node = -1;
 
  // Picker callbacks can run while the preview pipe publishes a newer luminance
  // cacheline, so take the cache ref under the same GUI state lock as other readers.
  dt_iop_gui_enter_critical_section(self);
  preview_entry = g->thumb_preview_entry;
  preview_width = g->thumb_preview_buf_width;
  preview_height = g->thumb_preview_buf_height;
  if(!IS_NULL_PTR(preview_entry))
    dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, TRUE, preview_entry);
  dt_iop_gui_leave_critical_section(self);
 
  if(IS_NULL_PTR(preview_entry) || preview_width < 1 || preview_height < 1)
  {
    if(!IS_NULL_PTR(preview_entry))
      dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, preview_entry);
    dt_print(DT_DEBUG_DEV, "[picker/toneequal] no preview mask picker=%p pipe=%p hash=%" PRIu64 "\n",
             (void *)picker, (void *)pipe, piece ? piece->global_hash : 0);
    _switch_cursors(self);
    return;
  }
 
  dt_dev_pixelpipe_cache_rdlock_entry(darktable.pixelpipe_cache, TRUE, preview_entry);
  const float *const preview_buf = (const float *const)dt_pixel_cache_entry_get_data(preview_entry);
  float picked = NAN;
  float picked_min = NAN;
  float picked_max = NAN;
  const gboolean sampled = _sample_picker_luminance_mask(preview_buf, preview_width, preview_height,
                                                         &picked, &picked_min, &picked_max);
  dt_dev_pixelpipe_cache_rdlock_entry(darktable.pixelpipe_cache, FALSE, preview_entry);
  dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, preview_entry);
 
  if(!sampled)
  {
    dt_print(DT_DEBUG_DEV, "[picker/toneequal] mask sample failed picker=%p pipe=%p hash=%" PRIu64 "\n",
             (void *)picker, (void *)pipe, piece ? piece->global_hash : 0);
    _switch_cursors(self);
    return;
  }
 
  g->cursor_valid = isfinite(picked) && picked > 0.0f;
  g->cursor_exposure = g->cursor_valid ? log2f(picked) : 0.0f;
 
  if(picker == g->exposure_boost)
  {
    if(isfinite(picked) && picked > 0.0f)
    {
      p->exposure_boost = log2f(CONTRAST_FULCRUM / picked);
      ++darktable.gui->reset;
      dt_bauhaus_slider_set(g->exposure_boost, p->exposure_boost);
      --darktable.gui->reset;
      invalidate_luminance_cache(self);
      dt_dev_add_history_item(darktable.develop, self, TRUE, TRUE);
      dt_print(DT_DEBUG_DEV,
               "[picker/toneequal] exposure picker=%p luminance=%g set=%g pipe=%p hash=%" PRIu64 "\n",
               (void *)picker, picked, p->exposure_boost, (void *)pipe, piece ? piece->global_hash : 0);
    }
    else
    {
      dt_print(DT_DEBUG_DEV,
               "[picker/toneequal] exposure picker=%p invalid luminance=%g pipe=%p hash=%" PRIu64 "\n",
               (void *)picker, picked, (void *)pipe, piece ? piece->global_hash : 0);
    }
  }
  else
  {
    const float fd_old = fminf(picked_min, picked_max);
    const float ld_old = fmaxf(picked_min, picked_max);
 
    if(isfinite(fd_old) && isfinite(ld_old) && fd_old > 0.0f && ld_old > fd_old)
    {
      const float s1 = CONTRAST_FULCRUM - exp2f(-7.0f);
      const float s2 = exp2f(-1.0f) - CONTRAST_FULCRUM;
      const float mix = fd_old * s2 + ld_old * s1;
      float contrast = log2f(mix / (CONTRAST_FULCRUM * (ld_old - fd_old)));
 
      // Blur-assisted detail modes need the same positive-contrast correction as
      // the legacy auto button because the sampled spread is measured upstream of
      // the guided filter blur and would otherwise undershoot in the final mask.
      if(p->details == DT_TONEEQ_EIGF && contrast > 0.0f)
      {
        const float correction = -0.0276f + 0.01823f * p->feathering + (0.7566f - 1.0f) * contrast;
        if(p->feathering < 5.0f)
          contrast += correction;
        else if(p->feathering < 10.0f)
          contrast += correction * (2.0f - p->feathering / 5.0f);
      }
      else if(p->details == DT_TONEEQ_GUIDED && contrast > 0.0f)
      {
        contrast = 0.0235f + 1.1225f * contrast;
      }
 
      p->contrast_boost = contrast;
      ++darktable.gui->reset;
      dt_bauhaus_slider_set(g->contrast_boost, p->contrast_boost);
      --darktable.gui->reset;
      invalidate_luminance_cache(self);
      dt_dev_add_history_item(darktable.develop, self, TRUE, TRUE);
      dt_print(DT_DEBUG_DEV,
               "[picker/toneequal] contrast picker=%p min=%g max=%g set=%g pipe=%p hash=%" PRIu64 "\n",
               (void *)picker, fd_old, ld_old, p->contrast_boost, (void *)pipe,
               piece ? piece->global_hash : 0);
    }
    else
    {
      dt_print(DT_DEBUG_DEV,
               "[picker/toneequal] contrast picker=%p invalid min=%g max=%g pipe=%p hash=%" PRIu64 "\n",
               (void *)picker, fd_old, ld_old, (void *)pipe, piece ? piece->global_hash : 0);
    }
  }
 
  dt_control_queue_redraw_center();
  gtk_widget_queue_draw(GTK_WIDGET(g->area));
  _switch_cursors(self);
}
 
 
void autoset(struct dt_iop_module_t *self, const struct dt_dev_pixelpipe_t *pipe,
             const struct dt_dev_pixelpipe_iop_t *piece, const void *i)
{
  if(piece->dsc_in.channels != 4) return;
 
  dt_iop_toneequalizer_params_t *p = (dt_iop_toneequalizer_params_t *)self->params;
  const dt_iop_roi_t *const roi_out = &piece->roi_out;
  const size_t width = roi_out->width;
  const size_t height = roi_out->height;
  const size_t num_elem = width * height;
  float *luminance = dt_pixelpipe_cache_alloc_align_float(num_elem, pipe);
  if(IS_NULL_PTR(luminance)) return;
 
  // Build the same luminance mask scalar field the picker edits, but with neutral
  // boost/contrast because autoset can only solve the exposure translation.
  luminance_mask((const float *const)i, luminance, width, height, piece->dsc_in.channels, p->method, 1.0f, 0.0f, 1.0f);
 
  float mean = 0.0f;
  size_t count = 0;
  __OMP_PARALLEL_FOR__(reduction(+:mean, count))
  for(size_t k = 0; k < num_elem; ++k)
  {
    const float value = luminance[k];
    if(!isfinite(value) || value <= 0.0f) continue;
    mean += value;
    count++;
  }
 
  dt_pixelpipe_cache_free_align(luminance);
  if(count == 0) return;
 
  const float picked = mean / (float)count;
  p->exposure_boost = log2f(CONTRAST_FULCRUM / picked);
}
 
void gui_init(struct dt_iop_module_t *self)
{
  dt_iop_toneequalizer_gui_data_t *g = IOP_GUI_ALLOC(toneequalizer);
 
  gui_cache_init(self);
 
  g->notebook = dt_ui_notebook_new();
 
  // Advanced view
 
  self->widget = dt_ui_notebook_page(g->notebook, N_("graph"), NULL);
 
  g->area = GTK_DRAWING_AREA(gtk_drawing_area_new());
  gtk_widget_set_hexpand(GTK_WIDGET(g->area), TRUE);
  gtk_box_pack_start(GTK_BOX(self->widget),
                     dt_ui_resizable_drawing_area(GTK_WIDGET(g->area),
                                                  "plugins/darkroom/toneequal/graphheight", 280, 120),
                     FALSE, FALSE, 0);
  gtk_widget_add_events(GTK_WIDGET(g->area), GDK_POINTER_MOTION_MASK | darktable.gui->scroll_mask
                                           | GDK_BUTTON_PRESS_MASK | GDK_BUTTON_RELEASE_MASK
                                           | GDK_ENTER_NOTIFY_MASK | GDK_LEAVE_NOTIFY_MASK);
  gtk_widget_set_can_focus(GTK_WIDGET(g->area), TRUE);
  g_signal_connect(G_OBJECT(g->area), "draw", G_CALLBACK(area_draw), self);
  g_signal_connect(G_OBJECT(g->area), "button-press-event", G_CALLBACK(area_button_press), self);
  g_signal_connect(G_OBJECT(g->area), "button-release-event", G_CALLBACK(area_button_release), self);
  g_signal_connect(G_OBJECT(g->area), "leave-notify-event", G_CALLBACK(area_leave_notify), self);
  g_signal_connect(G_OBJECT(g->area), "enter-notify-event", G_CALLBACK(area_enter_notify), self);
  g_signal_connect(G_OBJECT(g->area), "motion-notify-event", G_CALLBACK(area_motion_notify), self);
  gtk_widget_set_tooltip_text(GTK_WIDGET(g->area), _("double-click to reset the curve"));
 
  g->smoothing = dt_bauhaus_slider_new_with_range(darktable.bauhaus, DT_GUI_MODULE(self), -2.33f, +1.67f, 0, 0.0f, 2);
  dt_bauhaus_slider_set_soft_range(g->smoothing, -1.0f, 1.0f);
  dt_bauhaus_widget_set_label(g->smoothing, N_("curve smoothing"));
  gtk_widget_set_tooltip_text(g->smoothing, _("positive values will produce more progressive tone transitions\n"
                                              "but the curve might become oscillatory in some settings.\n"
                                              "negative values will avoid oscillations and behave more robustly\n"
                                              "but may produce brutal tone transitions and damage local contrast."));
  gtk_box_pack_start(GTK_BOX(self->widget), g->smoothing, FALSE, FALSE, 0);
  g_signal_connect(G_OBJECT(g->smoothing), "value-changed", G_CALLBACK(smoothing_callback), self);
 
  g->exposure_boost = dt_color_picker_new(self, DT_COLOR_PICKER_AREA,
                                          dt_bauhaus_slider_from_params(self, "exposure_boost"));
  dt_bauhaus_slider_set_soft_range(g->exposure_boost, -4.0, 4.0);
  dt_bauhaus_slider_set_format(g->exposure_boost, _(" EV"));
  gtk_widget_set_tooltip_text(g->exposure_boost, _("use this to slide the mask average exposure along channels\n"
                                                   "for a better control of the exposure correction with the available nodes.\n"
                                                   "the color picker will map the sampled tone to -4 EV."));
 
  g->contrast_boost = dt_color_picker_new(self, DT_COLOR_PICKER_AREA,
                                          dt_bauhaus_slider_from_params(self, "contrast_boost"));
  dt_bauhaus_slider_set_soft_range(g->contrast_boost, -2.0, 2.0);
  dt_bauhaus_slider_set_format(g->contrast_boost, _(" EV"));
  gtk_widget_set_tooltip_text(g->contrast_boost, _("use this to counter the averaging effect of the guided filter\n"
                                                   "and dilate the mask contrast around -4EV\n"
                                                   "this allows to spread the exposure histogram over more channels\n"
                                                   "for a better control of the exposure correction.\n"
                                                   "the color picker will fit the sampled spread inside the control range."));
 
  // Simple view
 
  self->widget = dt_ui_notebook_page(g->notebook, N_("sliders"), NULL);
 
  g->noise = dt_bauhaus_slider_from_params(self, "noise");
  dt_bauhaus_slider_set_format(g->noise, _(" EV"));
 
  g->ultra_deep_blacks = dt_bauhaus_slider_from_params(self, "ultra_deep_blacks");
  dt_bauhaus_slider_set_format(g->ultra_deep_blacks, _(" EV"));
 
  g->deep_blacks = dt_bauhaus_slider_from_params(self, "deep_blacks");
  dt_bauhaus_slider_set_format(g->deep_blacks, _(" EV"));
 
  g->blacks = dt_bauhaus_slider_from_params(self, "blacks");
  dt_bauhaus_slider_set_format(g->blacks, _(" EV"));
 
  g->shadows = dt_bauhaus_slider_from_params(self, "shadows");
  dt_bauhaus_slider_set_format(g->shadows, _(" EV"));
 
  g->midtones = dt_bauhaus_slider_from_params(self, "midtones");
  dt_bauhaus_slider_set_format(g->midtones, _(" EV"));
 
  g->highlights = dt_bauhaus_slider_from_params(self, "highlights");
  dt_bauhaus_slider_set_format(g->highlights, _(" EV"));
 
  g->whites = dt_bauhaus_slider_from_params(self, "whites");
  dt_bauhaus_slider_set_format(g->whites, _(" EV"));
 
  g->speculars = dt_bauhaus_slider_from_params(self, "speculars");
  dt_bauhaus_slider_set_format(g->speculars, _(" EV"));
 
  dt_bauhaus_widget_set_label(g->noise, N_("-8 EV"));
  dt_bauhaus_widget_set_label(g->ultra_deep_blacks, N_("-7 EV"));
  dt_bauhaus_widget_set_label(g->deep_blacks, N_("-6 EV"));
  dt_bauhaus_widget_set_label(g->blacks, N_("-5 EV"));
  dt_bauhaus_widget_set_label(g->shadows, N_("-4 EV"));
  dt_bauhaus_widget_set_label(g->midtones, N_("-3 EV"));
  dt_bauhaus_widget_set_label(g->highlights, N_("-2 EV"));
  dt_bauhaus_widget_set_label(g->whites, N_("-1 EV"));
  dt_bauhaus_widget_set_label(g->speculars, N_("+0 EV"));
 
  // Masking options
 
  self->widget = dt_ui_notebook_page(g->notebook, N_("masking"), NULL);
 
  g->method = dt_bauhaus_combobox_from_params(self, "method");
  dt_bauhaus_combobox_remove_at(g->method, DT_TONEEQ_LAST);
  gtk_widget_set_tooltip_text(g->method, _("preview the mask and chose the estimator that gives you the\n"
                                           "higher contrast between areas to dodge and areas to burn"));
 
  g->details = dt_bauhaus_combobox_from_params(self, N_("details"));
  dt_bauhaus_widget_set_label(g->details, N_("preserve details"));
  gtk_widget_set_tooltip_text(g->details, _("'no' affects global and local contrast (safe if you only add contrast)\n"
                                            "'guided filter' only affects global contrast and tries to preserve local contrast\n"
                                            "'averaged guided filter' is a geometric mean of 'no' and 'guided filter' methods\n"
                                            "'eigf' (exposure-independent guided filter) is a guided filter that is exposure-independent, it smooths shadows and highlights the same way (contrary to guided filter which smooths less the highlights)\n"
                                            "'averaged eigf' is a geometric mean of 'no' and 'exposure-independent guided filter' methods"));
 
  g->iterations = dt_bauhaus_slider_from_params(self, "iterations");
  dt_bauhaus_slider_set_soft_max(g->iterations, 5);
  gtk_widget_set_tooltip_text(g->iterations, _("number of passes of guided filter to apply\n"
                                               "helps diffusing the edges of the filter at the expense of speed"));
 
  g->blending = dt_bauhaus_slider_from_params(self, "blending");
  dt_bauhaus_slider_set_soft_range(g->blending, 1.0, 45.0);
  dt_bauhaus_slider_set_format(g->blending, "%");
  gtk_widget_set_tooltip_text(g->blending, _("diameter of the blur in percent of the largest image size\n"
                                             "warning: big values of this parameter can make the darkroom\n"
                                             "preview much slower if denoise profiled is used."));
 
  g->feathering = dt_bauhaus_slider_from_params(self, "feathering");
  dt_bauhaus_slider_set_soft_range(g->feathering, 0.1, 50.0);
  gtk_widget_set_tooltip_text(g->feathering, _("precision of the feathering:\n"
                                               "higher values force the mask to follow edges more closely\n"
                                               "but may void the effect of the smoothing\n"
                                               "lower values give smoother gradients and better smoothing\n"
                                               "but may lead to inaccurate edges taping and halos"));
 
  g->quantization = dt_bauhaus_slider_from_params(self, "quantization");
  dt_bauhaus_slider_set_format(g->quantization, _(" EV"));
  gtk_widget_set_tooltip_text(g->quantization, _("0 disables the quantization.\n"
                                                 "higher values posterize the luminance mask to help the guiding\n"
                                                 "produce piece-wise smooth areas when using high feathering values"));
 
  // start building top level widget
  self->widget = gtk_box_new(GTK_ORIENTATION_VERTICAL, DT_GUI_BOX_SPACING);
 
  const int active_page = dt_conf_get_int("plugins/darkroom/toneequal/gui_page");
  gtk_widget_show(gtk_notebook_get_nth_page(g->notebook, active_page));
  gtk_notebook_set_current_page(g->notebook, active_page);
 
  g_signal_connect(G_OBJECT(g->notebook), "button-press-event", G_CALLBACK(notebook_button_press), self);
  gtk_box_pack_start(GTK_BOX(self->widget), GTK_WIDGET(g->notebook), FALSE, FALSE, 0);
 
  GtkWidget *hbox = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, DT_GUI_BOX_SPACING);
  gtk_box_pack_start(GTK_BOX(hbox), dt_ui_label_new(_("display exposure mask")), TRUE, TRUE, 0);
  g->show_luminance_mask = dt_iop_togglebutton_new(self, NULL, N_("display exposure mask"), NULL, G_CALLBACK(show_luminance_mask_callback),
                                           FALSE, 0, 0, dtgtk_cairo_paint_showmask, hbox);
 
  dtgtk_togglebutton_set_paint(DTGTK_TOGGLEBUTTON(g->show_luminance_mask), dtgtk_cairo_paint_showmask, 0, NULL);
  dt_gui_add_class(g->show_luminance_mask, "dt_bauhaus_alignment");
  gtk_box_pack_start(GTK_BOX(self->widget), hbox, FALSE, FALSE, 0);
 
  // Force UI redraws when pipe starts/finishes computing and switch cursors
  DT_DEBUG_CONTROL_SIGNAL_CONNECT(darktable.signals, DT_SIGNAL_HISTORY_RESYNC,
                            G_CALLBACK(_develop_history_resync_callback), self);
  DT_DEBUG_CONTROL_SIGNAL_CONNECT(darktable.signals, DT_SIGNAL_CACHELINE_READY,
                            G_CALLBACK(_develop_cacheline_ready_callback), self);
  DT_DEBUG_CONTROL_SIGNAL_CONNECT(darktable.signals, DT_SIGNAL_DEVELOP_UI_PIPE_FINISHED,
                            G_CALLBACK(_develop_ui_pipe_finished_callback), self);
 
  DT_DEBUG_CONTROL_SIGNAL_CONNECT(darktable.signals, DT_SIGNAL_DEVELOP_HISTORY_CHANGE,
                            G_CALLBACK(_develop_ui_pipe_started_callback), self);
}
 
 
void gui_cleanup(struct dt_iop_module_t *self)
{
  dt_iop_toneequalizer_gui_data_t *g = (dt_iop_toneequalizer_gui_data_t *)self->gui_data;
  self->request_color_pick = DT_REQUEST_COLORPICK_OFF;
 
  dt_conf_set_int("plugins/darkroom/toneequal/gui_page", gtk_notebook_get_current_page (g->notebook));
 
  DT_DEBUG_CONTROL_SIGNAL_DISCONNECT(darktable.signals, G_CALLBACK(_develop_ui_pipe_finished_callback), self);
  DT_DEBUG_CONTROL_SIGNAL_DISCONNECT(darktable.signals, G_CALLBACK(_develop_ui_pipe_started_callback), self);
  DT_DEBUG_CONTROL_SIGNAL_DISCONNECT(darktable.signals, G_CALLBACK(_develop_history_resync_callback), self);
  DT_DEBUG_CONTROL_SIGNAL_DISCONNECT(darktable.signals, G_CALLBACK(_develop_cacheline_ready_callback), self);
 
  dt_pixel_cache_entry_t *preview_entry = NULL;
  dt_iop_gui_enter_critical_section(self);
  preview_entry = g->thumb_preview_entry;
  g->thumb_preview_entry = NULL;
  g->thumb_preview_hash = DT_PIXELPIPE_CACHE_HASH_INVALID;
  g->pending_preview_hash = DT_PIXELPIPE_CACHE_HASH_INVALID;
  g->thumb_preview_buf_width = 0;
  g->thumb_preview_buf_height = 0;
  g->luminance_valid = FALSE;
  dt_iop_gui_leave_critical_section(self);
  if(!IS_NULL_PTR(preview_entry))
    dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, preview_entry);
  if(g->desc) pango_font_description_free(g->desc);
  if(g->layout) g_object_unref(g->layout);
  if(g->cr) cairo_destroy(g->cr);
  if(g->cst) cairo_surface_destroy(g->cst);
 
  IOP_GUI_FREE;
}
 
// clang-format off
// modelines: These editor modelines have been set for all relevant files by tools/update_modelines.py
// vim: shiftwidth=2 expandtab tabstop=2 cindent
// kate: tab-indents: off; indent-width 2; replace-tabs on; indent-mode cstyle; remove-trailing-spaces modified;
// clang-format on