libs/histogram.c

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/*
    This file is part of darktable,
    Copyright (C) 2011 Henrik Andersson.
    Copyright (C) 2011-2012, 2016 johannes hanika.
    Copyright (C) 2012 Richard Wonka.
    Copyright (C) 2012-2014, 2016-2018 Tobias Ellinghaus.
    Copyright (C) 2013 José Carlos García Sogo.
    Copyright (C) 2013-2016 Roman Lebedev.
    Copyright (C) 2014 parafin.
    Copyright (C) 2016 Alexander V. Smal.
    Copyright (C) 2016 Asma.
    Copyright (C) 2017-2018, 2020-2021 Dan Torop.
    Copyright (C) 2018 Maurizio Paglia.
    Copyright (C) 2018 rawfiner.
    Copyright (C) 2019-2020 Aldric Renaudin.
    Copyright (C) 2019, 2021-2026 Aurélien PIERRE.
    Copyright (C) 2019 Edgardo Hoszowski.
    Copyright (C) 2019-2021 Pascal Obry.
    Copyright (C) 2019 Ulrich Pegelow.
    Copyright (C) 2020 Bill Ferguson.
    Copyright (C) 2020-2021 Chris Elston.
    Copyright (C) 2020 GrahamByrnes.
    Copyright (C) 2020 Hubert Kowalski.
    Copyright (C) 2020 Martin Straeten.
    Copyright (C) 2020-2021 Philippe Weyland.
    Copyright (C) 2020-2021 Ralf Brown.
    Copyright (C) 2021-2022 Diederik Ter Rahe.
    Copyright (C) 2021 luzpaz.
    Copyright (C) 2021 Marco Carrarini.
    Copyright (C) 2021 Mark-64.
    Copyright (C) 2021 Paolo DePetrillo.
    Copyright (C) 2021 paolodepetrillo.
    Copyright (C) 2021 Sakari Kapanen.
    Copyright (C) 2022 Martin Bařinka.
    Copyright (C) 2022 Philipp Lutz.
    Copyright (C) 2022 Victor Forsiuk.
    Copyright (C) 2024 Alynx Zhou.
    Copyright (C) 2024 Marrony Neris.
    
    darktable 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.
    
    darktable 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 darktable.  If not, see <http://www.gnu.org/licenses/>.
*/
 
#include <stdint.h>
 
#include "bauhaus/bauhaus.h"
#include "common/atomic.h"
#include "common/color_picker.h"
#include "common/color_vocabulary.h"
#include "common/darktable.h"
#include "common/debug.h"
#include "common/histogram.h"
#include "common/iop_profile.h"
#include "common/imagebuf.h"
#include "common/image_cache.h"
#include "common/math.h"
#include "control/conf.h"
#include "control/control.h"
#include "control/signal.h"
#include "develop/dev_pixelpipe.h"
#include "develop/develop.h"
#include "develop/pixelpipe_cache.h"
#include "dtgtk/drawingarea.h"
#include "dtgtk/button.h"
#include "gui/color_picker_proxy.h"
#include "gui/draw.h"
#include "gui/gtk.h"
#include "libs/lib.h"
#include "libs/lib_api.h"
#include "libs/colorpicker.h"
 
#ifdef GDK_WINDOWING_QUARTZ
#include "osx/osx.h"
#endif
 
#define HISTOGRAM_BINS 256
#define GAMMA 1.f / 2.f
#define DT_LIB_HISTOGRAM_SCOPE_MIN_VALUE (1.f / 256.f)
#define DT_LIB_HISTOGRAM_SCOPE_ENABLE_SMOOTHING 1
#define DT_LIB_HISTOGRAM_SCOPE_SMOOTH_SPATIAL_PASSES 1
#define DT_LIB_HISTOGRAM_SCOPE_SMOOTH_TONE_PASSES 4
#define DT_LIB_HISTOGRAM_SCOPE_SMOOTH_FORCE (256 * 0.33)
#define DT_LIB_HISTOGRAM_SCOPE_RESTRICTED_LABEL_OPERATOR CAIRO_OPERATOR_ADD
#define DT_LIB_HISTOGRAM_SCOPE_DEFAULT_HEIGHT 250
#define DT_LIB_HISTOGRAM_SCOPE_MIN_HEIGHT 120
#define DT_LIB_HISTOGRAM_SCOPE_MAX_HEIGHT 500
#define DT_LIB_HISTOGRAM_SCOPE_HANDLE_HEIGHT 8
#define DT_LIB_HISTOGRAM_SCOPE_HEIGHT_CONF "plugin/darkroom/histogram/scope_height"
 
DT_MODULE(1)
 
typedef enum dt_lib_histogram_scope_type_t
{
  DT_LIB_HISTOGRAM_SCOPE_HISTOGRAM = 0,
  DT_LIB_HISTOGRAM_SCOPE_WAVEFORM_HORIZONTAL,
  DT_LIB_HISTOGRAM_SCOPE_WAVEFORM_VERTICAL,
  DT_LIB_HISTOGRAM_SCOPE_PARADE_HORIZONTAL,
  DT_LIB_HISTOGRAM_SCOPE_PARADE_VERTICAL,
  DT_LIB_HISTOGRAM_SCOPE_VECTORSCOPE,
  DT_LIB_HISTOGRAM_SCOPE_N // needs to be the last one
} dt_lib_histogram_scope_type_t;
 
 
typedef struct dt_lib_histogram_cache_t
{
  // If any of those params changes, we need to recompute the Cairo buffer.
  float zoom;
  int width;
  int height;
  uint64_t hash;
  dt_lib_histogram_scope_type_t view;
} dt_lib_histogram_cache_t;
 
typedef enum dt_lib_colorpicker_model_t
{
  DT_LIB_COLORPICKER_MODEL_RGB = 0,
  DT_LIB_COLORPICKER_MODEL_LAB,
  DT_LIB_COLORPICKER_MODEL_LCH,
  DT_LIB_COLORPICKER_MODEL_HSL,
  DT_LIB_COLORPICKER_MODEL_HSV,
  DT_LIB_COLORPICKER_MODEL_NONE,
} dt_lib_colorpicker_model_t;
 
const gchar *dt_lib_colorpicker_model_names[]
  = { N_("RGB"), N_("Lab"), N_("LCh"), N_("HSL"), N_("HSV"), N_("none"), NULL };
const gchar *dt_lib_colorpicker_statistic_names[]
  = { N_("mean"), N_("min"), N_("max"), NULL };
 
 
typedef struct dt_lib_histogram_t
{
  struct dt_lib_module_t *module;
  GtkWidget *scope_draw;               // GtkDrawingArea -- scope, scale, and draggable overlays
  GtkWidget *scope_resize_handle;      // GtkDrawingArea -- vertical resize grip kept outside the rendered scope
  dt_backbuf_t *backbuf;               // reference to the dev backbuf currently in use
  const char *op;                      // pipeline stage ("initialscale" | "colorout" | "gamma")
  dt_lib_histogram_scope_type_t scope; // which scope/display type is active
  float zoom; // zoom level for the vectorscope
  int scope_height;
 
  dt_lib_histogram_cache_t cache;
  cairo_surface_t *cst;
 
  dt_lib_colorpicker_model_t model;
  dt_lib_colorpicker_statistic_t statistic;
  GtkWidget *color_mode_selector;
  GtkWidget *statistic_selector;
  GtkWidget *picker_button;
  GtkWidget *samples_container;
  GtkWidget *add_sample_button;
  GtkWidget *display_samples_check_box;
  GtkWidget *restrict_button;
  GArray *pending_hashes;
  guint refresh_idle_source;
  dt_dev_pixelpipe_cache_wait_t scope_wait;
  dt_dev_pixelpipe_cache_wait_t picker_wait;
  dt_dev_pixelpipe_cache_wait_t module_wait;
 
  dt_gui_collapsible_section_t cs;
 
} dt_lib_histogram_t;
 
typedef struct dt_histogram_pending_module_refresh_t
{
  dt_iop_module_t *module;
  uint64_t hash;
} dt_histogram_pending_module_refresh_t;
 
typedef struct dt_histogram_preview_refresh_state_t
{
  uint64_t initialscale_hash;
  uint64_t colorout_hash;
  uint64_t gamma_hash;
  GList *module_histograms;
} dt_histogram_preview_refresh_state_t;
 
static dt_histogram_preview_refresh_state_t _preview_refresh_state
    = { DT_PIXELPIPE_CACHE_HASH_INVALID, DT_PIXELPIPE_CACHE_HASH_INVALID,
        DT_PIXELPIPE_CACHE_HASH_INVALID, NULL };
static void _schedule_histogram_refresh(dt_lib_module_t *self);
static void _reset_cache(dt_lib_histogram_t *d);
 
static void _histogram_restart_cache_wait(gpointer user_data)
{
  dt_lib_module_t *self = (dt_lib_module_t *)user_data;
  if(IS_NULL_PTR(self)) return;
  _schedule_histogram_refresh(self);
}
 
static void _histogram_restart_scope_cache_wait(gpointer user_data)
{
  dt_lib_module_t *self = (dt_lib_module_t *)user_data;
  dt_lib_histogram_t *d = !IS_NULL_PTR(self) ? self->data : NULL;
  if(IS_NULL_PTR(d)) return;
 
  _reset_cache(d);
  _schedule_histogram_refresh(self);
}
 
static void _clear_pending_preview_histograms(void)
{
  g_list_free_full(_preview_refresh_state.module_histograms, g_free);
  _preview_refresh_state.module_histograms = NULL;
  _preview_refresh_state.initialscale_hash = DT_PIXELPIPE_CACHE_HASH_INVALID;
  _preview_refresh_state.colorout_hash = DT_PIXELPIPE_CACHE_HASH_INVALID;
  _preview_refresh_state.gamma_hash = DT_PIXELPIPE_CACHE_HASH_INVALID;
}
 
static void _refresh_module_histogram(const dt_dev_pixelpipe_t *pipe, const dt_dev_pixelpipe_iop_t *piece,
                                      const float *pixel, dt_iop_module_t *module)
{
  dt_dev_histogram_collection_params_t histogram_params = piece->histogram_params;
  dt_histogram_roi_t histogram_roi;
 
  if(IS_NULL_PTR(histogram_params.roi))
  {
    histogram_roi = (dt_histogram_roi_t){
      .width = piece->roi_in.width, .height = piece->roi_in.height,
      .crop_x = 0, .crop_y = 0, .crop_width = 0, .crop_height = 0
    };
    histogram_params.roi = &histogram_roi;
  }
 
  dt_iop_gui_enter_critical_section(module);
  dt_histogram_helper(&histogram_params, &module->histogram_stats, piece->dsc_in.cst, module->histogram_cst,
                      pixel, &module->histogram, module->histogram_middle_grey,
                      dt_ioppr_get_pipe_work_profile_info(pipe));
  dt_histogram_max_helper(&module->histogram_stats, piece->dsc_in.cst, module->histogram_cst,
                          &module->histogram, module->histogram_max);
  dt_iop_gui_leave_critical_section(module);
 
  if(module->widget) dt_control_queue_redraw_widget(module->widget);
}
 
static dt_backbuf_t *_get_histogram_backbuf(dt_develop_t *dev, const char *op)
{
  if(IS_NULL_PTR(dev) || IS_NULL_PTR(op)) return NULL;
 
  if(!strcmp(op, "initialscale"))
    return &dev->raw_histogram;
  else if(!strcmp(op, "colorout"))
    return &dev->output_histogram;
  else if(!strcmp(op, "gamma"))
    return &dev->display_histogram;
  else
    return NULL;
}
 
static void _clear_histogram_backbuf(dt_backbuf_t *backbuf)
{
  if(IS_NULL_PTR(backbuf)) return;
 
  /* Global histogram backbuffers keep one structural ref on top of the module-output lifetime.
   * Clearing that published view therefore means releasing the extra GUI-side keepalive ref here. */
  dt_dev_pixelpipe_cache_unref_hash(darktable.pixelpipe_cache, dt_dev_backbuf_get_hash(backbuf));
  dt_dev_set_backbuf(backbuf, 0, 0, 0, DT_PIXELPIPE_CACHE_HASH_INVALID, DT_PIXELPIPE_CACHE_HASH_INVALID);
}
 
static gboolean _refresh_global_histogram_backbuf_for_hash(dt_develop_t *dev, const char *op,
                                                           const uint64_t expected_hash)
{
  dt_backbuf_t *const backbuf = _get_histogram_backbuf(dev, op);
  if(IS_NULL_PTR(backbuf) || IS_NULL_PTR(dev) || IS_NULL_PTR(dev->preview_pipe)) return FALSE;
 
  const dt_dev_pixelpipe_iop_t *const piece = dt_dev_pixelpipe_get_module_piece(
      dev->preview_pipe, dt_iop_get_module_by_op_priority(dev->iop, op, 0));
  if(IS_NULL_PTR(piece))
  {
    _clear_histogram_backbuf(backbuf);
    return FALSE;
  }
 
  const dt_dev_pixelpipe_iop_t *const previous_piece
      = dt_dev_pixelpipe_get_prev_enabled_piece(dev->preview_pipe, piece);
 
  const dt_iop_roi_t *roi = &piece->roi_out;
  const dt_iop_buffer_dsc_t *dsc = &piece->dsc_out;
  uint64_t hash = piece->global_hash;
 
  if(!strcmp(op, "gamma"))
  {
    if(IS_NULL_PTR(previous_piece))
    {
      _clear_histogram_backbuf(backbuf);
      return FALSE;
    }
 
    roi = &previous_piece->roi_out;
    dsc = &previous_piece->dsc_out;
    hash = previous_piece->global_hash;
  }
 
  if(expected_hash != DT_PIXELPIPE_CACHE_HASH_INVALID && hash != expected_hash) return FALSE;
 
  dt_pixel_cache_entry_t *entry = NULL;
  if(hash == DT_PIXELPIPE_CACHE_HASH_INVALID
     || !dt_dev_pixelpipe_cache_peek_gui(dev->preview_pipe, !strcmp(op, "gamma") ? previous_piece : piece,
                                         NULL, &entry, NULL, NULL, NULL))
  {
    _clear_histogram_backbuf(backbuf);
    return FALSE;
  }
 
  const uint64_t previous_hash = dt_dev_backbuf_get_hash(backbuf);
  if(previous_hash != hash)
  {
    /* The module output already owns its producer ref. Tagging it as a global histogram backbuffer
     * reserves one additional consumer ref so GUI readers only need `peek()` and read locks later. */
    dt_dev_pixelpipe_cache_unref_hash(darktable.pixelpipe_cache, previous_hash);
    dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, TRUE, entry);
  }
 
  dt_dev_set_backbuf(backbuf, roi->width, roi->height, dsc->bpp, hash, DT_PIXELPIPE_CACHE_HASH_INVALID);
  return TRUE;
}
 
static gboolean _refresh_preview_module_histogram_for_hash(dt_develop_t *dev, dt_iop_module_t *module,
                                                           const uint64_t expected_hash)
{
  if(IS_NULL_PTR(dev) || IS_NULL_PTR(dev->preview_pipe) || IS_NULL_PTR(module)) return FALSE;
 
  const dt_dev_pixelpipe_iop_t *const piece = dt_dev_pixelpipe_get_module_piece(dev->preview_pipe, module);
  if(IS_NULL_PTR(piece) || !(piece->request_histogram & DT_REQUEST_ON)) return FALSE;
  if((piece->request_histogram & DT_REQUEST_ONLY_IN_GUI) && !dev->gui_attached) return FALSE;
 
  const dt_dev_pixelpipe_iop_t *const previous_piece
      = dt_dev_pixelpipe_get_prev_enabled_piece(dev->preview_pipe, piece);
  if(IS_NULL_PTR(previous_piece) || previous_piece->global_hash == DT_PIXELPIPE_CACHE_HASH_INVALID) return FALSE;
  if(expected_hash != DT_PIXELPIPE_CACHE_HASH_INVALID && previous_piece->global_hash != expected_hash) return FALSE;
  if(previous_piece->dsc_out.datatype != TYPE_FLOAT) return FALSE;
 
  void *input = NULL;
  dt_pixel_cache_entry_t *input_entry = NULL;
  dt_lib_module_t *const histogram_module = darktable.develop->color_picker.histogram_module;
  dt_lib_histogram_t *const d = !IS_NULL_PTR(histogram_module) ? histogram_module->data : NULL;
  if(!IS_NULL_PTR(d))
    dt_dev_pixelpipe_cache_wait_set_owner(&d->module_wait, "histogram-module-refresh", module);
  if(!dt_dev_pixelpipe_cache_peek_gui(dev->preview_pipe, previous_piece, &input, &input_entry,
                                      !IS_NULL_PTR(d) ? &d->module_wait : NULL,
                                      _histogram_restart_cache_wait, histogram_module))
    return FALSE;
 
  dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, TRUE, input_entry);
  dt_dev_pixelpipe_cache_rdlock_entry(darktable.pixelpipe_cache, TRUE, input_entry);
 
  const float *histogram_input = input;
  float *transformed_input = NULL;
  dt_iop_buffer_dsc_t input_dsc = previous_piece->dsc_out;
 
  if(input_dsc.cst != piece->dsc_in.cst
     && !(dt_iop_colorspace_is_rgb(input_dsc.cst) && dt_iop_colorspace_is_rgb(piece->dsc_in.cst)))
  {
    const size_t pixels = (size_t)piece->roi_in.width * (size_t)piece->roi_in.height;
    const size_t bytes = pixels * (size_t)piece->dsc_in.channels * sizeof(float);
    transformed_input = dt_alloc_align(bytes);
 
    if(IS_NULL_PTR(transformed_input))
    {
      dt_dev_pixelpipe_cache_rdlock_entry(darktable.pixelpipe_cache, FALSE, input_entry);
      dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, input_entry);
      return FALSE;
    }
 
    memcpy(transformed_input, input, bytes);
    dt_ioppr_transform_image_colorspace(module, transformed_input, transformed_input,
                                        piece->roi_in.width, piece->roi_in.height,
                                        input_dsc.cst, piece->dsc_in.cst, &input_dsc.cst,
                                        dt_ioppr_get_pipe_work_profile_info(dev->preview_pipe));
    histogram_input = transformed_input;
  }
  else if(input_dsc.cst != piece->dsc_in.cst)
  {
    input_dsc.cst = piece->dsc_in.cst;
  }
 
  _refresh_module_histogram(dev->preview_pipe, piece, histogram_input, module);
 
  dt_dev_pixelpipe_cache_rdlock_entry(darktable.pixelpipe_cache, FALSE, input_entry);
  dt_dev_pixelpipe_cache_ref_count_entry(darktable.pixelpipe_cache, FALSE, input_entry);
  dt_free_align(transformed_input);
 
  return TRUE;
}
 
static void _refresh_preview_histograms(dt_develop_t *dev)
{
  if(IS_NULL_PTR(dev) || !dev->gui_attached || IS_NULL_PTR(dev->preview_pipe)) return;
  if(!dev->preview_pipe->gui_observable_source) return;
  /* Do not grab preview_pipe->busy_mutex from GUI thread: it may be held by
   * the pipeline worker for long recomputations and would freeze the UI.
   * We rely on non-blocking cache probes and the cache-wait manager instead. */
 
  const char *ops[] = { "initialscale", "colorout", "gamma" };
  uint64_t *pending_hashes[] = {
    &_preview_refresh_state.initialscale_hash,
    &_preview_refresh_state.colorout_hash,
    &_preview_refresh_state.gamma_hash
  };
 
  for(size_t i = 0; i < G_N_ELEMENTS(ops); i++)
  {
    const dt_dev_pixelpipe_iop_t *piece = dt_dev_pixelpipe_get_module_piece(
        dev->preview_pipe, dt_iop_get_module_by_op_priority(dev->iop, ops[i], 0));
    if(IS_NULL_PTR(piece))
    {
      _clear_histogram_backbuf(_get_histogram_backbuf(dev, ops[i]));
      continue;
    }
 
    uint64_t hash = piece->global_hash;
    if(!strcmp(ops[i], "gamma"))
    {
      const dt_dev_pixelpipe_iop_t *const previous_piece
          = dt_dev_pixelpipe_get_prev_enabled_piece(dev->preview_pipe, piece);
      hash = previous_piece ? previous_piece->global_hash : DT_PIXELPIPE_CACHE_HASH_INVALID;
    }
 
    if(hash == DT_PIXELPIPE_CACHE_HASH_INVALID)
    {
      _clear_histogram_backbuf(_get_histogram_backbuf(dev, ops[i]));
      *pending_hashes[i] = DT_PIXELPIPE_CACHE_HASH_INVALID;
      continue;
    }
 
    // Avoid re-requesting the same cacheline on every history resync.
    // While the same hash is pending, we wait for DT_SIGNAL_CACHELINE_READY
    // to complete the refresh instead of feeding CACHE_REQUEST in a loop.
    if(*pending_hashes[i] == hash) continue;
 
    if(_refresh_global_histogram_backbuf_for_hash(dev, ops[i], hash))
      *pending_hashes[i] = DT_PIXELPIPE_CACHE_HASH_INVALID;
    else
      *pending_hashes[i] = hash;
  }
 
  GHashTable *seen_modules = g_hash_table_new(g_direct_hash, g_direct_equal);
  for(GList *node = g_list_first(dev->preview_pipe->nodes); node; node = g_list_next(node))
  {
    dt_dev_pixelpipe_iop_t *piece = node->data;
    if(IS_NULL_PTR(piece) || !piece->enabled) continue;
    if(!(piece->request_histogram & DT_REQUEST_ON)) continue;
    if((piece->request_histogram & DT_REQUEST_ONLY_IN_GUI) && !dev->gui_attached) continue;
 
    g_hash_table_insert(seen_modules, piece->module, piece->module);
 
    const dt_dev_pixelpipe_iop_t *const previous_piece
        = dt_dev_pixelpipe_get_prev_enabled_piece(dev->preview_pipe, piece);
    if(!IS_NULL_PTR(previous_piece)
       && !_refresh_preview_module_histogram_for_hash(dev, piece->module, previous_piece->global_hash))
    {
      gboolean found = FALSE;
      for(GList *l = _preview_refresh_state.module_histograms; l; l = g_list_next(l))
      {
        dt_histogram_pending_module_refresh_t *pending = l->data;
        if(IS_NULL_PTR(pending) || pending->module != piece->module) continue;
        pending->hash = previous_piece->global_hash;
        found = TRUE;
        break;
      }
 
      if(!found)
      {
        dt_histogram_pending_module_refresh_t *pending = g_malloc0(sizeof(*pending));
        pending->module = piece->module;
        pending->hash = previous_piece->global_hash;
        _preview_refresh_state.module_histograms
            = g_list_prepend(_preview_refresh_state.module_histograms, pending);
      }
    }
    else
    {
      for(GList *l = _preview_refresh_state.module_histograms; l;)
      {
        GList *next = g_list_next(l);
        dt_histogram_pending_module_refresh_t *pending = l->data;
        if(pending && pending->module == piece->module)
        {
          _preview_refresh_state.module_histograms
              = g_list_delete_link(_preview_refresh_state.module_histograms, l);
          g_free(pending);
        }
        l = next;
      }
    }
  }
 
  // Remove stale pending module refreshes.
  for(GList *l = _preview_refresh_state.module_histograms; l;)
  {
    GList *next = g_list_next(l);
    dt_histogram_pending_module_refresh_t *pending = l->data;
    if(IS_NULL_PTR(pending) || !g_hash_table_contains(seen_modules, pending->module))
    {
      _preview_refresh_state.module_histograms
          = g_list_delete_link(_preview_refresh_state.module_histograms, l);
      g_free(pending);
    }
    l = next;
  }
  g_hash_table_destroy(seen_modules);
}
 
static void _preview_history_resync_callback(gpointer instance, gpointer user_data)
{
  (void)instance;
  (void)user_data;
  _refresh_preview_histograms(darktable.develop);
}
 
static void _preview_cacheline_ready_callback(gpointer instance, const guint64 hash,
                                              const guint64 producer_node_key, gpointer user_data)
{
  (void)instance;
  (void)producer_node_key; // scope/module/picker buffer fetches match by producer node through
                           // the cache-wait manager; this backbuf-hash refresh trigger is exact-hash.
  (void)user_data;
 
  dt_develop_t *const dev = darktable.develop;
  if(IS_NULL_PTR(dev) || !dev->gui_attached || IS_NULL_PTR(dev->preview_pipe)) return;
  if(_preview_refresh_state.initialscale_hash == hash)
  {
    _refresh_global_histogram_backbuf_for_hash(dev, "initialscale", hash);
    _preview_refresh_state.initialscale_hash = DT_PIXELPIPE_CACHE_HASH_INVALID;
  }
 
  if(_preview_refresh_state.colorout_hash == hash)
  {
    _refresh_global_histogram_backbuf_for_hash(dev, "colorout", hash);
    _preview_refresh_state.colorout_hash = DT_PIXELPIPE_CACHE_HASH_INVALID;
  }
 
  if(_preview_refresh_state.gamma_hash == hash)
  {
    _refresh_global_histogram_backbuf_for_hash(dev, "gamma", hash);
    _preview_refresh_state.gamma_hash = DT_PIXELPIPE_CACHE_HASH_INVALID;
  }
 
  for(GList *l = _preview_refresh_state.module_histograms; l;)
  {
    GList *next = g_list_next(l);
    dt_histogram_pending_module_refresh_t *pending = l->data;
    if(pending->hash == hash)
    {
      _refresh_preview_module_histogram_for_hash(dev, pending->module, pending->hash);
      _preview_refresh_state.module_histograms = g_list_delete_link(_preview_refresh_state.module_histograms, l);
      g_free(pending);
    }
    l = next;
  }
}
 
const char *name(struct dt_lib_module_t *self)
{
  return _("scopes");
}
 
const char **views(dt_lib_module_t *self)
{
  static const char *v[] = {"darkroom", "studio_capture", NULL};
  return v;
}
 
uint32_t container(dt_lib_module_t *self)
{
  return DT_UI_CONTAINER_PANEL_LEFT_CENTER;
}
 
int expandable(dt_lib_module_t *self)
{
  return 1;
}
 
int position()
{
  return 1000;
}
 
static void _update_picker_output(dt_lib_module_t *self);
static void _update_sample_label(dt_lib_module_t *self, dt_colorpicker_sample_t *sample);
static void _update_everything(dt_lib_module_t *self);
 
 
void _backbuf_int_to_op(const int value, dt_lib_histogram_t *d)
{
  switch(value)
  {
    case 0:
    {
      d->op = "initialscale";
      break;
    }
    case 1:
    {
      d->op = "colorout";
      break;
    }
    case 2:
    {
      d->op = "gamma";
    }
  }
}
 
 
int _backbuf_op_to_int(dt_lib_histogram_t *d)
{
  if(!strcmp(d->op, "initialscale") || !strcmp(d->op, "demosaic")) return 0;
  if(!strcmp(d->op, "colorout")) return 1;
  if(!strcmp(d->op, "gamma")) return 2;
  return 2;
}
 
 
#ifdef _OPENMP
#pragma omp declare simd \
  aligned(rgb_in, xyz_out:64) \
  uniform(rgb_in, xyz_out)
#endif
void _scope_pixel_to_xyz(const dt_aligned_pixel_t rgb_in, dt_aligned_pixel_t xyz_out, dt_lib_histogram_t *d)
{
  if(_backbuf_op_to_int(d) > 0)
  {
    // We are in display RGB
    const dt_iop_order_iccprofile_info_t *const profile = darktable.develop->preview_pipe->output_profile_info;
    dt_ioppr_rgb_matrix_to_xyz(rgb_in, xyz_out, profile->matrix_in_transposed, profile->lut_in, profile->unbounded_coeffs_in,
                               profile->lutsize, profile->nonlinearlut);
  }
  else
  {
    // We are in sensor RGB
    const dt_iop_order_iccprofile_info_t *const profile = darktable.develop->preview_pipe->input_profile_info;
    dt_ioppr_rgb_matrix_to_xyz(rgb_in, xyz_out, profile->matrix_in_transposed, profile->lut_in, profile->unbounded_coeffs_in,
                               profile->lutsize, profile->nonlinearlut);
  }
}
 
 
#ifdef _OPENMP
#pragma omp declare simd \
  aligned(rgb_in, rgb_out:64) \
  uniform(rgb_in, rgb_out)
#endif
void _scope_pixel_to_display_rgb(const dt_aligned_pixel_t rgb_in, dt_aligned_pixel_t rgb_out, dt_lib_histogram_t *d)
{
  if(_backbuf_op_to_int(d) > 0)
  {
    // We are in display RGB
    for_each_channel(c)
      rgb_out[c] = rgb_in[c];
  }
  else
  {
    // We are in the sensor/input RGB profile. Convert directly between the
    // cached stage profile and the display profile so the swatch patch uses
    // the same authoritative ICC path as the rest of the GUI.
    const dt_iop_order_iccprofile_info_t *const profile_in = darktable.develop->preview_pipe->input_profile_info;
    const dt_iop_order_iccprofile_info_t *const profile_out = darktable.develop->preview_pipe->output_profile_info;
    dt_ioppr_transform_image_colorspace_rgb(rgb_in, rgb_out, 1, 1, profile_in, profile_out,
                                            "[histogram] sample swatch");
  }
}
 
static void _reset_cache(dt_lib_histogram_t *d)
{
  d->cache.view = DT_LIB_HISTOGRAM_SCOPE_N;
  d->cache.width = -1;
  d->cache.height = -1;
  d->cache.hash = (uint64_t)-1;
  d->cache.zoom = -1.;
}
 
static void _clear_pending_hashes(dt_lib_histogram_t *d)
{
  if(IS_NULL_PTR(d) || !d->pending_hashes) return;
  g_array_set_size(d->pending_hashes, 0);
}
 
static gboolean _has_pending_hash(const dt_lib_histogram_t *d, const uint64_t hash)
{
  if(IS_NULL_PTR(d) || !d->pending_hashes || hash == DT_PIXELPIPE_CACHE_HASH_INVALID) return FALSE;
 
  for(guint i = 0; i < d->pending_hashes->len; i++)
    if(g_array_index(d->pending_hashes, uint64_t, i) == hash) return TRUE;
 
  return FALSE;
}
 
static void _add_pending_hash(dt_lib_histogram_t *d, const uint64_t hash)
{
  if(IS_NULL_PTR(d) || !d->pending_hashes || hash == DT_PIXELPIPE_CACHE_HASH_INVALID || _has_pending_hash(d, hash)) return;
  g_array_append_val(d->pending_hashes, hash);
}
 
static gboolean _remove_pending_hash(dt_lib_histogram_t *d, const uint64_t hash)
{
  if(IS_NULL_PTR(d) || !d->pending_hashes || hash == DT_PIXELPIPE_CACHE_HASH_INVALID) return FALSE;
 
  for(guint i = 0; i < d->pending_hashes->len; i++)
  {
    if(g_array_index(d->pending_hashes, uint64_t, i) == hash)
    {
      g_array_remove_index(d->pending_hashes, i);
      return TRUE;
    }
  }
 
  return FALSE;
}
 
static uint64_t _get_live_histogram_hash(const char *op)
{
  dt_develop_t *const dev = darktable.develop;
  dt_dev_pixelpipe_t *const pipe = dev ? dev->preview_pipe : NULL;
  if(IS_NULL_PTR(dev) || IS_NULL_PTR(pipe) || IS_NULL_PTR(op)) return DT_PIXELPIPE_CACHE_HASH_INVALID;
  /* Avoid taking `pipe->busy_mutex` on the GUI thread: read the live module
   * hashes without the mutex and rely on the cache peek manager to handle
   * synchronization and retries for missing cachelines. */
  dt_iop_module_t *const module = dt_iop_get_module_by_op_priority(dev->iop, op, 0);
  if(IS_NULL_PTR(module)) return DT_PIXELPIPE_CACHE_HASH_INVALID;
 
  const dt_dev_pixelpipe_iop_t *piece = dt_dev_pixelpipe_get_module_piece(pipe, module);
  if(IS_NULL_PTR(piece)) return DT_PIXELPIPE_CACHE_HASH_INVALID;
 
  if(!strcmp(op, "gamma"))
    piece = dt_dev_pixelpipe_get_prev_enabled_piece(pipe, piece);
 
  const uint64_t hash = piece ? piece->global_hash : DT_PIXELPIPE_CACHE_HASH_INVALID;
  return hash;
}
 
static gboolean _histogram_refresh_idle(gpointer user_data)
{
  dt_lib_module_t *self = (dt_lib_module_t *)user_data;
  dt_lib_histogram_t *d = self ? self->data : NULL;
  if(IS_NULL_PTR(d)) return G_SOURCE_REMOVE;
 
  d->refresh_idle_source = 0;
  d->backbuf = _get_histogram_backbuf(darktable.develop, d->op);
  _update_everything(self);
  return G_SOURCE_REMOVE;
}
 
static void _schedule_histogram_refresh(dt_lib_module_t *self)
{
  dt_lib_histogram_t *d = self ? self->data : NULL;
  if(IS_NULL_PTR(d) || d->refresh_idle_source != 0) return;
  d->refresh_idle_source = g_idle_add(_histogram_refresh_idle, self);
}
 
static void _sync_pending_histogram_hashes(dt_lib_module_t *self)
{
  dt_lib_histogram_t *d = (dt_lib_histogram_t *)self->data;
  if(IS_NULL_PTR(d)) return;
 
  _clear_pending_hashes(d);
  _add_pending_hash(d, _get_live_histogram_hash(d->op));
 
  for(GSList *samples = darktable.develop->color_picker.samples; samples; samples = g_slist_next(samples))
  {
    dt_colorpicker_sample_t *sample = samples->data;
    if(sample->locked) continue;
    _add_pending_hash(d, _get_live_histogram_hash(sample->backbuf_op[0] ? sample->backbuf_op : d->op));
  }
 
  if(darktable.develop->color_picker.picker)
    _add_pending_hash(d, _get_live_histogram_hash(d->op));
 
  d->backbuf = _get_histogram_backbuf(darktable.develop, d->op);
  _update_everything(self);
}
 
 
static const dt_dev_pixelpipe_iop_t *_get_backbuf_source_piece(const dt_backbuf_t *backbuf, const char *op);
 
static gboolean _is_backbuf_ready(dt_lib_histogram_t *d)
{
  if(IS_NULL_PTR(d) || IS_NULL_PTR(d->backbuf)) return FALSE;
 
  return !IS_NULL_PTR(_get_backbuf_source_piece(d->backbuf, d->op));
}
 
static void _redraw_scopes(dt_lib_histogram_t *d)
{
  gtk_widget_queue_draw(d->scope_draw);
}
 
uint32_t _find_max_histogram(const uint32_t *const restrict bins, const size_t binning_size)
{
  uint32_t max_hist = 0;
  __OMP_PARALLEL_FOR_SIMD__(aligned(bins: 64)  reduction(max: max_hist) )
  for(size_t k = 0; k < binning_size; k++) if(bins[k] > max_hist) max_hist = bins[k];
 
  return max_hist;
}
 
static inline void _sample_raw_box_to_image_norm(const dt_colorpicker_sample_t *const sample, float box[4])
{
  memcpy(box, sample->box, sizeof(float) * 4);
  dt_dev_coordinates_raw_norm_to_image_norm(darktable.develop, box, 2);
}
 
static inline void _sample_raw_point_to_image_norm(const dt_colorpicker_sample_t *const sample, float point[2])
{
  point[0] = sample->point[0];
  point[1] = sample->point[1];
  dt_dev_coordinates_raw_norm_to_image_norm(darktable.develop, point, 1);
}
 
 
static inline void _bin_pixels_histogram_in_roi(const float *const restrict image, uint32_t *const restrict bins,
                                                const size_t min_x, const size_t max_x,
                                                const size_t min_y, const size_t max_y,
                                                const size_t width)
{
  //fprintf(stdout, "computing histogram from x = [%lu;%lu], y = [%lu;%lu]\n", min_x, max_x, min_y, max_y);
  // Process
#ifdef _OPENMP
#ifndef _WIN32
__OMP_PARALLEL_FOR__(reduction(+: bins[0: HISTOGRAM_BINS * 4])  collapse(3))
#else
__OMP_PARALLEL_FOR__(shared(bins)  collapse(3))
#endif
#endif
  for(size_t i = min_y; i < max_y; i++)
    for(size_t j = min_x; j < max_x; j++)
      for(size_t c = 0; c < 3; c++)
      {
        const float value = image[(i * width + j) * 4 + c];
        const size_t index = (size_t)CLAMP(roundf(value * (HISTOGRAM_BINS - 1)), 0, HISTOGRAM_BINS - 1);
        bins[index * 4 + c]++;
      }
}
 
 
static inline void _bin_pickers_histogram(const float *const restrict image,
                                          const size_t width, const size_t height,
                                          uint32_t *bins,
                                          dt_colorpicker_sample_t *sample)
{
  if(sample->size == DT_LIB_COLORPICKER_SIZE_BOX)
  {
    float image_box[4] = { 0.0f };
    _sample_raw_box_to_image_norm(sample, image_box);
    const size_t box[4] = {
      CLAMP((size_t)roundf(image_box[0] * width), 0, width),
      CLAMP((size_t)roundf(image_box[1] * height), 0, height),
      CLAMP((size_t)roundf(image_box[2] * width), 0, width),
      CLAMP((size_t)roundf(image_box[3] * height), 0, height)
    };
    _bin_pixels_histogram_in_roi(image, bins, box[0], box[2], box[1], box[3], width);
  }
  else
  {
    float image_point[2] = { 0.0f };
    _sample_raw_point_to_image_norm(sample, image_point);
    const size_t x = CLAMP((size_t)roundf(image_point[0] * width), 0, width - 1);
    const size_t y = CLAMP((size_t)roundf(image_point[1] * height), 0, height - 1);
    _bin_pixels_histogram_in_roi(image, bins, x, x + 1, y, y + 1, width);
  }
}
 
static gboolean _is_restricted(dt_lib_histogram_t *d)
{
  if(IS_NULL_PTR(d)) return FALSE;
  const gboolean restrict_active = !IS_NULL_PTR(d->restrict_button)
      && gtk_toggle_button_get_active(GTK_TOGGLE_BUTTON(d->restrict_button));
  const gboolean picker_active = !IS_NULL_PTR(d->picker_button)
      && gtk_toggle_button_get_active(GTK_TOGGLE_BUTTON(d->picker_button));
  return restrict_active && picker_active;
}
 
static void _process_histogram(dt_backbuf_t *backbuf, const char *op, cairo_t *cr, const int width,
                               const int height, dt_lib_histogram_t *d)
{
  // Histogram backbuffers already own their keepalive ref in the pipeline state. Drawing only borrows them.
  struct dt_pixel_cache_entry_t *entry = NULL;
  void *data = NULL;
  const dt_dev_pixelpipe_iop_t *const piece = _get_backbuf_source_piece(backbuf, op);
  if(IS_NULL_PTR(piece)) return;
  if(!IS_NULL_PTR(d))
    dt_dev_pixelpipe_cache_wait_set_owner(&d->scope_wait, "histogram-scope", d->module);
  if(!dt_dev_pixelpipe_cache_peek_gui(darktable.develop->preview_pipe, piece, &data, &entry,
                                      !IS_NULL_PTR(d) ? &d->scope_wait : NULL,
                                      _histogram_restart_scope_cache_wait,
                                      !IS_NULL_PTR(d) ? d->module : NULL))
  {
    return;
  }
 
  dt_dev_pixelpipe_cache_rdlock_entry(darktable.pixelpipe_cache, TRUE, entry);
 
  uint32_t *bins = calloc(4 * HISTOGRAM_BINS, sizeof(uint32_t));
  if(IS_NULL_PTR(bins)) 
  {
    dt_dev_pixelpipe_cache_rdlock_entry(darktable.pixelpipe_cache, FALSE, entry);
    return;
  }
 
  const gboolean restrict_mode = _is_restricted(d);
  if(restrict_mode)
  {
    // Bin only areas within color pickers
    GSList *samples = darktable.develop->color_picker.samples;
    while(samples)
    {
      dt_colorpicker_sample_t *sample = samples->data;
      _bin_pickers_histogram(data, backbuf->width, backbuf->height,
                             bins, sample);
      samples = g_slist_next(samples);
    }
 
    if(darktable.develop->color_picker.picker)
      _bin_pickers_histogram(data, backbuf->width, backbuf->height,
                             bins, darktable.develop->color_picker.primary_sample);
  }
  else
  {
    _bin_pixels_histogram_in_roi(data, bins, 0, backbuf->width, 0, backbuf->height, width);
  }
 
  dt_dev_pixelpipe_cache_rdlock_entry(darktable.pixelpipe_cache, FALSE, entry);
 
  uint32_t overall_histogram_max = _find_max_histogram(bins, 4 * HISTOGRAM_BINS);
 
  // Draw thingy
  if(overall_histogram_max > 0)
  {
    // Paint background
    cairo_rectangle(cr, 0, 0, width, height);
    set_color(cr, darktable.bauhaus->graph_bg);
    cairo_fill(cr);
 
    set_color(cr, darktable.bauhaus->graph_grid);
    dt_draw_grid(cr, 4, 0, 0, width, height);
 
    cairo_save(cr);
    cairo_push_group_with_content(cr, CAIRO_CONTENT_COLOR);
    cairo_translate(cr, 0, height);
    cairo_scale(cr, width / 255.0, - (double)height / (double)(1. + log(overall_histogram_max)));
    cairo_set_operator(cr, CAIRO_OPERATOR_ADD);
 
    for(int k = 0; k < 3; k++)
    {
      set_color(cr, darktable.bauhaus->graph_colors[k]);
      dt_draw_histogram_8(cr, bins, 4, k, FALSE);
    }
 
    cairo_pop_group_to_source(cr);
    cairo_set_operator(cr, CAIRO_OPERATOR_ADD);
    cairo_paint_with_alpha(cr, 0.5);
    cairo_restore(cr);
  }
 
  dt_free(bins);
}
 
 
static inline void _bin_pixels_waveform_in_roi(const float *const restrict image, uint32_t *const restrict bins,
                                               const size_t min_x, const size_t max_x,
                                               const size_t min_y, const size_t max_y,
                                               const size_t source_width, const size_t source_height,
                                               const size_t tone_bins, const size_t raster_extent,
                                               const gboolean vertical)
{
  if(vertical)
  {
    /* In vertical waveform/parade, pixel value is drawn along the widget width and source image
     * position along the widget height. We therefore loop on final raster rows and collect the
     * source rows that map there, so both axes have the same detail as the drawn surface. */
    __OMP_PARALLEL_FOR__(shared(bins))
    for(size_t raster_y = 0; raster_y < raster_extent; raster_y++)
    {
      const double source_y0d = (double)raster_y * (double)source_height / (double)raster_extent;
      const double source_y1d = (double)(raster_y + 1) * (double)source_height / (double)raster_extent;
      const size_t source_y0 = MAX(min_y, (size_t)floor(source_y0d));
      const size_t source_y1 = MIN(max_y, (size_t)ceil(source_y1d));
      if(source_y0 >= source_y1) continue;
 
      for(size_t i = source_y0; i < source_y1; i++)
      {
        const double overlap = MIN((double)(i + 1), source_y1d) - MAX((double)i, source_y0d);
        const uint32_t weight = MAX(1u, (uint32_t)round(overlap * 256.));
        __OMP_PARALLEL_FOR__(shared(bins) collapse(2))
        for(size_t j = min_x; j < max_x; j++)
          for(size_t c = 0; c < 3; c++)
          {
            const float value = image[(i * source_width + j) * 4 + c];
            const float tone_position = CLAMPF(value, 0.f, 1.f) * (float)(tone_bins - 1);
            const size_t tone0 = (size_t)floorf(tone_position);
            const size_t tone1 = MIN(tone0 + 1, tone_bins - 1);
            const float tone_mix = tone_position - (float)tone0;
            const uint32_t weight1 = (uint32_t)roundf((float)weight * tone_mix);
            const uint32_t weight0 = weight - weight1;
            bins[(raster_y * tone_bins + tone0) * 4 + c] += weight0;
            bins[(raster_y * tone_bins + tone1) * 4 + c] += weight1;
          }
      }
    }
  }
  else
  {
    /* In horizontal waveform/parade, pixel value is drawn along the widget height and source image
     * position along the widget width. Each final raster column owns disjoint bins, avoiding races. */
    __OMP_PARALLEL_FOR__(shared(bins))
    for(size_t raster_x = 0; raster_x < raster_extent; raster_x++)
    {
      const double source_x0d = (double)raster_x * (double)source_width / (double)raster_extent;
      const double source_x1d = (double)(raster_x + 1) * (double)source_width / (double)raster_extent;
      const size_t source_x0 = MAX(min_x, (size_t)floor(source_x0d));
      const size_t source_x1 = MIN(max_x, (size_t)ceil(source_x1d));
      if(source_x0 >= source_x1) continue;
 
      for(size_t j = source_x0; j < source_x1; j++)
      {
        const double overlap = MIN((double)(j + 1), source_x1d) - MAX((double)j, source_x0d);
        const uint32_t weight = MAX(1u, (uint32_t)round(overlap * 256.));
        __OMP_PARALLEL_FOR__(shared(bins) collapse(2))
        for(size_t i = min_y; i < max_y; i++)
          for(size_t c = 0; c < 3; c++)
          {
            const float value = image[(i * source_width + j) * 4 + c];
            const float tone_position = CLAMPF(value, 0.f, 1.f) * (float)(tone_bins - 1);
            const size_t tone0 = (size_t)floorf(tone_position);
            const size_t tone1 = MIN(tone0 + 1, tone_bins - 1);
            const float tone_mix = tone_position - (float)tone0;
            const uint32_t weight1 = (uint32_t)roundf((float)weight * tone_mix);
            const uint32_t weight0 = weight - weight1;
            bins[((tone_bins - 1 - tone0) * raster_extent + raster_x) * 4 + c] += weight0;
            bins[((tone_bins - 1 - tone1) * raster_extent + raster_x) * 4 + c] += weight1;
          }
      }
    }
  }
}
 
static inline void _bin_pickers_waveforms(const float *const restrict image, uint32_t *const restrict bins,
                                          const size_t width, const size_t height,
                                          const size_t tone_bins, const size_t raster_extent,
                                          const gboolean vertical, dt_colorpicker_sample_t *sample)
{
  if(sample->size == DT_LIB_COLORPICKER_SIZE_BOX)
  {
    float image_box[4] = { 0.0f };
    _sample_raw_box_to_image_norm(sample, image_box);
    const size_t box[4] = {
      CLAMP((size_t)roundf(image_box[0] * width), 0, width),
      CLAMP((size_t)roundf(image_box[1] * height), 0, height),
      CLAMP((size_t)roundf(image_box[2] * width), 0, width),
      CLAMP((size_t)roundf(image_box[3] * height), 0, height)
    };
    _bin_pixels_waveform_in_roi(image, bins, box[0], box[2], box[1], box[3],
                                width, height, tone_bins, raster_extent, vertical);
  }
  else
  {
    float image_point[2] = { 0.0f };
    _sample_raw_point_to_image_norm(sample, image_point);
    const size_t x = CLAMP((size_t)roundf(image_point[0] * width), 0, width - 1);
    const size_t y = CLAMP((size_t)roundf(image_point[1] * height), 0, height - 1);
    _bin_pixels_waveform_in_roi(image, bins, x, x + 1, y, y + 1,
                                width, height, tone_bins, raster_extent, vertical);
  }
}
 
 
static inline void _bin_pixels_waveform(const float *const restrict image, uint32_t *const restrict bins,
                                        const size_t width, const size_t height, const size_t binning_size,
                                        const size_t tone_bins, const size_t raster_extent,
                                        const gboolean vertical, const gboolean restricted)
{
  // Init
  __OMP_FOR_SIMD__(aligned(bins: 64) )
  for(size_t k = 0; k < binning_size; k++) bins[k] = 0;
 
  if(restricted)
  {
    // Bin only areas within color pickers
    GSList *samples = darktable.develop->color_picker.samples;
    while(samples)
    {
      dt_colorpicker_sample_t *sample = samples->data;
      _bin_pickers_waveforms(image, bins, width, height, tone_bins, raster_extent, vertical, sample);
      samples = g_slist_next(samples);
    }
 
    if(darktable.develop->color_picker.picker)
      _bin_pickers_waveforms(image, bins, width, height, tone_bins, raster_extent, vertical,
                             darktable.develop->color_picker.primary_sample);
  }
  else
  {
    // Bin the whole image
    _bin_pixels_waveform_in_roi(image, bins, 0, width, 0, height,
                                width, height, tone_bins, raster_extent, vertical);
  }
}
 
static void _create_waveform_image(const uint32_t *const restrict bins, uint8_t *const restrict image,
                                   const uint32_t max_hist,
                                   const size_t width, const size_t height)
{
  __OMP_FOR_SIMD__(aligned(image, bins: 64) )
  for(size_t k = 0; k < height * width * 4; k += 4)
  {
    image[k + 3] = 255; // alpha
 
    // We apply a slight "gamma" boost for legibility
    image[k + 2] = (uint8_t)CLAMP(roundf(powf((float)bins[k + 0] / (float)max_hist, GAMMA) * 255.f), 0, 255);
    image[k + 1] = (uint8_t)CLAMP(roundf(powf((float)bins[k + 1] / (float)max_hist, GAMMA) * 255.f), 0, 255);
    image[k + 0] = (uint8_t)CLAMP(roundf(powf((float)bins[k + 2] / (float)max_hist, GAMMA) * 255.f), 0, 255);
  }
}
 
static void _paint_waveform(cairo_t *cr, uint8_t *const restrict image, const int width, const int height,
                            const size_t img_width, const size_t img_height, const size_t tone_bins,
                            const gboolean vertical)
{
  const size_t stride = cairo_format_stride_for_width(CAIRO_FORMAT_ARGB32, img_width);
  cairo_surface_t *background = cairo_image_surface_create_for_data(image, CAIRO_FORMAT_ARGB32, img_width, img_height, stride);
  const double scale_w = (vertical) ? (double)width / (double)tone_bins
                                    : (double)width / (double)img_width;
  const double scale_h = (vertical) ? (double)height / (double)img_height
                                    : (double)height / (double)tone_bins;
  cairo_scale(cr, scale_w, scale_h);
  cairo_set_operator(cr, CAIRO_OPERATOR_ADD);
  cairo_set_source_surface(cr, background, 0., 0.);
  cairo_pattern_set_filter(cairo_get_source(cr), CAIRO_FILTER_BEST);
  cairo_paint(cr);
  cairo_surface_destroy(background);
}
 
 
static void _process_waveform(dt_backbuf_t *backbuf, const char *op, cairo_t *cr, const int width,
                              const int height, const gboolean vertical, const gboolean parade,
                              dt_lib_histogram_t *d)
{
  struct dt_pixel_cache_entry_t *entry = NULL;
  void *data = NULL;
  const dt_dev_pixelpipe_iop_t *const piece = _get_backbuf_source_piece(backbuf, op);
  if(IS_NULL_PTR(piece)) return;
  if(!IS_NULL_PTR(d))
    dt_dev_pixelpipe_cache_wait_set_owner(&d->scope_wait, "histogram-scope", d->module);
  if(!dt_dev_pixelpipe_cache_peek_gui(darktable.develop->preview_pipe, piece, &data, &entry,
                                      !IS_NULL_PTR(d) ? &d->scope_wait : NULL,
                                      _histogram_restart_scope_cache_wait,
                                      !IS_NULL_PTR(d) ? d->module : NULL))
  {
    return;
  }
 
  dt_dev_pixelpipe_cache_rdlock_entry(darktable.pixelpipe_cache, TRUE, entry);
 
  /* The value axis must match the final drawing axis: widget height for horizontal scopes and
   * widget width for vertical scopes. Keeping it fixed forces Cairo to stretch sparse
   * value rows/columns, which shows as hatching when the scope is resized. */
  const size_t tone_bins = MAX(2, (vertical) ? width : height);
  /* The source-position axis must also match the final raster size. Otherwise Cairo stretches the
   * preview-pipe dimensions to the scope allocation, which can leave visible regular stripes. */
  const size_t raster_extent = MAX(2, (vertical)
      ? (parade ? (height + 2) / 3 : height)
      : (parade ? (width + 2) / 3 : width));
  const size_t binning_size = 4 * tone_bins * raster_extent;
  const size_t img_width = (parade) ? width : ((vertical) ? tone_bins : raster_extent);
  const size_t img_height = (parade) ? height : ((vertical) ? raster_extent : tone_bins);
  const size_t image_size = 4 * img_width * img_height;
  const size_t source_axis = (vertical) ? backbuf->height : backbuf->width;
  float source_min = INFINITY;
  float source_max = -INFINITY;
  size_t source_clipped = 0;
  size_t source_nan = 0;
  const size_t source_step = MAX((size_t)1, (backbuf->width * backbuf->height) / 4096);
  for(size_t pixel = 0; pixel < backbuf->width * backbuf->height; pixel += source_step)
    for(size_t c = 0; c < 3; c++)
    {
      const float value = ((const float *)data)[pixel * 4 + c];
      if(isnan(value))
        source_nan++;
      else
      {
        source_min = fminf(source_min, value);
        source_max = fmaxf(source_max, value);
        source_clipped += (value < 0.f || value > 1.f);
      }
    }
  uint32_t *smooth_bins = NULL;
 
  if(darktable.unmuted & DT_DEBUG_VERBOSE)
    dt_print(DT_DEBUG_DEV,
            "[histogram/scope] waveform setup op=%s parade=%d vertical=%d widget=%dx%d backbuf=%" G_GSIZE_FORMAT "x%" G_GSIZE_FORMAT " "
            "tone_bins=%" G_GSIZE_FORMAT " raster_extent=%" G_GSIZE_FORMAT " source_axis=%" G_GSIZE_FORMAT
            " source_per_raster=%.4f binning_size=%" G_GSIZE_FORMAT " "
            "source_value=%0.6f..%0.6f clipped=%" G_GSIZE_FORMAT " nan=%" G_GSIZE_FORMAT " sample_step=%" G_GSIZE_FORMAT "\n",
            op, parade, vertical, width, height, backbuf->width, backbuf->height,
            tone_bins, raster_extent, source_axis, (double)source_axis / (double)raster_extent,
            binning_size, source_min, source_max, source_clipped, source_nan, source_step);
  uint32_t *const restrict bins = dt_pixelpipe_cache_alloc_align_cache(
      binning_size * sizeof(uint32_t),
      0);
  uint8_t *const restrict image = dt_pixelpipe_cache_alloc_align_cache(
      image_size * sizeof(uint8_t),
      0);
  if(IS_NULL_PTR(image) || IS_NULL_PTR(bins))
  {
    if(darktable.unmuted & DT_DEBUG_VERBOSE)
      dt_print(DT_DEBUG_DEV,
              "[histogram/scope] waveform allocation failed bins=%p image=%p binning_size=%" G_GSIZE_FORMAT
              " image_size=%" G_GSIZE_FORMAT "\n",
              (void *)bins, (void *)image, binning_size, image_size);
    goto error;
  }
 
  // 1. Pixel binning along columns/rows, aka compute a column/row-wise histogram
  _bin_pixels_waveform(data, bins, backbuf->width, backbuf->height, binning_size,
                       tone_bins, raster_extent, vertical, _is_restricted(d));
 
  const uint32_t *render_bins = bins;
  int smoothing_passes = 0;
#if DT_LIB_HISTOGRAM_SCOPE_ENABLE_SMOOTHING \
    && (DT_LIB_HISTOGRAM_SCOPE_SMOOTH_SPATIAL_PASSES > 0 \
        || DT_LIB_HISTOGRAM_SCOPE_SMOOTH_TONE_PASSES > 0)
  smooth_bins = dt_pixelpipe_cache_alloc_align_cache(binning_size * sizeof(uint32_t), 0);
  const uint32_t smoothing_force = CLAMP(DT_LIB_HISTOGRAM_SCOPE_SMOOTH_FORCE, 0, 256);
  if(!IS_NULL_PTR(smooth_bins) && smoothing_force > 0)
  {
    /* The waveform/parade is a spatially-indexed histogram. Even after fractional resampling,
     * isolated source-column content can create one-pixel density modulation that reads as stries.
     * The passes below are explicit at call site because the source/destination ownership matters:
     * bins and smooth_bins alternate roles, and render_bins always records the last valid raster. */
    const uint32_t original_force = 256u - smoothing_force;
 
    for(int pass = 0; pass < DT_LIB_HISTOGRAM_SCOPE_SMOOTH_SPATIAL_PASSES; pass++)
    {
      const uint32_t *const source_bins = render_bins;
      uint32_t *const target_bins = (source_bins == bins) ? smooth_bins : bins;
 
      if(vertical)
      {
        for(size_t axis = 0; axis < raster_extent; axis++)
        {
          const size_t axis_m2 = (axis > 1) ? axis - 2 : 0;
          const size_t axis_m1 = (axis > 0) ? axis - 1 : 0;
          const size_t axis_p1 = MIN(axis + 1, raster_extent - 1);
          const size_t axis_p2 = MIN(axis + 2, raster_extent - 1);
          for(size_t tone = 0; tone < tone_bins; tone++)
            for(size_t c = 0; c < 4; c++)
            {
              const size_t index = (axis * tone_bins + tone) * 4 + c;
              const uint64_t smoothed = source_bins[(axis_m2 * tone_bins + tone) * 4 + c]
                                      + 4u * source_bins[(axis_m1 * tone_bins + tone) * 4 + c]
                                      + 6u * source_bins[index]
                                      + 4u * source_bins[(axis_p1 * tone_bins + tone) * 4 + c]
                                      + source_bins[(axis_p2 * tone_bins + tone) * 4 + c];
              const uint64_t blended = original_force * source_bins[index]
                                     + smoothing_force * ((smoothed + 8u) / 16u);
              target_bins[index] = (uint32_t)((blended + 128u) / 256u);
            }
        }
      }
      else
      {
        for(size_t tone = 0; tone < tone_bins; tone++)
          for(size_t axis = 0; axis < raster_extent; axis++)
          {
            const size_t axis_m2 = (axis > 1) ? axis - 2 : 0;
            const size_t axis_m1 = (axis > 0) ? axis - 1 : 0;
            const size_t axis_p1 = MIN(axis + 1, raster_extent - 1);
            const size_t axis_p2 = MIN(axis + 2, raster_extent - 1);
            for(size_t c = 0; c < 4; c++)
            {
              const size_t index = (tone * raster_extent + axis) * 4 + c;
              const uint64_t smoothed = source_bins[(tone * raster_extent + axis_m2) * 4 + c]
                                      + 4u * source_bins[(tone * raster_extent + axis_m1) * 4 + c]
                                      + 6u * source_bins[index]
                                      + 4u * source_bins[(tone * raster_extent + axis_p1) * 4 + c]
                                      + source_bins[(tone * raster_extent + axis_p2) * 4 + c];
              const uint64_t blended = original_force * source_bins[index]
                                     + smoothing_force * ((smoothed + 8u) / 16u);
              target_bins[index] = (uint32_t)((blended + 128u) / 256u);
            }
          }
      }
 
      render_bins = target_bins;
      smoothing_passes++;
    }
 
    for(int pass = 0; pass < DT_LIB_HISTOGRAM_SCOPE_SMOOTH_TONE_PASSES; pass++)
    {
      const uint32_t *const source_bins = render_bins;
      uint32_t *const target_bins = (source_bins == bins) ? smooth_bins : bins;
 
      if(vertical)
      {
        for(size_t axis = 0; axis < raster_extent; axis++)
          for(size_t tone = 0; tone < tone_bins; tone++)
          {
            const size_t tone_m1 = (tone > 0) ? tone - 1 : 0;
            const size_t tone_p1 = MIN(tone + 1, tone_bins - 1);
            for(size_t c = 0; c < 4; c++)
            {
              const size_t index = (axis * tone_bins + tone) * 4 + c;
              const uint64_t smoothed = source_bins[(axis * tone_bins + tone_m1) * 4 + c]
                                      + 2u * source_bins[index]
                                      + source_bins[(axis * tone_bins + tone_p1) * 4 + c];
              const uint64_t blended = original_force * source_bins[index]
                                     + smoothing_force * ((smoothed + 2u) / 4u);
              target_bins[index] = (uint32_t)((blended + 128u) / 256u);
            }
          }
      }
      else
      {
        for(size_t tone = 0; tone < tone_bins; tone++)
        {
          const size_t tone_m1 = (tone > 0) ? tone - 1 : 0;
          const size_t tone_p1 = MIN(tone + 1, tone_bins - 1);
          for(size_t axis = 0; axis < raster_extent; axis++)
            for(size_t c = 0; c < 4; c++)
            {
              const size_t index = (tone * raster_extent + axis) * 4 + c;
              const uint64_t smoothed = source_bins[(tone_m1 * raster_extent + axis) * 4 + c]
                                      + 2u * source_bins[index]
                                      + source_bins[(tone_p1 * raster_extent + axis) * 4 + c];
              const uint64_t blended = original_force * source_bins[index]
                                     + smoothing_force * ((smoothed + 2u) / 4u);
              target_bins[index] = (uint32_t)((blended + 128u) / 256u);
            }
        }
      }
 
      render_bins = target_bins;
      smoothing_passes++;
    }
  }
#endif
 
  // 2. Paint image.
  // In a 1D histogram, pixel frequencies are shown as height (y axis) for each RGB quantum (x axis).
  // Here, we do a sort of 2D histogram : pixel frequencies are shown as opacity ("z" axis),
  // for each image column (x axis), for each RGB quantum (y axis)
  const uint32_t overall_max_hist = _find_max_histogram(render_bins, binning_size);
  size_t empty_axis = 0;
  uint64_t min_axis = UINT64_MAX;
  uint64_t max_axis = 0;
  uint32_t min_axis_peak = UINT32_MAX;
  uint32_t max_axis_peak = 0;
  for(size_t axis = 0; axis < raster_extent; axis++)
  {
    uint64_t axis_total = 0;
    uint32_t axis_peak = 0;
    for(size_t tone = 0; tone < tone_bins; tone++)
    {
      const size_t pixel = (vertical) ? axis * tone_bins + tone : tone * raster_extent + axis;
      for(size_t c = 0; c < 3; c++)
      {
        const uint32_t value = render_bins[pixel * 4 + c];
        axis_total += value;
        axis_peak = MAX(axis_peak, value);
      }
    }
 
    if(axis_total == 0) empty_axis++;
    min_axis = MIN(min_axis, axis_total);
    max_axis = MAX(max_axis, axis_total);
    min_axis_peak = MIN(min_axis_peak, axis_peak);
    max_axis_peak = MAX(max_axis_peak, axis_peak);
  }
  const size_t stride = cairo_format_stride_for_width(CAIRO_FORMAT_ARGB32, img_width);
  dt_print(DT_DEBUG_DEV,
           "[histogram/scope] waveform raster op=%s parade=%d vertical=%d image=%" G_GSIZE_FORMAT "x%" G_GSIZE_FORMAT
           " stride=%" G_GSIZE_FORMAT " overall_max=%u empty_axis=%" G_GSIZE_FORMAT " axis_total=%" PRIu64 "..%" PRIu64
           " axis_peak=%u..%u smooth=%d scale=%0.4fx%0.4f\n",
           op, parade, vertical, img_width, img_height, stride, overall_max_hist,
           empty_axis, min_axis, max_axis, min_axis_peak, max_axis_peak, smoothing_passes,
           (double)width / (double)img_width, (double)height / (double)img_height);
 
  // 3. Send everything to GUI buffer.
  if(overall_max_hist > 0)
  {
    if(parade)
    {
      /* Build the parade directly in the final widget raster. This keeps channel thirds on integer
       * device pixels and removes all Cairo source-offset/scaling interactions from the diagnostic
       * path: if stries remain, they are in the histogram bins, not in channel painting. */
      for(size_t k = 0; k < image_size; k++) image[k] = 0;
 
      for(size_t c = 0; c < 3; c++)
      {
        const size_t x0 = vertical ? 0 : c * width / 3;
        const size_t x1 = vertical ? width : (c + 1) * width / 3;
        const size_t y0 = vertical ? c * height / 3 : 0;
        const size_t y1 = vertical ? (c + 1) * height / 3 : height;
        const size_t channel_width = x1 - x0;
        const size_t channel_height = y1 - y0;
        if(channel_width == 0 || channel_height == 0) continue;
 
        for(size_t y = y0; y < y1; y++)
          for(size_t x = x0; x < x1; x++)
          {
            const size_t axis = vertical
                ? (y - y0) * raster_extent / channel_height
                : (x - x0) * raster_extent / channel_width;
            const size_t tone = vertical ? x : y;
            const size_t bin_index = vertical ? (axis * tone_bins + tone) * 4 + c
                                                : (tone * raster_extent + axis) * 4 + c;
            const uint8_t value = (uint8_t)CLAMP(roundf(powf((float)render_bins[bin_index] / (float)overall_max_hist, GAMMA) * 255.f), 0, 255);
            const size_t image_index = (y * img_width + x) * 4;
            image[image_index + 2 - c] = value;
            image[image_index + 3] = 255;
          }
      }
    }
    else
      _create_waveform_image(render_bins, image, overall_max_hist, img_width, img_height);
 
    cairo_save(cr);
 
    // Paint background - Color not exposed to user theme because this is tricky
    cairo_set_source_rgb(cr, 0.3, 0.3, 0.3);
    cairo_paint(cr);
 
    cairo_set_source_rgb(cr, 0.21, 0.21, 0.21);
    const gboolean raw_stage = (!strcmp(op, "initialscale") || !strcmp(op, "demosaic"));
    if(raw_stage)
    {
      /* The regular 4x4 grid has a tonal guide at 0.75, which is not an integer raw bit stop.
       * In raw mode, non-parade scopes keep only the global spatial guides here; the tone guides
       * are drawn below from powers of two. Parade intentionally has no spatial guides. */
      for(int k = 1; !parade && k < 4; k++)
      {
        if(vertical)
          dt_draw_line(cr, 0, (double)k * (double)height / 4.0, width, (double)k * (double)height / 4.0);
        else
          dt_draw_line(cr, (double)k * (double)width / 4.0, 0, (double)k * (double)width / 4.0, height);
        cairo_stroke(cr);
      }
    }
    else if(parade)
    {
      /* Parade already splits the spatial axis into RGB strips. Keep only the regular tone-axis
       * guides here so the grid does not add misleading source-position lines inside each strip. */
      for(int k = 1; k < 4; k++)
      {
        if(vertical)
          dt_draw_line(cr, (double)k * (double)width / 4.0, 0, (double)k * (double)width / 4.0, height);
        else
          dt_draw_line(cr, 0, (double)k * (double)height / 4.0, width, (double)k * (double)height / 4.0);
        cairo_stroke(cr);
      }
    }
    else
      dt_draw_grid(cr, 4, 0, 0, width, height);
 
    if(raw_stage)
    {
      /* Raw data is linear, so integer bit stops are powers of two in normalized tone space.
       * Drawing those stops on the tone axis makes exposure clipping and low-bit detail readable
       * without depending on the current scope height. */
      for(int stop = 0; stop <= 8; stop++)
      {
        const double value = 1.0 / (double)(1u << stop);
        if(value < (double)DT_LIB_HISTOGRAM_SCOPE_MIN_VALUE) break;
 
        if(vertical)
        {
          const double x = value * (double)width;
          dt_draw_line(cr, x, 0, x, height);
        }
        else
        {
          const double y = (1.0 - value) * (double)height;
          dt_draw_line(cr, 0, y, width, y);
        }
        cairo_stroke(cr);
      }
    }
 
    _paint_waveform(cr, image, width, height, img_width, img_height, tone_bins, vertical);
 
    cairo_restore(cr);
  }
 
error:;
  dt_pixelpipe_cache_free_align(smooth_bins);
  dt_pixelpipe_cache_free_align(bins);
  dt_pixelpipe_cache_free_align(image);
  dt_dev_pixelpipe_cache_rdlock_entry(darktable.pixelpipe_cache, FALSE, entry);
}
 
static float _Luv_to_vectorscope_coord_zoom(const float value, const float zoom)
{
  // Convert u, v coordinates of Luv vectors into x, y coordinates
  // into the space of the vectorscope square buffer
  return (value + zoom) * (HISTOGRAM_BINS - 1) / (2.f * zoom);
}
 
static float _vectorscope_coord_zoom_to_Luv(const float value, const float zoom)
{
  // Inverse of the above
  return value * (2.f * zoom) / (HISTOGRAM_BINS - 1) - zoom;
}
 
static void _bin_pixels_vectorscope_in_roi(const float *const restrict image, uint32_t *const restrict vectorscope,
                                           const size_t min_x, const size_t max_x, const size_t min_y,
                                           const size_t max_y, const size_t width, const float zoom,
                                           dt_lib_histogram_t *d)
{
#ifdef _OPENMP
#ifndef _WIN32
#pragma omp parallel for default(firstprivate) \
        reduction(+: vectorscope[0: HISTOGRAM_BINS * HISTOGRAM_BINS]) 
#else
#pragma omp parallel for default(firstprivate) \
        shared(vectorscope) 
#endif
#endif
  for(size_t i = min_y; i < max_y; i++)
    for(size_t j = min_x; j < max_x; j++)
    {
      dt_aligned_pixel_t XYZ_D50 = { 0.f };
      dt_aligned_pixel_t xyY = { 0.f };
      dt_aligned_pixel_t Luv = { 0.f };
      _scope_pixel_to_xyz(image + (i * width + j) * 4, XYZ_D50, d);
      dt_XYZ_to_xyY(XYZ_D50, xyY);
      dt_xyY_to_Luv(xyY, Luv);
 
      // Luv is sampled between 0 and 100.0f, u and v between +/- 220.f
      const size_t U_index = (size_t)CLAMP(roundf(_Luv_to_vectorscope_coord_zoom(Luv[1], zoom)), 0, HISTOGRAM_BINS - 1);
      const size_t V_index = (size_t)CLAMP(roundf(_Luv_to_vectorscope_coord_zoom(Luv[2], zoom)), 0, HISTOGRAM_BINS - 1);
 
      // We put V = 0 at the bottom of the image.
      vectorscope[(HISTOGRAM_BINS - 1 - V_index) * HISTOGRAM_BINS + U_index]++;
    }
}
 
static inline void _bin_pickers_vectorscope(const float *const restrict image,
                                            uint32_t *const restrict vectorscope, const size_t width,
                                            const size_t height, const float zoom, dt_lib_histogram_t *d,
                                            const dt_colorpicker_sample_t *const sample)
{
  if(sample->size == DT_LIB_COLORPICKER_SIZE_BOX)
  {
    float image_box[4] = { 0.0f };
    _sample_raw_box_to_image_norm(sample, image_box);
    const size_t box[4] = {
      CLAMP((size_t)roundf(image_box[0] * width), 0, width),
      CLAMP((size_t)roundf(image_box[1] * height), 0, height),
      CLAMP((size_t)roundf(image_box[2] * width), 0, width),
      CLAMP((size_t)roundf(image_box[3] * height), 0, height)
    };
    _bin_pixels_vectorscope_in_roi(image, vectorscope, box[0], box[2], box[1], box[3], width, zoom, d);
  }
  else
  {
    float image_point[2] = { 0.0f };
    _sample_raw_point_to_image_norm(sample, image_point);
    const size_t x = CLAMP((size_t)roundf(image_point[0] * width), 0, width - 1);
    const size_t y = CLAMP((size_t)roundf(image_point[1] * height), 0, height - 1);
    _bin_pixels_vectorscope_in_roi(image, vectorscope, x, x + 1, y, y + 1, width, zoom, d);
  }
}
 
 
static void _create_vectorscope_image(const uint32_t *const restrict vectorscope, uint8_t *const restrict image,
                                      const uint32_t max_hist, const float zoom)
{
  const dt_iop_order_iccprofile_info_t *const profile = darktable.develop->preview_pipe->output_profile_info;
  __OMP_PARALLEL_FOR__(collapse(2))
  for(size_t i = 0; i < HISTOGRAM_BINS; i++)
    for(size_t j = 0; j < HISTOGRAM_BINS; j++)
    {
      const size_t index = (HISTOGRAM_BINS - 1 - i) * HISTOGRAM_BINS + j;
      const float value = sqrtf((float)vectorscope[index] / (float)max_hist);
      dt_aligned_pixel_t RGB = { 0.f };
      // RGB gamuts tend to have a max chroma around L = 67
      dt_aligned_pixel_t Luv = { 25.f, _vectorscope_coord_zoom_to_Luv(j, zoom), _vectorscope_coord_zoom_to_Luv(i, zoom), 1.f };
      dt_aligned_pixel_t xyY = { 0.f };
      dt_aligned_pixel_t XYZ = { 0.f };
      dt_Luv_to_xyY(Luv, xyY);
      for(int c = 0; c < 2; c++) xyY[c] = fmaxf(xyY[c], 0.f);
      dt_xyY_to_XYZ(xyY, XYZ);
      for(int c = 0; c < 3; c++) XYZ[c] = fmaxf(XYZ[c], 0.f);
      dt_apply_transposed_color_matrix(XYZ, profile->matrix_out_transposed, RGB);
 
      // We will normalize RGB to get closer to display peak emission
      for(int c = 0; c < 3; c++) RGB[c] = fmaxf(RGB[c], 0.f);
      const float max_RGB = fmax(RGB[0], fmaxf(RGB[1], RGB[2]));
      for(int c = 0; c < 3; c++) RGB[c] /= max_RGB;
 
      image[index * 4 + 3] = (uint8_t)roundf(value * 255.f); // alpha
      // Premultiply alpha
      image[index * 4 + 2] = (uint8_t)roundf(powf(RGB[0] * value, 1.f / 2.2f) * 255.f);
      image[index * 4 + 1] = (uint8_t)roundf(powf(RGB[1] * value, 1.f / 2.2f) * 255.f);
      image[index * 4 + 0] = (uint8_t)roundf(powf(RGB[2] * value, 1.f / 2.2f) * 255.f);
    }
}
 
static void _bin_vectorscope(const float *const restrict image, uint32_t *const vectorscope,
                             const size_t width, const size_t height,
                             const float zoom, dt_lib_histogram_t *d)
{
  __OMP_FOR_SIMD__(aligned(vectorscope: 64) )
  for(size_t k = 0; k < HISTOGRAM_BINS * HISTOGRAM_BINS; k++) vectorscope[k] = 0;
 
  if(_is_restricted(d))
  {
    // Bin only areas within color pickers
    GSList *samples = darktable.develop->color_picker.samples;
    while(samples)
    {
      dt_colorpicker_sample_t *sample = samples->data;
      _bin_pickers_vectorscope(image, vectorscope, width, height, zoom, d, sample);
      samples = g_slist_next(samples);
    }
 
    if(darktable.develop->color_picker.picker)
      _bin_pickers_vectorscope(image, vectorscope, width, height, zoom, d,
                               darktable.develop->color_picker.primary_sample);
  }
  else
  {
    // Bin the whole image
    _bin_pixels_vectorscope_in_roi(image, vectorscope, 0, width, 0, height, width, zoom, d);
  }
}
 
 
static void _process_vectorscope(dt_backbuf_t *backbuf, const char *op, cairo_t *cr, const int width,
                                 const int height, const float zoom, dt_lib_histogram_t *d)
{
  dt_iop_order_iccprofile_info_t *profile = darktable.develop->preview_pipe->output_profile_info;
  if(IS_NULL_PTR(profile) || IS_NULL_PTR(d)) return;
 
  struct dt_pixel_cache_entry_t *entry = NULL;
  void *data = NULL;
  const dt_dev_pixelpipe_iop_t *const piece = _get_backbuf_source_piece(backbuf, op);
  if(IS_NULL_PTR(piece)) return;
  dt_dev_pixelpipe_cache_wait_set_owner(&d->scope_wait, "histogram-scope", d->module);
  if(!dt_dev_pixelpipe_cache_peek_gui(darktable.develop->preview_pipe, piece, &data, &entry, &d->scope_wait,
                                      _histogram_restart_scope_cache_wait, d->module))
  {
    return;
  }
 
  dt_dev_pixelpipe_cache_rdlock_entry(darktable.pixelpipe_cache, TRUE, entry);
 
  uint32_t *const restrict vectorscope = dt_pixelpipe_cache_alloc_align_cache(
      HISTOGRAM_BINS * HISTOGRAM_BINS * sizeof(uint32_t),
      0);
  uint8_t *const restrict image = dt_pixelpipe_cache_alloc_align_cache(
      4 * HISTOGRAM_BINS * HISTOGRAM_BINS * sizeof(uint8_t),
      0);
  if(IS_NULL_PTR(vectorscope) || IS_NULL_PTR(image)) goto error;
 
  _bin_vectorscope(data, vectorscope, backbuf->width, backbuf->height, zoom, d);
 
  const uint32_t max_hist = _find_max_histogram(vectorscope, HISTOGRAM_BINS * HISTOGRAM_BINS);
  _create_vectorscope_image(vectorscope, image, max_hist, zoom);
 
  // 2. Draw
  if(max_hist > 0)
  {
    const size_t stride = cairo_format_stride_for_width(CAIRO_FORMAT_ARGB32, HISTOGRAM_BINS);
    cairo_surface_t *background = cairo_image_surface_create_for_data(image, CAIRO_FORMAT_ARGB32, HISTOGRAM_BINS, HISTOGRAM_BINS, stride);
    const int side = MIN(width, height);
    cairo_translate(cr, (double)(width - side) / 2., (double)(height - side) / 2.);
    cairo_scale(cr, (double)side / HISTOGRAM_BINS, (double)side / HISTOGRAM_BINS);
 
    const double radius = (float)(HISTOGRAM_BINS - 1) / 2 - DT_PIXEL_APPLY_DPI(1.);
    const double x_center = (float)(HISTOGRAM_BINS - 1) / 2;
 
    // Background circle - Color will not be exposed to user theme because this is tricky
    cairo_set_source_rgb(cr, 0.3, 0.3, 0.3);
    cairo_arc(cr, x_center, x_center, radius, 0., 2. * M_PI);
    cairo_fill(cr);
 
    // Center circle
    cairo_set_source_rgb(cr, 0.2, 0.2, 0.2);
    cairo_arc(cr, x_center, x_center, 2., 0., 2. * M_PI);
    cairo_fill(cr);
 
    // Concentric circles
    for(int k = 0; k < 4; k++)
    {
      cairo_arc(cr, x_center, x_center, (double)k * HISTOGRAM_BINS / 8., 0., 2. * M_PI);
      cairo_stroke(cr);
    }
 
    // RGB space primaries and secondaries
    dt_aligned_pixel_t colors[6] = { { 1.f, 0.f, 0.f, 0.f }, { 1.f, 1.f, 0.f, 0.f }, { 0.f, 1.f, 0.f, 0.f },
                                     { 0.f, 1.f, 1.f, 0.f }, { 0.f, 0.f, 1.f, 0.f }, { 1.f, 0.f, 1.f, 0.f } };
 
    cairo_save(cr);
    cairo_arc(cr, x_center, x_center, radius, 0., 2. * M_PI);
    cairo_clip(cr);
 
    for(size_t k = 0; k < 6; k++)
    {
      dt_aligned_pixel_t XYZ_D50 = { 0.f };
      dt_aligned_pixel_t xyY = { 0.f };
      dt_aligned_pixel_t Luv = { 0.f };
      dt_ioppr_rgb_matrix_to_xyz(colors[k], XYZ_D50, profile->matrix_in_transposed, profile->lut_in, profile->unbounded_coeffs_in,
                                profile->lutsize, profile->nonlinearlut);
      dt_XYZ_to_xyY(XYZ_D50, xyY);
      dt_xyY_to_Luv(xyY, Luv);
 
      const double x = _Luv_to_vectorscope_coord_zoom(Luv[1], zoom);
      // Remember v = 0 is at the bottom of the square while Cairo puts y = 0 on top
      const double y = HISTOGRAM_BINS - 1 - _Luv_to_vectorscope_coord_zoom(Luv[2], zoom);
 
      // First, draw hue angles
      dt_aligned_pixel_t Lch = { 0.f };
      dt_Luv_to_Lch(Luv, Lch);
 
      const double delta_x = radius * cosf(Lch[2]);
      const double delta_y = radius * sinf(Lch[2]);
      const double destination_x = x_center + delta_x;
      const double destination_y = (HISTOGRAM_BINS - 1) - (x_center + delta_y);
      cairo_move_to(cr, x_center, x_center);
      cairo_line_to(cr, destination_x, destination_y);
      cairo_set_source_rgba(cr, colors[k][0], colors[k][1], colors[k][2], 0.5);
      cairo_stroke(cr);
 
      // Then draw color squares and ensure center is filled with scope background color
      const double half_square = DT_PIXEL_APPLY_DPI(4);
      cairo_arc(cr, x, y, half_square, 0, 2. * M_PI);
      cairo_set_source_rgb(cr, 0.3, 0.3, 0.3);
      cairo_fill_preserve(cr);
      cairo_set_source_rgb(cr, colors[k][0], colors[k][1], colors[k][2]);
      cairo_stroke(cr);
    }
    cairo_restore(cr);
 
    // Hues ring
    cairo_save(cr);
    cairo_arc(cr, x_center, x_center, radius - DT_PIXEL_APPLY_DPI(1.), 0., 2. * M_PI);
    cairo_set_source_rgb(cr, 0.33, 0.33, 0.33);
    cairo_set_line_width(cr, DT_PIXEL_APPLY_DPI(2.));
    cairo_stroke(cr);
    cairo_restore(cr);
 
    for(size_t h = 0; h < 180; h++)
    {
      dt_aligned_pixel_t Lch = { 50.f, 110.f, h / 180.f * 2.f * M_PI_F, 1.f };
      dt_aligned_pixel_t Luv = { 0.f };
      dt_aligned_pixel_t xyY = { 0.f };
      dt_aligned_pixel_t XYZ = { 0.f };
      dt_aligned_pixel_t RGB = { 0.f };
      dt_Lch_to_Luv(Lch, Luv);
      dt_Luv_to_xyY(Luv, xyY);
      dt_xyY_to_XYZ(xyY, XYZ);
      dt_apply_transposed_color_matrix(XYZ, profile->matrix_out_transposed, RGB);
      const float max_RGB = fmaxf(fmaxf(RGB[0], RGB[1]), RGB[2]);
      for(int c = 0; c < 3; c++) RGB[c] /= max_RGB;
      const double delta_x = (radius - DT_PIXEL_APPLY_DPI(1.)) * cosf(Lch[2]);
      const double delta_y = (radius - DT_PIXEL_APPLY_DPI(1.)) * sinf(Lch[2]);
      const double destination_x = x_center + delta_x;
      const double destination_y = (HISTOGRAM_BINS - 1) - (x_center + delta_y);
      cairo_set_source_rgba(cr, RGB[0], RGB[1], RGB[2], 0.7);
      cairo_arc(cr, destination_x, destination_y, DT_PIXEL_APPLY_DPI(1.), 0, 2. * M_PI);
      cairo_fill(cr);
    }
 
    // Actual vectorscope
    cairo_arc(cr, x_center, x_center, radius, 0., 2. * M_PI);
    cairo_clip(cr);
    cairo_set_source_surface(cr, background, 0., 0.);
    cairo_pattern_set_filter(cairo_get_source(cr), CAIRO_FILTER_BEST);
    cairo_paint(cr);
    cairo_surface_destroy(background);
 
    // Draw the skin tones area
    // Values obtained with :
    // get_skin_tones_range();
    const float max_c = 49.34f;
    const float min_c = 9.00f;
    const float max_h = 0.99f;
    const float min_h = 0.26f;
 
    const float n_w_x = min_c * cosf(max_h);
    const float n_w_y = min_c * sinf(max_h);
    const float n_e_x = max_c * cosf(max_h);
    const float n_e_y = max_c * sinf(max_h);
    const float s_e_x = max_c * cosf(min_h);
    const float s_e_y = max_c * sinf(min_h);
    const float s_w_x = min_c * cosf(min_h);
    const float s_w_y = min_c * sinf(min_h);
    cairo_move_to(cr, _Luv_to_vectorscope_coord_zoom(n_w_x, zoom),
                      (HISTOGRAM_BINS - 1) - _Luv_to_vectorscope_coord_zoom(n_w_y, zoom));
    cairo_line_to(cr, _Luv_to_vectorscope_coord_zoom(n_e_x, zoom),
                      (HISTOGRAM_BINS - 1) - _Luv_to_vectorscope_coord_zoom(n_e_y, zoom));
    cairo_line_to(cr, _Luv_to_vectorscope_coord_zoom(s_e_x, zoom),
                      (HISTOGRAM_BINS - 1) - _Luv_to_vectorscope_coord_zoom(s_e_y, zoom));
    cairo_line_to(cr, _Luv_to_vectorscope_coord_zoom(s_w_x, zoom),
                      (HISTOGRAM_BINS - 1) - _Luv_to_vectorscope_coord_zoom(s_w_y, zoom));
    cairo_line_to(cr, _Luv_to_vectorscope_coord_zoom(n_w_x, zoom),
                      (HISTOGRAM_BINS - 1) - _Luv_to_vectorscope_coord_zoom(n_w_y, zoom));
    cairo_set_source_rgb(cr, 0.2, 0.2, 0.2);
    cairo_stroke(cr);
  }
 
error:;
  dt_pixelpipe_cache_free_align(image);
  dt_pixelpipe_cache_free_align(vectorscope);
  dt_dev_pixelpipe_cache_rdlock_entry(darktable.pixelpipe_cache, FALSE, entry);
}
 
gboolean _needs_recompute(dt_lib_histogram_t *d, const int width, const int height)
{
  // Check if cache is up-to-date
  dt_lib_histogram_scope_type_t view = d->scope;
  gboolean hash_match = (d->cache.hash == dt_dev_backbuf_get_hash(d->backbuf));
  gboolean size_match = (d->cache.width == width && d->cache.height == height);
  gboolean zoom_match = (d->cache.zoom == d->zoom);
  gboolean view_match = (d->cache.view == view);
  gboolean has_surface = (!IS_NULL_PTR(d->cst));
  return !(hash_match && size_match && zoom_match && view_match && has_surface);
}
 
 
static gboolean _draw_callback(GtkWidget *widget, cairo_t *crf, gpointer user_data)
{
  // Note: the draw callback is called from our own callback (mapped to "preview pipe finished recomputing" signal)
  // but is also called by Gtk when the main window is resized, exposed, etc.
  dt_lib_histogram_t *d = (dt_lib_histogram_t *)user_data;
  if(IS_NULL_PTR(d->cst)) return 1;
  cairo_set_source_surface(crf, d->cst, 0, 0);
  cairo_paint(crf);
  return 0;
}
 
 
void _get_allocation_size(dt_lib_histogram_t *d, int *width, int *height)
{
  GtkAllocation allocation;
  gtk_widget_get_allocation(d->scope_draw, &allocation);
  *width = allocation.width;
  *height = allocation.height;
}
 
static void _process_restricted_text(dt_lib_histogram_t *d, cairo_t *cr, const int height)
{
  if(_is_restricted(d))
  {
    cairo_save(cr);
    cairo_set_operator(cr, DT_LIB_HISTOGRAM_SCOPE_RESTRICTED_LABEL_OPERATOR);
 
    PangoLayout *layout = pango_cairo_create_layout(cr);
    PangoFontDescription *desc = pango_font_description_copy_static(darktable.bauhaus->pango_font_desc);
    pango_font_description_set_absolute_size(desc, DT_PIXEL_APPLY_DPI(12.) * PANGO_SCALE);
    pango_layout_set_font_description(layout, desc);
    pango_layout_set_text(layout, _("Restricted"), -1);
 
    PangoRectangle ink;
    PangoRectangle logical;
    pango_layout_get_pixel_extents(layout, &ink, &logical);
 
    const double padding = DT_PIXEL_APPLY_DPI(2.);
    const double text_padding = DT_PIXEL_APPLY_DPI(1.5);
    const double label_x = padding;
    const double label_y = MAX(padding, height - logical.height - 2. * text_padding - padding);
 
    set_color(cr, darktable.bauhaus->graph_scope_restricted);
    cairo_move_to(cr, label_x + text_padding - ink.x, label_y + text_padding);
    pango_cairo_show_layout(cr, layout);
 
    pango_font_description_free(desc);
    g_object_unref(layout);
    cairo_restore(cr);
  }
}
 
gboolean _redraw_surface(dt_lib_histogram_t *d)
{
  if(IS_NULL_PTR(d->cst)) return 1;
 
  dt_times_t start;
  dt_get_times(&start);
 
  int width, height;
  _get_allocation_size(d, &width, &height);
 
  // Save cache integrity
  d->cache.hash = dt_dev_backbuf_get_hash(d->backbuf);
  d->cache.width = width;
  d->cache.height = height;
  d->cache.zoom = d->zoom;
  d->cache.view = d->scope;
 
  cairo_t *cr = cairo_create(d->cst);
 
  // Paint background
  gtk_render_background(gtk_widget_get_style_context(d->scope_draw), cr, 0, 0, width, height);
  cairo_set_line_width(cr, 1.); // we want exactly 1 px no matter the resolution
 
  // Paint content
  switch(d->scope)
  {
    case DT_LIB_HISTOGRAM_SCOPE_HISTOGRAM:
    {
      _process_histogram(d->backbuf, d->op, cr, width, height, d);
      break;
    }
    case DT_LIB_HISTOGRAM_SCOPE_WAVEFORM_HORIZONTAL:
    {
      _process_waveform(d->backbuf, d->op, cr, width, height, FALSE, FALSE, d);
      break;
    }
    case DT_LIB_HISTOGRAM_SCOPE_WAVEFORM_VERTICAL:
    {
      _process_waveform(d->backbuf, d->op, cr, width, height, TRUE, FALSE, d);
      break;
    }
    case DT_LIB_HISTOGRAM_SCOPE_PARADE_HORIZONTAL:
    {
      _process_waveform(d->backbuf, d->op, cr, width, height, FALSE, TRUE, d);
      break;
    }
    case DT_LIB_HISTOGRAM_SCOPE_PARADE_VERTICAL:
    {
      _process_waveform(d->backbuf, d->op, cr, width, height, TRUE, TRUE, d);
      break;
    }
    case DT_LIB_HISTOGRAM_SCOPE_VECTORSCOPE:
    {
      _process_vectorscope(d->backbuf, d->op, cr, width, height, d->zoom, d);
      break;
    }
    default:
      break;
  }
 
  _process_restricted_text(d, cr, height);
 
  cairo_destroy(cr);
  dt_show_times_f(&start, "[histogram]", "redraw");
  return 0;
}
 
static void _destroy_surface(dt_lib_histogram_t *d)
{
  if(d->cst && cairo_surface_get_reference_count(d->cst) > 0) cairo_surface_destroy(d->cst);
  if(d->cst && cairo_surface_get_reference_count(d->cst) == 0) d->cst = NULL;
}
 
gboolean _trigger_recompute(dt_lib_histogram_t *d)
{
  int width, height;
  _get_allocation_size(d, &width, &height);
 
  if(_is_backbuf_ready(d) && _needs_recompute(d, width, height))
  {
    _destroy_surface(d);
    // If width and height have changed, we need to recreate the surface.
    // Recreate it anyway.
    d->cst = dt_cairo_image_surface_create(CAIRO_FORMAT_ARGB32, width, height);
    _redraw_surface(d);
    // Don't send gtk_queue_redraw event from here, catch the return value and do it in the calling function
    //fprintf(stdout, "recreate histograms\n");
    return 1;
  }
 
  return 0;
}
 
static const dt_dev_pixelpipe_iop_t *_get_backbuf_source_piece(const dt_backbuf_t *backbuf, const char *op)
{
  dt_develop_t *const dev = darktable.develop;
  dt_dev_pixelpipe_t *const pipe = dev ? dev->preview_pipe : NULL;
  if(IS_NULL_PTR(dev) || IS_NULL_PTR(pipe) || IS_NULL_PTR(op) || IS_NULL_PTR(backbuf)) return NULL;
 
  dt_iop_module_t *const module = dt_iop_get_module_by_op_priority(dev->iop, op, 0);
  if(IS_NULL_PTR(module)) return NULL;
 
  const dt_dev_pixelpipe_iop_t *piece = dt_dev_pixelpipe_get_module_piece(pipe, module);
  if(IS_NULL_PTR(piece)) return NULL;
 
  if(!strcmp(op, "gamma"))
    piece = dt_dev_pixelpipe_get_prev_enabled_piece(pipe, piece);
 
  if(IS_NULL_PTR(piece) || piece->global_hash != dt_dev_backbuf_get_hash(backbuf)) return NULL;
  return piece;
}
 
static gboolean _resolve_backbuf_sampling_source(const char *const op, const dt_backbuf_t *const backbuf,
                                                 dt_iop_roi_t *const roi, dt_iop_buffer_dsc_t *const dsc,
                                                 double *const iop_order, int *const direction)
{
  dt_develop_t *const dev = darktable.develop;
  dt_dev_pixelpipe_t *const pipe = dev ? dev->preview_pipe : NULL;
  if(IS_NULL_PTR(dev) || IS_NULL_PTR(pipe) || IS_NULL_PTR(op) || IS_NULL_PTR(backbuf) || IS_NULL_PTR(roi) || IS_NULL_PTR(dsc) || !iop_order || IS_NULL_PTR(direction)) return FALSE;
  /* Avoid taking `pipe->busy_mutex` on the GUI thread: read live module state
   * without blocking and let the cache peek manager handle synchronization. */
  dt_iop_module_t *const module = dt_iop_get_module_by_op_priority(dev->iop, op, 0);
  if(IS_NULL_PTR(module)) return FALSE;
 
  const dt_dev_pixelpipe_iop_t *const piece = dt_dev_pixelpipe_get_module_piece(pipe, module);
  if(IS_NULL_PTR(piece)) return FALSE;
 
  uint64_t hash = piece->global_hash;
  *roi = piece->roi_out;
  *dsc = piece->dsc_out;
  *iop_order = module->iop_order;
  *direction = DT_DEV_TRANSFORM_DIR_FORW_EXCL;
 
  if(!strcmp(op, "gamma"))
  {
    const dt_dev_pixelpipe_iop_t *const previous_piece = dt_dev_pixelpipe_get_prev_enabled_piece(pipe, piece);
    if(IS_NULL_PTR(previous_piece)) return FALSE;
 
    hash = previous_piece->global_hash;
    *roi = previous_piece->roi_out;
    *dsc = previous_piece->dsc_out;
    *direction = DT_DEV_TRANSFORM_DIR_FORW_INCL;
  }
 
  const gboolean valid = hash == dt_dev_backbuf_get_hash(backbuf);
  return valid;
}
 
static void _pixelpipe_pick_from_image(const dt_backbuf_t *const backbuf,
                                       dt_colorpicker_sample_t *const sample, dt_lib_histogram_t *d,
                                       const char *op)
{
  struct dt_pixel_cache_entry_t *entry = NULL;
  void *data = NULL;
  const dt_dev_pixelpipe_iop_t *const source_piece = _get_backbuf_source_piece(backbuf, op);
  if(IS_NULL_PTR(source_piece)) return;
  dt_dev_pixelpipe_cache_wait_set_owner(&d->picker_wait, "histogram-picker", d->module);
  if(!dt_dev_pixelpipe_cache_peek_gui(darktable.develop->preview_pipe, source_piece, &data, &entry,
                                      &d->picker_wait, _histogram_restart_cache_wait, d->module))
  {
    return;
  }
 
  dt_dev_pixelpipe_cache_rdlock_entry(darktable.pixelpipe_cache, TRUE, entry);
 
  const float *const pixel = data;
  dt_iop_buffer_dsc_t dsc = {
    .channels = 4,
    .datatype = TYPE_FLOAT,
    .bpp = 4 * sizeof(float),
    .cst = IOP_CS_RGB
  };
  dt_iop_roi_t roi = {
    .x = 0,
    .y = 0,
    .width = (int)backbuf->width,
    .height = (int)backbuf->height,
    .scale = 1.0
  };
  double iop_order = 0.0;
  int direction = DT_DEV_TRANSFORM_DIR_FORW_EXCL;
  const gboolean have_live_stage = _resolve_backbuf_sampling_source(op, backbuf, &roi, &dsc, &iop_order, &direction);
  int box[4];
 
  if(have_live_stage)
  {
    dt_boundingbox_t fbox = { 0.0f };
 
    if(sample->size == DT_LIB_COLORPICKER_SIZE_BOX)
    {
      _sample_raw_box_to_image_norm(sample, fbox);
      dt_dev_coordinates_image_norm_to_preview_abs(darktable.develop, fbox, 2);
    }
    else if(sample->size == DT_LIB_COLORPICKER_SIZE_POINT)
    {
      _sample_raw_point_to_image_norm(sample, fbox);
      dt_dev_coordinates_image_norm_to_preview_abs(darktable.develop, fbox, 1);
      fbox[2] = fbox[0];
      fbox[3] = fbox[1];
    }
 
    dt_dev_distort_backtransform_plus(darktable.develop->preview_pipe, iop_order,
                                      direction, fbox, 2);
 
    /* The backtransform returns stage coordinates in the sampled piece space. Shift them by the
       stage ROI before clamping so the picker box matches the published cache window exactly. */
    fbox[0] -= roi.x;
    fbox[1] -= roi.y;
    fbox[2] -= roi.x;
    fbox[3] -= roi.y;
 
    box[0] = fminf(fbox[0], fbox[2]);
    box[1] = fminf(fbox[1], fbox[3]);
    box[2] = fmaxf(fbox[0], fbox[2]);
    box[3] = fmaxf(fbox[1], fbox[3]);
 
    if(sample->size == DT_LIB_COLORPICKER_SIZE_POINT)
    {
      box[2] += 1;
      box[3] += 1;
    }
 
    box[0] = MIN(roi.width - 1, MAX(0, box[0]));
    box[1] = MIN(roi.height - 1, MAX(0, box[1]));
    box[2] = MIN(roi.width - 1, MAX(0, box[2]));
    box[3] = MIN(roi.height - 1, MAX(0, box[3]));
  }
  else
  {
    dt_dev_pixelpipe_cache_rdlock_entry(darktable.pixelpipe_cache, FALSE, entry);
    return;
  }
 
  dt_aligned_pixel_t mean = { 0.0f };
  dt_aligned_pixel_t min = { INFINITY, INFINITY, INFINITY, INFINITY };
  dt_aligned_pixel_t max = { -INFINITY, -INFINITY, -INFINITY, -INFINITY };
 
  dt_color_picker_helper(&dsc, pixel, &roi, box, mean, min, max, dsc.cst, IOP_CS_RGB, NULL);
 
  for_four_channels(k)
  {
    sample->scope[DT_LIB_COLORPICKER_STATISTIC_MEAN][k] = mean[k];
    sample->scope[DT_LIB_COLORPICKER_STATISTIC_MIN][k] = min[k];
    sample->scope[DT_LIB_COLORPICKER_STATISTIC_MAX][k] = max[k];
  }
 
  dt_lib_histogram_t scope = *d;
  scope.op = op;
 
  for(dt_lib_colorpicker_statistic_t k = 0; k < DT_LIB_COLORPICKER_STATISTIC_N; k++)
  {
    _scope_pixel_to_display_rgb(sample->scope[k], sample->display[k], &scope);
 
    dt_aligned_pixel_t XYZ = { 0.f };
    _scope_pixel_to_xyz(sample->scope[k], XYZ, &scope);
    dt_XYZ_to_Lab(XYZ, sample->lab[k]);
  }
 
  dt_dev_pixelpipe_cache_rdlock_entry(darktable.pixelpipe_cache, FALSE, entry);
}
 
static void _pixelpipe_pick_samples(dt_lib_histogram_t *d)
{
  GSList *samples = darktable.develop->color_picker.samples;
  while(samples)
  {
    dt_colorpicker_sample_t *sample = samples->data;
    if(!sample->locked)
    {
      const char *const op = sample->backbuf_op[0] ? sample->backbuf_op : d->op;
      dt_backbuf_t *const backbuf = _get_histogram_backbuf(darktable.develop, op);
      if(backbuf) _pixelpipe_pick_from_image(backbuf, sample, d, op);
    }
    samples = g_slist_next(samples);
  }
 
  if(darktable.develop->color_picker.picker)
    _pixelpipe_pick_from_image(d->backbuf, darktable.develop->color_picker.primary_sample, d, d->op);
}
 
 
static void _update_everything(dt_lib_module_t *self)
{
  dt_lib_histogram_t *d = (dt_lib_histogram_t *)self->data;
 
  if(_trigger_recompute(d))
  {
    _redraw_scopes(d);
  }
 
  _pixelpipe_pick_samples(d);
 
  for(GSList *samples = darktable.develop->color_picker.samples;
      samples;
      samples = g_slist_next(samples))
  {
    _update_sample_label(self, samples->data);
  }
 
  _update_sample_label(self, darktable.develop->color_picker.primary_sample);
 
  // allow live sample button to work for iop samples
  gtk_widget_set_sensitive(GTK_WIDGET(d->add_sample_button),
                           !IS_NULL_PTR(darktable.develop->color_picker.picker));
}
 
static gboolean _refresh_global_picker(dt_lib_module_t *self)
{
  if(IS_NULL_PTR(self) || IS_NULL_PTR(self->data)) return FALSE;
 
  dt_lib_histogram_t *d = (dt_lib_histogram_t *)self->data;
  d->backbuf = _get_histogram_backbuf(darktable.develop, d->op);
 
  if(!_is_backbuf_ready(d)) return FALSE;
 
  /* In restricted mode the scope bins only picker rectangles/points. Moving the
   * global picker does not change the preview cache hash, so invalidate the
   * Cairo scope cache explicitly before recomputing from the same backbuffer. */
  if(dt_conf_get_bool("ui_last/colorpicker_restrict_histogram"))
    _reset_cache(d);
 
  _update_everything(self);
  return TRUE;
}
 
 
static void _lib_histogram_history_resync_callback(gpointer instance, dt_lib_module_t *self)
{
  (void)instance;
  _sync_pending_histogram_hashes(self);
}
 
static void _lib_histogram_cacheline_ready_callback(gpointer instance, const guint64 hash,
                                                    const guint64 producer_node_key, dt_lib_module_t *self)
{
  (void)instance;
  (void)producer_node_key;
  dt_lib_histogram_t *d = (dt_lib_histogram_t *)self->data;
  if(IS_NULL_PTR(d) || !_remove_pending_hash(d, hash)) return;
 
  _schedule_histogram_refresh(self);
}
 
// this is only called in darkroom view when history was resynchronized
void view_enter(struct dt_lib_module_t *self, struct dt_view_t *old_view, struct dt_view_t *new_view)
{
  dt_lib_histogram_t *d = self->data;
  _reset_cache(d);
 
  DT_DEBUG_CONTROL_SIGNAL_CONNECT(darktable.signals, DT_SIGNAL_HISTORY_RESYNC,
                                  G_CALLBACK(_preview_history_resync_callback), NULL);
  DT_DEBUG_CONTROL_SIGNAL_CONNECT(darktable.signals, DT_SIGNAL_CACHELINE_READY,
                                  G_CALLBACK(_preview_cacheline_ready_callback), NULL);
  DT_DEBUG_CONTROL_SIGNAL_CONNECT(darktable.signals, DT_SIGNAL_HISTORY_RESYNC,
                                  G_CALLBACK(_lib_histogram_history_resync_callback), self);
  DT_DEBUG_CONTROL_SIGNAL_CONNECT(darktable.signals, DT_SIGNAL_CACHELINE_READY,
                                  G_CALLBACK(_lib_histogram_cacheline_ready_callback), self);
}
 
void view_leave(struct dt_lib_module_t *self, struct dt_view_t *old_view, struct dt_view_t *new_view)
{
  dt_lib_histogram_t *d = self->data;
  _reset_cache(d);
  dt_dev_pixelpipe_cache_wait_cleanup(&d->scope_wait, "histogram-view-leave-scope");
  dt_dev_pixelpipe_cache_wait_cleanup(&d->picker_wait, "histogram-view-leave-picker");
  dt_dev_pixelpipe_cache_wait_cleanup(&d->module_wait, "histogram-view-leave-module");
 
  _clear_pending_preview_histograms();
  _clear_pending_hashes(d);
  if(d->refresh_idle_source != 0)
  {
    g_source_remove(d->refresh_idle_source);
    d->refresh_idle_source = 0;
  }
 
  DT_DEBUG_CONTROL_SIGNAL_DISCONNECT(darktable.signals, G_CALLBACK(_preview_history_resync_callback), NULL);
  DT_DEBUG_CONTROL_SIGNAL_DISCONNECT(darktable.signals, G_CALLBACK(_preview_cacheline_ready_callback), NULL);
  DT_DEBUG_CONTROL_SIGNAL_DISCONNECT(darktable.signals, G_CALLBACK(_lib_histogram_history_resync_callback), self);
  DT_DEBUG_CONTROL_SIGNAL_DISCONNECT(darktable.signals, G_CALLBACK(_lib_histogram_cacheline_ready_callback), self);
}
 
 
static void _set_stage(dt_lib_module_t *self, int value)
{
  dt_lib_histogram_t *d = (dt_lib_histogram_t *)self->data;
  _backbuf_int_to_op(value, d);
  dt_conf_set_string("plugin/darkroom/histogram/op", d->op);
 
  // Vectorscope is meaningless for raw Bayer data
  if(!strcmp(d->op, "initialscale") && d->scope == DT_LIB_HISTOGRAM_SCOPE_VECTORSCOPE)
  {
    d->scope = DT_LIB_HISTOGRAM_SCOPE_HISTOGRAM;
    dt_conf_set_int("plugin/darkroom/histogram/display", d->scope);
  }
 
  _refresh_preview_histograms(darktable.develop);
  _sync_pending_histogram_hashes(self);
}
 
static void _set_scope(dt_lib_module_t *self, dt_lib_histogram_scope_type_t scope)
{
  dt_lib_histogram_t *d = (dt_lib_histogram_t *)self->data;
  d->scope = scope;
  dt_conf_set_int("plugin/darkroom/histogram/display", d->scope);
  if(_trigger_recompute(d)) _redraw_scopes(d);
}
 
 
static void _resize_callback(GtkWidget *widget, GdkRectangle *allocation, dt_lib_histogram_t *d)
{
  _reset_cache(d);
  _trigger_recompute(d);
  // Don't start a redraw from here, Gtk does it automatically on resize event
}
 
static gboolean _area_scrolled_callback(GtkWidget *widget, GdkEventScroll *event, dt_lib_histogram_t *d)
{
  if(d->scope != DT_LIB_HISTOGRAM_SCOPE_VECTORSCOPE) return FALSE;
 
  int delta_y = 0;
  if(!dt_gui_get_scroll_unit_deltas(event, NULL, &delta_y)) return TRUE;
 
  const float new_value = 4.f * delta_y + d->zoom;
 
  if(new_value < 512.f && new_value > 32.f)
  {
    d->zoom = new_value;
    dt_conf_set_float("plugin/darkroom/histogram/zoom", new_value);
    if(_is_backbuf_ready(d))
    {
      _redraw_surface(d);
      _redraw_scopes(d);
    }
  }
  return TRUE;
}
 
static int _scope_resize_handle_get_size(gpointer user_data)
{
  dt_lib_histogram_t *d = (dt_lib_histogram_t *)user_data;
  return gtk_widget_get_allocated_height(d->scope_draw);
}
 
static int _scope_resize_handle_resize(int requested_size, gboolean finished, gpointer user_data)
{
  dt_lib_histogram_t *d = (dt_lib_histogram_t *)user_data;
  int window_height;
  gtk_window_get_size(GTK_WINDOW(dt_ui_main_window(darktable.gui->ui)), NULL, &window_height);
 
  const int min_height = DT_PIXEL_APPLY_DPI(DT_LIB_HISTOGRAM_SCOPE_MIN_HEIGHT);
  const int max_height = MAX(min_height, MIN(DT_PIXEL_APPLY_DPI(DT_LIB_HISTOGRAM_SCOPE_MAX_HEIGHT),
                                            window_height * 3 / 4));
  d->scope_height = CLAMP(requested_size, min_height, max_height);
 
  gtk_widget_set_size_request(d->scope_draw, -1, d->scope_height);
  gtk_widget_queue_resize(d->scope_draw);
  if(finished)
    dt_conf_set_int(DT_LIB_HISTOGRAM_SCOPE_HEIGHT_CONF, d->scope_height);
 
  return d->scope_height;
}
 
void _set_params(dt_lib_histogram_t *d)
{
  d->op = dt_conf_get_string_const("plugin/darkroom/histogram/op");
  if(!strcmp(d->op, "demosaic"))
  {
    d->op = "initialscale";
    dt_conf_set_string("plugin/darkroom/histogram/op", d->op);
  }
  d->backbuf = _get_histogram_backbuf(darktable.develop, d->op);
  d->zoom = fminf(fmaxf(dt_conf_get_float("plugin/darkroom/histogram/zoom"), 32.f), 252.f);
 
  d->scope = (dt_lib_histogram_scope_type_t)CLAMP(
      dt_conf_get_int("plugin/darkroom/histogram/display"), 0, DT_LIB_HISTOGRAM_SCOPE_N - 1);
 
  // Vectorscope is not valid on raw Bayer data; fall back to histogram
  if(!strcmp(d->op, "initialscale") && d->scope == DT_LIB_HISTOGRAM_SCOPE_VECTORSCOPE)
    d->scope = DT_LIB_HISTOGRAM_SCOPE_HISTOGRAM;
}
 
 
static gboolean _sample_draw_callback(GtkWidget *widget, cairo_t *cr, dt_colorpicker_sample_t *sample)
{
  const guint width = gtk_widget_get_allocated_width(widget);
  const guint height = gtk_widget_get_allocated_height(widget);
 
  set_color(cr, sample->swatch);
  cairo_rectangle(cr, 0, 0, width, height);
  cairo_fill (cr);
 
  // if the sample is locked we want to add a lock
  if(sample->locked)
  {
    const int border = DT_PIXEL_APPLY_DPI(2);
    const int icon_width = width - 2 * border;
    const int icon_height = height - 2 * border;
    if(icon_width > 0 && icon_height > 0)
    {
      GdkRGBA fg_color;
      gtk_style_context_get_color(gtk_widget_get_style_context(widget), gtk_widget_get_state_flags(widget), &fg_color);
 
      gdk_cairo_set_source_rgba(cr, &fg_color);
      dtgtk_cairo_paint_lock(cr, border, border, icon_width, icon_height, 0, NULL);
    }
  }
 
  return FALSE;
}
 
static void _update_sample_label(dt_lib_module_t *self, dt_colorpicker_sample_t *sample)
{
  dt_lib_histogram_t *d = self->data;
  const dt_lib_colorpicker_statistic_t statistic
      = (d->model == DT_LIB_COLORPICKER_MODEL_RGB) ? d->statistic : DT_LIB_COLORPICKER_STATISTIC_MEAN;
 
  sample->swatch.red   = sample->display[statistic][0];
  sample->swatch.green = sample->display[statistic][1];
  sample->swatch.blue  = sample->display[statistic][2];
  for_each_channel(ch)
    sample->label_rgb[ch]  = (int)roundf(sample->scope[statistic][ch] * 255.f);
 
  // Setting the output label
  char text[128] = { 0 };
  dt_aligned_pixel_t alt = { 0 };
 
  switch(d->model)
  {
    case DT_LIB_COLORPICKER_MODEL_RGB:
      snprintf(text, sizeof(text), "%6d %6d %6d", sample->label_rgb[0], sample->label_rgb[1], sample->label_rgb[2]);
      break;
 
    case DT_LIB_COLORPICKER_MODEL_LAB:
      snprintf(text, sizeof(text), "%6.02f %6.02f %6.02f",
               CLAMP(sample->lab[statistic][0], .0f, 100.0f), sample->lab[statistic][1], sample->lab[statistic][2]);
      break;
 
    case DT_LIB_COLORPICKER_MODEL_LCH:
      dt_Lab_2_LCH(sample->lab[statistic], alt);
      snprintf(text, sizeof(text), "%6.02f %6.02f %6.02f", CLAMP(alt[0], .0f, 100.0f), alt[1], alt[2] * 360.f);
      break;
 
    case DT_LIB_COLORPICKER_MODEL_HSL:
      dt_RGB_2_HSL(sample->scope[statistic], alt);
      snprintf(text, sizeof(text), "%6.02f %6.02f %6.02f", alt[0] * 360.f, alt[1] * 100.f, alt[2] * 100.f);
      break;
 
    case DT_LIB_COLORPICKER_MODEL_HSV:
      dt_RGB_2_HSV(sample->scope[statistic], alt);
      snprintf(text, sizeof(text), "%6.02f %6.02f %6.02f", alt[0] * 360.f, alt[1] * 100.f, alt[2] * 100.f);
      break;
 
    default:
    case DT_LIB_COLORPICKER_MODEL_NONE:
      snprintf(text, sizeof(text), "\342\227\216");
      break;
  }
 
  if(g_strcmp0(gtk_label_get_text(GTK_LABEL(sample->output_label)), text))
    gtk_label_set_text(GTK_LABEL(sample->output_label), text);
 
  gtk_widget_queue_draw(sample->color_patch);
}
 
static void _update_picker_output(dt_lib_module_t *self)
{
  _update_everything(self);
}
 
static void _picker_button_toggled(GtkToggleButton *button, dt_lib_histogram_t *d)
{
  const gboolean picker_active = gtk_toggle_button_get_active(button);
  gtk_widget_set_sensitive(GTK_WIDGET(d->add_sample_button), picker_active);
 
  const gboolean restrict_active = !IS_NULL_PTR(d->restrict_button)
      && gtk_toggle_button_get_active(GTK_TOGGLE_BUTTON(d->restrict_button));
  if(restrict_active)
  {
    /* The picker state is part of restricted-scope rendering but not of the
     * preview backbuffer hash. Invalidate on both activation and deactivation
     * so the same cached pixels are rebinned for the newly selected scope. */
    _reset_cache(d);
    if(_trigger_recompute(d)) _redraw_scopes(d);
  }
}
 
/* set sample area proxy impl */
 
static void _set_sample_box_area(dt_lib_module_t *self, const dt_boundingbox_t box)
{
  dt_lib_colorpicker_set_box_area(darktable.lib, box);
  dt_lib_histogram_t *d = self->data;
  if(dt_conf_get_bool("ui_last/colorpicker_restrict_histogram"))
    _reset_cache(d);
  _update_everything(self);
}
 
static void _set_sample_point(dt_lib_module_t *self, const float pos[2])
{
  dt_lib_colorpicker_set_point(darktable.lib, pos);
  dt_lib_histogram_t *d = self->data;
  if(dt_conf_get_bool("ui_last/colorpicker_restrict_histogram"))
    _reset_cache(d);
  _update_everything(self);
}
 
 
static gboolean _sample_tooltip_callback(GtkWidget *widget, gint x, gint y, gboolean keyboard_mode,
                                         GtkTooltip *tooltip, const dt_colorpicker_sample_t *sample)
{
  gchar **sample_parts = g_malloc0_n(14, sizeof(char*));
 
  sample_parts[3] = g_strdup_printf("%22s(0x%02X%02X%02X)\n<big><b>%14s</b></big>", " ",
                                    CLAMP(sample->label_rgb[0], 0, 255), CLAMP(sample->label_rgb[1], 0, 255),
                                    CLAMP(sample->label_rgb[2], 0, 255), _("RGB"));
  sample_parts[7] = g_strdup_printf("\n<big><b>%14s</b></big>", _("Lab"));
 
  for(int i = 0; i < DT_LIB_COLORPICKER_STATISTIC_N; i++)
  {
    sample_parts[i] = g_strdup_printf("<span background='#%02X%02X%02X'>%32s</span>",
                                      (int)roundf(CLAMP(sample->display[i][0], 0.f, 1.f) * 255.f),
                                      (int)roundf(CLAMP(sample->display[i][1], 0.f, 1.f) * 255.f),
                                      (int)roundf(CLAMP(sample->display[i][2], 0.f, 1.f) * 255.f), " ");
 
    sample_parts[i + 4] = g_strdup_printf("<span foreground='#FF7F7F'>%6d</span>  "
                                          "<span foreground='#7FFF7F'>%6d</span>  "
                                          "<span foreground='#7F7FFF'>%6d</span>  %s",
                                          (int)roundf(sample->scope[i][0] * 255.f),
                                          (int)roundf(sample->scope[i][1] * 255.f),
                                          (int)roundf(sample->scope[i][2] * 255.f),
                                          _(dt_lib_colorpicker_statistic_names[i]));
 
    sample_parts[i + 8] = g_strdup_printf("%6.02f  %6.02f  %6.02f  %s",
                                          sample->lab[i][0], sample->lab[i][1], sample->lab[i][2],
                                          _(dt_lib_colorpicker_statistic_names[i]));
  }
 
  dt_aligned_pixel_t color;
  dt_Lab_2_LCH(sample->lab[DT_LIB_COLORPICKER_STATISTIC_MEAN], color);
  sample_parts[11] = g_strdup_printf("\n<big><b>%14s</b></big>", _("color"));
  sample_parts[12] = g_strdup_printf("%6s", Lch_to_color_name(color));
 
  gchar *tooltip_text = g_strjoinv("\n", sample_parts);
  g_strfreev(sample_parts);
 
  gtk_tooltip_set_markup(tooltip, tooltip_text);
 
  dt_free(tooltip_text);
 
  return TRUE;
}
 
static void _statistic_changed(GtkWidget *widget, dt_lib_module_t *self)
{
  dt_lib_histogram_t *d = self->data;
  d->statistic = dt_bauhaus_combobox_get(widget);
  darktable.develop->color_picker.statistic = (int)d->statistic;
  dt_conf_set_string("ui_last/colorpicker_mode", dt_lib_colorpicker_statistic_names[d->statistic]);
  _update_everything(self);
}
 
static void _color_mode_changed(GtkWidget *widget, dt_lib_module_t *self)
{
  dt_lib_histogram_t *d = self->data;
  d->model = dt_bauhaus_combobox_get(widget);
  dt_conf_set_string("ui_last/colorpicker_model", dt_lib_colorpicker_model_names[d->model]);
  _update_everything(self);
}
 
static void _label_size_allocate_callback(GtkWidget *widget, GdkRectangle *allocation, gpointer user_data)
{
  gint label_width;
  gtk_label_set_attributes(GTK_LABEL(widget), NULL);
 
  PangoStretch stretch = PANGO_STRETCH_NORMAL;
 
  while(gtk_widget_get_preferred_width(widget, NULL, &label_width),
        label_width > allocation->width && stretch != PANGO_STRETCH_ULTRA_CONDENSED)
  {
    stretch--;
 
    PangoAttrList *attrlist = pango_attr_list_new();
    PangoAttribute *attr = pango_attr_stretch_new(stretch);
    pango_attr_list_insert(attrlist, attr);
    gtk_label_set_attributes(GTK_LABEL(widget), attrlist);
    pango_attr_list_unref(attrlist);
  }
}
 
static gboolean _sample_enter_callback(GtkWidget *widget, GdkEvent *event, dt_colorpicker_sample_t *sample)
{
  if(darktable.develop->color_picker.picker)
  {
    darktable.develop->color_picker.selected_sample = sample;
    dt_control_queue_redraw_center();
  }
 
  return FALSE;
}
 
static gboolean _sample_leave_callback(GtkWidget *widget, GdkEvent *event, gpointer data)
{
  if(event->crossing.detail == GDK_NOTIFY_INFERIOR) return FALSE;
 
  if(darktable.develop->color_picker.selected_sample)
  {
    darktable.develop->color_picker.selected_sample = NULL;
    dt_control_queue_redraw_center();
  }
 
  return FALSE;
}
 
static void _remove_sample(dt_colorpicker_sample_t *sample)
{
  gtk_widget_destroy(sample->container);
  darktable.develop->color_picker.samples
    = g_slist_remove(darktable.develop->color_picker.samples, (gpointer)sample);
  dt_free(sample);
}
 
static void _remove_sample_cb(GtkButton *widget, dt_colorpicker_sample_t *sample)
{
  dt_lib_module_t *self = darktable.develop->color_picker.histogram_module;
  dt_lib_histogram_t *d = self ? self->data : NULL;
  if(dt_conf_get_bool("ui_last/colorpicker_restrict_histogram") && !IS_NULL_PTR(d))
    _reset_cache(d);
 
  _remove_sample(sample);
  dt_control_queue_redraw_center();
  if(!IS_NULL_PTR(self))
    _update_everything(self);
}
 
static gboolean _live_sample_button(GtkWidget *widget, GdkEventButton *event, dt_colorpicker_sample_t *sample)
{
  if(event->button == 1)
  {
    sample->locked = !sample->locked;
    gtk_widget_queue_draw(widget);
  }
  else if(event->button == 3)
  {
    // copy to active picker
    dt_lib_module_t *self = darktable.develop->color_picker.histogram_module;
    dt_iop_color_picker_t *picker = darktable.develop->color_picker.picker;
 
    // no active picker, too much iffy GTK work to activate a default
    if(IS_NULL_PTR(picker)) return FALSE;
 
    if(sample->size == DT_LIB_COLORPICKER_SIZE_POINT)
    {
      float point[2] = { 0.0f };
      _sample_raw_point_to_image_norm(sample, point);
      _set_sample_point(self, point);
    }
    else if(sample->size == DT_LIB_COLORPICKER_SIZE_BOX)
    {
      dt_boundingbox_t box = { 0.0f };
      _sample_raw_box_to_image_norm(sample, box);
      _set_sample_box_area(self, box);
    }
    else
      return FALSE;
 
    dt_control_queue_redraw_center();
  }
  return FALSE;
}
 
static void _add_sample(GtkButton *widget, dt_lib_module_t *self)
{
  dt_lib_histogram_t *d = self->data;
 
  if(IS_NULL_PTR(darktable.develop->color_picker.picker))
    return;
 
  dt_colorpicker_sample_t *sample = (dt_colorpicker_sample_t *)malloc(sizeof(dt_colorpicker_sample_t));
  if(IS_NULL_PTR(sample)) return;
 
  memcpy(sample, darktable.develop->color_picker.primary_sample, sizeof(dt_colorpicker_sample_t));
  sample->locked = FALSE;
  g_strlcpy(sample->backbuf_op, d->op ? d->op : "", sizeof(sample->backbuf_op));
 
  sample->container = gtk_event_box_new();
  gtk_widget_add_events(sample->container, GDK_ENTER_NOTIFY_MASK | GDK_LEAVE_NOTIFY_MASK);
  g_signal_connect(G_OBJECT(sample->container), "enter-notify-event", G_CALLBACK(_sample_enter_callback), sample);
  g_signal_connect(G_OBJECT(sample->container), "leave-notify-event", G_CALLBACK(_sample_leave_callback), sample);
 
  GtkWidget *container = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, DT_GUI_BOX_SPACING);
  gtk_container_add(GTK_CONTAINER(sample->container), container);
 
  sample->color_patch = gtk_drawing_area_new();
  gtk_widget_add_events(sample->color_patch, GDK_BUTTON_PRESS_MASK);
  gtk_widget_set_tooltip_text(sample->color_patch, _("hover to highlight sample on canvas,\n"
                                                     "click to lock sample,\n"
                                                     "right-click to load sample area into active color picker"));
  g_signal_connect(G_OBJECT(sample->color_patch), "button-press-event", G_CALLBACK(_live_sample_button), sample);
  g_signal_connect(G_OBJECT(sample->color_patch), "draw", G_CALLBACK(_sample_draw_callback), sample);
 
  GtkWidget *color_patch_wrapper = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, DT_GUI_BOX_SPACING);
  gtk_widget_set_name(color_patch_wrapper, "live-sample");
  gtk_box_pack_start(GTK_BOX(color_patch_wrapper), sample->color_patch, TRUE, TRUE, 0);
  gtk_box_pack_start(GTK_BOX(container), color_patch_wrapper, TRUE, TRUE, 0);
 
  sample->output_label = gtk_label_new("");
  dt_gui_add_class(sample->output_label, "dt_monospace");
  gtk_label_set_ellipsize(GTK_LABEL(sample->output_label), PANGO_ELLIPSIZE_START);
  gtk_label_set_selectable(GTK_LABEL(sample->output_label), TRUE);
  gtk_widget_set_has_tooltip(sample->output_label, TRUE);
  g_signal_connect(G_OBJECT(sample->output_label), "query-tooltip", G_CALLBACK(_sample_tooltip_callback), sample);
  g_signal_connect(G_OBJECT(sample->output_label), "size-allocate", G_CALLBACK(_label_size_allocate_callback), sample);
  gtk_box_pack_start(GTK_BOX(container), sample->output_label, TRUE, TRUE, 0);
 
  GtkWidget *delete_button = dtgtk_togglebutton_new(dtgtk_cairo_paint_remove, 0, NULL);
  g_signal_connect(G_OBJECT(delete_button), "clicked", G_CALLBACK(_remove_sample_cb), sample);
  gtk_box_pack_start(GTK_BOX(container), delete_button, FALSE, FALSE, 0);
 
  gtk_box_pack_start(GTK_BOX(d->samples_container), sample->container, FALSE, FALSE, 0);
  gtk_widget_show_all(sample->container);
 
  darktable.develop->color_picker.samples
      = g_slist_append(darktable.develop->color_picker.samples, sample);
 
  // remove emphasis on primary sample from mouseover on this button
  darktable.develop->color_picker.selected_sample = NULL;
 
  // Updating the display
  if(dt_conf_get_bool("ui_last/colorpicker_restrict_histogram"))
    _reset_cache(d);
  _update_everything(self);
}
 
static void _display_samples_changed(GtkToggleButton *button, dt_lib_module_t *self)
{
  dt_conf_set_bool("ui_last/colorpicker_display_samples", gtk_toggle_button_get_active(button));
  darktable.develop->color_picker.display_samples = gtk_toggle_button_get_active(button);
  _update_everything(self);
  dt_control_queue_redraw_center();
}
 
static void _restrict_histogram_changed(GtkToggleButton *button, dt_lib_module_t *self)
{
  dt_lib_histogram_t *d = self->data;
  const gboolean restrict_active = gtk_toggle_button_get_active(button);
  const gboolean picker_active = !IS_NULL_PTR(d->picker_button)
      && gtk_toggle_button_get_active(GTK_TOGGLE_BUTTON(d->picker_button));
  dt_conf_set_bool("ui_last/colorpicker_restrict_histogram", restrict_active);
  darktable.develop->color_picker.restrict_histogram = restrict_active;
 
  if(picker_active)
  {
    /* Restrict toggling changes the scope bins between full-image and picker
     * geometry while the preview backbuffer hash stays identical. Make the
     * cached Cairo surface dirty so _update_everything() renders the new mode. */
    _reset_cache(d);
  }
  _update_everything(self);
}
 
void gui_reset(dt_lib_module_t *self)
{
  dt_lib_histogram_t *d = self->data;
  dt_colorpicker_sample_t *const primary_sample = darktable.develop->color_picker.primary_sample;
 
  dt_iop_color_picker_reset(NULL, FALSE);
 
  // Resetting the picked colors
  for(int i = 0; i < 3; i++)
  {
    for(int s = 0; s < DT_LIB_COLORPICKER_STATISTIC_N; s++)
    {
      primary_sample->display[s][i] = 0.f;
      primary_sample->scope[s][i] = 0.f;
      primary_sample->lab[s][i] = 0.f;
    }
    primary_sample->label_rgb[i] = 0;
  }
  primary_sample->swatch.red = primary_sample->swatch.green
    = primary_sample->swatch.blue = 0.0;
 
  _update_picker_output(self);
 
  // Removing any live samples
  while(darktable.develop->color_picker.samples)
    _remove_sample(darktable.develop->color_picker.samples->data);
 
  // Resetting GUI elements
  dt_bauhaus_combobox_set(d->statistic_selector, 0);
  dt_bauhaus_combobox_set(d->color_mode_selector, 0);
  if(gtk_toggle_button_get_active(GTK_TOGGLE_BUTTON(d->display_samples_check_box)))
    gtk_toggle_button_set_active(GTK_TOGGLE_BUTTON(d->display_samples_check_box), FALSE);
 
  _reset_cache(d);
  _set_params(d);
  _destroy_surface(d);
  _trigger_recompute(d);
 
  dt_dev_pixelpipe_update_history_preview(darktable.develop);
}
 
static void _pref_stage_toggled(GtkCheckMenuItem *item, gpointer user_data)
{
  if(!gtk_check_menu_item_get_active(item)) return;
  dt_lib_module_t *self = (dt_lib_module_t *)g_object_get_data(G_OBJECT(item), "self");
  _set_stage(self, GPOINTER_TO_INT(user_data));
}
 
static void _pref_display_toggled(GtkCheckMenuItem *item, gpointer user_data)
{
  if(!gtk_check_menu_item_get_active(item)) return;
  dt_lib_module_t *self = (dt_lib_module_t *)g_object_get_data(G_OBJECT(item), "self");
  _set_scope(self, (dt_lib_histogram_scope_type_t)GPOINTER_TO_INT(user_data));
}
 
void set_preferences(void *menu, dt_lib_module_t *self)
{
  dt_lib_histogram_t *d = (dt_lib_histogram_t *)self->data;
 
  // "Show data from" submenu
  GtkWidget *mi_stage = gtk_menu_item_new_with_label(_("Show data from"));
  GtkWidget *submenu_stage = gtk_menu_new();
  gtk_menu_item_set_submenu(GTK_MENU_ITEM(mi_stage), submenu_stage);
 
  const char *stage_labels[] = { N_("Raw image"), N_("Output color profile"), N_("Final display"), NULL };
  const int current_stage = _backbuf_op_to_int(d);
  GSList *stage_group = NULL;
  for(int i = 0; stage_labels[i]; i++)
  {
    GtkWidget *item = gtk_radio_menu_item_new_with_label(stage_group, _(stage_labels[i]));
    stage_group = gtk_radio_menu_item_get_group(GTK_RADIO_MENU_ITEM(item));
    if(i == current_stage) gtk_check_menu_item_set_active(GTK_CHECK_MENU_ITEM(item), TRUE);
    g_object_set_data(G_OBJECT(item), "self", self);
    g_signal_connect(G_OBJECT(item), "toggled", G_CALLBACK(_pref_stage_toggled), GINT_TO_POINTER(i));
    gtk_menu_shell_append(GTK_MENU_SHELL(submenu_stage), item);
  }
  gtk_widget_show_all(mi_stage);
  gtk_menu_shell_append(GTK_MENU_SHELL(menu), mi_stage);
 
  // "Display" submenu
  GtkWidget *mi_display = gtk_menu_item_new_with_label(_("Display"));
  GtkWidget *submenu_display = gtk_menu_new();
  gtk_menu_item_set_submenu(GTK_MENU_ITEM(mi_display), submenu_display);
 
  const char *display_labels[] = {
    N_("Histogram"), N_("Waveform (horizontal)"), N_("Waveform (vertical)"),
    N_("Parade (horizontal)"), N_("Parade (vertical)"), N_("Vectorscope"), NULL
  };
  const gboolean vectorscope_ok = strcmp(d->op, "initialscale");
  GSList *display_group = NULL;
  for(int i = 0; display_labels[i]; i++)
  {
    GtkWidget *item = gtk_radio_menu_item_new_with_label(display_group, _(display_labels[i]));
    display_group = gtk_radio_menu_item_get_group(GTK_RADIO_MENU_ITEM(item));
    if((dt_lib_histogram_scope_type_t)i == d->scope)
      gtk_check_menu_item_set_active(GTK_CHECK_MENU_ITEM(item), TRUE);
    if(i == DT_LIB_HISTOGRAM_SCOPE_VECTORSCOPE)
      gtk_widget_set_sensitive(item, vectorscope_ok);
    g_object_set_data(G_OBJECT(item), "self", self);
    g_signal_connect(G_OBJECT(item), "toggled", G_CALLBACK(_pref_display_toggled), GINT_TO_POINTER(i));
    gtk_menu_shell_append(GTK_MENU_SHELL(submenu_display), item);
  }
  gtk_widget_show_all(mi_display);
  gtk_menu_shell_append(GTK_MENU_SHELL(menu), mi_display);
}
 
void gui_init(dt_lib_module_t *self)
{
  /* initialize ui widgets */
  dt_lib_histogram_t *d = (dt_lib_histogram_t *)dt_pixelpipe_cache_alloc_align_cache(sizeof(dt_lib_histogram_t), 0);
  if(d) memset(d, 0, sizeof(dt_lib_histogram_t));
  self->data = (void *)d;
  d->module = self;
  d->cst = NULL;
  d->pending_hashes = g_array_new(FALSE, FALSE, sizeof(uint64_t));
  d->refresh_idle_source = 0;
 
  self->widget = gtk_box_new(GTK_ORIENTATION_VERTICAL, DT_GUI_BOX_SPACING);
  d->scope_draw = gtk_drawing_area_new();
  gtk_widget_add_events(GTK_WIDGET(d->scope_draw), darktable.gui->scroll_mask);
  d->scope_height = dt_conf_key_exists(DT_LIB_HISTOGRAM_SCOPE_HEIGHT_CONF)
      ? dt_conf_get_int(DT_LIB_HISTOGRAM_SCOPE_HEIGHT_CONF)
      : DT_PIXEL_APPLY_DPI(DT_LIB_HISTOGRAM_SCOPE_DEFAULT_HEIGHT);
  d->scope_height = CLAMP(d->scope_height,
                          DT_PIXEL_APPLY_DPI(DT_LIB_HISTOGRAM_SCOPE_MIN_HEIGHT),
                          DT_PIXEL_APPLY_DPI(DT_LIB_HISTOGRAM_SCOPE_MAX_HEIGHT));
  gtk_widget_set_size_request(d->scope_draw, -1, d->scope_height);
  g_signal_connect(G_OBJECT(d->scope_draw), "draw", G_CALLBACK(_draw_callback), d);
  g_signal_connect(G_OBJECT(d->scope_draw), "scroll-event", G_CALLBACK(_area_scrolled_callback), d);
  g_signal_connect(G_OBJECT(d->scope_draw), "size-allocate", G_CALLBACK(_resize_callback), d);
 
  // The grip floats on the scope's bottom edge (overlay) so it takes no layout space and leaves no
  // margin-like gap; invisible until hovered.
  GtkWidget *scope_overlay = gtk_overlay_new();
  gtk_container_add(GTK_CONTAINER(scope_overlay), d->scope_draw);
  gtk_box_pack_start(GTK_BOX(self->widget), scope_overlay, FALSE, FALSE, 0);
 
  d->scope_resize_handle = dt_bauhaus_resize_handle_new(GTK_ORIENTATION_VERTICAL, FALSE,
                                                        _("Drag to resize the scope vertically"),
                                                        _scope_resize_handle_get_size,
                                                        _scope_resize_handle_resize, d);
  gtk_overlay_add_overlay(GTK_OVERLAY(scope_overlay), d->scope_resize_handle);
 
  dt_gui_new_collapsible_section
      (&d->cs,
      "plugins/darkroom/colorpicker/show",
      _("Color picker"),
      GTK_BOX(self->widget), GTK_PACK_END);
 
  // The develop module owns the picker state because both the preview pipe and the GUI need to
  // observe it. Histogram only binds its widgets to that shared state.
  darktable.develop->color_picker.histogram_module = self;
  darktable.develop->color_picker.refresh_global_picker = _refresh_global_picker;
  darktable.develop->color_picker.display_samples = dt_conf_get_bool("ui_last/colorpicker_display_samples");
  darktable.develop->color_picker.restrict_histogram = dt_conf_get_bool("ui_last/colorpicker_restrict_histogram");
  darktable.develop->color_picker.primary_sample->swatch.alpha = 1.0;
 
  const char *str = dt_conf_get_string_const("ui_last/colorpicker_model");
  const char **names = dt_lib_colorpicker_model_names;
  for(dt_lib_colorpicker_model_t i=0; *names; names++, i++)
    if(g_strcmp0(str, *names) == 0)
      d->model = i;
 
  str = dt_conf_get_string_const("ui_last/colorpicker_mode");
  names = dt_lib_colorpicker_statistic_names;
  for(dt_lib_colorpicker_statistic_t i=0; *names; names++, i++)
    if(g_strcmp0(str, *names) == 0)
      d->statistic = i;
 
  // The color patch
  GtkWidget *color_patch_wrapper = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, DT_GUI_BOX_SPACING);
  gtk_widget_set_name(GTK_WIDGET(color_patch_wrapper), "color-picker-area");
 
  // The picker button, mode and statistic combo boxes
  GtkWidget *picker_row = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, DT_GUI_BOX_SPACING);
  gtk_box_pack_start(GTK_BOX(d->cs.container), picker_row, TRUE, TRUE, 0);
 
  d->statistic_selector = dt_bauhaus_combobox_new_full(
      darktable.bauhaus, NULL, NULL, _("select which statistic to show"), d->statistic,
      (GtkCallback)_statistic_changed, self, dt_lib_colorpicker_statistic_names);
  dt_bauhaus_combobox_set_entries_ellipsis(d->statistic_selector, PANGO_ELLIPSIZE_NONE);
  dt_bauhaus_widget_set_label(d->statistic_selector, NULL);
  gtk_widget_set_valign(d->statistic_selector, GTK_ALIGN_CENTER);
  gtk_box_pack_start(GTK_BOX(picker_row), d->statistic_selector, TRUE, TRUE, 0);
 
  d->color_mode_selector = dt_bauhaus_combobox_new_full(
      darktable.bauhaus, NULL, NULL, _("select which color mode to use"), d->model,
      (GtkCallback)_color_mode_changed, self, dt_lib_colorpicker_model_names);
  dt_bauhaus_combobox_set_entries_ellipsis(d->color_mode_selector, PANGO_ELLIPSIZE_NONE);
  dt_bauhaus_widget_set_label(d->color_mode_selector, NULL);
  gtk_widget_set_valign(d->color_mode_selector, GTK_ALIGN_CENTER);
  gtk_box_pack_start(GTK_BOX(picker_row), d->color_mode_selector, TRUE, TRUE, 0);
 
  d->picker_button = dt_color_picker_new(NULL, DT_COLOR_PICKER_POINT_AREA, picker_row);
  gtk_widget_set_tooltip_text(d->picker_button, _("turn on color picker\nctrl+click or right-click to select an area"));
  gtk_widget_set_name(GTK_WIDGET(d->picker_button), "color-picker-button");
  g_signal_connect(G_OBJECT(d->picker_button), "toggled", G_CALLBACK(_picker_button_toggled), d);
 
  // The small sample, label and add button
  GtkWidget *sample_row_events = gtk_event_box_new();
  gtk_widget_add_events(sample_row_events, GDK_ENTER_NOTIFY_MASK | GDK_LEAVE_NOTIFY_MASK);
  g_signal_connect(G_OBJECT(sample_row_events), "enter-notify-event", G_CALLBACK(_sample_enter_callback),
                   darktable.develop->color_picker.primary_sample);
  g_signal_connect(G_OBJECT(sample_row_events), "leave-notify-event", G_CALLBACK(_sample_leave_callback),
                   darktable.develop->color_picker.primary_sample);
  gtk_box_pack_start(GTK_BOX(d->cs.container), sample_row_events, TRUE, TRUE, 0);
 
  GtkWidget *sample_row = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, DT_GUI_BOX_SPACING);
  gtk_container_add(GTK_CONTAINER(sample_row_events), sample_row);
 
  darktable.develop->color_picker.primary_sample->color_patch = gtk_drawing_area_new();
  g_signal_connect(G_OBJECT(darktable.develop->color_picker.primary_sample->color_patch), "draw",
                   G_CALLBACK(_sample_draw_callback), darktable.develop->color_picker.primary_sample);
 
  color_patch_wrapper = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, DT_GUI_BOX_SPACING);
  gtk_widget_set_name(color_patch_wrapper, "live-sample");
  gtk_box_pack_start(GTK_BOX(color_patch_wrapper), darktable.develop->color_picker.primary_sample->color_patch, TRUE, TRUE, 0);
  gtk_box_pack_start(GTK_BOX(sample_row), color_patch_wrapper, TRUE, TRUE, 0);
 
  GtkWidget *label = darktable.develop->color_picker.primary_sample->output_label = gtk_label_new("");
  gtk_label_set_justify(GTK_LABEL(label), GTK_JUSTIFY_CENTER);
  gtk_label_set_ellipsize(GTK_LABEL(label), PANGO_ELLIPSIZE_START);
  gtk_label_set_selectable(GTK_LABEL(label), TRUE);
  dt_gui_add_class(label, "dt_monospace");
  gtk_widget_set_has_tooltip(label, TRUE);
  g_signal_connect(G_OBJECT(label), "query-tooltip", G_CALLBACK(_sample_tooltip_callback),
                   darktable.develop->color_picker.primary_sample);
  g_signal_connect(G_OBJECT(label), "size-allocate", G_CALLBACK(_label_size_allocate_callback),
                   darktable.develop->color_picker.primary_sample);
  gtk_box_pack_start(GTK_BOX(sample_row), label, TRUE, TRUE, 0);
 
  d->add_sample_button = dtgtk_button_new(dtgtk_cairo_paint_square_plus, 0, NULL);
  gtk_widget_set_sensitive(GTK_WIDGET(d->add_sample_button), FALSE);
  g_signal_connect(G_OBJECT(d->add_sample_button), "clicked", G_CALLBACK(_add_sample), self);
  gtk_box_pack_end(GTK_BOX(sample_row), d->add_sample_button, FALSE, FALSE, 0);
 
  // Adding the live samples section
  label = dt_ui_section_label_new(_("Live samples"));
  gtk_box_pack_start(GTK_BOX(d->cs.container), label, TRUE, TRUE, 0);
 
  d->samples_container = gtk_box_new(GTK_ORIENTATION_VERTICAL, DT_GUI_BOX_SPACING);
  gtk_box_pack_start(GTK_BOX(d->cs.container),
                     dt_ui_scroll_wrap(d->samples_container, 1, "plugins/darkroom/colorpicker/windowheight",
                                       DT_UI_RESIZE_DYNAMIC), TRUE, TRUE, 0);
 
  d->display_samples_check_box = gtk_check_button_new_with_label(_("Display samples on image"));
  gtk_label_set_ellipsize(GTK_LABEL(gtk_bin_get_child(GTK_BIN(d->display_samples_check_box))),
                          PANGO_ELLIPSIZE_MIDDLE);
  gtk_toggle_button_set_active(GTK_TOGGLE_BUTTON(d->display_samples_check_box),
                               dt_conf_get_bool("ui_last/colorpicker_display_samples"));
  g_signal_connect(G_OBJECT(d->display_samples_check_box), "toggled",
                   G_CALLBACK(_display_samples_changed), self);
  gtk_box_pack_start(GTK_BOX(d->cs.container), d->display_samples_check_box, TRUE, TRUE, 0);
 
  d->restrict_button = gtk_check_button_new_with_label(_("Restrict scope to selection"));
  gtk_label_set_ellipsize(GTK_LABEL(gtk_bin_get_child(GTK_BIN(d->restrict_button))), PANGO_ELLIPSIZE_MIDDLE);
  gboolean restrict_histogram = dt_conf_get_bool("ui_last/colorpicker_restrict_histogram");
  gtk_toggle_button_set_active(GTK_TOGGLE_BUTTON(d->restrict_button), restrict_histogram);
  g_signal_connect(G_OBJECT(d->restrict_button), "toggled", G_CALLBACK(_restrict_histogram_changed), self);
  gtk_box_pack_start(GTK_BOX(d->cs.container), d->restrict_button, TRUE, TRUE, 0);
 
  _reset_cache(d);
  _set_params(d);
}
 
void gui_cleanup(dt_lib_module_t *self)
{
  if(IS_NULL_PTR(self->data)) return;
  dt_lib_histogram_t *d = self->data;
  dt_dev_pixelpipe_cache_wait_cleanup(&d->scope_wait, "histogram-gui-cleanup-scope");
  dt_dev_pixelpipe_cache_wait_cleanup(&d->picker_wait, "histogram-gui-cleanup-picker");
  dt_dev_pixelpipe_cache_wait_cleanup(&d->module_wait, "histogram-gui-cleanup-module");
  _clear_pending_preview_histograms();
  _clear_pending_hashes(d);
  if(d->refresh_idle_source != 0)
  {
    g_source_remove(d->refresh_idle_source);
    d->refresh_idle_source = 0;
  }
  if(d->pending_hashes) g_array_free(d->pending_hashes, TRUE);
  _destroy_surface(d);
  dt_iop_color_picker_reset(NULL, FALSE);
 
  darktable.develop->color_picker.histogram_module = NULL;
  darktable.develop->color_picker.refresh_global_picker = NULL;
  while(darktable.develop->color_picker.samples)
    _remove_sample(darktable.develop->color_picker.samples->data);
 
  dt_pixelpipe_cache_free_align(self->data);
  self->data = NULL;
}
 
// 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