masks.h

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/*
    This file is part of darktable,
    Copyright (C) 2013-2021 darktable developers.
 
    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/>.
*/
 
#pragma once
 
#include "common/darktable.h"
#include "common/opencl.h"
#include "develop/pixelpipe.h"
#include "dtgtk/button.h"
#include "dtgtk/gradientslider.h"
#include "gui/draw.h"
#include "control/control.h"
 
#include <assert.h>
 
#ifdef __cplusplus
extern "C" {
#endif
 
#define DEVELOP_MASKS_VERSION (6)
 
typedef enum dt_masks_type_t
{
  DT_MASKS_NONE = 0, // keep first
  DT_MASKS_CIRCLE = 1 << 0,
  DT_MASKS_POLYGON = 1 << 1,
  DT_MASKS_GROUP = 1 << 2,
  DT_MASKS_CLONE = 1 << 3,
  DT_MASKS_GRADIENT = 1 << 4,
  DT_MASKS_ELLIPSE = 1 << 5,
  DT_MASKS_BRUSH = 1 << 6,
  DT_MASKS_NON_CLONE = 1 << 7
} dt_masks_type_t;
 
typedef enum dt_masks_state_t
{
  DT_MASKS_STATE_NONE = 0,
  DT_MASKS_STATE_USE = 1 << 0,
  DT_MASKS_STATE_SHOW = 1 << 1,
  DT_MASKS_STATE_INVERSE = 1 << 2,
  DT_MASKS_STATE_UNION = 1 << 3,
  DT_MASKS_STATE_INTERSECTION = 1 << 4,
  DT_MASKS_STATE_DIFFERENCE = 1 << 5,
  DT_MASKS_STATE_EXCLUSION = 1 << 6
} dt_masks_state_t;
 
typedef enum dt_masks_points_states_t
{
  DT_MASKS_POINT_STATE_NORMAL = 1,
  DT_MASKS_POINT_STATE_USER = 2
} dt_masks_points_states_t;
 
typedef enum dt_masks_gradient_states_t
{
  DT_MASKS_GRADIENT_STATE_LINEAR = 1,
  DT_MASKS_GRADIENT_STATE_SIGMOIDAL = 2
} dt_masks_gradient_states_t;
 
typedef enum dt_masks_increment_t
{
  DT_MASKS_INCREMENT_ABSOLUTE = 0,
  DT_MASKS_INCREMENT_SCALE = 1,
  DT_MASKS_INCREMENT_OFFSET = 2
} dt_masks_increment_t;
 
typedef enum dt_masks_edit_mode_t
{
  DT_MASKS_EDIT_OFF = 0,
  DT_MASKS_EDIT_FULL = 1,
  DT_MASKS_EDIT_RESTRICTED = 2
} dt_masks_edit_mode_t;
 
typedef enum dt_masks_pressure_sensitivity_t
{
  DT_MASKS_PRESSURE_OFF = 0,
  DT_MASKS_PRESSURE_HARDNESS_REL = 1,
  DT_MASKS_PRESSURE_HARDNESS_ABS = 2,
  DT_MASKS_PRESSURE_OPACITY_REL = 3,
  DT_MASKS_PRESSURE_OPACITY_ABS = 4,
  DT_MASKS_PRESSURE_BRUSHSIZE_REL = 5
} dt_masks_pressure_sensitivity_t;
 
typedef enum dt_masks_ellipse_flags_t
{
  DT_MASKS_ELLIPSE_EQUIDISTANT = 0,
  DT_MASKS_ELLIPSE_PROPORTIONAL = 1
} dt_masks_ellipse_flags_t;
 
typedef enum dt_masks_source_pos_type_t
{
  DT_MASKS_SOURCE_POS_RELATIVE = 0,
  DT_MASKS_SOURCE_POS_RELATIVE_TEMP = 1,
  DT_MASKS_SOURCE_POS_ABSOLUTE = 2
} dt_masks_source_pos_type_t;
 
typedef struct dt_masks_node_circle_t
{
  float center[2]; // point in normalized input space
  float radius;
  float border;
} dt_masks_node_circle_t;
 
typedef struct dt_masks_node_ellipse_t
{
  float center[2];
  float radius[2];
  float rotation;
  float border;
  dt_masks_ellipse_flags_t flags;
} dt_masks_node_ellipse_t;
 
typedef struct dt_masks_node_polygon_t
{
  float node[2];
  float ctrl1[2];
  float ctrl2[2];
  float border[2];
  dt_masks_points_states_t state;
} dt_masks_node_polygon_t;
 
typedef struct dt_masks_node_brush_t
{
  float node[2];
  float ctrl1[2];
  float ctrl2[2];
  float border[2];
  float density;
  float hardness;
  dt_masks_points_states_t state;
} dt_masks_node_brush_t;
 
typedef struct dt_masks_anchor_gradient_t
{
  float center[2];
  float rotation;
  float extent;
  float steepness;
  float curvature;
  dt_masks_gradient_states_t state;
} dt_masks_anchor_gradient_t;
 
typedef struct dt_masks_form_group_t
{
  int formid;
  int parentid;
  int state;
  float opacity;
} dt_masks_form_group_t;
 
 
/*
* Type of user interaction to map with internal properties of masks.
* Those were initially handled implicitly by Shift/Ctrl/Shift+Ctrl + mouse scroll
* at the scope of each mask type, which is a shitty design when using Wacom tablets.
* This case is now covered by the DT_MASK_INTERACTION_UNDEF.
* Otherwise, when calling the mouse_scroll callback from GUI, we set the case
* explicitly, along with a value.
*/
typedef enum dt_masks_interaction_t
{
  DT_MASKS_INTERACTION_UNDEF = 0,    // let it be deduced contextually from key modifiers, implicit
  DT_MASKS_INTERACTION_SIZE = 1,     // property of the form (shape), explicit
  DT_MASKS_INTERACTION_HARDNESS = 2, // property of the form (shape), explicit
  DT_MASKS_INTERACTION_OPACITY = 3,  // property of the group in which the form is included, explicit
  DT_MASKS_INTERACTION_LAST
} dt_masks_interaction_t;
 
typedef struct dt_masks_functions_t
{
  int point_struct_size;   // sizeof(struct dt_masks_point_*_t)
  void (*sanitize_config)(dt_masks_type_t type_flags);
  void (*set_form_name)(struct dt_masks_form_t *const form, const size_t nb);
  void (*set_hint_message)(const struct dt_masks_form_gui_t *const gui, const struct dt_masks_form_t *const form,
                           const int opacity, char *const __restrict__ msgbuf, const size_t msgbuf_len);
  void (*duplicate_points)(struct dt_develop_t *const dev, struct dt_masks_form_t *base, struct dt_masks_form_t *dest);
  void (*initial_source_pos)(const float iwd, const float iht, float *x, float *y);
  void (*get_distance)(float x, float y, float as, struct dt_masks_form_gui_t *gui, int index, int num_points,
                       int *inside, int *inside_border, int *near, int *inside_source, float *dist);
  int (*get_points)(dt_develop_t *dev, float x, float y, float radius_a, float radius_b, float rotation,
                    float **points, int *points_count);
  int (*get_points_border)(dt_develop_t *dev, struct dt_masks_form_t *form, float **points, int *points_count,
                           float **border, int *border_count, int source, const dt_iop_module_t *const module);
  int (*get_mask)(const dt_iop_module_t *const module, const dt_dev_pixelpipe_iop_t *const piece,
                  struct dt_masks_form_t *const form,
                  float **buffer, int *width, int *height, int *posx, int *posy);
  int (*get_mask_roi)(const dt_iop_module_t *const fmodule, const dt_dev_pixelpipe_iop_t *const piece,
                      struct dt_masks_form_t *const form,
                      const dt_iop_roi_t *roi, float *buffer);
  int (*get_area)(const dt_iop_module_t *const module, const dt_dev_pixelpipe_iop_t *const piece,
                  struct dt_masks_form_t *const form,
                  int *width, int *height, int *posx, int *posy);
  int (*get_source_area)(dt_iop_module_t *module, dt_dev_pixelpipe_iop_t *piece, struct dt_masks_form_t *form,
                         int *width, int *height, int *posx, int *posy);
  /* Mouse pzx and pzy are normalized coordinates in full image space */
  int (*mouse_moved)(struct dt_iop_module_t *module, float pzx, float pzy, double pressure, int which,
                     struct dt_masks_form_t *form, int parentid, struct dt_masks_form_gui_t *gui, int index);
  /* Mouse pzx and pzy are normalized coordinates in full image space */
  int (*mouse_scrolled)(struct dt_iop_module_t *module, float pzx, float pzy, int up, const int delta_y, uint32_t state,
                        struct dt_masks_form_t *form, int parentid, struct dt_masks_form_gui_t *gui, int index,
                        dt_masks_interaction_t interaction);
  /* Mouse pzx and pzy are normalized coordinates in full image space */
  int (*button_pressed)(struct dt_iop_module_t *module, float pzx, float pzy,
                        double pressure, int which, int type, uint32_t state,
                        struct dt_masks_form_t *form, int parentid, struct dt_masks_form_gui_t *gui, int index);
  /* Mouse pzx and pzy are normalized coordinates in full image space */
  int (*button_released)(struct dt_iop_module_t *module, float pzx, float pzy, int which, uint32_t state,
                         struct dt_masks_form_t *form, int parentid, struct dt_masks_form_gui_t *gui, int index);
  void (*post_expose)(cairo_t *cr, float zoom_scale, struct dt_masks_form_gui_t *gui, int index, int num_points);
  // The function to draw the shape in question
  void (*draw_shape)(cairo_t *cr, const float *points, const int points_count, const int nb, const gboolean border, const gboolean source);
  void (*init_ctrl_points)(struct dt_masks_form_t *form);
} dt_masks_functions_t;
 
typedef struct dt_masks_form_t
{
  GList *points; // list of point structures (nodes)
  dt_masks_type_t type;
  const dt_masks_functions_t *functions;
 
  // position of the origin point of source (used only for clone)
  float source[2];
  // name of the form
  char name[128];
  // id used to store the form
  int formid;
  // version of the form
  int version;
} dt_masks_form_t;
 
typedef struct dt_masks_form_gui_points_t
{
  float *points;   // points in anormalized out space
  int points_count;
  float *border;   // border points in anormalized out space
  int border_count;
  float *source;   // source point in anormalized out space
  int source_count;
  gboolean clockwise;
} dt_masks_form_gui_points_t;
 
typedef struct dt_masks_dynbuf_t
{
  float *buffer;
  char tag[128];
  size_t pos;
  size_t size;
} dt_masks_dynbuf_t;
 
 
typedef struct dt_masks_form_gui_t
{
  // points used to draw the form
  GList *points; // list of dt_masks_form_gui_points_t 
 
  // points used to sample mouse moves
  dt_masks_dynbuf_t *guipoints, *guipoints_payload;
  int guipoints_count;
 
  // values for mouse positions, etc...
 
  // Mouse position (in anormalized out space)
  float pos[2];
  // delta movement of the mouse (in anormalized out space)
  float delta[2];
  // scroll offset
  float scrollx, scrolly;
  // Position of a clone mask's source point
  float pos_source[2];
 
  // TRUE if mouse has leaved the center window
  gboolean mouse_leaved_center;
  gboolean form_selected;
  gboolean border_selected;
  gboolean source_selected;
  gboolean pivot_selected;
  dt_masks_edit_mode_t edit_mode;
  int node_selected;
  int node_edited;
  int handle_selected;
  int seg_selected;
  int handle_border_selected;
  int source_pos_type;
 
  gboolean form_dragging;
  gboolean source_dragging;
  gboolean form_rotating;
  gboolean border_toggling;
  gboolean gradient_toggling;
  int node_dragging;
  int handle_dragging;
  int seg_dragging;
  int handle_border_dragging;
 
  int group_selected;
 
 
  gboolean creation;
  gboolean creation_closing_form;
  dt_iop_module_t *creation_module;
 
  dt_masks_pressure_sensitivity_t pressure_sensitivity;
 
  // ids
  int formid;
  uint64_t pipe_hash;
} dt_masks_form_gui_t;
 
extern const dt_masks_functions_t dt_masks_functions_circle;
extern const dt_masks_functions_t dt_masks_functions_ellipse;
extern const dt_masks_functions_t dt_masks_functions_brush;
extern const dt_masks_functions_t dt_masks_functions_polygon;
extern const dt_masks_functions_t dt_masks_functions_gradient;
extern const dt_masks_functions_t dt_masks_functions_group;
 
void dt_masks_init_form_gui(dt_masks_form_gui_t *gui);
 
int dt_masks_get_points_border(dt_develop_t *dev, dt_masks_form_t *form, float **points, int *points_count,
                               float **border, int *border_count, int source, dt_iop_module_t *module);
 
int dt_masks_get_area(dt_iop_module_t *module, dt_dev_pixelpipe_iop_t *piece, dt_masks_form_t *form,
                      int *width, int *height, int *posx, int *posy);
int dt_masks_get_source_area(dt_iop_module_t *module, dt_dev_pixelpipe_iop_t *piece, dt_masks_form_t *form,
                             int *width, int *height, int *posx, int *posy);
static inline int dt_masks_get_mask(const dt_iop_module_t *const module, const dt_dev_pixelpipe_iop_t *const piece,
                      dt_masks_form_t *const form,
                      float **buffer, int *width, int *height, int *posx, int *posy)
{
  return form->functions ? form->functions->get_mask(module, piece, form, buffer, width, height, posx, posy) : 0;
}
static inline int dt_masks_get_mask_roi(const dt_iop_module_t *const module, const dt_dev_pixelpipe_iop_t *const piece,
                          dt_masks_form_t *const form, const dt_iop_roi_t *roi, float *buffer)
{
  return form->functions ? form->functions->get_mask_roi(module, piece, form, roi, buffer) : 0;
}
 
int dt_masks_group_render_roi(dt_iop_module_t *module, dt_dev_pixelpipe_iop_t *piece, dt_masks_form_t *form,
                              const dt_iop_roi_t *roi, float *buffer);
 
// returns current masks version
int dt_masks_version(void);
 
void dt_masks_append_form(dt_develop_t *dev, dt_masks_form_t *form);
void dt_masks_remove_form(dt_develop_t *dev, dt_masks_form_t *form);
 
// update masks from older versions
int dt_masks_legacy_params(dt_develop_t *dev, void *params, const int old_version, const int new_version);
/*
 * TODO:
 *
 * int
 * dt_masks_legacy_params(
 *   dt_develop_t *dev,
 *   const void *const old_params, const int old_version,
 *   void *new_params,             const int new_version);
 */
 
dt_masks_form_t *dt_masks_create(dt_masks_type_t type);
dt_masks_form_t *dt_masks_create_ext(dt_masks_type_t type);
void dt_masks_replace_current_forms(dt_develop_t *dev, GList *forms);
dt_masks_form_t *dt_masks_get_from_id_ext(GList *forms, int id);
dt_masks_form_t *dt_masks_get_from_id(dt_develop_t *dev, int id);
 
void dt_masks_read_masks_history(dt_develop_t *dev, const int32_t imgid);
void dt_masks_write_masks_history_item(const int32_t imgid, const int num, dt_masks_form_t *form);
void dt_masks_free_form(dt_masks_form_t *form);
void dt_masks_cleanup_unused(dt_develop_t *dev);
 
void dt_masks_change_form_gui(dt_masks_form_t *newform);
void dt_masks_clear_form_gui(dt_develop_t *dev);
void dt_masks_reset_form_gui(void);
void dt_masks_soft_reset_form_gui(dt_masks_form_gui_t *gui);
void dt_masks_reset_show_masks_icons(void);
 
int dt_masks_events_mouse_moved(struct dt_iop_module_t *module, double x, double y, double pressure,
                                int which);
int dt_masks_events_button_released(struct dt_iop_module_t *module, double x, double y, int which,
                                    uint32_t state);
int dt_masks_events_button_pressed(struct dt_iop_module_t *module, double x, double y, double pressure,
                                   int which, int type, uint32_t state);
int dt_masks_events_mouse_scrolled(struct dt_iop_module_t *module, double x, double y, int up, uint32_t state, int delta_y);
 
gboolean dt_masks_is_corner_node(const dt_masks_form_gui_points_t *gpt, const int index, const int nb, const int coord_offset);
 
void dt_masks_draw_source(cairo_t *cr, dt_masks_form_gui_t *gui, const int index, const int nb, 
  const float zoom_scale, const shape_draw_function_t *functions);
 
void dt_masks_events_post_expose(struct dt_iop_module_t *module, cairo_t *cr, int32_t width, int32_t height,
                                 int32_t pointerx, int32_t pointery);
int dt_masks_events_mouse_leave(struct dt_iop_module_t *module);
int dt_masks_events_mouse_enter(struct dt_iop_module_t *module);
 
void dt_masks_gui_form_create(dt_masks_form_t *form, dt_masks_form_gui_t *gui, int index,
                              struct dt_iop_module_t *module);
 
gboolean dt_masks_gui_delete(struct dt_iop_module_t *module, dt_masks_form_t *form, dt_masks_form_gui_t *gui, const int parentid);
 
void dt_masks_gui_form_remove(dt_masks_form_t *form, dt_masks_form_gui_t *gui, int index);
void dt_masks_gui_form_test_create(dt_masks_form_t *form, dt_masks_form_gui_t *gui, struct dt_iop_module_t *module);
void dt_masks_gui_form_save_creation(dt_develop_t *dev, struct dt_iop_module_t *module, dt_masks_form_t *form,
                                     dt_masks_form_gui_t *gui);
void dt_masks_group_ungroup(dt_masks_form_t *dest_grp, dt_masks_form_t *grp);
void dt_masks_group_update_name(dt_iop_module_t *module);
dt_masks_form_group_t *dt_masks_group_add_form(dt_masks_form_t *grp, dt_masks_form_t *form);
 
void dt_masks_iop_value_changed_callback(GtkWidget *widget, struct dt_iop_module_t *module);
dt_masks_edit_mode_t dt_masks_get_edit_mode(struct dt_iop_module_t *module);
void dt_masks_set_edit_mode(struct dt_iop_module_t *module, dt_masks_edit_mode_t value);
void dt_masks_iop_update(struct dt_iop_module_t *module);
void dt_masks_iop_combo_populate(GtkWidget *w, void *module);
void dt_masks_iop_use_same_as(struct dt_iop_module_t *module, struct dt_iop_module_t *src);
uint64_t dt_masks_group_get_hash(uint64_t hash, dt_masks_form_t *form);
 
void dt_masks_form_remove(struct dt_iop_module_t *module, dt_masks_form_t *grp, dt_masks_form_t *form);
int dt_masks_form_change_opacity(dt_masks_form_t *form, int parentid, int up, const int flow);
void dt_masks_form_move(dt_masks_form_t *grp, int formid, int up);
int dt_masks_form_duplicate(dt_develop_t *dev, int formid);
/* returns a duplicate tof form, including the formid */
dt_masks_form_t *dt_masks_dup_masks_form(const dt_masks_form_t *form);
/* duplicate the list of forms, replace item in the list with form with the same formid */
GList *dt_masks_dup_forms_deep(GList *forms, dt_masks_form_t *form);
 
int dt_masks_point_in_form_exact(float x, float y, float *points, int points_start, int points_count);
int dt_masks_point_in_form_near(float x, float y, float *points, int points_start, int points_count, float distance, int *near);
 
void dt_masks_select_form(struct dt_iop_module_t *module, dt_masks_form_t *sel);
 
void dt_masks_draw_clone_source_pos(cairo_t *cr, const float zoom_scale, const float x, const float y);
void dt_masks_set_source_pos_initial_state(dt_masks_form_gui_t *gui, const uint32_t state, const float pzx,
                                           const float pzy);
void dt_masks_set_source_pos_initial_value(dt_masks_form_gui_t *gui, dt_masks_form_t *form,
                                                   const float pzx, const float pzy);
void dt_masks_calculate_source_pos_value(dt_masks_form_gui_t *gui, const int mask_type, const float initial_xpos,
                                         const float initial_ypos, const float xpos, const float ypos, float *px,
                                         float *py, const int adding);
float dt_masks_rotate_with_anchor(dt_develop_t *dev, const float anchor[2], const float center[2], dt_masks_form_gui_t *gui);
 
float dt_masks_form_get_opacity(dt_masks_form_t *form, int parentid);
int dt_masks_form_set_opacity(dt_masks_form_t *form, int parentid, float opacity, dt_masks_increment_t offset, const int flow);
 
float dt_masks_get_set_conf_value(dt_masks_form_t *form, char *feature, float new_value, float v_min, float v_max,
                                  dt_masks_increment_t increment, const int flow);
 
void dt_masks_extend_border(float *const mask, const int width, const int height, const int border);
void dt_masks_blur_9x9_coeff(float *coeffs, const float sigma);
void dt_masks_blur_9x9(float *const src, float *const out, const int width, const int height, const float sigma);
void dt_masks_calc_rawdetail_mask(float *const src, float *const out, float *const tmp, const int width,
                                  const int height, const dt_aligned_pixel_t wb);
void dt_masks_calc_detail_mask(float *const src, float *const out, float *const tmp, const int width, const int height, const float threshold, const gboolean detail);
 
void dt_group_events_post_expose(cairo_t *cr, float zoom_scale, dt_masks_form_t *form,
                                 dt_masks_form_gui_t *gui);
 
static inline gboolean _dt_masks_dynbuf_growto(dt_masks_dynbuf_t *a, size_t size)
{
  const size_t newsize = dt_round_size_sse(sizeof(float) * size) / sizeof(float);
  float *newbuf = dt_alloc_align_float(newsize);
  if (!newbuf)
  {
    // not much we can do here except emit an error message
    fprintf(stderr, "critical: out of memory for dynbuf '%s' with size request %zu!\n", a->tag, size);
    return FALSE;
  }
  if (a->buffer)
  {
    memcpy(newbuf, a->buffer, a->size * sizeof(float));
    dt_print(DT_DEBUG_MASKS, "[masks dynbuf '%s'] grows to size %lu (is %p, was %p)\n", a->tag,
             (unsigned long)a->size, newbuf, a->buffer);
    dt_free_align(a->buffer);
  }
  a->size = newsize;
  a->buffer = newbuf;
  return TRUE;
}
 
static inline dt_masks_dynbuf_t *dt_masks_dynbuf_init(size_t size, const char *tag)
{
  assert(size > 0);
  dt_masks_dynbuf_t *a = (dt_masks_dynbuf_t *)calloc(1, sizeof(dt_masks_dynbuf_t));
 
  if(a != NULL)
  {
    g_strlcpy(a->tag, tag, sizeof(a->tag)); //only for debugging purposes
    a->pos = 0;
    if(_dt_masks_dynbuf_growto(a, size))
      dt_print(DT_DEBUG_MASKS, "[masks dynbuf '%s'] with initial size %lu (is %p)\n", a->tag,
               (unsigned long)a->size, a->buffer);
    if(a->buffer == NULL)
    {
      free(a);
      a = NULL;
    }
  }
  return a;
}
 
static inline void dt_masks_dynbuf_add_2(dt_masks_dynbuf_t *a, float value1, float value2)
{
  assert(a != NULL);
  assert(a->pos <= a->size);
  if(__builtin_expect(a->pos + 2 >= a->size, 0))
  {
    if (a->size == 0 || !_dt_masks_dynbuf_growto(a, 2 * (a->size+1)))
      return;
  }
  a->buffer[a->pos++] = value1;
  a->buffer[a->pos++] = value2;
}
 
// Return a pointer to N floats past the current end of the dynbuf's contents, marking them as already in use.
// The caller should then fill in the reserved elements using the returned pointer.
static inline float *dt_masks_dynbuf_reserve_n(dt_masks_dynbuf_t *a, const int n)
{
  assert(a != NULL);
  assert(a->pos <= a->size);
  if(__builtin_expect(a->pos + n >= a->size, 0))
  {
    if(a->size == 0) return NULL;
    size_t newsize = a->size;
    while(a->pos + n >= newsize) newsize *= 2;
    if (!_dt_masks_dynbuf_growto(a, newsize))
    {
      return NULL;
    }
  }
  // get the current end of the (possibly reallocated) buffer, then mark the next N items as in-use
  float *reserved = a->buffer + a->pos;
  a->pos += n;
  return reserved;
}
 
static inline void dt_masks_dynbuf_add_zeros(dt_masks_dynbuf_t *a, const int n)
{
  assert(a != NULL);
  assert(a->pos <= a->size);
  if(__builtin_expect(a->pos + n >= a->size, 0))
  {
    if(a->size == 0) return;
    size_t newsize = a->size;
    while(a->pos + n >= newsize) newsize *= 2;
    if (!_dt_masks_dynbuf_growto(a, newsize))
    {
      return;
    }
  }
  // now that we've ensured a sufficiently large buffer add N zeros to the end of the existing data
  memset(a->buffer + a->pos, 0, n * sizeof(float));
  a->pos += n;
}
 
 
static inline float dt_masks_dynbuf_get(dt_masks_dynbuf_t *a, int offset)
{
  assert(a != NULL);
  // offset: must be negative distance relative to end of buffer
  assert(offset < 0);
  assert((long)a->pos + offset >= 0);
  return (a->buffer[a->pos + offset]);
}
 
static inline void dt_masks_dynbuf_set(dt_masks_dynbuf_t *a, int offset, float value)
{
  assert(a != NULL);
  // offset: must be negative distance relative to end of buffer
  assert(offset < 0);
  assert((long)a->pos + offset >= 0);
  a->buffer[a->pos + offset] = value;
}
 
static inline float *dt_masks_dynbuf_buffer(dt_masks_dynbuf_t *a)
{
  assert(a != NULL);
  return a->buffer;
}
 
static inline size_t dt_masks_dynbuf_position(dt_masks_dynbuf_t *a)
{
  assert(a != NULL);
  return a->pos;
}
 
static inline void dt_masks_dynbuf_reset(dt_masks_dynbuf_t *a)
{
  assert(a != NULL);
  a->pos = 0;
}
 
static inline float *dt_masks_dynbuf_harvest(dt_masks_dynbuf_t *a)
{
  // take out data buffer and make dynamic buffer obsolete
  if(a == NULL) return NULL;
  float *r = a->buffer;
  a->buffer = NULL;
  a->pos = a->size = 0;
  return r;
}
 
static inline void dt_masks_dynbuf_free(dt_masks_dynbuf_t *a)
{
  if(a == NULL) return;
  dt_print(DT_DEBUG_MASKS, "[masks dynbuf '%s'] freed (was %p)\n", a->tag,
          a->buffer);
  dt_free_align(a->buffer);
  free(a);
}
 
static inline int dt_masks_roundup(int num, int mult)
{
  const int rem = num % mult;
 
  return (rem == 0) ? num : num + mult - rem;
}
 
gboolean dt_masks_is_within_radius(const float px, const float py,
                                        const float cx, const float cy,
                                        const float radius);
 
#ifdef __cplusplus
}
#endif
 
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