Color Management: Improve wide gamut color buttons and pickers

These should at least show the correct colors and gamut now, following the
color picking space in the OpenColorIO config.

However the ACES config use sRGB as the color_picking role, which means
that the color picker only shows a limited a gamut. There is apparently is
not agreement on the interpretation of this role, so we might have to stop
using it.

Additionally, if you set the color_picking role to something like ACEScg +
sRGB transfer function, the widgets do show all the colors in the gamut,
however the gamut is probably too large to be practical for most uses. So
we need some UI solution for this regardless.

Ref #144911

Pull Request: https://projects.blender.org/blender/blender/pulls/144565

source/blender/editors/interface/interface_draw.cc

@@ -1668,7 +1668,9 @@ void ui_draw_but_CURVE(ARegion *region, uiBut *but, const uiWidgetColors *wcol,
     grid.xmax = grid.xmin + zoomx;
     grid.ymin = rect->ymin + zoomy * (-offsy);
     grid.ymax = grid.ymin + zoomy;
-    ui_draw_gradient(&grid, col, UI_GRAD_H, 1.0f);
+
+    const ColorManagedDisplay *display = ui_block_cm_display_get(but->block);
+    ui_draw_gradient(&grid, col, UI_GRAD_H, 1.0f, display);
   }
 
   GPU_line_width(1.0f);

source/blender/editors/interface/interface_intern.hh

@@ -1143,7 +1143,11 @@ void ui_layout_panel_popup_scroll_apply(Panel *panel, const float dy);
 /**
  * Draws in resolution of 48x4 colors.
  */
-void ui_draw_gradient(const rcti *rect, const float hsv[3], eButGradientType type, float alpha);
+void ui_draw_gradient(const rcti *rect,
+                      const float hsv[3],
+                      eButGradientType type,
+                      float alpha,
+                      const ColorManagedDisplay *display);
 
 /**
  * Draws rounded corner segments but inverted. Imagine each corner like a filled right triangle,

source/blender/editors/interface/interface_widgets.cc

@@ -49,6 +49,8 @@
 
 #include "UI_abstract_view.hh"
 
+#include "IMB_colormanagement.hh"
+
 #ifdef WITH_INPUT_IME
 #  include "WM_types.hh"
 #endif
@@ -1037,10 +1039,8 @@ static void widgetbase_set_uniform_colors_ubv(uiWidgetBase *wtb,
                                               const uchar *col2,
                                               const uchar *outline,
                                               const uchar *emboss,
-                                              const uchar *tria,
+                                              const uchar *tria)
-                                              const bool alpha_check)
 {
-  widgetbase_set_uniform_alpha_check(wtb, alpha_check);
   rgba_float_args_set_ch(wtb->uniform_params.color_inner1, col1[0], col1[1], col1[2], col1[3]);
   rgba_float_args_set_ch(wtb->uniform_params.color_inner2, col2[0], col2[1], col2[2], col2[3]);
   rgba_float_args_set_ch(
@@ -1143,19 +1143,13 @@ static void draw_widgetbase_batch(uiWidgetBase *wtb)
   }
 }
 
-static void widgetbase_draw_ex(uiWidgetBase *wtb,
+static void widgetbase_draw(uiWidgetBase *wtb, const uiWidgetColors *wcol)
-                               const uiWidgetColors *wcol,
-                               bool show_alpha_checkers)
 {
   uchar inner_col1[4] = {0};
   uchar inner_col2[4] = {0};
   uchar emboss_col[4] = {0};
   uchar outline_col[4] = {0};
   uchar tria_col[4] = {0};
-  /* For color widget. */
-  if (wcol->shaded != 0) {
-    show_alpha_checkers = false;
-  }
 
   /* backdrop non AA */
   if (wtb->draw_inner) {
@@ -1192,11 +1186,9 @@ static void widgetbase_draw_ex(uiWidgetBase *wtb,
   }
 
   /* Draw everything in one draw-call. */
-  if (inner_col1[3] || inner_col2[3] || outline_col[3] || emboss_col[3] || tria_col[3] ||
+  if (inner_col1[3] || inner_col2[3] || outline_col[3] || emboss_col[3] || tria_col[3]) {
-      show_alpha_checkers)
-  {
     widgetbase_set_uniform_colors_ubv(
-        wtb, inner_col1, inner_col2, outline_col, emboss_col, tria_col, show_alpha_checkers);
+        wtb, inner_col1, inner_col2, outline_col, emboss_col, tria_col);
 
     GPU_blend(GPU_BLEND_ALPHA);
     draw_widgetbase_batch(wtb);
@@ -1204,9 +1196,38 @@ static void widgetbase_draw_ex(uiWidgetBase *wtb,
   }
 }
 
-static void widgetbase_draw(uiWidgetBase *wtb, const uiWidgetColors *wcol)
+/* widgetbase_draw variation for drawing colors, with full float color for wide gamut. */
+static void widgetbase_draw_color(uiWidgetBase *wtb,
+                                  const uiWidgetColors *wcol,
+                                  float color[4],
+                                  bool show_alpha_checkers)
 {
-  widgetbase_draw_ex(wtb, wcol, false);
+  const uchar unused_col[4] = {0};
+  uchar emboss_col[4] = {0};
+  uchar outline_col[4] = {0};
+
+  if (wtb->draw_outline) {
+    outline_col[0] = wcol->outline[0];
+    outline_col[1] = wcol->outline[1];
+    outline_col[2] = wcol->outline[2];
+    outline_col[3] = wcol->outline[3];
+
+    /* Emboss shadow if enabled, and inner and outline colors are not fully transparent. */
+    if ((wtb->draw_emboss) && (wcol->inner[3] != 0.0f || wcol->outline[3] != 0.0f)) {
+      UI_GetThemeColor4ubv(TH_WIDGET_EMBOSS, emboss_col);
+    }
+  }
+
+  /* Draw everything in one draw-call. */
+  widgetbase_set_uniform_alpha_check(wtb, show_alpha_checkers);
+  widgetbase_set_uniform_colors_ubv(
+      wtb, unused_col, unused_col, outline_col, emboss_col, unused_col);
+  copy_v4_v4(wtb->uniform_params.color_inner1, color);
+  copy_v4_v4(wtb->uniform_params.color_inner2, color);
+
+  GPU_blend(GPU_BLEND_ALPHA);
+  draw_widgetbase_batch(wtb);
+  GPU_blend(GPU_BLEND_NONE);
 }
 
 /** \} */
@@ -3051,7 +3072,7 @@ static void ui_draw_but_HSVCIRCLE(uiBut *but, const uiWidgetColors *wcol, const
   const float radius = float(min_ii(BLI_rcti_size_x(rect), BLI_rcti_size_y(rect))) / 2.0f;
 
   ColorPicker *cpicker = static_cast<ColorPicker *>(but->custom_data);
-  float rgb[3], hsv[3], rgb_center[3];
+  float rgb[3], hsv[3], rgb_center[3], rgb_perceptual[3];
   const bool is_color_gamma = ui_but_is_color_gamma(but);
 
   /* Initialize for compatibility. */
@@ -3059,8 +3080,13 @@ static void ui_draw_but_HSVCIRCLE(uiBut *but, const uiWidgetColors *wcol, const
 
   /* Compute current hue. */
   ui_but_v3_get(but, rgb);
-  ui_scene_linear_to_perceptual_space(but, rgb);
+  copy_v3_v3(rgb_perceptual, rgb);
-  ui_color_picker_rgb_to_hsv_compat(rgb, hsv);
+  ui_scene_linear_to_perceptual_space(but, rgb_perceptual);
+  ui_color_picker_rgb_to_hsv_compat(rgb_perceptual, hsv);
+
+  if (!is_color_gamma) {
+    ui_block_cm_to_display_space_v3(but->block, rgb);
+  }
 
   CLAMP(hsv[2], 0.0f, 1.0f); /* for display only */
 
@@ -3138,9 +3164,7 @@ static void ui_draw_but_HSVCIRCLE(uiBut *but, const uiWidgetColors *wcol, const
 
   /* cursor */
   copy_v3_v3(hsv, cpicker->hsv_perceptual);
-  ui_but_v3_get(but, rgb);
+  ui_color_picker_rgb_to_hsv_compat(rgb_perceptual, hsv);
-  ui_scene_linear_to_perceptual_space(but, rgb);
-  ui_color_picker_rgb_to_hsv_compat(rgb, hsv);
 
   float xpos, ypos;
   ui_hsvcircle_pos_from_vals(cpicker, rect, hsv, &xpos, &ypos);
@@ -3154,10 +3178,22 @@ static void ui_draw_but_HSVCIRCLE(uiBut *but, const uiWidgetColors *wcol, const
 /** \name Draw Custom Buttons
  * \{ */
 
+static void ui_draw_gradient_hsv_to_rgb(
+    const ColorManagedDisplay *display, float h, float s, float v, float rgb[3])
+{
+  hsv_to_rgb(h, s, v, rgb, rgb + 1, rgb + 2);
+
+  if (display) {
+    IMB_colormanagement_color_picking_to_scene_linear_v3(rgb, rgb);
+    IMB_colormanagement_scene_linear_to_display_v3(rgb, display);
+  }
+}
+
 void ui_draw_gradient(const rcti *rect,
                       const float hsv[3],
                       const eButGradientType type,
-                      const float alpha)
+                      const float alpha,
+                      const ColorManagedDisplay *display)
 {
   /* allows for 4 steps (red->yellow) */
   const int steps = 48;
@@ -3172,44 +3208,44 @@ void ui_draw_gradient(const rcti *rect,
 
   switch (type) {
     case UI_GRAD_SV:
-      hsv_to_rgb(h, 0.0, 0.0, &col1[0][0], &col1[0][1], &col1[0][2]);
+      ui_draw_gradient_hsv_to_rgb(display, h, 0.0, 0.0, col1[0]);
-      hsv_to_rgb(h, 0.0, 0.333, &col1[1][0], &col1[1][1], &col1[1][2]);
+      ui_draw_gradient_hsv_to_rgb(display, h, 0.0, 0.333, col1[1]);
-      hsv_to_rgb(h, 0.0, 0.666, &col1[2][0], &col1[2][1], &col1[2][2]);
+      ui_draw_gradient_hsv_to_rgb(display, h, 0.0, 0.666, col1[2]);
-      hsv_to_rgb(h, 0.0, 1.0, &col1[3][0], &col1[3][1], &col1[3][2]);
+      ui_draw_gradient_hsv_to_rgb(display, h, 0.0, 1.0, col1[3]);
       break;
     case UI_GRAD_HV:
-      hsv_to_rgb(0.0, s, 0.0, &col1[0][0], &col1[0][1], &col1[0][2]);
+      ui_draw_gradient_hsv_to_rgb(display, 0.0, s, 0.0, col1[0]);
-      hsv_to_rgb(0.0, s, 0.333, &col1[1][0], &col1[1][1], &col1[1][2]);
+      ui_draw_gradient_hsv_to_rgb(display, 0.0, s, 0.333, col1[1]);
-      hsv_to_rgb(0.0, s, 0.666, &col1[2][0], &col1[2][1], &col1[2][2]);
+      ui_draw_gradient_hsv_to_rgb(display, 0.0, s, 0.666, col1[2]);
-      hsv_to_rgb(0.0, s, 1.0, &col1[3][0], &col1[3][1], &col1[3][2]);
+      ui_draw_gradient_hsv_to_rgb(display, 0.0, s, 1.0, col1[3]);
       break;
     case UI_GRAD_HS:
-      hsv_to_rgb(0.0, 0.0, v, &col1[0][0], &col1[0][1], &col1[0][2]);
+      ui_draw_gradient_hsv_to_rgb(display, 0.0, 0.0, v, col1[0]);
-      hsv_to_rgb(0.0, 0.333, v, &col1[1][0], &col1[1][1], &col1[1][2]);
+      ui_draw_gradient_hsv_to_rgb(display, 0.0, 0.333, v, col1[1]);
-      hsv_to_rgb(0.0, 0.666, v, &col1[2][0], &col1[2][1], &col1[2][2]);
+      ui_draw_gradient_hsv_to_rgb(display, 0.0, 0.666, v, col1[2]);
-      hsv_to_rgb(0.0, 1.0, v, &col1[3][0], &col1[3][1], &col1[3][2]);
+      ui_draw_gradient_hsv_to_rgb(display, 0.0, 1.0, v, col1[3]);
       break;
     case UI_GRAD_H:
-      hsv_to_rgb(0.0, 1.0, 1.0, &col1[0][0], &col1[0][1], &col1[0][2]);
+      ui_draw_gradient_hsv_to_rgb(display, 0.0, 1.0, 1.0, col1[0]);
       copy_v3_v3(col1[1], col1[0]);
       copy_v3_v3(col1[2], col1[0]);
       copy_v3_v3(col1[3], col1[0]);
       break;
     case UI_GRAD_S:
-      hsv_to_rgb(1.0, 0.0, 1.0, &col1[1][0], &col1[1][1], &col1[1][2]);
+      ui_draw_gradient_hsv_to_rgb(display, 1.0, 0.0, 1.0, col1[1]);
       copy_v3_v3(col1[0], col1[1]);
       copy_v3_v3(col1[2], col1[1]);
       copy_v3_v3(col1[3], col1[1]);
       break;
     case UI_GRAD_V:
-      hsv_to_rgb(1.0, 1.0, 0.0, &col1[2][0], &col1[2][1], &col1[2][2]);
+      ui_draw_gradient_hsv_to_rgb(display, 1.0, 1.0, 0.0, col1[2]);
       copy_v3_v3(col1[0], col1[2]);
       copy_v3_v3(col1[1], col1[2]);
       copy_v3_v3(col1[3], col1[2]);
       break;
     default:
       BLI_assert_msg(0, "invalid 'type' argument");
-      hsv_to_rgb(1.0, 1.0, 1.0, &col1[2][0], &col1[2][1], &col1[2][2]);
+      ui_draw_gradient_hsv_to_rgb(display, 1.0, 1.0, 1.0, col1[2]);
       copy_v3_v3(col1[0], col1[2]);
       copy_v3_v3(col1[1], col1[2]);
       copy_v3_v3(col1[3], col1[2]);
@@ -3239,39 +3275,39 @@ void ui_draw_gradient(const rcti *rect,
     /* new color */
     switch (type) {
       case UI_GRAD_SV:
-        hsv_to_rgb(h, dx, 0.0, &col1[0][0], &col1[0][1], &col1[0][2]);
+        ui_draw_gradient_hsv_to_rgb(display, h, dx, 0.0, col1[0]);
-        hsv_to_rgb(h, dx, 0.333, &col1[1][0], &col1[1][1], &col1[1][2]);
+        ui_draw_gradient_hsv_to_rgb(display, h, dx, 0.333, col1[1]);
-        hsv_to_rgb(h, dx, 0.666, &col1[2][0], &col1[2][1], &col1[2][2]);
+        ui_draw_gradient_hsv_to_rgb(display, h, dx, 0.666, col1[2]);
-        hsv_to_rgb(h, dx, 1.0, &col1[3][0], &col1[3][1], &col1[3][2]);
+        ui_draw_gradient_hsv_to_rgb(display, h, dx, 1.0, col1[3]);
         break;
       case UI_GRAD_HV:
-        hsv_to_rgb(dx_next, s, 0.0, &col1[0][0], &col1[0][1], &col1[0][2]);
+        ui_draw_gradient_hsv_to_rgb(display, dx_next, s, 0.0, col1[0]);
-        hsv_to_rgb(dx_next, s, 0.333, &col1[1][0], &col1[1][1], &col1[1][2]);
+        ui_draw_gradient_hsv_to_rgb(display, dx_next, s, 0.333, col1[1]);
-        hsv_to_rgb(dx_next, s, 0.666, &col1[2][0], &col1[2][1], &col1[2][2]);
+        ui_draw_gradient_hsv_to_rgb(display, dx_next, s, 0.666, col1[2]);
-        hsv_to_rgb(dx_next, s, 1.0, &col1[3][0], &col1[3][1], &col1[3][2]);
+        ui_draw_gradient_hsv_to_rgb(display, dx_next, s, 1.0, col1[3]);
         break;
       case UI_GRAD_HS:
-        hsv_to_rgb(dx_next, 0.0, v, &col1[0][0], &col1[0][1], &col1[0][2]);
+        ui_draw_gradient_hsv_to_rgb(display, dx_next, 0.0, v, col1[0]);
-        hsv_to_rgb(dx_next, 0.333, v, &col1[1][0], &col1[1][1], &col1[1][2]);
+        ui_draw_gradient_hsv_to_rgb(display, dx_next, 0.333, v, col1[1]);
-        hsv_to_rgb(dx_next, 0.666, v, &col1[2][0], &col1[2][1], &col1[2][2]);
+        ui_draw_gradient_hsv_to_rgb(display, dx_next, 0.666, v, col1[2]);
-        hsv_to_rgb(dx_next, 1.0, v, &col1[3][0], &col1[3][1], &col1[3][2]);
+        ui_draw_gradient_hsv_to_rgb(display, dx_next, 1.0, v, col1[3]);
         break;
       case UI_GRAD_H:
         /* annoying but without this the color shifts - could be solved some other way
          * - campbell */
-        hsv_to_rgb(dx_next, 1.0, 1.0, &col1[0][0], &col1[0][1], &col1[0][2]);
+        ui_draw_gradient_hsv_to_rgb(display, dx_next, 1.0, 1.0, col1[0]);
         copy_v3_v3(col1[1], col1[0]);
         copy_v3_v3(col1[2], col1[0]);
         copy_v3_v3(col1[3], col1[0]);
         break;
       case UI_GRAD_S:
-        hsv_to_rgb(h, dx, 1.0, &col1[1][0], &col1[1][1], &col1[1][2]);
+        ui_draw_gradient_hsv_to_rgb(display, h, dx, 1.0, col1[1]);
         copy_v3_v3(col1[0], col1[1]);
         copy_v3_v3(col1[2], col1[1]);
         copy_v3_v3(col1[3], col1[1]);
         break;
       case UI_GRAD_V:
-        hsv_to_rgb(h, 1.0, dx, &col1[2][0], &col1[2][1], &col1[2][2]);
+        ui_draw_gradient_hsv_to_rgb(display, h, 1.0, dx, col1[2]);
         copy_v3_v3(col1[0], col1[2]);
         copy_v3_v3(col1[1], col1[2]);
         copy_v3_v3(col1[3], col1[2]);
@@ -3363,8 +3399,9 @@ void ui_hsvcube_pos_from_vals(
 static void ui_draw_but_HSVCUBE(uiBut *but, const rcti *rect)
 {
   const uiButHSVCube *hsv_but = (uiButHSVCube *)but;
-  float rgb[3];
+  float rgb[3], rgb_perceptual[3];
   float x = 0.0f, y = 0.0f;
+  const ColorManagedDisplay *display = ui_block_cm_display_get(but->block);
   ColorPicker *cpicker = static_cast<ColorPicker *>(but->custom_data);
   float *hsv = cpicker->hsv_perceptual;
   float hsv_n[3];
@@ -3376,10 +3413,15 @@ static void ui_draw_but_HSVCUBE(uiBut *but, const rcti *rect)
   copy_v3_v3(hsv_n, hsv);
 
   ui_but_v3_get(but, rgb);
-  ui_scene_linear_to_perceptual_space(but, rgb);
+  copy_v3_v3(rgb_perceptual, rgb);
-  rgb_to_hsv_compat_v(rgb, hsv_n);
+  ui_scene_linear_to_perceptual_space(but, rgb_perceptual);
+  rgb_to_hsv_compat_v(rgb_perceptual, hsv_n);
 
-  ui_draw_gradient(rect, hsv_n, hsv_but->gradient_type, 1.0f);
+  if (!ui_but_is_color_gamma(but)) {
+    ui_block_cm_to_display_space_v3(but->block, rgb);
+  }
+
+  ui_draw_gradient(rect, hsv_n, hsv_but->gradient_type, 1.0f, display);
 
   ui_hsvcube_pos_from_vals(hsv_but, rect, hsv_n, &x, &y);
 
@@ -4147,18 +4189,15 @@ static void widget_swatch(uiBut *but,
     ui_block_cm_to_display_space_v3(but->block, col);
   }
 
-  rgba_float_to_uchar(wcol->inner, col);
+  const bool show_alpha_checkers = col[3] < 1.0f;
-  const bool show_alpha_checkers = (wcol->inner[3] < 255);
-
-  wcol->shaded = 0;
 
   /* Now we reduce alpha of the inner color (i.e. the color shown)
    * so that this setting can look grayed out, while retaining
    * the checkerboard (for transparent values). This is needed
    * here as the effects of ui_widget_color_disabled() are overwritten. */
-  wcol->inner[3] *= widget_alpha_factor(state);
+  col[3] *= widget_alpha_factor(state);
 
-  widgetbase_draw_ex(&wtb, wcol, show_alpha_checkers);
+  widgetbase_draw_color(&wtb, wcol, col, show_alpha_checkers);
   if (color_but->is_pallete_color &&
       ((Palette *)but->rnapoin.owner_id)->active_color == color_but->palette_color_index)
   {