UI: Support canceling Eyedropper color picking operations

Have `eyedropper_color_sample_fl` return success, in case platform
sampling starts but is canceled (Async return on MacOS). Removes any
chance of returning black color on failures.

Pull Request: https://projects.blender.org/blender/blender/pulls/133124

intern/ghost/intern/GHOST_SystemCocoa.mm

@@ -891,6 +891,7 @@ GHOST_TSuccess GHOST_SystemCocoa::getPixelAtCursor(float r_color[3]) const
   @autoreleasepool {
     NSColorSampler *sampler = [[NSColorSampler alloc] init];
     __block BOOL selectCompleted = NO;
+    __block BOOL samplingSucceeded = NO;
 
     [sampler showSamplerWithSelectionHandler:^(NSColor *selectedColor) {
       dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.1 * NSEC_PER_SEC)),
@@ -904,6 +905,7 @@ GHOST_TSuccess GHOST_SystemCocoa::getPixelAtCursor(float r_color[3]) const
                            r_color[1] = [rgbColor greenComponent];
                            r_color[2] = [rgbColor blueComponent];
                          }
+                         samplingSucceeded = YES;
                        }
                        selectCompleted = YES;
                      });
@@ -913,8 +915,9 @@ GHOST_TSuccess GHOST_SystemCocoa::getPixelAtCursor(float r_color[3]) const
       [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode
                                beforeDate:[NSDate dateWithTimeIntervalSinceNow:0.05]];
     }
+
+    return samplingSucceeded ? GHOST_kSuccess : GHOST_kFailure;
   }
-  return GHOST_kSuccess;
 }
 
 GHOST_TSuccess GHOST_SystemCocoa::setMouseCursorPosition(int32_t x, int32_t y)

source/blender/editors/interface/eyedroppers/eyedropper_color.cc

@@ -430,7 +430,7 @@ static bool eyedropper_cryptomatte_sample_fl(bContext *C,
   return false;
 }
 
-void eyedropper_color_sample_fl(bContext *C,
+bool eyedropper_color_sample_fl(bContext *C,
                                 Eyedropper *eye,
                                 const int event_xy[2],
                                 float r_col[3])
@@ -454,20 +454,20 @@ void eyedropper_color_sample_fl(bContext *C,
       if (area->spacetype == SPACE_IMAGE) {
         SpaceImage *sima = static_cast<SpaceImage *>(area->spacedata.first);
         if (ED_space_image_color_sample(sima, region, mval, r_col, nullptr)) {
-          return;
+          return true;
         }
       }
       else if (area->spacetype == SPACE_NODE) {
         SpaceNode *snode = static_cast<SpaceNode *>(area->spacedata.first);
         Main *bmain = CTX_data_main(C);
         if (ED_space_node_color_sample(bmain, snode, region, mval, r_col)) {
-          return;
+          return true;
         }
       }
       else if (area->spacetype == SPACE_CLIP) {
         SpaceClip *sc = static_cast<SpaceClip *>(area->spacedata.first);
         if (ED_space_clip_color_sample(sc, region, mval, r_col)) {
-          return;
+          return true;
         }
       }
       else if (eye != nullptr && area->spacetype == SPACE_VIEW3D) {
@@ -479,30 +479,33 @@ void eyedropper_color_sample_fl(bContext *C,
           eye->viewport_session->init(region);
         }
         if (eye->viewport_session->sample(mval, r_col)) {
-          return;
+          return true;
         }
       }
     }
   }
 
+  /* Other areas within a Blender window. */
   if (win) {
-    /* Other areas within a Blender window. */
     if (!WM_window_pixels_read_sample(C, win, event_xy_win, r_col)) {
       WM_window_pixels_read_sample_from_offscreen(C, win, event_xy_win, r_col);
     }
     const char *display_device = CTX_data_scene(C)->display_settings.display_device;
     ColorManagedDisplay *display = IMB_colormanagement_display_get_named(display_device);
     IMB_colormanagement_display_to_scene_linear_v3(r_col, display);
+    return true;
   }
-  else if ((WM_capabilities_flag() & WM_CAPABILITY_DESKTOP_SAMPLE) &&
-           WM_desktop_cursor_sample_read(r_col))
-  {
-    /* Outside of the Blender window if we support it. */
-    IMB_colormanagement_srgb_to_scene_linear_v3(r_col, r_col);
-  }
-  else {
-    zero_v3(r_col);
+
+  /* Outside the Blender window if we support it. */
+  if ((WM_capabilities_flag() & WM_CAPABILITY_DESKTOP_SAMPLE)) {
+    if (WM_desktop_cursor_sample_read(r_col)) {
+      IMB_colormanagement_srgb_to_scene_linear_v3(r_col, r_col);
+      return true;
+    }
   }
+
+  zero_v3(r_col);
+  return false;
 }
 
 /* sets the sample color RGB, maintaining A */
@@ -538,7 +541,9 @@ static void eyedropper_color_sample(bContext *C, Eyedropper *eye, const int even
     }
   }
   else {
-    eyedropper_color_sample_fl(C, eye, event_xy, col);
+    if (!eyedropper_color_sample_fl(C, eye, event_xy, col)) {
+      return;
+    }
   }
 
   if (!eye->crypto_node) {

source/blender/editors/interface/eyedroppers/eyedropper_intern.hh

@@ -48,7 +48,7 @@ void eyedropper_win_area_find(const bContext *C,
  * \note Exposed by 'eyedropper_intern.hh' for use with color band picking.
  */
 struct Eyedropper;
-void eyedropper_color_sample_fl(bContext *C,
+bool eyedropper_color_sample_fl(bContext *C,
                                 struct Eyedropper *eye,
                                 const int event_xy[2],
                                 float r_col[3]);