source/blender/editors/screen/area.cc

@@ -931,16 +931,37 @@ static void fullscreen_azone_init(ScrArea *area, ARegion *region)
   BLI_rcti_init(&az->rect, az->x1, az->x2, az->y1, az->y2);
 }
 
+/**
+ * Return true if the background color alpha is close to fully transparent. That is, a value of
+ * less than 50 on a [0-255] scale (arbitrary/eyeballed threshold). Assumes the region uses
+ * #TH_BACK for its background.
+ */
+static bool region_back_is_barely_visible(const ScrArea *area, const ARegion *region)
+{
+  /* Ensure the right theme is active, may not be the case on startup, for example. */
+  bThemeState theme_state;
+  UI_Theme_Store(&theme_state);
+  UI_SetTheme(area->spacetype, region->regiontype);
+
+  uchar back[4];
+  UI_GetThemeColor4ubv(TH_BACK, back);
+
+  UI_Theme_Restore(&theme_state);
+
+  return back[3] < 50;
+}
+
 #define AZONEPAD_EDGE (0.1f * U.widget_unit)
 #define AZONEPAD_ICON (0.45f * U.widget_unit)
-static void region_azone_edge(AZone *az, ARegion *region)
+static void region_azone_edge(const ScrArea *area, AZone *az, const ARegion *region)
 {
   /* If there is no visible region background, users typically expect the #AZone to be closer to
    * the content, so move it a bit. Headers-like regions are usually thin and there's not much
    * padding around them, so don't touch the #AZone there (also avoids mouse hover conflicts with
    * actual contents).
    * Note that this is an arbitrary amount that matches nicely with numbers elsewhere. */
-  const int overlap_padding = (region->overlap && !RGN_TYPE_IS_HEADER_ANY(region->regiontype)) ?
+  const int overlap_padding = (region->overlap && region_back_is_barely_visible(area, region) &&
+                               !RGN_TYPE_IS_HEADER_ANY(region->regiontype)) ?
                                   int(0.4f * U.widget_unit) :
                                   0;
 
@@ -1059,7 +1080,7 @@ static void region_azone_edge_init(ScrArea *area,
     region_azone_tab_plus(area, az, region);
   }
   else {
-    region_azone_edge(az, region);
+    region_azone_edge(area, az, region);
   }
 }