source/blender/editors/asset/intern/asset_shelf.cc

@@ -476,9 +476,12 @@ void ED_asset_shelf_header_region(const bContext *C, ARegion *region)
 
 int ED_asset_shelf_header_region_size()
 {
-  /* The asset shelf tends to look like a separate area. Making the shelf header smaller than a
-   * normal header helps a bit. */
-  return ED_area_headersize() * 0.85f;
+  /* Use a height that lets widgets sit just on top of the separator line drawn at the lower edge
+   * of the region (widgets will be centered).
+   *
+   * Note that this is usually a bit less than the header size. The asset shelf tends to look like
+   * a separate area, so making the shelf header smaller than a header helps. */
+  return UI_UNIT_Y + (UI_BUTTON_SECTION_SEPERATOR_LINE_WITH * 2);
 }
 
 void ED_asset_shelf_region_blend_read_data(BlendDataReader *reader, ARegion *region)

source/blender/editors/include/UI_interface_c.hh

@@ -838,6 +838,8 @@ void UI_block_lock_set(uiBlock *block, bool val, const char *lockstr);
 void UI_block_lock_clear(uiBlock *block);
 
 #define UI_BUTTON_SECTION_MERGE_DISTANCE (UI_UNIT_X * 3)
+/* Separator line between regions if the #uiButtonSectionsAlign is not #None. */
+#define UI_BUTTON_SECTION_SEPERATOR_LINE_WITH (U.pixelsize * 2)
 
 enum class uiButtonSectionsAlign : int16_t { None, Top, Bottom };
 /**

source/blender/editors/interface/interface_button_sections.cc

@@ -145,7 +145,7 @@ static void ui_draw_button_sections_alignment_separator(const ARegion *region,
                                                         const uiButtonSectionsAlign align,
                                                         const float corner_radius)
 {
-  const int separator_line_width = 2 * U.pixelsize;
+  const int separator_line_width = UI_BUTTON_SECTION_SEPERATOR_LINE_WITH;
 
   float bg_color[4];
   UI_GetThemeColor4fv(colorid, bg_color);