UI: hide redundant menu separators automatically

Differential Revision: https://developer.blender.org/D4682

source/blender/editors/include/UI_interface.h

@@ -520,6 +520,7 @@ bool UI_but_is_tool(const uiBut *but);
 #define UI_but_is_decorator(but) ((but)->func == ui_but_anim_decorate_cb)
 
 bool UI_block_is_empty(const uiBlock *block);
+bool UI_block_can_add_separator(const uiBlock *block);
 
 /* interface_region_menu_popup.c */
 /**

source/blender/editors/interface/interface_layout.c

@@ -2968,6 +2968,9 @@ void uiItemS_ex(uiLayout *layout, float factor)
 {
   uiBlock *block = layout->root->block;
   bool is_menu = ui_block_is_menu(block);
+  if (is_menu && !UI_block_can_add_separator(block)) {
+    return;
+  }
   int space = (is_menu) ? 0.45f * UI_UNIT_X : 0.3f * UI_UNIT_X;
   space *= factor;
 

source/blender/editors/interface/interface_query.c

@@ -473,6 +473,15 @@ bool UI_block_is_empty(const uiBlock *block)
   return true;
 }
 
+bool UI_block_can_add_separator(const uiBlock *block)
+{
+  if (ui_block_is_menu(block)) {
+    const uiBut *but = block->buttons.last;
+    return (but && !ELEM(but->type, UI_BTYPE_SEPR_LINE, UI_BTYPE_SEPR));
+  }
+  return true;
+}
+
 /** \} */
 
 /* -------------------------------------------------------------------- */