fix for annoyance where header menus would get scroller arrows added because it would be clamped within the screen a few pixels.

This was caused from using theme shadow setting to clip the popups and a hard-coded value to translate the popup within screen bounds - these values should be the same.

source/blender/editors/include/UI_interface.h

@@ -85,6 +85,9 @@ typedef struct uiLayout uiLayout;
 #define UI_MAX_DRAW_STR 400
 #define UI_MAX_NAME_STR 128
 
+/* use for clamping popups within the screen */
+#define UI_SCREEN_MARGIN 10
+
 /* uiBlock->dt */
 #define UI_EMBOSS       0   /* use widget style for drawing */
 #define UI_EMBOSSN      1   /* Nothing, only icon and/or text */

source/blender/editors/interface/interface.c

@@ -319,6 +319,7 @@ static void ui_popup_bounds_block(const bContext *C, uiBlock *block, eBlockBound
 	wmWindow *window = CTX_wm_window(C);
 	int startx, starty, endx, endy, width, height, oldwidth, oldheight;
 	int oldbounds, xmax, ymax;
+	const int margin = UI_SCREEN_MARGIN;
 
 	oldbounds = block->bounds;
 
@@ -356,20 +357,20 @@ static void ui_popup_bounds_block(const bContext *C, uiBlock *block, eBlockBound
 	startx = window->eventstate->x + block->rect.xmin + (block->mx * width) / oldwidth;
 	starty = window->eventstate->y + block->rect.ymin + (block->my * height) / oldheight;
 
-	if (startx < 10)
-		startx = 10;
-	if (starty < 10)
-		starty = 10;
+	if (startx < margin)
+		startx = margin;
+	if (starty < margin)
+		starty = margin;
 
 	endx = startx + width;
 	endy = starty + height;
 
 	if (endx > xmax) {
-		endx = xmax - 10;
+		endx = xmax - margin;
 		startx = endx - width;
 	}
-	if (endy > ymax - 20) {
-		endy = ymax - 20;
+	if (endy > ymax - margin) {
+		endy = ymax - margin;
 		starty = endy - height;
 	}
 

source/blender/editors/interface/interface_regions.c

@@ -1532,7 +1532,7 @@ static void ui_block_region_draw(const bContext *C, ARegion *ar)
 static void ui_popup_block_clip(wmWindow *window, uiBlock *block)
 {
 	uiBut *bt;
-	int width = UI_ThemeMenuShadowWidth();
+	int width = UI_SCREEN_MARGIN;
 	int winx, winy;
 
 	if (block->flag & UI_BLOCK_NO_WIN_CLIP) {