fix [#32938] The Splash Screen doesn't show up correctly .....

applying window clipping to the splash on startup gave strange/annoying problems.

source/blender/editors/include/UI_interface.h

@@ -108,7 +108,7 @@ typedef struct uiLayout uiLayout;
 #define UI_BLOCK_REDRAW         2
 #define UI_BLOCK_SEARCH_MENU    4
 #define UI_BLOCK_NUMSELECT      8
-/*#define UI_BLOCK_ENTER_OK		16*/ /*UNUSED*/
+#define UI_BLOCK_NO_WIN_CLIP    16      /* don't apply window clipping */ /* was UI_BLOCK_ENTER_OK */
 #define UI_BLOCK_CLIPBOTTOM     32
 #define UI_BLOCK_CLIPTOP        64
 #define UI_BLOCK_MOVEMOUSE_QUIT 128

source/blender/editors/interface/interface_regions.c

@@ -1548,7 +1548,11 @@ static void ui_block_region_draw(const bContext *C, ARegion *ar)
 static void ui_popup_block_clip(wmWindow *window, uiBlock *block)
 {
 	int winx, winy;
-	
+
+	if (block->flag & UI_BLOCK_NO_WIN_CLIP) {
+		return;
+	}
+
 	wm_window_get_size(window, &winx, &winy);
 	
 	if (block->rect.xmin < MENU_SHADOW_SIDE)

source/blender/windowmanager/intern/wm_operators.c

@@ -1320,7 +1320,11 @@ static uiBlock *wm_block_create_splash(bContext *C, ARegion *ar, void *UNUSED(ar
 #endif  /* WITH_BUILDINFO */
 
 	block = uiBeginBlock(C, ar, "_popup", UI_EMBOSS);
-	uiBlockSetFlag(block, UI_BLOCK_KEEP_OPEN);
+
+	/* note on UI_BLOCK_NO_WIN_CLIP, the window size is not always synchronized
+	 * with the OS when the splash shows, window clipping in this case gives
+	 * ugly results and clipping the splash isn't useful anyway, just disable it [#32938] */
+	uiBlockSetFlag(block, UI_BLOCK_KEEP_OPEN | UI_BLOCK_NO_WIN_CLIP);
 	
 	but = uiDefBut(block, BUT_IMAGE, 0, "", 0, 10, 501, 282, ibuf, 0.0, 0.0, 0, 0, ""); /* button owns the imbuf now */
 	uiButSetFunc(but, wm_block_splash_close, block, NULL);