don't use DwmFlush WaitForVerticalBlank

src/dd.c

@@ -1560,17 +1560,8 @@ HRESULT dd_WaitForVerticalBlank(DWORD dwFlags, HANDLE hEvent)
 {
     if (g_config.maxgameticks == -2)
     {
-        /* Workaround for DwmFlush() freeze (e.g. slow alt+tab) issue on windows 7 SP1 */
+        if (fpsl_wait_for_vblank())
-        if (g_ddraw.renderer == ogl_render_main && !IsWine() && !IsWindows8OrGreater())
+            return DD_OK;
-        {
-            if (fpsl_wait_for_vblank())
-                return DD_OK;
-        }
-        else
-        {
-            if (fpsl_dwm_flush() || fpsl_wait_for_vblank())
-                return DD_OK;
-        }
     }
 
     if (!g_ddraw.flip_limiter.tick_length)