Adwaita: control surface for resize tiled windows

- window resizing control area is implemented as where the shadows are drawn
- create a 'fake' shadow for the tiled case to allow easier resizing of
  the tiled window ratio even if it's offset to the side of the border

Fixes https://gitlab.gnome.org/GNOME/gtk/-/issues/3670

diff --git a/gtk/theme/Adwaita/_common.scss b/gtk/theme/Adwaita/_common.scss
index ed26a7d29082e6f2036b08283182f509a0c11233..6b4a7349545f2e1f02ea64a1bd43bc4506756ca6 100644 (file)
--- a/gtk/theme/Adwaita/_common.scss
+++ b/gtk/theme/Adwaita/_common.scss
@@ -4117,9 +4117,11 @@ window {
   &.tiled-right,
   &.tiled-bottom {
    border-radius: 0;
-   box-shadow: 0 0 0 1px $_wm_border_backdrop;
-
-   &:backdrop { box-shadow: 0 0 0 1px $_wm_border_backdrop; }
+   box-shadow: 0 0 0 1px $_wm_border_backdrop,
+               0 0 0 20px transparent; //transparent control workaround -- #3670
+   }
+   &:backdrop { box-shadow: 0 0 0 1px $_wm_border_backdrop,
+                            0 0 0 20px transparent; // #3670
   }
 
   &.popup { box-shadow: none; }