[gtk/wip/jimmac/specialcase-close-button] Adwaita: specialcase close button

[Jakub Steiner <jimmac src gnome org>]

commit f0b62e77d75cf5a6492c9f0ca95df337bb28fb34
Author: Jakub Steiner <jimmac gmail com>
Date:   Wed Dec 2 15:23:43 2020 +0100

    Adwaita: specialcase close button
    
    Fixes https://gitlab.gnome.org/GNOME/gtk/-/issues/3427

 gtk/theme/Adwaita/_common.scss | 14 ++++++++++++++
 1 file changed, 14 insertions(+)
---
diff --git a/gtk/theme/Adwaita/_common.scss b/gtk/theme/Adwaita/_common.scss
index 19812ded36..5e79ff6f84 100644
--- a/gtk/theme/Adwaita/_common.scss
+++ b/gtk/theme/Adwaita/_common.scss
@@ -1393,6 +1393,20 @@ windowcontrols {
     margin: 0 2px;
     min-width: 0;
     min-height: 0;
+
+    &.close {
+      background-image: none;
+      border: none;
+      box-shadow: none;
+      background-color: transparent;
+      &:hover { background-color: darken($headerbar_color,25%); }
+      &:active { background-color: darken($headerbar_color,35%); }
+      &:backdrop:hover image { color: $selected_fg_color; }
+         /* because of clickthrough and the destructive nature,
+            make an exception about hovering over an unfocused
+            window close button */
+
+    }
   }
 }