[gnome-shell-sass] screenshot-ui: Add a check icon to selected window

[Florian Müllner <fmuellner src gnome org>]

commit 2d085b3453e07c30b2a2e7e2c610286cf549f6da
Author: Ivan Molodetskikh <yalterz gmail com>
Date:   Fri Dec 17 08:58:00 2021 +0300

    screenshot-ui: Add a check icon to selected window
    
    Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1954>

 widgets/_screenshot.scss | 13 +++++++++++++
 1 file changed, 13 insertions(+)
---
diff --git a/widgets/_screenshot.scss b/widgets/_screenshot.scss
index 0a626aa..0abc0f8 100644
--- a/widgets/_screenshot.scss
+++ b/widgets/_screenshot.scss
@@ -113,6 +113,14 @@
   border: 6px transparent;
 }
 
+.screenshot-ui-window-selector-check {
+  transition-duration: 200ms;
+  color: transparent;
+  border-radius: 99px;
+  border-width: 12px;
+  icon-size: 24px;
+}
+
 .screenshot-ui-window-selector-window {
   &:hover {
     .screenshot-ui-window-selector-window-border {
@@ -124,6 +132,11 @@
       border-color: $selected_bg_color;
       background-color: transparentize($selected_bg_color, 0.8);
     }
+
+    .screenshot-ui-window-selector-check {
+      color: white;
+      background-color: $selected_bg_color;
+    }
   }
 }