[libadwaita/wip/exalm/treeview-fix] stylesheet: Fix treeview accel editor color

[Alexander Mikhaylenko <alexm src gnome org>]

commit 3f1a68ff643854fb03a11d5106acc866a2cf6b44
Author: Alexander Mikhaylenko <alexm gnome org>
Date:   Thu May 20 00:02:41 2021 +0500

    stylesheet: Fix treeview accel editor color
    
    It should be grey like the row selection. It's also overlaid on top of the
    row so it can't be transparent and has to be pre-blended on top of the
    background color.

 src/stylesheet/widgets/_trees.scss | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)
---
diff --git a/src/stylesheet/widgets/_trees.scss b/src/stylesheet/widgets/_trees.scss
index 04a6b698..bd381fcb 100644
--- a/src/stylesheet/widgets/_trees.scss
+++ b/src/stylesheet/widgets/_trees.scss
@@ -1,3 +1,6 @@
+// To be used for opaque elements overlaid atop the selected row
+$treeview_selection_opaque: mix(opacify($menu_selected_color, 1), $base_color, 100% * 
alpha($menu_selected_color));
+
 columnview.view,
 treeview.view {
   border-left-color: $treeview_borders_color; // this is actually the tree lines color,
@@ -115,7 +118,10 @@ treeview.view {
     }
   }
 
-  acceleditor > label { background-color: $selected_bg_color; } // see tests/testaccel to test
+  acceleditor > label {
+    // see tests/testaccel in GTK to test
+    background-color: $treeview_selection_opaque;
+  }
 }
 
 %column_header_button {