[gtk/wip/jimmac/backdrop-titles] theme: tone down unfocused title labels

[Jakub Steiner <jimmac src gnome org>]

commit be6413b0e7edc3ff3c18dbb2cb5afd5a907d366b
Author: Jakub Steiner <jimmac gmail com>
Date:   Fri Sep 23 17:01:24 2022 +0200

    theme: tone down unfocused title labels
    
    - mimic libadwaita in toning down unfocused titles. Cargo culting the
      filter instead of using normal opacity property.
    
    Fixes https://gitlab.gnome.org/GNOME/gtk/-/issues/4468

 gtk/theme/Default/_common.scss | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/gtk/theme/Default/_common.scss b/gtk/theme/Default/_common.scss
index ea7415faf2..d627cf9674 100644
--- a/gtk/theme/Default/_common.scss
+++ b/gtk/theme/Default/_common.scss
@@ -1500,6 +1500,8 @@ headerbar {
     background-image: none;
 
     transition: $backdrop_transition;
+
+    .title { filter: opacity(.5); }
   }
 
   .title {