[libadwaita/wip/exalm/oapcity] stylesheet: Fix notebook disabled state

[Alexander Mikhaylenko <alexm src gnome org>]

commit 5d0822302f3f5aa0ddf5cbb06e0b912cc299ff13
Author: Alexander Mikhaylenko <alexm gnome org>
Date:   Fri Oct 22 12:11:47 2021 +0500

    stylesheet: Fix notebook disabled state

 src/stylesheet/widgets/_notebook.scss | 8 ++++++++
 1 file changed, 8 insertions(+)
---
diff --git a/src/stylesheet/widgets/_notebook.scss b/src/stylesheet/widgets/_notebook.scss
index 6d25a601..d8f900fc 100644
--- a/src/stylesheet/widgets/_notebook.scss
+++ b/src/stylesheet/widgets/_notebook.scss
@@ -132,6 +132,14 @@ notebook {
         outline-color: transparent;
       }
 
+      &:disabled {
+        filter: opacity($disabled_opacity);
+
+        label, button {
+          filter: none;
+        }
+      }
+
       // colors the button like the label, overridden otherwise
       button.flat {
         color: gtkalpha(currentColor, 0.3);