Bug 1884452 - Allow users to disable non-native titlebar buttons on L…

…inux. r=dao,stransky,desktop-theme-reviewers

If we wanted to provide this, it's not super-hard... But not sure if
worth it.

Differential Revision: https://phabricator.services.mozilla.com/D204246

browser/themes/linux/browser.css

@@ -233,21 +233,24 @@
     appearance: auto;
   }
 
-  /* When using lightweight themes, use our own buttons since native ones might
-   * assume a native background in order to be visible. */
-  &:-moz-lwtheme {
-    padding-inline: 3px;
-
-    > .toolbarbutton-icon {
-      appearance: none;
-      border-radius: 100%;
-      background-position: center center;
-      background-repeat: no-repeat;
-      -moz-context-properties: stroke;
-      stroke: currentColor;
-      /* Roughly the Adwaita size */
-      width: 24px;
-      height: 24px;
+  /* stylelint-disable-next-line media-query-no-invalid */
+  @media (-moz-bool-pref: "widget.gtk.non-native-titlebar-buttons.enabled") {
+    /* When using lightweight themes, use our own buttons since native ones might
+     * assume a native background in order to be visible. */
+    &:-moz-lwtheme {
+      padding-inline: 3px;
+
+      > .toolbarbutton-icon {
+        appearance: none;
+        border-radius: 100%;
+        background-position: center center;
+        background-repeat: no-repeat;
+        -moz-context-properties: stroke;
+        stroke: currentColor;
+        /* Roughly the Adwaita size */
+        width: 24px;
+        height: 24px;
+      }
     }
   }
 

modules/libpref/init/StaticPrefList.yaml

@@ -16037,6 +16037,12 @@
   mirror: always
   rust: true
 
+# Whether non-native titlebar buttons are enabled for lightweight themes.
+- name: widget.gtk.non-native-titlebar-buttons.enabled
+  type: RelaxedAtomicBool
+  value: true
+  mirror: always
+
 # Whether selection colors for the non-system theme get passed from the system
 # GTK theme.
 - name: widget.gtk.alt-theme.selection