keybindings: Restore window opacity keybindings.

This was inadvertantly removed during the 5.4 rebase.

Fixes linuxmint/cinnamon#11852.

Author: mtwebster

src/core/keybindings.c

@@ -4072,6 +4072,25 @@ handle_rotate_monitor (MetaDisplay    *display,
   meta_monitor_manager_rotate_monitor (monitor_manager);
 }
 
+static void
+handle_opacity (MetaDisplay    *display,
+                MetaWindow     *window,
+                ClutterKeyEvent *event,
+                MetaKeyBinding *binding,
+                gpointer        dummy)
+{
+    MetaKeyBindingAction action = meta_prefs_get_keybinding_action (binding->name);
+
+    if (action == META_KEYBINDING_ACTION_DECREASE_OPACITY)
+      {
+        meta_window_decrease_opacity (window);
+      }
+    else
+      {
+        meta_window_increase_opacity (window);
+      }
+}
+
 static void
 handle_restore_shortcuts (MetaDisplay     *display,
                           MetaWindow      *window,
@@ -4925,6 +4944,20 @@ init_builtin_key_bindings (MetaDisplay *display)
                           META_KEYBINDING_ACTION_MOVE_TO_CENTER,
                           handle_move_to_center, 0);
 
+  add_builtin_keybinding (display,
+                          "increase-opacity",
+                          common_keybindings,
+                          META_KEY_BINDING_PER_WINDOW,
+                          META_KEYBINDING_ACTION_INCREASE_OPACITY,
+                          handle_opacity, 0);
+
+  add_builtin_keybinding (display,
+                          "decrease-opacity",
+                          common_keybindings,
+                          META_KEY_BINDING_PER_WINDOW,
+                          META_KEYBINDING_ACTION_DECREASE_OPACITY,
+                          handle_opacity, 0);
+
   g_object_unref (common_keybindings);
   g_object_unref (mutter_keybindings);
   g_object_unref (mutter_wayland_keybindings);

src/meta/prefs.h

@@ -374,6 +374,8 @@ gboolean    meta_prefs_get_invert_flip_direction (void);
  * @META_KEYBINDING_ACTION_MOVE_TO_SIDE_E: FILLME
  * @META_KEYBINDING_ACTION_MOVE_TO_SIDE_W: FILLME
  * @META_KEYBINDING_ACTION_MOVE_TO_CENTER: FILLME
+ * META_KEYBINDING_ACTION_INCREASE_OPACITY: FILLME,
+ * META_KEYBINDING_ACTION_DECREASE_OPACITY: FILLME,
  * @META_KEYBINDING_ACTION_OVERLAY_KEY: FILLME
  * @META_KEYBINDING_ACTION_LOCATE_POINTER_KEY: FILLME
  * @META_KEYBINDING_ACTION_ALWAYS_ON_TOP: FILLME
@@ -474,6 +476,8 @@ typedef enum _MetaKeyBindingAction
   META_KEYBINDING_ACTION_MOVE_TO_SIDE_E,
   META_KEYBINDING_ACTION_MOVE_TO_SIDE_W,
   META_KEYBINDING_ACTION_MOVE_TO_CENTER,
+  META_KEYBINDING_ACTION_INCREASE_OPACITY,
+  META_KEYBINDING_ACTION_DECREASE_OPACITY,
   META_KEYBINDING_ACTION_OVERLAY_KEY,
   META_KEYBINDING_ACTION_LOCATE_POINTER_KEY,
   META_KEYBINDING_ACTION_ISO_NEXT_GROUP,