Handle some keybindings even when a compositor grab is active

Do not ignore all key events automatically when a compositor grab
is active, and introduce a flag for masking which keybindings should
be active.
This does not mean that automatically all keybindings are active
when the compositor is modal, it merely moves the policy down to
the handler.

https://bugzilla.gnome.org/show_bug.cgi?id=613543

src/core/display.c

@@ -1961,9 +1961,6 @@ event_callback (XEvent   *event,
     {
     case KeyPress:
     case KeyRelease:
-      if (display->grab_op == META_GRAB_OP_COMPOSITOR)
-        break;
-
       /* For key events, it's important to enforce single-handling, or
        * we can get into a confused state. So if a keybinding is
        * handled (because it's one of our hot-keys, or because we are

src/core/keybindings.c

@@ -1463,6 +1463,10 @@ process_event (MetaKeyBinding       *bindings,
            bindings[i].mask))
         continue;
 
+      if (display->grab_op != META_GRAB_OP_NONE &&
+          (handler->flags & META_KEY_BINDING_HANDLE_WHEN_GRABBED) == 0)
+        continue;
+
       /*
        * window must be non-NULL for on_window to be true,
        * and so also window must be non-NULL if we get here and
@@ -1712,6 +1716,11 @@ meta_display_process_key_event (MetaDisplay *display,
                           "Processing event for keyboard workspace switching\n");
               keep_grab = process_workspace_switch_grab (display, screen, event, keysym);
               break;
+
+            case META_GRAB_OP_COMPOSITOR:
+              /* Compositor grabs don't go through meta_display_begin_grab_op(),
+                 so all_keys_grabbed is always false for them */
+              g_assert_not_reached ();
  
             default:
               break;
@@ -3774,28 +3783,28 @@ init_builtin_key_bindings (MetaDisplay *display)
   add_builtin_keybinding (display,
                           "switch-to-workspace-left",
                           common_keybindings,
-                          META_KEY_BINDING_NONE,
+                          META_KEY_BINDING_HANDLE_WHEN_GRABBED,
                           META_KEYBINDING_ACTION_WORKSPACE_LEFT,
                           handle_switch_to_workspace, META_MOTION_LEFT);
 
   add_builtin_keybinding (display,
                           "switch-to-workspace-right",
                           common_keybindings,
-                          META_KEY_BINDING_NONE,
+                          META_KEY_BINDING_HANDLE_WHEN_GRABBED,
                           META_KEYBINDING_ACTION_WORKSPACE_RIGHT,
                           handle_switch_to_workspace, META_MOTION_RIGHT);
 
   add_builtin_keybinding (display,
                           "switch-to-workspace-up",
                           common_keybindings,
-                          META_KEY_BINDING_NONE,
+                          META_KEY_BINDING_HANDLE_WHEN_GRABBED,
                           META_KEYBINDING_ACTION_WORKSPACE_UP,
                           handle_switch_to_workspace, META_MOTION_UP);
 
   add_builtin_keybinding (display,
                           "switch-to-workspace-down",
                           common_keybindings,
-                          META_KEY_BINDING_NONE,
+                          META_KEY_BINDING_HANDLE_WHEN_GRABBED,
                           META_KEYBINDING_ACTION_WORKSPACE_DOWN,
                           handle_switch_to_workspace, META_MOTION_DOWN);
 
@@ -3841,14 +3850,14 @@ init_builtin_key_bindings (MetaDisplay *display)
   add_builtin_keybinding (display,
                           "switch-panels",
                           common_keybindings,
-                          META_KEY_BINDING_REVERSES,
+                          META_KEY_BINDING_REVERSES | META_KEY_BINDING_HANDLE_WHEN_GRABBED,
                           META_KEYBINDING_ACTION_SWITCH_PANELS,
                           handle_switch, META_TAB_LIST_DOCKS);
 
   add_builtin_keybinding (display,
                           "switch-panels-backward",
                           common_keybindings,
-                          REVERSES_AND_REVERSED,
+                          REVERSES_AND_REVERSED | META_KEY_BINDING_HANDLE_WHEN_GRABBED,
                           META_KEYBINDING_ACTION_SWITCH_PANELS_BACKWARD,
                           handle_switch, META_TAB_LIST_DOCKS);
 
@@ -3926,14 +3935,14 @@ init_builtin_key_bindings (MetaDisplay *display)
   add_builtin_keybinding (display,
                           "panel-main-menu",
                           common_keybindings,
-                          META_KEY_BINDING_NONE,
+                          META_KEY_BINDING_HANDLE_WHEN_GRABBED,
                           META_KEYBINDING_ACTION_PANEL_MAIN_MENU,
                           handle_panel, META_KEYBINDING_ACTION_PANEL_MAIN_MENU);
 
   add_builtin_keybinding (display,
                           "panel-run-dialog",
                           common_keybindings,
-                          META_KEY_BINDING_NONE,
+                          META_KEY_BINDING_HANDLE_WHEN_GRABBED,
                           META_KEYBINDING_ACTION_PANEL_RUN_DIALOG,
                           handle_panel, META_KEYBINDING_ACTION_PANEL_RUN_DIALOG);
 

src/meta/prefs.h

@@ -236,6 +236,7 @@ typedef enum
   META_KEY_BINDING_REVERSES    = 1 << 2,
   META_KEY_BINDING_IS_REVERSED = 1 << 3,
   META_KEY_BINDING_IS_SINGLE   = 1 << 4,
+  META_KEY_BINDING_HANDLE_WHEN_GRABBED = 1 << 5,
 } MetaKeyBindingFlags;
 
 typedef struct