keyboard: broadcast modifiers

...to all clients rather than just the one with keyboard focus on keyboard
enter/create, modifer press/release and wlr_seat_set_keyboard().

This enables:

- Clients such as panels to display the current keyboard layout without
  introducing new wayland protocols or other IPC.

- Unfocused xdg-shell clients to understand button press with keyboard
  modifiers for example Ctrl+click.

The keymap is forwarded to all clients in wlr_seat_set_keyboard(). When a
keymap contains multiple layouts, the selection is made via modifiers,
which previously were only sent to the client with keyboard focus.

Tested with: https://github.com/johanmalm/keyboard-layout

Ref: https://gitlab.freedesktop.org/wlroots/wlroots/-/merge_requests/4496

Fixes: #2271

diff --git a/src/input/keyboard.c b/src/input/keyboard.c
index 01557e618f7ac1d093bf7c9005cb1622bafda780..f0ceb7dae4f8f6d2bc99aa0729392d2503ca576b 100644 (file)
--- a/src/input/keyboard.c
+++ b/src/input/keyboard.c
@@ -80,6 +80,43 @@ end_cycling(struct server *server)
        should_cancel_cycling_on_next_key_release = false;
 }
 
+static struct wlr_seat_client *
+seat_client_from_keyboard_resource(struct wl_resource *resource)
+{
+       return wl_resource_get_user_data(resource);
+}
+
+static void
+broadcast_modifiers_to_unfocused_clients(struct wlr_seat *seat,
+               const struct wlr_keyboard_modifiers *modifiers)
+{
+       struct wlr_seat_client *client;
+       wl_list_for_each(client, &seat->clients, link) {
+               if (client == seat->keyboard_state.focused_client) {
+                       /*
+                        * We've already notified the focused client by calling
+                        * wlr_seat_keyboard_notify_modifiers()
+                        */
+                       continue;
+               }
+               uint32_t serial = wlr_seat_client_next_serial(client);
+               struct wl_resource *resource;
+               wl_resource_for_each(resource, &client->keyboards) {
+                       if (!seat_client_from_keyboard_resource(resource)) {
+                               continue;
+                       }
+                       if (!modifiers) {
+                               wl_keyboard_send_modifiers(resource, serial, 0,
+                                       0, 0, 0);
+                       } else {
+                               wl_keyboard_send_modifiers(resource, serial,
+                                       modifiers->depressed, modifiers->latched,
+                                       modifiers->locked, modifiers->group);
+                       }
+               }
+       }
+}
+
 static void
 keyboard_modifiers_notify(struct wl_listener *listener, void *data)
 {
@@ -112,8 +149,31 @@ keyboard_modifiers_notify(struct wl_listener *listener, void *data)
        }
 
        if (!input_method_keyboard_grab_forward_modifiers(keyboard)) {
+               /* Send modifiers to focused client */
                wlr_seat_keyboard_notify_modifiers(seat->seat,
                        &wlr_keyboard->modifiers);
+
+               /*
+                * Also broadcast them to non-keyboard-focused clients.
+                *
+                * The Wayland protocol does not specify that modifiers are
+                * broadcast, so this is not something clients can rely on in
+                * other compositors.
+                *
+                * Sway used to broadcast modifiers but stopped doing so to
+                * avoid waking up all clients when the modifiers change.
+                *
+                * By testing with foot and Ctrl+scroll to change font size, it
+                * appears that Mutter does not pass modifiers to unfocused
+                * clients, whereas KWin and Weston pass modifiers to clients
+                * with pointer-focus.
+                *
+                * This could be made configurable if there are unintended
+                * consequences. If so, modifiers ought to still be passed to
+                * clients with pointer-focus (see issue #2271)
+                */
+               broadcast_modifiers_to_unfocused_clients(seat->seat,
+                       &wlr_keyboard->modifiers);
        }
 }