xwayland: Allow shells to make xwayland surfaces fullscreen

The fullscreen state for xwayland surfaces can currently only be
effectively set from the client side. This commit enables
libweston-desktop based shells to properly set the fullscreen state
for xwayland surfaces.

Signed-off-by: Alexandros Frantzis <alexandros.frantzis@collabora.com>

libweston/desktop/xwayland.c

@@ -65,6 +65,7 @@ struct weston_desktop_xwayland_surface {
 	bool added;
 	enum weston_desktop_xwayland_surface_state state;
 	enum weston_desktop_xwayland_surface_state prev_state;
+	bool state_updated;
 };
 
 static void
@@ -85,6 +86,10 @@ weston_desktop_xwayland_surface_change_state(struct weston_desktop_xwayland_surf
 	}
 
 	wsurface = weston_desktop_surface_get_surface(surface->surface);
+	/* In some cases when adding a surface, the state may be updated by the
+	 * shell (e.g., to fullscreen). Track if this has happened and respect
+	 * the updated value. */
+	surface->state_updated = false;
 
 	if (surface->state != state) {
 		if (surface->state == XWAYLAND) {
@@ -126,7 +131,13 @@ weston_desktop_xwayland_surface_change_state(struct weston_desktop_xwayland_surf
 			weston_surface_map(wsurface);
 		}
 
+		/* If the surface state was updated by the shell during this
+		 * call, respect the updated value, otherwise assign the new
+		 * value. */
+		if (!surface->state_updated) {
 			surface->state = state;
+			surface->state_updated = true;
+		}
 	}
 
 	if (parent != NULL)
@@ -194,6 +205,19 @@ weston_desktop_xwayland_surface_set_size(struct weston_desktop_surface *dsurface
 	surface->client_interface->send_configure(wsurface, width, height);
 }
 
+static void
+weston_desktop_xwayland_surface_set_fullscreen(struct weston_desktop_surface *dsurface,
+					       void *user_data, bool fullscreen)
+{
+	struct weston_desktop_xwayland_surface *surface = user_data;
+	struct weston_surface *wsurface =
+		weston_desktop_surface_get_surface(surface->surface);
+
+	surface->state = fullscreen ? FULLSCREEN : TOPLEVEL;
+	surface->state_updated = true;
+	surface->client_interface->send_fullscreen(wsurface, fullscreen);
+}
+
 static void
 weston_desktop_xwayland_surface_destroy(struct weston_desktop_surface *dsurface,
 					void *user_data)
@@ -244,6 +268,7 @@ weston_desktop_xwayland_surface_get_fullscreen(struct weston_desktop_surface *ds
 static const struct weston_desktop_surface_implementation weston_desktop_xwayland_surface_internal_implementation = {
 	.committed = weston_desktop_xwayland_surface_committed,
 	.set_size = weston_desktop_xwayland_surface_set_size,
+	.set_fullscreen = weston_desktop_xwayland_surface_set_fullscreen,
 
 	.get_maximized = weston_desktop_xwayland_surface_get_maximized,
 	.get_fullscreen = weston_desktop_xwayland_surface_get_fullscreen,

xwayland/window-manager.c

@@ -3130,9 +3130,30 @@ send_position(struct weston_surface *surface, int32_t x, int32_t y)
 	}
 }
 
+static void
+send_fullscreen(struct weston_surface *surface, bool fullscreen)
+{
+	struct weston_wm_window *window = get_wm_window(surface);
+
+	if (!window || !window->wm)
+		return;
+
+	if (window->fullscreen == fullscreen)
+		return;
+
+	window->fullscreen = fullscreen;
+	weston_wm_window_set_net_wm_state(window);
+
+	if (window->fullscreen) {
+		window->saved_width = window->width;
+		window->saved_height = window->height;
+	}
+}
+
 static const struct weston_xwayland_client_interface shell_client = {
 	send_configure,
 	send_close,
+	send_fullscreen,
 };
 
 static int

xwayland/xwayland-internal-interface.h

@@ -32,6 +32,7 @@ struct weston_desktop_xwayland_surface;
 struct weston_xwayland_client_interface {
 	void (*send_configure)(struct weston_surface *surface, int32_t width, int32_t height);
 	void (*send_close)(struct weston_surface *surface);
+	void (*send_fullscreen)(struct weston_surface *surface, bool fullscreen);
 };
 
 struct weston_desktop_xwayland_interface {