Decorations: handle results of kde-server-decoration negotiations

include/decorations.h

@@ -3,7 +3,13 @@
 #define __LAB_DECORATIONS_H
 
 struct server;
+struct view;
+struct wlr_surface;
 
+void kde_server_decoration_init(struct server *server);
 void xdg_server_decoration_init(struct server *server);
 
+void kde_server_decoration_update_default(void);
+void kde_server_decoration_set_view(struct view *view, struct wlr_surface *surface);
+
 #endif /* __LAB_DECORATIONS_H */

include/labwc.h

@@ -34,7 +34,6 @@
 #include <wlr/types/wlr_pointer_constraints_v1.h>
 #include <wlr/types/wlr_pointer_gestures_v1.h>
 #include <wlr/types/wlr_seat.h>
-#include <wlr/types/wlr_server_decoration.h>
 #include <wlr/types/wlr_subcompositor.h>
 #include <wlr/types/wlr_xcursor_manager.h>
 #include <wlr/types/wlr_xdg_activation_v1.h>
@@ -220,6 +219,7 @@ struct server {
 	struct wl_listener new_xdg_surface;
 	struct wl_listener new_layer_surface;
 
+	struct wl_listener kde_server_decoration;
 	struct wl_listener xdg_toplevel_decoration;
 #if HAVE_XWAYLAND
 	struct wlr_xwayland *xwayland;

src/decorations/kde-deco.c

@@ -0,0 +1,132 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <assert.h>
+#include <wlr/types/wlr_server_decoration.h>
+#include "common/list.h"
+#include "common/mem.h"
+#include "decorations.h"
+#include "labwc.h"
+#include "view.h"
+
+static struct wl_list decorations;
+static struct wlr_server_decoration_manager *kde_deco_mgr;
+
+struct kde_deco {
+	struct wl_list link;  /* decorations */
+	struct wlr_server_decoration *wlr_kde_decoration;
+	struct view *view;
+	struct wl_listener mode;
+	struct wl_listener destroy;
+};
+
+static void
+handle_destroy(struct wl_listener *listener, void *data)
+{
+	struct kde_deco *kde_deco = wl_container_of(listener, kde_deco, destroy);
+	wl_list_remove(&kde_deco->destroy.link);
+	wl_list_remove(&kde_deco->mode.link);
+	wl_list_remove(&kde_deco->link);
+	free(kde_deco);
+}
+
+static void
+handle_mode(struct wl_listener *listener, void *data)
+{
+	struct kde_deco *kde_deco = wl_container_of(listener, kde_deco, mode);
+	if (!kde_deco->view) {
+		return;
+	}
+
+	enum wlr_server_decoration_manager_mode client_mode =
+		kde_deco->wlr_kde_decoration->mode;
+
+	switch (client_mode) {
+	case WLR_SERVER_DECORATION_MANAGER_MODE_SERVER:
+		kde_deco->view->ssd_preference = LAB_SSD_PREF_SERVER;
+		break;
+	case WLR_SERVER_DECORATION_MANAGER_MODE_NONE:
+	case WLR_SERVER_DECORATION_MANAGER_MODE_CLIENT:
+		kde_deco->view->ssd_preference = LAB_SSD_PREF_CLIENT;
+		break;
+	default:
+		wlr_log(WLR_ERROR, "Unspecified kde decoration variant "
+			"requested: %u", client_mode);
+	}
+
+	view_set_decorations(kde_deco->view,
+		kde_deco->view->ssd_preference == LAB_SSD_PREF_SERVER);
+}
+
+static void
+handle_new_server_decoration(struct wl_listener *listener, void *data)
+{
+	struct wlr_server_decoration *wlr_deco = data;
+	struct kde_deco *kde_deco = znew(*kde_deco);
+	kde_deco->wlr_kde_decoration = wlr_deco;
+
+	if (wlr_surface_is_xdg_surface(wlr_deco->surface)) {
+		/*
+		 * Depending on the application event flow, the supplied
+		 * wlr_surface may already have been set up as a xdg_surface
+		 * or not (e.g. for GTK4). In the second case, the xdg.c
+		 * new_surface handler will try to set the view via
+		 * kde_server_decoration_set_view().
+		 */
+		struct wlr_xdg_surface *xdg_surface =
+			wlr_xdg_surface_from_wlr_surface(wlr_deco->surface);
+		if (xdg_surface && xdg_surface->data) {
+			kde_deco->view = (struct view *)xdg_surface->data;
+			handle_mode(&kde_deco->mode, wlr_deco);
+		}
+	}
+
+	wl_signal_add(&wlr_deco->events.destroy, &kde_deco->destroy);
+	kde_deco->destroy.notify = handle_destroy;
+
+	wl_signal_add(&wlr_deco->events.mode, &kde_deco->mode);
+	kde_deco->mode.notify = handle_mode;
+
+	wl_list_append(&decorations, &kde_deco->link);
+}
+
+void
+kde_server_decoration_set_view(struct view *view, struct wlr_surface *surface)
+{
+	struct kde_deco *kde_deco;
+	wl_list_for_each(kde_deco, &decorations, link) {
+		if (kde_deco->wlr_kde_decoration->surface == surface) {
+			if (!kde_deco->view) {
+				kde_deco->view = view;
+				handle_mode(&kde_deco->mode, kde_deco->wlr_kde_decoration);
+			}
+			return;
+		}
+	}
+}
+
+void
+kde_server_decoration_update_default(void)
+{
+	assert(kde_deco_mgr);
+	wlr_server_decoration_manager_set_default_mode(kde_deco_mgr,
+		rc.xdg_shell_server_side_deco
+		? WLR_SERVER_DECORATION_MANAGER_MODE_SERVER
+		: WLR_SERVER_DECORATION_MANAGER_MODE_CLIENT);
+}
+
+void
+kde_server_decoration_init(struct server *server)
+{
+	assert(!kde_deco_mgr);
+	kde_deco_mgr = wlr_server_decoration_manager_create(server->wl_display);
+	if (!kde_deco_mgr) {
+		wlr_log(WLR_ERROR, "unable to create the kde server deco manager");
+		exit(EXIT_FAILURE);
+	}
+
+	wl_list_init(&decorations);
+	kde_server_decoration_update_default();
+
+	wl_signal_add(&kde_deco_mgr->events.new_decoration, &server->kde_server_decoration);
+	server->kde_server_decoration.notify = handle_new_server_decoration;
+}
+

src/decorations/meson.build

@@ -1,3 +1,4 @@
 labwc_sources += files(
+  'kde-deco.c',
   'xdg-deco.c',
 )

src/server.c

@@ -53,6 +53,7 @@ reload_config_and_theme(void)
 	menu_reconfigure(g_server);
 	seat_reconfigure(g_server);
 	regions_reconfigure(g_server);
+	kde_server_decoration_update_default();
 }
 
 static int
@@ -310,18 +311,8 @@ server_init(struct server *server)
 	wl_signal_add(&server->xdg_shell->events.new_surface,
 		&server->new_xdg_surface);
 
-	/* Disable CSD */
+	kde_server_decoration_init(server);
 	xdg_server_decoration_init(server);
-	struct wlr_server_decoration_manager *deco_mgr = NULL;
-	deco_mgr = wlr_server_decoration_manager_create(server->wl_display);
-	if (!deco_mgr) {
-		wlr_log(WLR_ERROR, "unable to create the server deco manager");
-		exit(EXIT_FAILURE);
-	}
-	wlr_server_decoration_manager_set_default_mode(
-		deco_mgr, rc.xdg_shell_server_side_deco
-		? WLR_SERVER_DECORATION_MANAGER_MODE_SERVER
-		: WLR_SERVER_DECORATION_MANAGER_MODE_CLIENT);
 
 	server->xdg_activation = wlr_xdg_activation_v1_create(server->wl_display);
 	if (!server->xdg_activation) {

src/xdg.c

@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-only
 #include <assert.h>
 #include "common/mem.h"
+#include "decorations.h"
 #include "labwc.h"
 #include "node.h"
 #include "view.h"
@@ -48,38 +49,22 @@ handle_new_xdg_popup(struct wl_listener *listener, void *data)
 static bool
 has_ssd(struct view *view)
 {
+	/*
+	 * view->ssd_preference may be set by the decoration implementation
+	 * e.g. src/decorations/xdg-deco.c or src/decorations/kde-deco.c.
+	 */
 	switch (view->ssd_preference) {
 	case LAB_SSD_PREF_SERVER:
 		return true;
 	case LAB_SSD_PREF_CLIENT:
 		return false;
 	default:
-		break;
-	}
-
-	if (!rc.xdg_shell_server_side_deco) {
 		/*
-		 * User prefers client side decorations and
-		 * the view didn't negotiate server side ones.
+		 * We don't know anything about the client preference
+		 * so fall back to core.decoration settings in rc.xml
 		 */
-		return false;
+		return rc.xdg_shell_server_side_deco;
 	}
-
-	/*
-	 * Some XDG shells refuse to disable CSD in which case their
-	 * geometry.{x,y} seems to be greater than zero. We filter on that
-	 * on the assumption that this will remain true.
-	 *
-	 * TODO: Replace this with a proper implementation of
-	 *       the KDE decoration variant as can be seen at
-	 *       https://github.com/swaywm/sway/blob/master/sway/decoration.c
-	 */
-	struct wlr_xdg_surface_state *current =
-		&xdg_surface_from_view(view)->current;
-	if (current->geometry.x || current->geometry.y) {
-		return false;
-	}
-	return true;
 }
 
 static void
@@ -560,9 +545,18 @@ xdg_surface_new(struct wl_listener *listener, void *data)
 	node_descriptor_create(&view->scene_tree->node,
 		LAB_NODE_DESC_VIEW, view);
 
-	/* In support of xdg_toplevel_decoration */
+	/* In support of xdg_toplevel_decoration and kde_server_decoration */
 	xdg_surface->data = view;
 
+	/*
+	 * GTK4 initializes the decorations on the wl_surface before
+	 * converting it into a xdg surface. This call takes care of
+	 * connecting the view to an existing decoration. If there
+	 * is no existing decoration object available for the
+	 * wl_surface, this call is a no-op.
+	 */
+	kde_server_decoration_set_view(view, xdg_surface->surface);
+
 	/* In support of xdg popups */
 	xdg_surface->surface->data = tree;