Set Cage's window title to toplevel's title

When using the Wayland or X11 backend, Cage is drawn inside a window.
This commit sets this window's title to that of the currently focused
toplevel window inside Cage.

Fixes #29.

cage.c

@@ -17,6 +17,8 @@
 #include <unistd.h>
 #include <wayland-server.h>
 #include <wlr/backend.h>
+#include <wlr/backend/wayland.h>
+#include <wlr/backend/x11.h>
 #include <wlr/render/wlr_renderer.h>
 #include <wlr/types/wlr_compositor.h>
 #include <wlr/types/wlr_data_device.h>
@@ -36,11 +38,31 @@
 #include "output.h"
 #include "seat.h"
 #include "server.h"
+#include "view.h"
 #include "xdg_shell.h"
 #if CAGE_HAS_XWAYLAND
 #include "xwayland.h"
 #endif
 
+void
+set_window_title(struct cg_server *server, struct cg_view *view)
+{
+	struct wlr_output *output = server->output->wlr_output;
+	bool is_wl = wlr_output_is_wl(output);
+	bool is_x11 = wlr_output_is_x11(output);
+
+	if (!is_wl && !is_x11) {
+		return;
+	}
+
+	const char *title = view_get_title(view);
+	if (is_wl) {
+		wlr_wl_output_set_title(output, title);
+	} else if (is_x11) {
+		wlr_x11_output_set_title(output, title);
+	}
+}
+
 static bool
 spawn_primary_client(char *argv[], pid_t *pid_out)
 {

seat.c

@@ -724,7 +724,8 @@ seat_set_focus(struct cg_seat *seat, struct cg_view *view)
 		wl_list_insert(&server->views, &view->link);
 	}
 
-        view_activate(view, true);
+	view_activate(view, true);
+	set_window_title(server, view);
 
 	struct wlr_keyboard *keyboard = wlr_seat_get_keyboard(wlr_seat);
 	if (keyboard) {

server.h

@@ -14,6 +14,7 @@
 
 #include "output.h"
 #include "seat.h"
+#include "view.h"
 
 struct cg_server {
 	struct wl_display *wl_display;
@@ -37,4 +38,6 @@ struct cg_server {
 #endif
 };
 
+void set_window_title(struct cg_server *server, struct cg_view *view);
+
 #endif

view.c

@@ -6,8 +6,11 @@
  * See the LICENSE file accompanying this file.
  */
 
+#define _POSIX_C_SOURCE 200809L
+
 #include <stdbool.h>
 #include <stdlib.h>
+#include <string.h>
 #include <wayland-server.h>
 #include <wlr/types/wlr_box.h>
 #include <wlr/types/wlr_output.h>
@@ -18,6 +21,13 @@
 #include "server.h"
 #include "view.h"
 
+char *
+view_get_title(struct cg_view *view)
+{
+	const char *title = view->get_title(view);
+	return strndup(title, strlen(title));
+}
+
 void
 view_activate(struct cg_view *view, bool activate)
 {

view.h

@@ -41,6 +41,7 @@ struct cg_view {
 	// TODO: allow applications to go to fullscreen from maximized?
 	// struct wl_listener request_fullscreen;
 
+	char *(*get_title)(struct cg_view *view);
 	void (*activate)(struct cg_view *view, bool activate);
 	void (*maximize)(struct cg_view *view, int output_width, int output_height);
 	void (*get_geometry)(struct cg_view *view, int *width_out, int *height_out);
@@ -52,6 +53,7 @@ struct cg_view {
 	bool (*is_parent)(struct cg_view *parent, struct cg_view *child);
 };
 
+char *view_get_title(struct cg_view *view);
 void view_activate(struct cg_view *view, bool activate);
 void view_for_each_surface(struct cg_view *view, wlr_surface_iterator_func_t iterator, void *data);
 struct wlr_surface *view_wlr_surface_at(struct cg_view *view, double sx, double sy,

xdg_shell.c

@@ -14,6 +14,12 @@
 #include "server.h"
 #include "view.h"
 
+static char *
+get_title(struct cg_view *view)
+{
+	return view->xdg_surface->toplevel->title;
+}
+
 static void
 activate(struct cg_view *view, bool activate)
 {
@@ -109,6 +115,7 @@ handle_xdg_shell_surface_new(struct wl_listener *listener, void *data)
 	view->destroy.notify = handle_xdg_shell_surface_destroy;
 	wl_signal_add(&xdg_surface->events.destroy, &view->destroy);
 
+	view->get_title = get_title;
 	view->activate = activate;
 	view->maximize = maximize;
 	view->get_geometry = get_geometry;

xwayland.c

@@ -14,6 +14,12 @@
 #include "server.h"
 #include "view.h"
 
+static char *
+get_title(struct cg_view *view)
+{
+	return view->xwayland_surface->title;
+}
+
 static void
 activate(struct cg_view *view, bool activate)
 {
@@ -101,6 +107,7 @@ handle_xwayland_surface_new(struct wl_listener *listener, void *data)
 	view->destroy.notify = handle_xwayland_surface_destroy;
 	wl_signal_add(&xwayland_surface->events.destroy, &view->destroy);
 
+	view->get_title = get_title;
 	view->activate = activate;
 	view->maximize = maximize;
 	view->get_geometry = get_geometry;