xwayland: add optional support for libdecor

When running rootful, the Xwayland window is not decorated (as all
Wayland surfaces), which makes it quite inconvenient to move on screen.

libdecor is "a client-side decorations library for Wayland clients"
which can be used precisely for adding decorations to Wayland surfaces.

Add optional support for libdecor in Xwayland to gain decorations when
running rootful and a new command line option "-decorate".

Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Closes: https://gitlab.freedesktop.org/xorg/xserver/-/issues/1332

hw/xwayland/man/Xwayland.man

@@ -46,6 +46,14 @@ Like all of the X servers, \fIXwayland\fP accepts the command line options
 described in the \fIXserver\fP(@miscmansuffix@) manual page.
 The following additional arguments are supported as well.
 .TP 8
+.B \-decorate
+Add decorations to the Xwayland root window when running rootful.
+
+This option has no effect when \fIXwayland\fP is built without libdecor
+support (optional).
+
+This option is not compatible with rootless mode (\fI-rootless\fP).
+.TP 8
 .B \-eglstream
 Use EGLStream backend for NVidia GPUs. If \fIXwayland\fP was compiled with
 EGLStream support, this option will instruct \fIXwayland\fP to try that

hw/xwayland/meson.build

@@ -128,6 +128,10 @@ if libdrm_dep.found()
     xwayland_dep += libdrm_dep
 endif
 
+if have_libdecor
+    xwayland_dep += libdecor_dep
+endif
+
 xwayland_server = executable(
     'Xwayland',
     srcs,
@@ -158,6 +162,7 @@ xwayland_data.set('PACKAGE_VERSION', meson.project_version())
 xwayland_data.set('xwayland_path', xwayland_path)
 xwayland_data.set('have_glamor', build_glamor ? 'true' : 'false')
 xwayland_data.set('have_eglstream', build_eglstream ? 'true' : 'false')
+xwayland_data.set('have_libdecor', have_libdecor ? 'true' : 'false')
 configure_file(
     input: 'xwayland.pc.in',
     output: 'xwayland.pc',

hw/xwayland/xwayland-screen.c

@@ -513,6 +513,33 @@ xwl_display_pollout (struct xwl_screen *xwl_screen, int timeout)
     return xserver_poll(&poll_fd, 1, timeout);
 }
 
+#ifdef XWL_HAS_LIBDECOR
+static void
+xwl_dispatch_events_with_libdecor(struct xwl_screen *xwl_screen)
+{
+    int ret = 0;
+
+    assert(!xwl_screen->rootless);
+
+    ret = libdecor_dispatch(xwl_screen->libdecor_context, 0);
+    if (ret == -1)
+        xwl_give_up("failed to dispatch Wayland events with libdecor: %s\n",
+                    strerror(errno));
+}
+
+static void
+handle_libdecor_error(struct libdecor *context,
+                      enum libdecor_error error,
+                      const char *message)
+{
+    xwl_give_up("libdecor error (%d): %s\n", error, message);
+}
+
+static struct libdecor_interface libdecor_iface = {
+    .error = handle_libdecor_error,
+};
+#endif
+
 static void
 xwl_dispatch_events (struct xwl_screen *xwl_screen)
 {
@@ -551,6 +578,12 @@ socket_handler(int fd, int ready, void *data)
 {
     struct xwl_screen *xwl_screen = data;
 
+#ifdef XWL_HAS_LIBDECOR
+    if (xwl_screen->libdecor_context) {
+        xwl_dispatch_events_with_libdecor(xwl_screen);
+        return;
+    }
+#endif
     xwl_read_events (xwl_screen);
 }
 
@@ -565,12 +598,24 @@ block_handler(void *data, void *timeout)
     struct xwl_screen *xwl_screen = data;
 
     xwl_screen_post_damage(xwl_screen);
+#ifdef XWL_HAS_LIBDECOR
+    if (xwl_screen->libdecor_context) {
+        xwl_dispatch_events_with_libdecor(xwl_screen);
+        return;
+    }
+#endif
     xwl_dispatch_events (xwl_screen);
 }
 
 void
 xwl_sync_events (struct xwl_screen *xwl_screen)
 {
+#ifdef XWL_HAS_LIBDECOR
+    if (xwl_screen->libdecor_context) {
+        xwl_dispatch_events_with_libdecor(xwl_screen);
+        return;
+    }
+#endif
     xwl_dispatch_events (xwl_screen);
     xwl_read_events (xwl_screen);
 }
@@ -689,6 +734,13 @@ xwl_screen_init(ScreenPtr pScreen, int argc, char **argv)
             xwl_screen->host_grab = 1;
             xwl_screen->has_grab = 1;
         }
+        else if (strcmp(argv[i], "-decorate") == 0) {
+#ifdef XWL_HAS_LIBDECOR
+            xwl_screen->decorate = 1;
+#else
+            ErrorF("This build does not have libdecor support\n");
+#endif
+        }
     }
 
     if (use_fixed_size) {
@@ -745,11 +797,17 @@ xwl_screen_init(ScreenPtr pScreen, int argc, char **argv)
                              &registry_listener, xwl_screen);
     xwl_screen_roundtrip(xwl_screen);
 
+
     if (xwl_screen->fullscreen && xwl_screen->rootless) {
         ErrorF("error, cannot set fullscreen when running rootless\n");
         return FALSE;
     }
 
+    if (xwl_screen->fullscreen && xwl_screen->decorate) {
+        ErrorF("error, cannot use the decorate option when running fullscreen\n");
+        return FALSE;
+    }
+
     if (xwl_screen->fullscreen && !xwl_screen_has_viewport_support(xwl_screen)) {
         ErrorF("missing viewport support in the compositor, ignoring fullscreen\n");
         xwl_screen->fullscreen = FALSE;
@@ -796,7 +854,16 @@ xwl_screen_init(ScreenPtr pScreen, int argc, char **argv)
         return FALSE;
 #endif
 
+#ifdef XWL_HAS_LIBDECOR
+    if (xwl_screen->decorate && !xwl_screen->rootless) {
+        xwl_screen->libdecor_context = libdecor_new(xwl_screen->display, &libdecor_iface);
+        xwl_screen->wayland_fd = libdecor_get_fd(xwl_screen->libdecor_context);
+    }
+    else
+#endif
+    {
         xwl_screen->wayland_fd = wl_display_get_fd(xwl_screen->display);
+    }
     SetNotifyFd(xwl_screen->wayland_fd, socket_handler, X_NOTIFY_READ, xwl_screen);
     RegisterBlockAndWakeupHandlers(block_handler, wakeup_handler, xwl_screen);
 

hw/xwayland/xwayland-screen.h

@@ -38,6 +38,10 @@
 #include "xwayland-glamor.h"
 #include "xwayland-drm-lease.h"
 
+#ifdef XWL_HAS_LIBDECOR
+#include <libdecor.h>
+#endif
+
 struct xwl_format {
     uint32_t format;
     int num_modifiers;
@@ -61,6 +65,7 @@ struct xwl_screen {
     int fullscreen;
     int host_grab;
     int has_grab;
+    int decorate;
 
     CreateScreenResourcesProcPtr CreateScreenResources;
     CloseScreenProcPtr CloseScreen;
@@ -123,6 +128,10 @@ struct xwl_screen {
 
     /* The preferred GLVND vendor. If NULL, "mesa" is assumed. */
     const char *glvnd_vendor;
+#ifdef XWL_HAS_LIBDECOR
+    int libdecor_fd;
+    struct libdecor *libdecor_context;
+#endif
 };
 
 /* Apps which use randr/vidmode to change the mode when going fullscreen,

hw/xwayland/xwayland-window.c

@@ -498,6 +498,11 @@ xwl_window_rootful_update_title(struct xwl_window *xwl_window)
 
     snprintf(title, sizeof(title), "Xwayland on :%s%s", display, grab_message);
 
+#ifdef XWL_HAS_LIBDECOR
+    if (xwl_window->libdecor_frame)
+        libdecor_frame_set_title(xwl_window->libdecor_frame, title);
+    else
+#endif
     if (xwl_window->xdg_toplevel)
         xdg_toplevel_set_title(xwl_window->xdg_toplevel, title);
 }
@@ -507,10 +512,78 @@ xwl_window_rootful_set_app_id(struct xwl_window *xwl_window)
 {
     const char *app_id = "org.freedesktop.Xwayland";
 
+#ifdef XWL_HAS_LIBDECOR
+    if (xwl_window->libdecor_frame)
+        libdecor_frame_set_app_id(xwl_window->libdecor_frame, app_id);
+    else
+#endif
     if (xwl_window->xdg_toplevel)
         xdg_toplevel_set_app_id(xwl_window->xdg_toplevel, app_id);
 }
 
+#ifdef XWL_HAS_LIBDECOR
+static void
+xwl_window_update_libdecor_size(struct xwl_window *xwl_window, int width, int height)
+{
+    struct libdecor_state *state;
+
+    if (xwl_window->libdecor_frame) {
+	state = libdecor_state_new(width, height);
+	libdecor_frame_commit(xwl_window->libdecor_frame, state, NULL);
+	libdecor_state_free(state);
+    }
+}
+
+static void
+handle_libdecor_configure(struct libdecor_frame *frame,
+                          struct libdecor_configuration *configuration,
+                          void *data)
+{
+    struct xwl_window *xwl_window = data;
+    struct xwl_screen *xwl_screen = xwl_window->xwl_screen;
+    struct libdecor_state *state;
+
+    state = libdecor_state_new(xwl_screen->width, xwl_screen->height);
+    libdecor_frame_commit(frame, state, configuration);
+    libdecor_state_free(state);
+
+    if (libdecor_frame_has_capability(frame, LIBDECOR_ACTION_RESIZE))
+        libdecor_frame_unset_capabilities(frame, LIBDECOR_ACTION_RESIZE);
+    if (libdecor_frame_has_capability(frame, LIBDECOR_ACTION_FULLSCREEN))
+        libdecor_frame_unset_capabilities(frame, LIBDECOR_ACTION_FULLSCREEN);
+}
+
+static void
+handle_libdecor_close(struct libdecor_frame *frame,
+                      void *data)
+{
+    DebugF("Terminating on compositor request");
+    GiveUp(0);
+}
+
+static void
+handle_libdecor_commit(struct libdecor_frame *frame,
+                       void *data)
+{
+    struct xwl_window *xwl_window = data;
+    wl_surface_commit(xwl_window->surface);
+}
+
+static void
+handle_libdecor_dismiss_popup(struct libdecor_frame *frame,
+                              const char *seat_name,
+                              void *data)
+{
+}
+
+static struct libdecor_frame_interface libdecor_frame_iface = {
+    handle_libdecor_configure,
+    handle_libdecor_close,
+    handle_libdecor_commit,
+    handle_libdecor_dismiss_popup,
+};
+#endif
+
 static void
 xdg_surface_handle_configure(void *data,
                              struct xdg_surface *xdg_surface,
@@ -591,6 +664,19 @@ xwl_create_root_surface(struct xwl_window *xwl_window)
     WindowPtr window = xwl_window->window;
     struct wl_region *region;
 
+
+#ifdef XWL_HAS_LIBDECOR
+    if (xwl_screen->decorate) {
+        xwl_window->libdecor_frame =
+            libdecor_decorate(xwl_screen->libdecor_context,
+                              xwl_window->surface,
+                              &libdecor_frame_iface,
+                              xwl_window);
+        libdecor_frame_map(xwl_window->libdecor_frame);
+    }
+    else
+#endif
+    {
         xwl_window->xdg_surface =
             xdg_wm_base_get_xdg_surface(xwl_screen->xdg_wm_base, xwl_window->surface);
         if (xwl_window->xdg_surface == NULL) {
@@ -614,6 +700,7 @@ xwl_create_root_surface(struct xwl_window *xwl_window)
         xdg_toplevel_add_listener(xwl_window->xdg_toplevel,
                                   &xdg_toplevel_listener,
                                   NULL);
+    }
 
     xwl_window_rootful_update_title(xwl_window);
     xwl_window_rootful_set_app_id(xwl_window);
@@ -908,8 +995,14 @@ xwl_resize_window(WindowPtr window,
     xwl_screen->ResizeWindow = screen->ResizeWindow;
     screen->ResizeWindow = xwl_resize_window;
 
-    if (xwl_window && (xwl_window_get(window) || xwl_window_is_toplevel(window)))
+    if (xwl_window) {
+        if (xwl_window_get(window) || xwl_window_is_toplevel(window))
             xwl_window_check_resolution_change_emulation(xwl_window);
+#ifdef XWL_HAS_LIBDECOR
+        if (window == screen->root)
+            xwl_window_update_libdecor_size(xwl_window, width, height);
+#endif
+    }
 }
 
 void

hw/xwayland/xwayland-window.h

@@ -58,6 +58,9 @@ struct xwl_window {
     struct xorg_list frame_callback_list;
     Bool present_flipped;
 #endif
+#ifdef XWL_HAS_LIBDECOR
+    struct libdecor_frame *libdecor_frame;
+#endif
 };
 
 struct xwl_window *xwl_window_get(WindowPtr window);

hw/xwayland/xwayland.c

@@ -106,6 +106,9 @@ ddxUseMsg(void)
     ErrorF("-version               show the server version and exit\n");
     ErrorF("-noTouchPointerEmulation  disable touch pointer emulation\n");
     ErrorF("-force-xrandr-emulation   force non-native modes to be exposed when viewporter is not exposed by the compositor\n");
+#ifdef XWL_HAS_LIBDECOR
+    ErrorF("-decorate              add decorations to Xwayland when rootful (experimental)\n");
+#endif
 }
 
 static int init_fd = -1;
@@ -237,6 +240,9 @@ ddxProcessArgument(int argc, char *argv[], int i)
     else if (strcmp(argv[i], "-host-grab") == 0) {
         return 1;
     }
+    else if (strcmp(argv[i], "-decorate") == 0) {
+        return 1;
+    }
 
     return 0;
 }

hw/xwayland/xwayland.pc.in

@@ -16,3 +16,4 @@ have_force_xrandr_emulation=true
 have_geometry=true
 have_fullscreen=true
 have_host_grab=true
+have_decorate=@have_libdecor@

include/meson.build

@@ -415,6 +415,7 @@ configure_file(output : 'xwin-config.h',
 xwayland_data = configuration_data()
 xwayland_data.set('XWL_HAS_GLAMOR', build_glamor and (gbm_dep.found() or build_eglstream) ? '1' : false)
 xwayland_data.set('XWL_HAS_EGLSTREAM', build_eglstream ? '1' : false)
+xwayland_data.set('XWL_HAS_LIBDECOR', have_libdecor ? '1' : false)
 
 configure_file(output : 'xwayland-config.h',
                input : 'xwayland-config.h.meson.in',

include/xwayland-config.h.meson.in

@@ -9,3 +9,6 @@
 
 /* Build eglstream support for Xwayland */
 #mesondefine XWL_HAS_EGLSTREAM
+
+/* Build Xwayland with libdecor support*/
+#mesondefine XWL_HAS_LIBDECOR

meson.build

@@ -336,6 +336,21 @@ if build_glamor
     epoxy_dep = dependency('epoxy', required: false)
 endif
 
+if build_xwayland
+    libdecor_dep = dependency('libdecor-0', required: false)
+    libdecor_option = get_option('libdecor')
+    if libdecor_option == 'auto'
+        have_libdecor = libdecor_dep.found()
+    else
+        have_libdecor = libdecor_option == 'true'
+        if have_libdecor and not libdecor_dep.found()
+            error('libdecor support requested but not found')
+        endif
+    endif
+else
+    have_libdecor = false
+endif
+
 eglstream_option = get_option('xwayland_eglstream')
 if build_xwayland and build_glamor
     eglstream_dep = dependency('wayland-eglstream-protocols', required:false)

meson_options.txt

@@ -135,6 +135,8 @@ option('libunwind', type: 'boolean', value: false,
         description: 'Use libunwind for backtrace reporting')
 
 option('xwayland-path', type: 'string', description: 'Directory containing Xwayland executable')
+option('libdecor', type: 'combo', choices: ['true', 'false', 'auto'], value: 'auto',
+        description: 'Whether Xwayland should use libdecor when running rootful.')
 
 option('docs', type: 'combo', choices: ['true', 'false', 'auto'], value: 'auto',
         description: 'Build documentation')