csd-background: Run as a wayland client if gtk-layer-shell is (#437)

available.

Current csd-background runs with xwayland and requires special
handling built in to muffin to 'make it work'.

Benefits:
- Allows running as a wayland client
- Enables free re-use of background surfaces by Cinnamon consumers.
- Eliminates need for special handling in wayland sessions by
  muffin.

Author: mtwebster

debian/control

@@ -14,6 +14,7 @@ Build-Depends:
  libfontconfig1-dev,
  libglib2.0-dev (>= 2.37.3),
  libgtk-3-dev (>= 3.9.10),
+ libgtk-layer-shell-dev,
  libgudev-1.0-dev [linux-any],
  liblcms2-dev,
  libnotify-dev (>= 0.7.0),
@@ -24,6 +25,7 @@ Build-Depends:
  libsystemd-dev [linux-any],
  libupower-glib-dev (>= 0.99.11),
  libwacom-dev (>= 0.4) [!s390x !hurd-any !kfreebsd-any],
+ libwayland-dev,
  libx11-dev,
  libxext-dev,
  libxi-dev,

debian/rules

@@ -15,6 +15,7 @@ DEB_HOST_MULTIARCH ?= $(shell dpkg-architecture -qDEB_HOST_MULTIARCH)
 override_dh_auto_configure:
 	dh_auto_configure -- \
 	    --libexecdir=/usr/libexec \
+		-D gtk_layer_shell=true \
 	    $(CONFFLAGS)
 
 

meson.build

@@ -89,6 +89,14 @@ if not get_option('use_logind').disabled()
     endif
 endif
 
+gtk_layer_shell_enabled = get_option('gtk_layer_shell')
+gtk_layer_shell = dependency('', required: false)
+wayland_client = dependency('', required: false)
+if gtk_layer_shell_enabled
+    gtk_layer_shell = dependency('gtk-layer-shell-0', version: '>= 0.8', required: true)
+    wayland_client = dependency('wayland-client', required: true)
+endif
+
 cc = meson.get_compiler('c')
 math = cc.find_library('m', required: false)
 
@@ -105,6 +113,9 @@ csd_conf.set_quoted('LIBEXECDIR', join_paths(prefix, libexecdir))
 csd_conf.set_quoted('SYSCONFDIR', sysconfdir)
 csd_conf.set_quoted('LIBDIR', libdir)
 csd_conf.set10('HAVE_TIMERFD', has_timerfd_create)
+if gtk_layer_shell_enabled
+    csd_conf.set('HAVE_GTK_LAYER_SHELL', 1)
+endif
 
 if gudev.found()
     cargs += '-DHAVE_GUDEV'

meson_options.txt

@@ -70,3 +70,9 @@ option(
     value: '/usr/share/zoneinfo/zone.tab',
     description: 'Path to tzdata zone.tab or zone1970.tab'
 )
+option(
+    'gtk_layer_shell',
+    type: 'boolean',
+    value: false,
+    description: 'Use gtk-layer-shell for native Wayland background windows'
+)

plugins/background/csd-background-manager.c

@@ -37,6 +37,9 @@
 #include <gio/gio.h>
 #include <gdk/gdk.h>
 #include <gdk/gdkx.h>
+#ifdef GDK_WINDOWING_WAYLAND
+#include <gdk/gdkwayland.h>
+#endif
 
 #define GNOME_DESKTOP_USE_UNSTABLE_API
 #include <libcinnamon-desktop/gnome-bg.h>
@@ -59,11 +62,14 @@ struct CsdBackgroundManagerPrivate
         guint        proxy_signal_id;
 
         GPtrArray   *mbs;
+
+        guint        screen_changed_id;
 };
 
 static void     csd_background_manager_finalize    (GObject             *object);
 
 static void setup_bg (CsdBackgroundManager *manager);
+static void setup_monitors (CsdBackgroundManager *manager);
 static void connect_screen_signals (CsdBackgroundManager *manager);
 
 G_DEFINE_TYPE (CsdBackgroundManager, csd_background_manager, G_TYPE_OBJECT)
@@ -77,6 +83,13 @@ draw_background_wayland_session (CsdBackgroundManager *manager)
 
     cinnamon_settings_profile_start (NULL);
 
+    if (!manager->priv->mbs || manager->priv->mbs->len == 0 ||
+        manager->priv->screen_changed_id != 0)
+    {
+        cinnamon_settings_profile_end (NULL);
+        return;
+    }
+
     for (i = 0; i < manager->priv->mbs->len; i++)
     {
         GtkImage *image;
@@ -127,29 +140,19 @@ draw_background_x11_session (CsdBackgroundManager *manager)
 }
 
 static gboolean
-session_is_wayland (void)
+using_wayland_backend (void)
 {
-    static gboolean session_is_wayland = FALSE;
-    static gsize once_init = 0;
-
-    if (g_once_init_enter (&once_init)) {
-        const gchar *env = g_getenv ("XDG_SESSION_TYPE");
-        if (env && g_strcmp0 (env, "wayland") == 0) {
-            session_is_wayland = TRUE;
-        }
-
-        g_debug ("Session is Wayland? %d", session_is_wayland);
-
-        g_once_init_leave (&once_init, 1);
-    }
-
-    return session_is_wayland;
+#ifdef GDK_WINDOWING_WAYLAND
+    return GDK_IS_WAYLAND_DISPLAY (gdk_display_get_default ());
+#else
+    return FALSE;
+#endif
 }
 
 static void
 draw_background (CsdBackgroundManager *manager)
 {
-    if (session_is_wayland ()) {
+    if (using_wayland_backend ()) {
         draw_background_wayland_session (manager);
     } else {
         draw_background_x11_session (manager);
@@ -177,12 +180,31 @@ settings_change_event_cb (GSettings            *settings,
         return FALSE;
 }
 
+static gboolean
+on_screen_changed_idle (gpointer user_data)
+{
+        CsdBackgroundManager *manager = CSD_BACKGROUND_MANAGER (user_data);
+
+        manager->priv->screen_changed_id = 0;
+
+        if (using_wayland_backend ()) {
+                setup_monitors (manager);
+        }
+
+        draw_background (manager);
+
+        return G_SOURCE_REMOVE;
+}
+
 static void
 on_screen_size_changed (GdkScreen            *screen,
                         CsdBackgroundManager *manager)
 {
+        if (manager->priv->screen_changed_id != 0)
+                return;
 
-        draw_background (manager);
+        manager->priv->screen_changed_id =
+                g_timeout_add (250, on_screen_changed_idle, manager);
 }
 
 static void
@@ -193,6 +215,9 @@ setup_monitors (CsdBackgroundManager *manager)
 
     display = gdk_display_get_default ();
 
+    if (!display)
+        return;
+
     g_clear_pointer (&manager->priv->mbs, g_ptr_array_unref);
     manager->priv->mbs = g_ptr_array_new_with_free_func ((GDestroyNotify) g_object_unref);
 
@@ -251,7 +276,7 @@ setup_bg_and_draw_background (CsdBackgroundManager *manager)
 {
         setup_bg (manager);
 
-        if (session_is_wayland ()) {
+        if (using_wayland_backend ()) {
             setup_monitors (manager);
         }
 
@@ -396,6 +421,8 @@ csd_background_manager_stop (CsdBackgroundManager *manager)
 
         g_debug ("Stopping background manager");
 
+        g_clear_handle_id (&manager->priv->screen_changed_id, g_source_remove);
+
         disconnect_screen_signals (manager);
 
         if (manager->priv->proxy) {

plugins/background/main.c

@@ -1,3 +1,8 @@
+#include "config.h"
+
+#include <glib.h>
+#include <gdk/gdk.h>
+
 #define NEW csd_background_manager_new
 #define START csd_background_manager_start
 #define STOP csd_background_manager_stop
@@ -12,8 +17,34 @@
 // Setting this to TRUE makes the plugin force GDK_SCALE=1
 #define FORCE_GDK_SCALE TRUE
 
-// This plugin must run under x11/xwayland
+// When gtk-layer-shell is available, check at runtime if the compositor
+// supports wlr-layer-shell. If not, fall back to X11/XWayland.
+#ifdef HAVE_GTK_LAYER_SHELL
+#include "wayland-utils.h"
+
+static void
+pre_gtk_init (void)
+{
+    if (csd_check_layer_shell_support ()) {
+        g_message ("csd-background: using Wayland backend, gtk-layer-shell supported");
+    } else {
+        g_message ("csd-background: not a Wayland session or wlr-layer-shell protocol not supported, using X11 backend");
+        gdk_set_allowed_backends ("x11");
+    }
+}
+
+#define PRE_GTK_INIT pre_gtk_init
+#define FORCE_X11_BACKEND FALSE
+#else
+static void
+pre_gtk_init (void)
+{
+    g_message ("csd-background: gtk-layer-shell not built, using X11 backend");
+}
+
+#define PRE_GTK_INIT pre_gtk_init
 #define FORCE_X11_BACKEND TRUE
+#endif
 
 #include "csd-background-manager.h"
 

plugins/background/meson.build

@@ -13,6 +13,10 @@ background_deps = [
     libnotify,
 ]
 
+if gtk_layer_shell_enabled
+    background_deps += gtk_layer_shell
+endif
+
 executable(
     'csd-background',
     background_sources,