nautilus-desktop: draw background when screen is not composited

At least GNOME Flashback session with Metacity still can be used
without compositing manager. Since transparency is not available
nautilus currently draw black background.

Fix it by checking if compositing manager is running and if it is
not then get background surface from root window and draw it on
nautilus desktop window.

https://bugzilla.gnome.org/show_bug.cgi?id=769360

1 files changed, 103 insertions, 0 deletions

diff --git a/nautilus-desktop/nautilus-desktop-window.c b/nautilus-desktop/nautilus-desktop-window.c
index 7c3abecb6..c8909dabe 100644
--- a/nautilus-desktop/nautilus-desktop-window.c
+++ b/nautilus-desktop/nautilus-desktop-window.c
@@ -32,6 +32,9 @@
 #include <gio/gio.h>
 #include <glib/gi18n.h>
 
+#define GNOME_DESKTOP_USE_UNSTABLE_API
+#include <libgnome-desktop/gnome-bg.h>
+
 #include <eel/eel-vfs-extensions.h>
 #include <src/nautilus-file-utilities.h>
 #include <src/nautilus-icon-names.h>
@@ -45,12 +48,92 @@ struct NautilusDesktopWindowDetails {
 	gboolean loaded;
 
 	GtkWidget *desktop_selection;
+
+	gboolean composited;
+	cairo_surface_t *surface;
 };
 
 G_DEFINE_TYPE (NautilusDesktopWindow, nautilus_desktop_window, 
 	       NAUTILUS_TYPE_WINDOW);
 
 static void
+background_changed (NautilusDesktopWindow *window)
+{
+	GtkWidget *widget = GTK_WIDGET (window);
+	GdkScreen *screen = gtk_widget_get_screen (widget);
+
+	g_clear_pointer (&window->details->surface, cairo_surface_destroy);
+
+	window->details->surface = gnome_bg_get_surface_from_root (screen);
+	gtk_widget_queue_draw (widget);
+}
+
+static GdkFilterReturn
+filter_func (GdkXEvent             *xevent,
+             GdkEvent              *event,
+             NautilusDesktopWindow *window)
+{
+	XEvent *xev = (XEvent *) xevent;
+	GdkAtom gdkatom;
+
+	if (xev->type != PropertyNotify) {
+		return GDK_FILTER_CONTINUE;
+	}
+
+	gdkatom = gdk_atom_intern_static_string ("_XROOTPMAP_ID");
+	if (xev->xproperty.atom != gdk_x11_atom_to_xatom (gdkatom)) {
+		return GDK_FILTER_CONTINUE;
+	}
+
+	background_changed (window);
+
+	return GDK_FILTER_CONTINUE;
+}
+
+static void
+nautilus_desktop_window_composited_changed (GtkWidget *widget)
+{
+	NautilusDesktopWindow *window = NAUTILUS_DESKTOP_WINDOW (widget);
+	GdkScreen *screen = gtk_widget_get_screen (widget);
+	gboolean composited = gdk_screen_is_composited (screen);
+	GdkWindow *root;
+	gint events;
+
+	if (window->details->composited == composited) {
+		return;
+	}
+
+	window->details->composited = composited;
+	root = gdk_screen_get_root_window (screen);
+
+	if (composited) {
+		gdk_window_remove_filter (root, (GdkFilterFunc) filter_func, window);
+
+		g_clear_pointer (&window->details->surface, cairo_surface_destroy);
+	} else {
+		events = gdk_window_get_events (root);
+
+		gdk_window_set_events (root, events | GDK_PROPERTY_CHANGE_MASK);
+		gdk_window_add_filter (root, (GdkFilterFunc) filter_func, window);
+		background_changed (window);
+	}
+}
+
+static gboolean
+nautilus_desktop_window_draw (GtkWidget *widget,
+                              cairo_t   *cr)
+{
+	NautilusDesktopWindow *window = NAUTILUS_DESKTOP_WINDOW (widget);
+
+	if (window->details->surface) {
+		cairo_set_source_surface (cr, window->details->surface, 0, 0);
+		cairo_paint (cr);
+	}
+
+	return GTK_WIDGET_CLASS (nautilus_desktop_window_parent_class)->draw (widget, cr);
+}
+
+static void
 nautilus_desktop_window_update_directory (NautilusDesktopWindow *window)
 {
 	GFile *location;
@@ -74,8 +157,21 @@ nautilus_desktop_window_update_directory (NautilusDesktopWindow *window)
 static void
 nautilus_desktop_window_finalize (GObject *obj)
 {
+	NautilusDesktopWindow *window = NAUTILUS_DESKTOP_WINDOW (obj);
+	GdkScreen *screen;
+	GdkWindow *root;
+
 	nautilus_desktop_link_monitor_shutdown ();
 
+	if (window->details->composited == FALSE) {
+		screen = gtk_widget_get_screen (GTK_WIDGET (window));
+		root = gdk_screen_get_root_window (screen);
+
+		gdk_window_remove_filter (root, (GdkFilterFunc) filter_func, window);
+	}
+
+	g_clear_pointer (&window->details->surface, cairo_surface_destroy);
+
 	G_OBJECT_CLASS (nautilus_desktop_window_parent_class)->finalize (obj);
 }
 
@@ -221,11 +317,16 @@ nautilus_desktop_window_constructed (GObject *obj)
 static void
 nautilus_desktop_window_init (NautilusDesktopWindow *window)
 {
+	GtkWidget *widget = GTK_WIDGET (window);
+	GdkScreen *screen = gtk_widget_get_screen (widget);
+
 	window->details = G_TYPE_INSTANCE_GET_PRIVATE (window, NAUTILUS_TYPE_DESKTOP_WINDOW,
 						       NautilusDesktopWindowDetails);
 	gtk_style_context_add_class (gtk_widget_get_style_context (GTK_WIDGET (window)),
 				     "nautilus-desktop-window");
 
+	window->details->composited = gdk_screen_is_composited (screen);
+	nautilus_desktop_window_composited_changed (widget);
 }
 
 static void
@@ -401,6 +502,8 @@ nautilus_desktop_window_class_init (NautilusDesktopWindowClass *klass)
 	wclass->unrealize = unrealize;
 	wclass->map = map;
 	wclass->delete_event = nautilus_desktop_window_delete_event;
+	wclass->composited_changed = nautilus_desktop_window_composited_changed;
+	wclass->draw = nautilus_desktop_window_draw;
 
 	nclass->sync_title = real_sync_title;
 	nclass->close = real_window_close;