diff -up gnome-desktop-2.28.1/libgnome-desktop/gnome-bg.c.per-monitor-background gnome-desktop-2.28.1/libgnome-desktop/gnome-bg.c

--- gnome-desktop-2.28.1/libgnome-desktop/gnome-bg.c.per-monitor-background	2009-08-19 11:51:03.000000000 -0400

+++ gnome-desktop-2.28.1/libgnome-desktop/gnome-bg.c	2009-11-09 17:05:49.839583495 -0500

@@ -168,6 +168,9 @@ static gboolean   get_thumb_annotations 

 					 int                   *orig_height);

 /* Cache */

+static GdkPixbuf *get_pixbuf_for_size  (GnomeBG               *bg,

+					int                    width,

+					int                    height);

 static GdkPixbuf *get_pixbuf           (GnomeBG               *bg);

 static void       clear_cache          (GnomeBG               *bg);

 static gboolean   is_different         (GnomeBG               *bg,

@@ -685,12 +688,13 @@ get_scaled_pixbuf (GnomeBGPlacement plac

 }

 static void

-draw_image (GnomeBGPlacement  placement,

-	    GdkPixbuf        *pixbuf,

-	    GdkPixbuf        *dest)

+draw_image_region (GnomeBGPlacement  placement,

+		   GdkPixbuf        *pixbuf,

+		   GdkPixbuf        *dest,

+		   GdkRectangle     *region)

 {

-	int dest_width = gdk_pixbuf_get_width (dest);

-	int dest_height = gdk_pixbuf_get_height (dest);

+	int dest_width = region->width;

+	int dest_height = region->height;

 	int x, y, w, h;

 	GdkPixbuf *scaled;

@@ -708,7 +712,7 @@ draw_image (GnomeBGPlacement  placement,

 	case GNOME_BG_PLACEMENT_CENTERED:

 	case GNOME_BG_PLACEMENT_FILL_SCREEN:

 	case GNOME_BG_PLACEMENT_SCALED:

-		pixbuf_blend (scaled, dest, 0, 0, w, h, x, y, 1.0);

+		pixbuf_blend (scaled, dest, 0, 0, w, h, x + region->x, y + region->y, 1.0);

 		break;

 	default:

 		g_assert_not_reached ();

@@ -718,15 +722,62 @@ draw_image (GnomeBGPlacement  placement,

 	g_object_unref (scaled);

 }

-void

-gnome_bg_draw (GnomeBG *bg, GdkPixbuf *dest)

+static void

+draw_image (GnomeBGPlacement  placement,

+	    GdkPixbuf        *pixbuf,

+	    GdkPixbuf        *dest)

+{

+	GdkRectangle rect;

+

+	rect.x = 0;

+	rect.y = 0;

+	rect.width = gdk_pixbuf_get_width (dest);

+	rect.height = gdk_pixbuf_get_height (dest);

+

+	draw_image_region (placement, pixbuf, dest, &rect);

+}

+

+static void

+draw_on_monitor (GnomeBG *bg, GdkPixbuf *dest, GdkRectangle *region)

+{

+	draw_image_region (bg->placement, get_pixbuf_for_size (bg, region->width, region->height), dest, region);

+}

+

+static void

+draw_each_monitor (GnomeBG *bg, GdkPixbuf *dest, GdkScreen *screen)

+{

+	if (bg->placement == GNOME_BG_PLACEMENT_TILED) {

+		/* don't worry about aligning on every monitor */

+		draw_image (bg->placement, get_pixbuf (bg), dest);

+	} else {

+		gint num_monitors;

+		GdkRectangle rect;

+		int monitor;

+

+		num_monitors = gdk_screen_get_n_monitors (screen);

+

+		for (monitor = 0; monitor < num_monitors; monitor++) {

+			gdk_screen_get_monitor_geometry (screen, monitor, &rect);

+			draw_on_monitor (bg, dest, &rect);

+		}

+	}

+}

+

+static void

+draw_on_screen (GnomeBG *bg, GdkPixbuf *dest, GdkScreen *screen)

 {

 	if (!bg)

 		return;

 	draw_color (bg, dest);

-	draw_image (bg->placement, get_pixbuf (bg), dest);

+	draw_each_monitor (bg, dest, screen);

+}

+

+void

+gnome_bg_draw (GnomeBG *bg, GdkPixbuf *dest)

+{

+	draw_on_screen (bg, dest, gdk_screen_get_default ());

 }

 gboolean

@@ -883,7 +934,7 @@ gnome_bg_create_pixmap (GnomeBG	    *bg,

 		pixbuf = gdk_pixbuf_new (GDK_COLORSPACE_RGB, FALSE, 8,

 					 width, height);

-		gnome_bg_draw (bg, pixbuf);

+		draw_on_screen (bg, pixbuf, gdk_drawable_get_screen (GDK_DRAWABLE (window)));

 		gdk_draw_pixbuf (pixmap, NULL, pixbuf,

 				 0, 0,

 				 0, 0, width, height,

@@ -1880,13 +1931,16 @@ find_best_size (GSList *sizes, gint widt

 }

 static GdkPixbuf *

-get_pixbuf (GnomeBG *bg)

+get_pixbuf_for_size (GnomeBG *bg, gint best_width, gint best_height)

 {

 	/* FIXME: this ref=TRUE/FALSE stuff is crazy */

-	

+	gint width, height;

 	guint time_until_next_change;

 	gboolean ref = FALSE;

-	

+

+	width = (best_width > 0) ? best_width : bg->last_pixmap_width;

+	height = (best_height > 0) ? best_height : bg->last_pixmap_height;

+

 	if (!bg->pixbuf_cache && bg->filename) {

 		ref = TRUE;

 		bg->file_mtime = get_mtime (bg->filename);

@@ -1906,15 +1960,15 @@ get_pixbuf (GnomeBG *bg)

 				time_until_next_change = (guint)get_slide_timeout (slide);

 				if (slide->fixed) {

 					FileSize *size;

-					size = find_best_size (slide->file1, bg->last_pixmap_width, bg->last_pixmap_height);

+					size = find_best_size (slide->file1, width, height);

 					bg->pixbuf_cache = get_as_pixbuf (bg, size->file);

 				}

 				else {

 					FileSize *size;

 					GdkPixbuf *p1, *p2;

-					size = find_best_size (slide->file1, bg->last_pixmap_width, bg->last_pixmap_height);

+					size = find_best_size (slide->file1, width, height);

 					p1 = get_as_pixbuf (bg, size->file);

-					size = find_best_size (slide->file2, bg->last_pixmap_width, bg->last_pixmap_height);

+					size = find_best_size (slide->file2, width, height);

 					p2 = get_as_pixbuf (bg, size->file);

@@ -1943,6 +1997,22 @@ get_pixbuf (GnomeBG *bg)

 	return bg->pixbuf_cache;

 }

+static GdkPixbuf *

+get_pixbuf (GnomeBG *bg)

+{

+	GdkPixbuf   *pixbuf;

+	GdkScreen   *screen;

+	GdkRectangle rect;

+

+	screen = gdk_screen_get_default ();

+

+	/* default to caching the primary monitor */

+	gdk_screen_get_monitor_geometry (screen, 0, &rect);

+	pixbuf = get_pixbuf_for_size (bg, rect.width, rect.height);

+

+	return pixbuf;

+}

+

 static gboolean

 is_different (GnomeBG    *bg,

 	      const char *filename)