From 6260814285faf4b9a943763353b53e64eb41ac11 Mon Sep 17 00:00:00 2001
From: "Owen W. Taylor" <otaylor@fishsoup.net>
Date: Mon, 15 Nov 2010 16:19:28 -0500
Subject: [PATCH] Turn off background repeats for a full-size image

If we have repeats on for a full-sized image, then if the background
is displayed scaled (for example, in a desktop preview mode) then we
can get artifacts along the edge of the background where the repeat
of the opposite edge is blended in by bilinear scaling. So turn off
repeats when the screen and background image sizes match.

https://bugzilla.gnome.org/show_bug.cgi?id=634833
---
 src/compositor/compositor.c            |  4 +--
 src/compositor/meta-background-actor.c | 34 ++++++++++++++++++++++++++
 src/compositor/meta-background-actor.h |  7 +++---
 3 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/src/compositor/compositor.c b/src/compositor/compositor.c
index 4b848b4d0..058114b14 100644
--- a/src/compositor/compositor.c
+++ b/src/compositor/compositor.c
@@ -1081,8 +1081,8 @@ meta_compositor_sync_screen_size (MetaCompositor  *compositor,
   g_return_if_fail (info);
 
   clutter_actor_set_size (info->stage, width, height);
-  /* Background actor always requests the screen size */
-  clutter_actor_queue_relayout (info->background_actor);
+
+  meta_background_actor_screen_size_changed (META_BACKGROUND_ACTOR (info->background_actor));
 
   meta_verbose ("Changed size for stage on screen %d to %dx%d\n",
 		meta_screen_get_screen_number (screen),
diff --git a/src/compositor/meta-background-actor.c b/src/compositor/meta-background-actor.c
index af8677803..d26fa8a6e 100644
--- a/src/compositor/meta-background-actor.c
+++ b/src/compositor/meta-background-actor.c
@@ -55,6 +55,26 @@ struct _MetaBackgroundActor
 
 G_DEFINE_TYPE (MetaBackgroundActor, meta_background_actor, CLUTTER_TYPE_ACTOR);
 
+static void
+update_wrap_mode (MetaBackgroundActor *self)
+{
+  int width, height;
+  CoglMaterialWrapMode wrap_mode;
+
+  meta_screen_get_size (self->screen, &width, &height);
+
+  /* We turn off repeating when we have a full-screen pixmap to keep from
+   * getting artifacts from one side of the image sneaking into the other
+   * side of the image via bilinear filtering.
+   */
+  if (width == self->texture_width && height == self->texture_height)
+    wrap_mode = COGL_PIPELINE_WRAP_MODE_CLAMP_TO_EDGE;
+  else
+    wrap_mode = COGL_PIPELINE_WRAP_MODE_REPEAT;
+
+  cogl_material_set_layer_wrap_mode (self->material, 0, wrap_mode);
+}
+
 static void
 set_texture (MetaBackgroundActor *self,
              CoglHandle           texture)
@@ -73,6 +93,8 @@ set_texture (MetaBackgroundActor *self,
   self->texture_width = cogl_texture_get_width (texture);
   self->texture_height = cogl_texture_get_height (texture);
 
+  update_wrap_mode (self);
+
   clutter_actor_queue_redraw (CLUTTER_ACTOR (self));
 }
 
@@ -378,3 +400,15 @@ meta_background_actor_set_visible_region (MetaBackgroundActor *self,
     }
 }
 
+/**
+ * meta_background_actor_screen_size_changed:
+ * @self: a #MetaBackgroundActor
+ *
+ * Called by the compositor when the size of the #MetaScreen changes
+ */
+void
+meta_background_actor_screen_size_changed (MetaBackgroundActor *self)
+{
+  update_wrap_mode (self);
+  clutter_actor_queue_relayout (CLUTTER_ACTOR (self));
+}
diff --git a/src/compositor/meta-background-actor.h b/src/compositor/meta-background-actor.h
index b211c4b64..448171aa2 100644
--- a/src/compositor/meta-background-actor.h
+++ b/src/compositor/meta-background-actor.h
@@ -50,8 +50,9 @@ GType meta_background_actor_get_type (void);
 
 ClutterActor *meta_background_actor_new (MetaScreen *screen);
 
-void meta_background_actor_update             (MetaBackgroundActor *actor);
-void meta_background_actor_set_visible_region (MetaBackgroundActor *self,
-                                               cairo_region_t      *visible_region);
+void meta_background_actor_update              (MetaBackgroundActor *actor);
+void meta_background_actor_set_visible_region  (MetaBackgroundActor *self,
+                                                cairo_region_t      *visible_region);
+void meta_background_actor_screen_size_changed (MetaBackgroundActor *self);
 
 #endif /* META_BACKGROUND_ACTOR_H */