[mutter/gnome-3-32] background: Reload when GPU memory is invalidated

[Marco Trevisan <marcotrevi src gnome org>]

commit 5a486f5b6bf5f838db5dc2bfc5819a0cba5d2d19
Author: Daniel van Vugt <daniel van vugt canonical com>
Date:   Thu May 23 18:15:28 2019 +0800

    background: Reload when GPU memory is invalidated
    
    Fixes corrupt background wallpaper when resuming from suspend on the
    Nvidia driver.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/issues/1084
    
    (cherry picked from commit a5265365dd268e15a461a58000a10b122d0bccba)
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/777

 src/compositor/meta-background.c | 46 +++++++++++++++++++++++++++++++---------
 1 file changed, 36 insertions(+), 10 deletions(-)
---
diff --git a/src/compositor/meta-background.c b/src/compositor/meta-background.c
index c033395fe..387ce5dd3 100644
--- a/src/compositor/meta-background.c
+++ b/src/compositor/meta-background.c
@@ -252,12 +252,11 @@ static void
 set_file (MetaBackground       *self,
           GFile               **filep,
           MetaBackgroundImage **imagep,
-          GFile                *file)
+          GFile                *file,
+          gboolean              force_reload)
 {
-  if (!file_equal0 (*filep, file))
+  if (force_reload || !file_equal0 (*filep, file))
     {
-      g_clear_object (filep);
-
       if (*imagep)
         {
           g_signal_handlers_disconnect_by_func (*imagep,
@@ -267,11 +266,12 @@ set_file (MetaBackground       *self,
           *imagep = NULL;
         }
 
+      g_set_object (filep, file);
+
       if (file)
         {
           MetaBackgroundImageCache *cache = meta_background_image_cache_get_default ();
 
-          *filep = g_object_ref (file);
           *imagep = meta_background_image_cache_load (cache, file);
           g_signal_connect (*imagep, "loaded",
                             G_CALLBACK (on_background_loaded), self);
@@ -279,6 +279,32 @@ set_file (MetaBackground       *self,
     }
 }
 
+static void
+on_gl_video_memory_purged (MetaBackground *self)
+{
+  MetaBackgroundImageCache *cache = meta_background_image_cache_get_default ();
+
+  /* The GPU memory that just got invalidated is the texture inside
+   * self->background_image1,2 and/or its mipmaps. However, to save memory the
+   * original pixbuf isn't kept in RAM so we can't do a simple re-upload. The
+   * only copy of the image was the one in texture memory that got invalidated.
+   * So we need to do a full reload from disk.
+   */
+  if (self->file1)
+    {
+      meta_background_image_cache_purge (cache, self->file1);
+      set_file (self, &self->file1, &self->background_image1, self->file1, TRUE);
+    }
+
+  if (self->file2)
+    {
+      meta_background_image_cache_purge (cache, self->file2);
+      set_file (self, &self->file2, &self->background_image2, self->file2, TRUE);
+    }
+
+  mark_changed (self);
+}
+
 static void
 meta_background_dispose (GObject *object)
 {
@@ -287,8 +313,8 @@ meta_background_dispose (GObject *object)
   free_color_texture (self);
   free_wallpaper_texture (self);
 
-  set_file (self, &self->file1, &self->background_image1, NULL);
-  set_file (self, &self->file2, &self->background_image2, NULL);
+  set_file (self, &self->file1, &self->background_image1, NULL, FALSE);
+  set_file (self, &self->file2, &self->background_image2, NULL, FALSE);
 
   set_display (self, NULL);
 
@@ -312,7 +338,7 @@ meta_background_constructed (GObject *object)
   G_OBJECT_CLASS (meta_background_parent_class)->constructed (object);
 
   g_signal_connect_object (self->display, "gl-video-memory-purged",
-                           G_CALLBACK (mark_changed), object, G_CONNECT_SWAPPED);
+                           G_CALLBACK (on_gl_video_memory_purged), object, G_CONNECT_SWAPPED);
 
   g_signal_connect_object (monitor_manager, "monitors-changed",
                            G_CALLBACK (on_monitors_changed), self,
@@ -937,8 +963,8 @@ meta_background_set_blend (MetaBackground          *self,
   g_return_if_fail (META_IS_BACKGROUND (self));
   g_return_if_fail (blend_factor >= 0.0 && blend_factor <= 1.0);
 
-  set_file (self, &self->file1, &self->background_image1, file1);
-  set_file (self, &self->file2, &self->background_image2, file2);
+  set_file (self, &self->file1, &self->background_image1, file1, FALSE);
+  set_file (self, &self->file2, &self->background_image2, file2, FALSE);
 
   self->blend_factor = blend_factor;
   self->style = style;