[mutter] background: downscale background to fit in texture limits

[Ray Strode <halfline src gnome org>]

commit 15e01152da335f5a9e7617674ffa54cb1bdef957
Author: Ray Strode <rstrode redhat com>
Date:   Fri Jun 14 16:11:30 2013 -0400

    background: downscale background to fit in texture limits
    
    Some cards have 2k texture limits, which can be smaller than
    commonly sized backgrounds.
    
    This commit downscales the background in this situation, so that
    it won't fail to load.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=702283

 src/compositor/meta-background.c |   30 ++++++++++++++++++++++++++++++
 1 files changed, 30 insertions(+), 0 deletions(-)
---
diff --git a/src/compositor/meta-background.c b/src/compositor/meta-background.c
index fca5dce..35ca45c 100644
--- a/src/compositor/meta-background.c
+++ b/src/compositor/meta-background.c
@@ -32,6 +32,8 @@
 
 #include <clutter/clutter.h>
 
+#include <GL/gl.h>
+
 #include "cogl-utils.h"
 #include "compositor-private.h"
 #include "mutter-enum-types.h"
@@ -971,6 +973,7 @@ load_file (GTask            *task,
 {
   GError *error = NULL;
   GdkPixbuf *pixbuf;
+  int max_texture_size = 0;
 
   pixbuf = gdk_pixbuf_new_from_file (task_data->filename,
                                      &error);
@@ -981,6 +984,33 @@ load_file (GTask            *task,
       return;
     }
 
+  glGetIntegerv (GL_MAX_TEXTURE_SIZE, &max_texture_size);
+
+  if (glGetError () != GL_NO_ERROR)
+      max_texture_size = 0;
+
+  if (max_texture_size > 0) {
+      double width, height;
+
+      width = gdk_pixbuf_get_width (pixbuf);
+      height = gdk_pixbuf_get_height (pixbuf);
+
+      if (width > max_texture_size || height > max_texture_size) {
+          GdkPixbuf *scaled_pixbuf;
+
+          if (width > height) {
+              width = max_texture_size;
+              height *= max_texture_size / width;
+          } else {
+              width *= max_texture_size / height;
+              height = max_texture_size;
+          }
+          scaled_pixbuf = gdk_pixbuf_scale_simple (pixbuf, width, height, GDK_INTERP_BILINEAR);
+          g_object_unref (pixbuf);
+          pixbuf = scaled_pixbuf;
+      }
+  }
+
   g_task_return_pointer (task, pixbuf, (GDestroyNotify) g_object_unref);
 }