[gnome-shell] st_theme_node_prerender_shadow: guard against failure to allocate a texture

[Owen Taylor <otaylor src gnome org>]

commit 8b7464c6487faeab7ad4862d8ac20b2b421036ca
Author: Owen W. Taylor <otaylor fishsoup net>
Date:   Mon Oct 26 13:35:49 2015 -0400

    st_theme_node_prerender_shadow: guard against failure to allocate a texture
    
    If we are trying to render a shadow at a size that is very large in one
    direction, but small in the other direction (so that we don't 9-slice
    the texture), then allocating the backing texture for the offscreen
    buffer may fail due to texture-size limits. Don't crash in that case.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=757150

 src/st/st-theme-node-drawing.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)
---
diff --git a/src/st/st-theme-node-drawing.c b/src/st/st-theme-node-drawing.c
index 95386dc..9ce5683 100644
--- a/src/st/st-theme-node-drawing.c
+++ b/src/st/st-theme-node-drawing.c
@@ -2162,7 +2162,7 @@ st_theme_node_prerender_shadow (StThemeNodePaintState *state)
   guint border_radius[4];
   int max_borders[4];
   int center_radius, corner_id;
-  CoglHandle buffer, offscreen;
+  CoglHandle buffer, offscreen = COGL_INVALID_HANDLE;
 
   /* Get infos from the node */
   if (state->alloc_width < node->box_shadow_min_width ||
@@ -2203,7 +2203,8 @@ st_theme_node_prerender_shadow (StThemeNodePaintState *state)
                                        state->box_shadow_height,
                                        COGL_TEXTURE_NO_SLICING,
                                        COGL_PIXEL_FORMAT_ANY);
-  offscreen = cogl_offscreen_new_with_texture (buffer);
+  if (buffer != COGL_INVALID_HANDLE)
+    offscreen = cogl_offscreen_new_with_texture (buffer);
 
   if (offscreen != COGL_INVALID_HANDLE)
     {
@@ -2220,7 +2221,9 @@ st_theme_node_prerender_shadow (StThemeNodePaintState *state)
       state->box_shadow_pipeline = _st_create_shadow_pipeline (st_theme_node_get_box_shadow (node),
                                                                buffer);
     }
-  cogl_handle_unref (buffer);
+
+  if (buffer != COGL_INVALID_HANDLE)
+    cogl_handle_unref (buffer);
 }
 
 static void