[gtk] gl renderer: Don't forget the offset when rendering blur nodes

[Timm Bäder <baedert src gnome org>]

commit b2ff6e91cdb0dc7259cd5fc5fda2907b8ded2307
Author: Timm Bäder <mail baedert org>
Date:   Sat Jan 5 09:18:27 2019 +0100

    gl renderer: Don't forget the offset when rendering blur nodes

 gsk/gl/gskglrenderer.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
---
diff --git a/gsk/gl/gskglrenderer.c b/gsk/gl/gskglrenderer.c
index da97872828..11cca74318 100644
--- a/gsk/gl/gskglrenderer.c
+++ b/gsk/gl/gskglrenderer.c
@@ -1081,13 +1081,14 @@ render_blur_node (GskGLRenderer       *self,
                   RenderOpBuilder     *builder,
                   const GskQuadVertex *vertex_data)
 {
-  const float min_x = node->bounds.origin.x;
-  const float min_y = node->bounds.origin.y;
+  const float min_x = builder->dx + node->bounds.origin.x;
+  const float min_y = builder->dy + node->bounds.origin.y;
   const float max_x = min_x + node->bounds.size.width;
   const float max_y = min_y + node->bounds.size.height;
   int texture_id;
   gboolean is_offscreen;
   RenderOp op;
+
   add_offscreen_ops (self, builder,
                      &node->bounds,
                      gsk_blur_node_get_child (node),