[gtk/wip/baedert/transforms6] gl renderer: Fix offscreen-drawn transform nodes

[Timm Bäder <baedert src gnome org>]

commit 2ce5a49b8460fd6888fcd379d4c86c9830b9abaa
Author: Timm Bäder <mail baedert org>
Date:   Wed Dec 12 07:54:26 2018 +0100

    gl renderer: Fix offscreen-drawn transform nodes
    
    We need to vertically flip them if they are indeed drawn offscreen, like
    everything else. Also use the child bounds for the offscreen texture,
    because that's what we draw offscreen.

 gsk/gl/gskglrenderer.c | 51 ++++++++++++++++++++++++++++++++++----------------
 1 file changed, 35 insertions(+), 16 deletions(-)
---
diff --git a/gsk/gl/gskglrenderer.c b/gsk/gl/gskglrenderer.c
index ff66e803e9..0a17aa0639 100644
--- a/gsk/gl/gskglrenderer.c
+++ b/gsk/gl/gskglrenderer.c
@@ -804,35 +804,54 @@ render_transform_node (GskGLRenderer   *self,
     }
   else
     {
-      const float min_x = node->bounds.origin.x;
-      const float min_y = node->bounds.origin.y;
-      const float max_x = min_x + node->bounds.size.width;
-      const float max_y = min_y + node->bounds.size.height;
-      const GskQuadVertex vertex_data[GL_N_VERTICES] = {
-        { { min_x, min_y }, { 0, 1 }, },
-        { { min_x, max_y }, { 0, 0 }, },
-        { { max_x, min_y }, { 1, 1 }, },
-
-        { { max_x, max_y }, { 1, 0 }, },
-        { { min_x, max_y }, { 0, 0 }, },
-        { { max_x, min_y }, { 1, 1 }, },
-      };
+      const float min_x = child->bounds.origin.x;
+      const float min_y = child->bounds.origin.y;
+      const float max_x = min_x + child->bounds.size.width;
+      const float max_y = min_y + child->bounds.size.height;
       int texture_id;
       gboolean is_offscreen;
       /* For non-trivial transforms, we draw everything on a texture and then
        * draw the texture transformed. */
+
       /* TODO: We should compute a modelview containing only the "non-trivial"
        *       part (e.g. the rotation) and use that. We want to keep the scale
        *       for the texture.
        */
+
       add_offscreen_ops (self, builder,
-                         &node->bounds,
+                         &child->bounds,
                          child,
-                         &texture_id, &is_offscreen,
+                         &texture_id,
+                         &is_offscreen,
                          FALSE, TRUE);
       ops_set_texture (builder, texture_id);
       ops_set_program (builder, &self->blit_program);
-      ops_draw (builder, vertex_data);
+
+      if (is_offscreen)
+        {
+          ops_draw (builder, (GskQuadVertex[GL_N_VERTICES]) {
+            { { min_x, min_y }, { 0, 1 }, },
+            { { min_x, max_y }, { 0, 0 }, },
+            { { max_x, min_y }, { 1, 1 }, },
+
+            { { max_x, max_y }, { 1, 0 }, },
+            { { min_x, max_y }, { 0, 0 }, },
+            { { max_x, min_y }, { 1, 1 }, },
+          });
+        }
+      else
+        {
+          ops_draw (builder, (GskQuadVertex[GL_N_VERTICES]) {
+            { { min_x, min_y }, { 0, 0 }, },
+            { { min_x, max_y }, { 0, 1 }, },
+            { { max_x, min_y }, { 1, 0 }, },
+
+            { { max_x, max_y }, { 1, 1 }, },
+            { { min_x, max_y }, { 0, 1 }, },
+            { { max_x, min_y }, { 1, 0 }, },
+          });
+
+        }
     }
   ops_pop_modelview (builder);
 }