[gtk/wip/otte/transform: 8/8] rendernode: Implement diffing of transform nodes

[Benjamin Otte <otte src gnome org>]

commit dbe58452d75d97f10650728b69c8981e33dc74d8
Author: Benjamin Otte <otte redhat com>
Date:   Mon Mar 4 22:11:57 2019 +0100

    rendernode: Implement diffing of transform nodes
    
    This reinstates diffing in the same way that it worked for offset nodes.
    
    It would be possible to add diffing for affine transforms or even all
    transforms, but I think this is unnecessary right now - and also quite
    expensive to compute.

 gsk/gskrendernodeimpl.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 63 insertions(+), 1 deletion(-)
---
diff --git a/gsk/gskrendernodeimpl.c b/gsk/gskrendernodeimpl.c
index 48dbcb76cd..7fa58c4db3 100644
--- a/gsk/gskrendernodeimpl.c
+++ b/gsk/gskrendernodeimpl.c
@@ -2427,6 +2427,68 @@ gsk_transform_node_draw (GskRenderNode *node,
   gsk_render_node_draw (self->child, cr);
 }
 
+static void
+gsk_transform_node_diff (GskRenderNode  *node1,
+                         GskRenderNode  *node2,
+                         cairo_region_t *region)
+{
+  GskTransformNode *self1 = (GskTransformNode *) node1;
+  GskTransformNode *self2 = (GskTransformNode *) node2;
+
+  if (!gsk_transform_equal (self1->transform, self2->transform))
+    {
+      gsk_render_node_diff_impossible (node1, node2, region);
+      return;
+    }
+
+  if (self1->child == self2->child)
+    return;
+
+  switch (gsk_transform_get_category (self1->transform))
+    {
+    case GSK_TRANSFORM_CATEGORY_IDENTITY:
+      gsk_render_node_diff (self1->child, self2->child, region);
+      break;
+
+    case GSK_TRANSFORM_CATEGORY_2D_TRANSLATE:
+      {
+        cairo_region_t *sub;
+        float dx, dy;
+
+        gsk_transform_to_translate (self1->transform, &dx, &dy);
+        sub = cairo_region_create ();
+        gsk_render_node_diff (self1->child, self2->child, sub);
+        cairo_region_translate (sub, floor (dx), floor (dy));
+        if (floor (dx) != dx)
+          {
+            cairo_region_t *tmp = cairo_region_copy (sub);
+            cairo_region_translate (tmp, 1, 0);
+            cairo_region_union (sub, tmp);
+            cairo_region_destroy (sub);
+          }
+        if (floor (dy) != dy)
+          {
+            cairo_region_t *tmp = cairo_region_copy (sub);
+            cairo_region_translate (tmp, 0, 1);
+            cairo_region_union (sub, tmp);
+            cairo_region_destroy (sub);
+          }
+        cairo_region_union (region, sub);
+        cairo_region_destroy (sub);
+      }
+      break;
+
+    case GSK_TRANSFORM_CATEGORY_UNKNOWN:
+    case GSK_TRANSFORM_CATEGORY_ANY:
+    case GSK_TRANSFORM_CATEGORY_3D:
+    case GSK_TRANSFORM_CATEGORY_2D:
+    case GSK_TRANSFORM_CATEGORY_2D_AFFINE:
+    default:
+      gsk_render_node_diff_impossible (node1, node2, region);
+      break;
+    }
+}
+
 #define GSK_TRANSFORM_NODE_VARIANT_TYPE "(idddddddddddddddduv)"
 
 static GVariant *
@@ -2502,7 +2564,7 @@ static const GskRenderNodeClass GSK_TRANSFORM_NODE_CLASS = {
   gsk_transform_node_finalize,
   gsk_transform_node_draw,
   gsk_render_node_can_diff_true,
-  gsk_render_node_diff_impossible,
+  gsk_transform_node_diff,
   gsk_transform_node_serialize,
   gsk_transform_node_deserialize
 };