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.

1 files changed, 63 insertions, 1 deletions

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
 };