gsk: Introduce mask nodes

Add GskMaskNode, and support it in the render node
parser, in the inspector and in GtkSnapshot.

The rendering is just fallback for now.

Based on old work by Timm Bäder.

1 files changed, 146 insertions, 0 deletions

diff --git a/gsk/gskrendernodeimpl.c b/gsk/gskrendernodeimpl.c
index 376d32cb4e..f9de3752d3 100644
--- a/gsk/gskrendernodeimpl.c
+++ b/gsk/gskrendernodeimpl.c
@@ -5185,6 +5185,135 @@ gsk_blur_node_get_radius (const GskRenderNode *node)
 }
 
 /* }}} */
+/* {{{ GSK_MASK_NODE */
+
+/**
+ * GskMaskNode:
+ *
+ * A render node masking one child node with another.
+ *
+ * Since: 4.10
+ */
+typedef struct _GskMaskNode GskMaskNode;
+
+struct _GskMaskNode
+{
+  GskRenderNode render_node;
+
+  GskRenderNode *mask;
+  GskRenderNode *source;
+};
+
+static void
+gsk_mask_node_finalize (GskRenderNode *node)
+{
+  GskMaskNode *self = (GskMaskNode *) node;
+
+  gsk_render_node_unref (self->source);
+  gsk_render_node_unref (self->mask);
+}
+
+static void
+gsk_mask_node_draw (GskRenderNode *node,
+                    cairo_t       *cr)
+{
+  GskMaskNode *self = (GskMaskNode *) node;
+  cairo_pattern_t *mask_pattern;
+
+  cairo_push_group (cr);
+  gsk_render_node_draw (self->source, cr);
+  cairo_pop_group_to_source (cr);
+
+  cairo_push_group (cr);
+  gsk_render_node_draw (self->mask, cr);
+  mask_pattern = cairo_pop_group (cr);
+
+  cairo_mask (cr, mask_pattern);
+}
+
+static void
+gsk_mask_node_diff (GskRenderNode  *node1,
+                    GskRenderNode  *node2,
+                    cairo_region_t *region)
+{
+  GskMaskNode *self1 = (GskMaskNode *) node1;
+  GskMaskNode *self2 = (GskMaskNode *) node2;
+
+  gsk_render_node_diff (self1->source, self2->source, region);
+  gsk_render_node_diff (self1->mask, self2->mask, region);
+}
+
+/**
+ * gsk_mask_node_new:
+ * @source: The bottom node to be drawn
+ * @mask: The node to be blended onto the @bottom node
+ *
+ * Creates a `GskRenderNode` that will use @blend_mode to blend the @top
+ * node onto the @bottom node.
+ *
+ * Returns: (transfer full) (type GskMaskNode): A new `GskRenderNode`
+ *
+ * Since: 4.10
+ */
+GskRenderNode *
+gsk_mask_node_new (GskRenderNode *source,
+                   GskRenderNode *mask)
+{
+  GskMaskNode *self;
+
+  g_return_val_if_fail (GSK_IS_RENDER_NODE (source), NULL);
+  g_return_val_if_fail (GSK_IS_RENDER_NODE (mask), NULL);
+
+  self = gsk_render_node_alloc (GSK_MASK_NODE);
+  self->source = gsk_render_node_ref (source);
+  self->mask = gsk_render_node_ref (mask);
+
+  graphene_rect_union (&source->bounds, &mask->bounds, &self->render_node.bounds);
+
+  return &self->render_node;
+}
+
+/**
+ * gsk_mask_node_get_source:
+ * @node: (type GskBlendNode): a mask `GskRenderNode`
+ *
+ * Retrieves the source `GskRenderNode` child of the @node.
+ *
+ * Returns: (transfer none): the source child node
+ *
+ * Since: 4.10
+ */
+GskRenderNode *
+gsk_mask_node_get_source (const GskRenderNode *node)
+{
+  const GskMaskNode *self = (const GskMaskNode *) node;
+
+  g_return_val_if_fail (GSK_IS_RENDER_NODE_TYPE (node, GSK_MASK_NODE), NULL);
+
+  return self->source;
+}
+
+/**
+ * gsk_mask_node_get_mask:
+ * @node: (type GskBlendNode): a mask `GskRenderNode`
+ *
+ * Retrieves the mask `GskRenderNode` child of the @node.
+ *
+ * Returns: (transfer none): the mask child node
+ *
+ * Since: 4.10
+ */
+GskRenderNode *
+gsk_mask_node_get_mask (const GskRenderNode *node)
+{
+  const GskMaskNode *self = (const GskMaskNode *) node;
+
+  g_return_val_if_fail (GSK_IS_RENDER_NODE_TYPE (node, GSK_MASK_NODE), NULL);
+
+  return self->mask;
+}
+
+/* }}} */
 /* {{{ GSK_DEBUG_NODE */
 
 /**
@@ -5556,6 +5685,7 @@ GSK_DEFINE_RENDER_NODE_TYPE (gsk_blend_node, GSK_BLEND_NODE)
 GSK_DEFINE_RENDER_NODE_TYPE (gsk_cross_fade_node, GSK_CROSS_FADE_NODE)
 GSK_DEFINE_RENDER_NODE_TYPE (gsk_text_node, GSK_TEXT_NODE)
 GSK_DEFINE_RENDER_NODE_TYPE (gsk_blur_node, GSK_BLUR_NODE)
+GSK_DEFINE_RENDER_NODE_TYPE (gsk_mask_node, GSK_MASK_NODE)
 GSK_DEFINE_RENDER_NODE_TYPE (gsk_gl_shader_node, GSK_GL_SHADER_NODE)
 GSK_DEFINE_RENDER_NODE_TYPE (gsk_debug_node, GSK_DEBUG_NODE)
 
@@ -5949,6 +6079,22 @@ gsk_render_node_init_types_once (void)
   {
     const GskRenderNodeTypeInfo node_info =
     {
+      GSK_MASK_NODE,
+      sizeof (GskMaskNode),
+      NULL,
+      gsk_mask_node_finalize,
+      gsk_mask_node_draw,
+      NULL,
+      gsk_mask_node_diff,
+    };
+
+    GType node_type = gsk_render_node_type_register_static (I_("GskMaskNode"), &node_info);
+    gsk_render_node_types[GSK_MASK_NODE] = node_type;
+  }
+
+  {
+    const GskRenderNodeTypeInfo node_info =
+    {
       GSK_GL_SHADER_NODE,
       sizeof (GskGLShaderNode),
       NULL,