Extract canvas layer flows, pen modes, and node attributes

src/legacy_ui_node_attributes.h

@@ -0,0 +1,17 @@
+#pragma once
+
+#include <cstdint>
+
+namespace tinyxml2 {
+class XMLAttribute;
+}
+
+class Node;
+
+enum class kAttribute : uint16_t;
+
+namespace pp::panopainter {
+
+void parse_legacy_ui_node_attribute(Node& node, kAttribute ka, const tinyxml2::XMLAttribute* attr);
+
+} // namespace pp::panopainter