Add document face compositor bridge

src/paint_renderer/compositor.h

@@ -1,11 +1,14 @@
 #pragma once
 
+#include "document/document.h"
 #include "foundation/result.h"
 #include "paint/blend.h"
 #include "renderer_api/renderer_api.h"
 
+#include <cstddef>
 #include <cstdint>
 #include <span>
+#include <vector>
 
 namespace pp::paint_renderer {
 
@@ -83,11 +86,29 @@ struct CanvasStrokeFeedbackPlan {
     bool compatibility_fallback = false;
 };
 
+struct DocumentFaceCompositeRequest {
+    const pp::document::CanvasDocument* document = nullptr;
+    std::size_t frame_index = 0;
+    std::uint32_t face_index = 0;
+    pp::paint::Rgba clear_color {};
+};
+
+struct DocumentFaceCompositeResult {
+    pp::renderer::Extent2D extent {};
+    std::vector<pp::paint::Rgba> pixels;
+    std::size_t visited_layer_count = 0;
+    std::size_t composited_layer_count = 0;
+    std::size_t face_payload_count = 0;
+};
+
 [[nodiscard]] pp::foundation::Status composite_layer(
     std::span<pp::paint::Rgba> destination,
     pp::renderer::Extent2D extent,
     LayerCompositeView layer) noexcept;
 
+[[nodiscard]] pp::foundation::Result<DocumentFaceCompositeResult> composite_document_face(
+    DocumentFaceCompositeRequest request);
+
 [[nodiscard]] bool stroke_composite_requires_feedback(
     pp::paint::BlendMode layer_blend_mode,
     pp::paint::StrokeBlendMode stroke_blend_mode,