Export document frame faces as PNGs

src/paint_renderer/compositor.h

@@ -139,6 +139,13 @@ struct RecordedDocumentFrameUploadResult {
     std::size_t transition_command_count = 0;
 };
 
+struct DocumentFrameFacePngExportResult {
+    DocumentFrameCompositeResult composite {};
+    std::array<std::vector<std::byte>, pp::document::cube_face_count> face_pngs {};
+    std::size_t face_count = 0;
+    std::uint64_t encoded_bytes = 0;
+};
+
 [[nodiscard]] pp::foundation::Status composite_layer(
     std::span<pp::paint::Rgba> destination,
     pp::renderer::Extent2D extent,
@@ -157,6 +164,9 @@ struct RecordedDocumentFrameUploadResult {
 [[nodiscard]] pp::foundation::Result<RecordedDocumentFrameUploadResult> record_document_frame_upload(
     DocumentFrameUploadRequest request);
 
+[[nodiscard]] pp::foundation::Result<DocumentFrameFacePngExportResult> export_document_frame_face_pngs(
+    DocumentFrameCompositeRequest request);
+
 [[nodiscard]] bool stroke_composite_requires_feedback(
     pp::paint::BlendMode layer_blend_mode,
     pp::paint::StrokeBlendMode stroke_blend_mode,