Export captured canvas snapshots through document writer

src/app_core/document_canvas.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include "document/document.h"
+#include "document/ppi_export.h"
 #include "foundation/result.h"
 
 #include <algorithm>
@@ -77,6 +78,11 @@ struct DocumentCanvasSaveSnapshotReport {
     bool can_export_ppi = false;
 };
 
+struct DocumentCanvasPpiExportResult {
+    DocumentCanvasSaveSnapshotReport report;
+    std::vector<std::byte> bytes;
+};
+
 class DocumentCanvasClearServices {
 public:
     virtual ~DocumentCanvasClearServices() = default;
@@ -242,6 +248,27 @@ public:
     };
 }
 
+[[nodiscard]] inline pp::foundation::Result<DocumentCanvasPpiExportResult>
+export_document_canvas_save_snapshot_to_ppi(const DocumentCanvasSnapshotResult& snapshot)
+{
+    const auto report = make_document_canvas_save_snapshot_report(snapshot);
+    if (!report.can_export_ppi) {
+        return pp::foundation::Result<DocumentCanvasPpiExportResult>::failure(
+            pp::foundation::Status::invalid_argument(
+                "canvas document snapshot still requires renderer payload readback"));
+    }
+
+    auto bytes = pp::document::export_ppi_project_document(snapshot.document);
+    if (!bytes) {
+        return pp::foundation::Result<DocumentCanvasPpiExportResult>::failure(bytes.status());
+    }
+
+    return pp::foundation::Result<DocumentCanvasPpiExportResult>::success(DocumentCanvasPpiExportResult {
+        .report = report,
+        .bytes = std::move(bytes.value()),
+    });
+}
+
 [[nodiscard]] inline pp::foundation::Result<DocumentCanvasClearPlan> plan_document_canvas_clear(
     bool has_canvas,
     float r = 0.0F,