Export layer collections through paint renderer

src/app_core/document_export.h

@@ -41,6 +41,11 @@ struct DocumentCubeFaceExportPayload {
     std::span<const std::byte> bytes;
 };
 
+struct DocumentExportCollectionPngPayload {
+    std::string path_suffix;
+    std::span<const std::byte> bytes;
+};
+
 struct DocumentExportSuggestedName {
     std::string name;
 };
@@ -190,6 +195,16 @@ public:
     virtual void publish_exported_image(std::string_view path) = 0;
 };
 
+class DocumentExportCollectionWriteServices {
+public:
+    virtual ~DocumentExportCollectionWriteServices() = default;
+
+    virtual pp::foundation::Status write_binary_file(
+        std::string_view path,
+        std::span<const std::byte> bytes) = 0;
+    virtual void publish_exported_image(std::string_view path) = 0;
+};
+
 [[nodiscard]] constexpr DocumentExportStartDecision plan_document_export_start(
     bool requires_license,
     bool license_valid,
@@ -608,6 +623,41 @@ document_cube_face_export_names() noexcept
     return pp::foundation::Result<DocumentCubeFaceExportTarget>::success(std::move(target));
 }
 
+[[nodiscard]] inline std::string document_export_two_digit_index(std::size_t index)
+{
+    auto value = std::to_string(index);
+    if (value.size() < 2U) {
+        value.insert(value.begin(), '0');
+    }
+    return value;
+}
+
+[[nodiscard]] inline std::string make_document_layer_export_path_suffix(
+    std::size_t layer_index,
+    std::string_view layer_name)
+{
+    std::string suffix;
+    const auto index = document_export_two_digit_index(layer_index);
+    suffix.reserve(10U + index.size() + layer_name.size());
+    suffix += "-layer";
+    suffix += index;
+    suffix += "-";
+    suffix += layer_name;
+    suffix += ".png";
+    return suffix;
+}
+
+[[nodiscard]] inline std::string make_document_animation_frame_export_path_suffix(std::size_t frame_index)
+{
+    std::string suffix;
+    const auto index = document_export_two_digit_index(frame_index);
+    suffix.reserve(5U + index.size());
+    suffix += "-";
+    suffix += index;
+    suffix += ".png";
+    return suffix;
+}
+
 [[nodiscard]] inline pp::foundation::Result<DocumentExportSuggestedName> make_document_export_suggested_name(
     std::string_view document_name,
     std::string_view suffix)
@@ -656,6 +706,41 @@ document_cube_face_export_names() noexcept
     return pp::foundation::Status::success();
 }
 
+[[nodiscard]] inline pp::foundation::Status execute_document_export_collection_write(
+    const DocumentExportCollectionTarget& target,
+    std::span<const DocumentExportCollectionPngPayload> payloads,
+    DocumentExportCollectionWriteServices& services)
+{
+    if (target.stem_path.empty()) {
+        return pp::foundation::Status::invalid_argument("export collection target requires a stem path");
+    }
+
+    if (payloads.empty()) {
+        return pp::foundation::Status::invalid_argument("export collection payloads must not be empty");
+    }
+
+    for (const auto& payload : payloads) {
+        if (payload.path_suffix.empty()) {
+            return pp::foundation::Status::invalid_argument("export collection payload suffix must not be empty");
+        }
+        if (payload.bytes.empty()) {
+            return pp::foundation::Status::invalid_argument("export collection payload must not be empty");
+        }
+
+        std::string path;
+        path.reserve(target.stem_path.size() + payload.path_suffix.size());
+        path += target.stem_path;
+        path += payload.path_suffix;
+        const auto write_status = services.write_binary_file(path, payload.bytes);
+        if (!write_status.ok()) {
+            return write_status;
+        }
+        services.publish_exported_image(path);
+    }
+
+    return pp::foundation::Status::success();
+}
+
 [[nodiscard]] inline pp::foundation::Status execute_document_export_file(
     const DocumentExportFileTarget& target,
     DocumentExportServices& services)