Project legacy canvas metadata into documents

src/app_core/document_canvas.h

@@ -1,8 +1,17 @@
 #pragma once
 
+#include "document/document.h"
 #include "foundation/result.h"
 
+#include <algorithm>
 #include <cmath>
+#include <cstddef>
+#include <cstdint>
+#include <span>
+#include <string>
+#include <string_view>
+#include <utility>
+#include <vector>
 
 namespace pp::app {
 
@@ -17,6 +26,34 @@ struct DocumentCanvasClearPlan {
     bool no_op = true;
 };
 
+struct DocumentCanvasLayerSnapshotInput {
+    std::string_view name;
+    bool visible = true;
+    bool alpha_locked = false;
+    float opacity = 1.0F;
+    int blend_mode = 0;
+    std::span<const std::uint32_t> frame_durations_ms;
+    std::size_t pending_face_payloads = 0;
+};
+
+struct DocumentCanvasSnapshotInput {
+    bool has_canvas = true;
+    std::uint32_t width = 0;
+    std::uint32_t height = 0;
+    std::size_t active_layer_index = 0;
+    std::size_t active_frame_index = 0;
+    std::span<const DocumentCanvasLayerSnapshotInput> layers;
+};
+
+struct DocumentCanvasSnapshotResult {
+    pp::document::CanvasDocument document;
+    std::size_t layer_count = 0;
+    std::size_t frame_count = 0;
+    std::size_t pending_face_payloads = 0;
+    bool metadata_only = true;
+    bool requires_renderer_payload_readback = false;
+};
+
 class DocumentCanvasClearServices {
 public:
     virtual ~DocumentCanvasClearServices() = default;
@@ -35,6 +72,115 @@ public:
     return pp::foundation::Status::success();
 }
 
+[[nodiscard]] inline pp::foundation::Result<DocumentCanvasSnapshotResult> plan_document_canvas_snapshot(
+    DocumentCanvasSnapshotInput input)
+{
+    if (!input.has_canvas) {
+        return pp::foundation::Result<DocumentCanvasSnapshotResult>::failure(
+            pp::foundation::Status::invalid_argument("document canvas snapshot requires a canvas"));
+    }
+
+    if (input.layers.empty()) {
+        return pp::foundation::Result<DocumentCanvasSnapshotResult>::failure(
+            pp::foundation::Status::invalid_argument("document canvas snapshot requires at least one layer"));
+    }
+
+    std::size_t frame_count = 1U;
+    std::size_t pending_face_payloads = 0U;
+    for (const auto& layer : input.layers) {
+        frame_count = std::max(frame_count, layer.frame_durations_ms.size());
+        pending_face_payloads += layer.pending_face_payloads;
+    }
+
+    if (input.active_layer_index >= input.layers.size()) {
+        return pp::foundation::Result<DocumentCanvasSnapshotResult>::failure(
+            pp::foundation::Status::out_of_range("active canvas layer is outside the document snapshot"));
+    }
+
+    if (input.active_frame_index >= frame_count) {
+        return pp::foundation::Result<DocumentCanvasSnapshotResult>::failure(
+            pp::foundation::Status::out_of_range("active canvas frame is outside the document snapshot"));
+    }
+
+    std::vector<pp::document::AnimationFrame> root_frames;
+    root_frames.reserve(frame_count);
+    for (std::size_t frame_index = 0; frame_index < frame_count; ++frame_index) {
+        std::uint32_t duration_ms = 100U;
+        for (const auto& layer : input.layers) {
+            if (frame_index < layer.frame_durations_ms.size()) {
+                duration_ms = layer.frame_durations_ms[frame_index];
+                break;
+            }
+        }
+        root_frames.push_back(pp::document::AnimationFrame { .duration_ms = duration_ms });
+    }
+
+    std::vector<std::string> layer_names;
+    std::vector<std::vector<pp::document::AnimationFrame>> layer_frames;
+    std::vector<pp::document::DocumentLayerConfig> layer_configs;
+    layer_names.reserve(input.layers.size());
+    layer_frames.reserve(input.layers.size());
+    layer_configs.reserve(input.layers.size());
+
+    for (std::size_t layer_index = 0; layer_index < input.layers.size(); ++layer_index) {
+        const auto& layer = input.layers[layer_index];
+        if (layer.name.empty()) {
+            layer_names.push_back("Layer " + std::to_string(layer_index + 1U));
+        } else {
+            layer_names.push_back(std::string(layer.name));
+        }
+
+        layer_frames.push_back({});
+        auto& frames = layer_frames.back();
+        frames.reserve(layer.frame_durations_ms.empty() ? root_frames.size() : layer.frame_durations_ms.size());
+        if (layer.frame_durations_ms.empty()) {
+            frames = root_frames;
+        } else {
+            for (const auto duration_ms : layer.frame_durations_ms) {
+                frames.push_back(pp::document::AnimationFrame { .duration_ms = duration_ms });
+            }
+        }
+
+        layer_configs.push_back(pp::document::DocumentLayerConfig {
+            .name = layer_names.back(),
+            .visible = layer.visible,
+            .alpha_locked = layer.alpha_locked,
+            .opacity = layer.opacity,
+            .blend_mode = static_cast<pp::paint::BlendMode>(layer.blend_mode),
+            .frames = std::span<const pp::document::AnimationFrame>(frames),
+        });
+    }
+
+    auto document = pp::document::CanvasDocument::create_from_snapshot(pp::document::DocumentSnapshotConfig {
+        .width = input.width,
+        .height = input.height,
+        .layers = std::span<const pp::document::DocumentLayerConfig>(layer_configs),
+        .frames = std::span<const pp::document::AnimationFrame>(root_frames),
+    });
+    if (!document) {
+        return pp::foundation::Result<DocumentCanvasSnapshotResult>::failure(document.status());
+    }
+
+    auto active_status = document.value().set_active_layer(input.active_layer_index);
+    if (!active_status.ok()) {
+        return pp::foundation::Result<DocumentCanvasSnapshotResult>::failure(active_status);
+    }
+
+    active_status = document.value().set_active_frame(input.active_frame_index);
+    if (!active_status.ok()) {
+        return pp::foundation::Result<DocumentCanvasSnapshotResult>::failure(active_status);
+    }
+
+    return pp::foundation::Result<DocumentCanvasSnapshotResult>::success(DocumentCanvasSnapshotResult {
+        .document = std::move(document.value()),
+        .layer_count = input.layers.size(),
+        .frame_count = frame_count,
+        .pending_face_payloads = pending_face_payloads,
+        .metadata_only = true,
+        .requires_renderer_payload_readback = pending_face_payloads > 0U,
+    });
+}
+
 [[nodiscard]] inline pp::foundation::Result<DocumentCanvasClearPlan> plan_document_canvas_clear(
     bool has_canvas,
     float r = 0.0F,