Route layer panel view through app core

src/app_core/document_layer.h

@@ -8,6 +8,7 @@
 #include <string>
 #include <string_view>
 #include <utility>
+#include <vector>
 
 namespace pp::app {
 
@@ -84,6 +85,33 @@ struct DocumentLayerMergePlan {
     bool create_history = true;
 };
 
+struct DocumentLayerPanelInput {
+    int layer_index = 0;
+    std::string name;
+    float opacity = 1.0F;
+    bool visible = true;
+    bool alpha_locked = false;
+    int blend_mode = 0;
+};
+
+struct DocumentLayerPanelLayerView {
+    int layer_index = 0;
+    std::string name;
+    float opacity = 1.0F;
+    bool visible = true;
+    bool alpha_locked = false;
+    int blend_mode = 0;
+    bool current = false;
+};
+
+struct DocumentLayerPanelView {
+    int current_index = 0;
+    float current_opacity = 1.0F;
+    bool current_alpha_locked = false;
+    int current_blend_mode = 0;
+    std::vector<DocumentLayerPanelLayerView> layers;
+};
+
 class DocumentLayerMenuServices {
 public:
     virtual ~DocumentLayerMenuServices() = default;
@@ -158,6 +186,60 @@ public:
     return pp::foundation::Status::success();
 }
 
+[[nodiscard]] inline pp::foundation::Result<DocumentLayerPanelView> plan_document_layer_panel_view(
+    const std::vector<DocumentLayerPanelInput>& layers,
+    int current_index)
+{
+    if (layers.empty()) {
+        return pp::foundation::Result<DocumentLayerPanelView>::failure(
+            pp::foundation::Status::invalid_argument("layer panel requires at least one layer"));
+    }
+
+    const auto current_status = validate_layer_index(static_cast<int>(layers.size()), current_index);
+    if (!current_status.ok()) {
+        return pp::foundation::Result<DocumentLayerPanelView>::failure(current_status);
+    }
+
+    DocumentLayerPanelView view;
+    view.current_index = current_index;
+    view.layers.reserve(layers.size());
+
+    for (const auto& input : layers) {
+        const auto index_status = validate_layer_index(static_cast<int>(layers.size()), input.layer_index);
+        if (!index_status.ok()) {
+            return pp::foundation::Result<DocumentLayerPanelView>::failure(index_status);
+        }
+
+        if (!std::isfinite(input.opacity) || input.opacity < 0.0F || input.opacity > 1.0F) {
+            return pp::foundation::Result<DocumentLayerPanelView>::failure(
+                pp::foundation::Status::out_of_range("layer opacity must be finite and within 0..1"));
+        }
+
+        if (input.blend_mode < 0 || input.blend_mode >= document_layer_legacy_blend_mode_count) {
+            return pp::foundation::Result<DocumentLayerPanelView>::failure(
+                pp::foundation::Status::out_of_range("layer blend mode is outside the supported range"));
+        }
+
+        const bool current = input.layer_index == current_index;
+        DocumentLayerPanelLayerView layer;
+        layer.layer_index = input.layer_index;
+        layer.name = input.name;
+        layer.opacity = input.opacity;
+        layer.visible = input.visible;
+        layer.alpha_locked = input.alpha_locked;
+        layer.blend_mode = input.blend_mode;
+        layer.current = current;
+        if (current) {
+            view.current_opacity = input.opacity;
+            view.current_alpha_locked = input.alpha_locked;
+            view.current_blend_mode = input.blend_mode;
+        }
+        view.layers.push_back(std::move(layer));
+    }
+
+    return pp::foundation::Result<DocumentLayerPanelView>::success(std::move(view));
+}
+
 [[nodiscard]] inline pp::foundation::Result<DocumentLayerRenamePlan> plan_document_layer_rename(
     std::string_view old_name,
     std::string_view requested_name)