Unify dock leaves around single-tab stacks

new_editor/src/Shell/UIEditorWorkspaceModel.cpp

@@ -22,6 +22,55 @@ bool IsValidSplitRatio(float value) {
     return std::isfinite(value) && value > 0.0f && value < 1.0f;
 }
 
+std::string BuildSingleTabPanelNodeId(std::string_view stackNodeId) {
+    if (stackNodeId.empty()) {
+        return "single-tab-panel";
+    }
+
+    return std::string(stackNodeId) + "__panel";
+}
+
+UIEditorWorkspaceNode WrapStandalonePanelAsTabStack(UIEditorWorkspaceNode panelNode) {
+    UIEditorWorkspaceNode panelChild = std::move(panelNode);
+    const std::string stackNodeId = panelChild.nodeId;
+    panelChild.nodeId = BuildSingleTabPanelNodeId(stackNodeId);
+
+    UIEditorWorkspaceNode tabStack = {};
+    tabStack.kind = UIEditorWorkspaceNodeKind::TabStack;
+    tabStack.nodeId = stackNodeId;
+    tabStack.selectedTabIndex = 0u;
+    tabStack.children.push_back(std::move(panelChild));
+    return tabStack;
+}
+
+void CanonicalizeNodeRecursive(
+    UIEditorWorkspaceNode& node,
+    bool allowStandalonePanelLeaf) {
+    if (node.kind == UIEditorWorkspaceNodeKind::Panel) {
+        if (!allowStandalonePanelLeaf) {
+            node = WrapStandalonePanelAsTabStack(std::move(node));
+        }
+        return;
+    }
+
+    for (UIEditorWorkspaceNode& child : node.children) {
+        CanonicalizeNodeRecursive(
+            child,
+            node.kind == UIEditorWorkspaceNodeKind::TabStack);
+    }
+
+    if (node.kind == UIEditorWorkspaceNodeKind::TabStack &&
+        !node.children.empty() &&
+        node.selectedTabIndex >= node.children.size()) {
+        node.selectedTabIndex = node.children.size() - 1u;
+    }
+
+    if (node.kind == UIEditorWorkspaceNodeKind::Split &&
+        node.children.size() == 1u) {
+        node = std::move(node.children.front());
+    }
+}
+
 const UIEditorPanelDescriptor& RequirePanelDescriptor(
     const UIEditorPanelRegistry& registry,
     std::string_view panelId) {
@@ -274,7 +323,7 @@ UIEditorWorkspaceModel BuildDefaultEditorShellWorkspaceModel() {
         RequirePanelDescriptor(registry, "editor-foundation-root");
 
     UIEditorWorkspaceModel workspace = {};
-    workspace.root = BuildUIEditorWorkspacePanel(
+    workspace.root = BuildUIEditorWorkspaceSingleTabStack(
         "editor-foundation-root-node",
         rootPanel.panelId,
         rootPanel.defaultTitle,
@@ -297,6 +346,22 @@ UIEditorWorkspaceNode BuildUIEditorWorkspacePanel(
     return node;
 }
 
+UIEditorWorkspaceNode BuildUIEditorWorkspaceSingleTabStack(
+    std::string nodeId,
+    std::string panelId,
+    std::string title,
+    bool placeholder) {
+    UIEditorWorkspaceNode panel = BuildUIEditorWorkspacePanel(
+        BuildSingleTabPanelNodeId(nodeId),
+        std::move(panelId),
+        std::move(title),
+        placeholder);
+    return BuildUIEditorWorkspaceTabStack(
+        std::move(nodeId),
+        { std::move(panel) },
+        0u);
+}
+
 UIEditorWorkspaceNode BuildUIEditorWorkspaceTabStack(
     std::string nodeId,
     std::vector<UIEditorWorkspaceNode> panels,
@@ -345,6 +410,12 @@ UIEditorWorkspaceValidationResult ValidateUIEditorWorkspace(
     return {};
 }
 
+UIEditorWorkspaceModel CanonicalizeUIEditorWorkspaceModel(
+    UIEditorWorkspaceModel workspace) {
+    CanonicalizeNodeRecursive(workspace.root, false);
+    return workspace;
+}
+
 std::vector<UIEditorWorkspaceVisiblePanel> CollectUIEditorWorkspaceVisiblePanels(
     const UIEditorWorkspaceModel& workspace) {
     std::vector<UIEditorWorkspaceVisiblePanel> visiblePanels = {};