4 files changed, 141 insertions, 3 deletions

diff --git a/include/cru/ui/controls/Control.h b/include/cru/ui/controls/Control.h
index 242db3f4..1d976970 100644
--- a/include/cru/ui/controls/Control.h
+++ b/include/cru/ui/controls/Control.h
@@ -9,9 +9,11 @@ namespace cru::ui::controls {
  *  \remarks If you want to write a new control. You should override following
  * methods:
  *  - GetControlType()
+ *  - GetRenderObject()
  *  - ForEachChild(const std::function<void(Control*)>& predicate)
  *  - RemoveChild(Control* child)
- *  - GetRenderObject()
+ * The last two methods are totally for convenient control tree management. The
+ * former one is even not used.
  */
 class CRU_UI_API Control : public Object {
  protected:
diff --git a/include/cru/ui/controls/TreeView.h b/include/cru/ui/controls/TreeView.h
index b36ca553..6c3c360b 100644
--- a/include/cru/ui/controls/TreeView.h
+++ b/include/cru/ui/controls/TreeView.h
@@ -1,5 +1,6 @@
 #pragma once
 #include "Control.h"
+#include "cru/ui/render/TreeRenderObject.h"
 
 namespace cru::ui::controls {
 class TreeView;
@@ -7,31 +8,67 @@ class TreeView;
 class CRU_UI_API TreeViewItem : public Object {
   friend TreeView;
 
+ private:
+  TreeViewItem(TreeView* tree_view, TreeViewItem* parent,
+               render::TreeRenderObjectItem* render_object_item);
+  ~TreeViewItem() override;
+
  public:
-  TreeViewItem(TreeView* tree_view, TreeViewItem* parent);
   CRU_DELETE_COPY(TreeViewItem)
   CRU_DELETE_MOVE(TreeViewItem)
-  ~TreeViewItem() override;
 
   TreeView* GetTreeView() { return tree_view_; }
   TreeViewItem* GetParent() { return parent_; }
 
+  render::TreeRenderObjectItem* GetRenderObjectItem() const {
+    return render_object_item_;
+  }
+
   const std::vector<TreeViewItem*>& GetChildren() const { return children_; }
   Index GetChildCount() const { return children_.size(); }
   TreeViewItem* GetChildAt(Index index) {
     Expects(index >= 0 && index < children_.size());
     return children_[index];
   }
+  Index IndexOf(TreeViewItem* item) const;
 
   TreeViewItem* AddItem(Index position);
   void RemoveItem(Index position);
+  void RemoveFromParent();
+
+  Control* GetControl() const { return control_; }
+  void SetControl(Control* control);
+
+  void TraverseDescendants(std::function<void(TreeViewItem*)> callback);
 
  private:
   TreeView* tree_view_;
+  render::TreeRenderObjectItem* render_object_item_;
   TreeViewItem* parent_;
   std::vector<TreeViewItem*> children_;
 
   Control* control_;
 };
 
+class CRU_UI_API TreeView : public Control {
+ public:
+  constexpr static StringView kControlType = u"TreeView";
+
+  TreeView();
+  CRU_DELETE_COPY(TreeView)
+  CRU_DELETE_MOVE(TreeView)
+  ~TreeView() override;
+
+  String GetControlType() const override { return kControlType.ToString(); }
+  render::TreeRenderObject* GetRenderObject() { return &render_object_; }
+
+  void ForEachChild(const std::function<void(Control*)>& predicate) override;
+  void RemoveChild(Control* control) override;
+
+  TreeViewItem* GetRootItem() { return &root_item_; }
+
+ private:
+  render::TreeRenderObject render_object_;
+  TreeViewItem root_item_;
+};
 }  // namespace cru::ui::controls
diff --git a/src/ui/controls/TreeView.cpp b/src/ui/controls/TreeView.cpp
index e69de29b..659aef00 100644
--- a/src/ui/controls/TreeView.cpp
+++ b/src/ui/controls/TreeView.cpp
@@ -0,0 +1,87 @@
+#include "cru/ui/controls/TreeView.h"
+
+namespace cru::ui::controls {
+TreeViewItem::TreeViewItem(TreeView* tree_view, TreeViewItem* parent,
+                           render::TreeRenderObjectItem* render_object_item)
+    : tree_view_(tree_view),
+      parent_(parent),
+      render_object_item_(render_object_item) {}
+
+TreeViewItem::~TreeViewItem() {
+  if (control_) {
+    control_->SetParent(nullptr);
+  }
+
+  for (auto item : children_) {
+    delete item;
+  }
+}
+
+Index TreeViewItem::IndexOf(TreeViewItem* item) const {
+  auto result = std::find(children_.begin(), children_.end(), item);
+  if (result == children_.end()) {
+    return -1;
+  }
+  return result - children_.begin();
+}
+
+void TreeViewItem::RemoveFromParent() {
+  if (parent_ == nullptr) return;
+  parent_->RemoveItem(parent_->IndexOf(this));
+}
+
+TreeViewItem* TreeViewItem::AddItem(Index position) {
+  auto render_object_item = render_object_item_->AddItem(position);
+  auto item = new TreeViewItem(tree_view_, this, render_object_item);
+  children_.insert(children_.begin() + position, item);
+  return item;
+}
+
+void TreeViewItem::RemoveItem(Index position) {
+  Expects(position >= 0 && position < children_.size());
+  delete children_[position];
+  children_.erase(children_.begin() + position);
+  render_object_item_->RemoveItem(position);
+}
+
+void TreeViewItem::SetControl(Control* control) {
+  if (control_) {
+    control_->SetParent(nullptr);
+    render_object_item_->SetRenderObject(nullptr);
+  }
+  control_ = control;
+  if (control) {
+    control->SetParent(tree_view_);
+    render_object_item_->SetRenderObject(control->GetRenderObject());
+  }
+}
+
+void TreeViewItem::TraverseDescendants(
+    std::function<void(TreeViewItem*)> callback) {
+  callback(this);
+  for (auto item : children_) {
+    TraverseDescendants(callback);
+  }
+}
+
+TreeView::TreeView()
+    : root_item_(this, nullptr, render_object_.GetRootItem()) {}
+
+TreeView::~TreeView() {}
+
+void TreeView::ForEachChild(const std::function<void(Control*)>& predicate) {
+  root_item_.TraverseDescendants([&predicate](TreeViewItem* item) {
+    if (auto control = item->GetControl()) {
+      predicate(control);
+    }
+  });
+}
+
+void TreeView::RemoveChild(Control* control) {
+  root_item_.TraverseDescendants([&control](TreeViewItem* item) {
+    if (item->GetControl() == control) {
+      item->SetControl(nullptr);
+    }
+  });
+}
+}  // namespace cru::ui::controls
diff --git a/src/ui/render/TreeRenderObject.cpp b/src/ui/render/TreeRenderObject.cpp
index 9bf74535..8bf662e4 100644
--- a/src/ui/render/TreeRenderObject.cpp
+++ b/src/ui/render/TreeRenderObject.cpp
@@ -9,6 +9,11 @@ TreeRenderObjectItem::TreeRenderObjectItem(TreeRenderObject* tree_render_object,
     : tree_render_object_(tree_render_object), parent_(parent) {}
 
 TreeRenderObjectItem::~TreeRenderObjectItem() {
+  if (render_object_) {
+    render_object_->SetParent(nullptr);
+    render_object_ = nullptr;
+  }
+
   for (auto child : children_) {
     delete child;
   }
@@ -16,7 +21,14 @@ TreeRenderObjectItem::~TreeRenderObjectItem() {
 
 void TreeRenderObjectItem::SetRenderObject(RenderObject* render_object) {
   if (render_object == render_object_) return;
+  if (render_object_) {
+    render_object_->SetParent(nullptr);
+  }
   render_object_ = render_object;
+  if (render_object) {
+    assert(render_object->GetParent() == nullptr);
+    render_object->SetParent(tree_render_object_);
+  }
   tree_render_object_->InvalidateLayout();
 }