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1 files changed, 144 insertions, 0 deletions

diff --git a/include/cru/ui/render/ScrollBar.hpp b/include/cru/ui/render/ScrollBar.hpp
new file mode 100644
index 00000000..a9be49a3
--- /dev/null
+++ b/include/cru/ui/render/ScrollBar.hpp
@@ -0,0 +1,144 @@
+#pragma once
+#include "Base.hpp"
+#include "cru/common/Base.hpp"
+#include "cru/common/Event.hpp"
+#include "cru/platform/graphics/Base.hpp"
+#include "cru/platform/graphics/Painter.hpp"
+#include "cru/platform/gui/UiApplication.hpp"
+#include "cru/ui/Base.hpp"
+#include "cru/ui/controls/Control.hpp"
+
+#include <gsl/pointers>
+#include <memory>
+#include <optional>
+
+namespace cru::ui::render {
+class ScrollRenderObject;
+
+enum class ScrollKind { Absolute, Page, Line };
+
+struct Scroll {
+  Direction direction;
+  ScrollKind kind;
+  float offset;
+};
+
+enum class ScrollBarAreaKind {
+  UpArrow,    // Line up
+  DownArrow,  // Line down
+  UpThumb,    // Page up
+  DownThumb,  // Page down
+  Thumb
+};
+
+class ScrollBar : public Object {
+ public:
+  explicit ScrollBar(gsl::not_null<ScrollRenderObject*> render_object);
+
+  CRU_DELETE_COPY(ScrollBar)
+  CRU_DELETE_MOVE(ScrollBar)
+
+  ~ScrollBar() override = default;
+
+ public:
+  bool IsEnabled() const { return is_enabled_; }
+  void SetEnabled(bool value);
+
+  void Draw(platform::graphics::IPainter* painter);
+
+  virtual std::optional<ScrollBarAreaKind> HitTest(const Point& point) = 0;
+
+  IEvent<Scroll>* ScrollAttemptEvent() { return &scroll_attempt_event_; }
+
+  void InstallHandlers(controls::Control* control);
+  void UninstallHandlers() { InstallHandlers(nullptr); }
+
+  gsl::not_null<std::shared_ptr<platform::graphics::IBrush>>
+  GetCollapseThumbBrush() const;
+
+ protected:
+  virtual void OnDraw(platform::graphics::IPainter* painter, bool expand) = 0;
+
+ protected:
+  gsl::not_null<ScrollRenderObject*> render_object_;
+
+ private:
+  bool is_enabled_ = true;
+
+  bool is_expanded_ = false;
+
+  std::shared_ptr<platform::graphics::IBrush> collapse_thumb_brush_;
+
+  EventRevokerListGuard event_guard_;
+
+  Event<Scroll> scroll_attempt_event_;
+};
+
+class HorizontalScrollBar : public ScrollBar {
+ public:
+  explicit HorizontalScrollBar(
+      gsl::not_null<ScrollRenderObject*> render_object);
+
+  CRU_DELETE_COPY(HorizontalScrollBar)
+  CRU_DELETE_MOVE(HorizontalScrollBar)
+
+  ~HorizontalScrollBar() override = default;
+
+ public:
+  std::optional<ScrollBarAreaKind> HitTest(const Point& point) override;
+
+ protected:
+  void OnDraw(platform::graphics::IPainter* painter, bool expand) override;
+};
+
+class VerticalScrollBar : public ScrollBar {
+ public:
+  explicit VerticalScrollBar(gsl::not_null<ScrollRenderObject*> render_object);
+
+  CRU_DELETE_COPY(VerticalScrollBar)
+  CRU_DELETE_MOVE(VerticalScrollBar)
+
+  ~VerticalScrollBar() override = default;
+
+ public:
+  std::optional<ScrollBarAreaKind> HitTest(const Point& point) override;
+
+ protected:
+  void OnDraw(platform::graphics::IPainter* painter, bool expand) override;
+};
+
+// A delegate to draw scrollbar and register related events.
+class ScrollBarDelegate : public Object {
+ public:
+  explicit ScrollBarDelegate(gsl::not_null<ScrollRenderObject*> render_object);
+
+  CRU_DELETE_COPY(ScrollBarDelegate)
+  CRU_DELETE_MOVE(ScrollBarDelegate)
+
+  ~ScrollBarDelegate() override = default;
+
+ public:
+  bool IsHorizontalBarEnabled() const { return horizontal_bar_.IsEnabled(); }
+  void SetHorizontalBarEnabled(bool value) {
+    horizontal_bar_.SetEnabled(value);
+  }
+
+  bool IsVerticalBarEnabled() const { return horizontal_bar_.IsEnabled(); }
+  void SetVerticalBarEnabled(bool value) { horizontal_bar_.SetEnabled(value); }
+
+  IEvent<Scroll>* ScrollAttemptEvent() { return &scroll_attempt_event_; }
+
+  void DrawScrollBar(platform::graphics::IPainter* painter);
+
+  void InstallHandlers(controls::Control* control);
+  void UninstallHandlers() { InstallHandlers(nullptr); }
+
+ private:
+  gsl::not_null<ScrollRenderObject*> render_object_;
+
+  HorizontalScrollBar horizontal_bar_;
+  VerticalScrollBar vertical_bar_;
+
+  Event<Scroll> scroll_attempt_event_;
+};
+}  // namespace cru::ui::render