feat: Scroll bar. Only collapse state.

8 files changed, 342 insertions, 7 deletions

diff --git a/include/cru/platform/GraphBase.hpp b/include/cru/platform/GraphBase.hpp
index b580ad31..6bf2736f 100644
--- a/include/cru/platform/GraphBase.hpp
+++ b/include/cru/platform/GraphBase.hpp
@@ -316,6 +316,12 @@ struct Color {
                  (hex >> 24) & mask);
   }
 
+  constexpr Color WithAlpha(std::uint8_t new_alpha) const {
+    auto result = *this;
+    result.alpha = new_alpha;
+    return result;
+  }
+
   std::uint8_t red;
   std::uint8_t green;
   std::uint8_t blue;
diff --git a/include/cru/ui/render/RenderObject.hpp b/include/cru/ui/render/RenderObject.hpp
index 2b166efc..8bcd4c62 100644
--- a/include/cru/ui/render/RenderObject.hpp
+++ b/include/cru/ui/render/RenderObject.hpp
@@ -2,6 +2,7 @@
 #include "Base.hpp"
 
 #include "MeasureRequirement.hpp"
+#include "cru/common/Base.hpp"
 #include "cru/common/Event.hpp"
 #include "cru/ui/Base.hpp"
 
@@ -63,9 +64,7 @@ class RenderObject : public Object {
   ~RenderObject() override = default;
 
   controls::Control* GetAttachedControl() const { return control_; }
-  void SetAttachedControl(controls::Control* new_control) {
-    control_ = new_control;
-  }
+  void SetAttachedControl(controls::Control* new_control);
 
   host::WindowHost* GetWindowHost() const { return window_host_; }
 
@@ -76,6 +75,7 @@ class RenderObject : public Object {
   void AddChild(RenderObject* render_object, Index position);
   void RemoveChild(Index position);
 
+  RenderObject* GetFirstChild() const;
   void TraverseDescendants(const std::function<void(RenderObject*)>& action);
 
   // Offset from parent's lefttop to lefttop of this render object. Margin is
@@ -131,6 +131,9 @@ class RenderObject : public Object {
   // This will set offset of this render object and call OnLayoutCore.
   void Layout(const Point& offset);
 
+  virtual Rect GetPaddingRect() const;
+  virtual Rect GetContentRect() const;
+
   void Draw(platform::graphics::IPainter* painter);
 
   // Param point must be relative the lefttop of render object including margin.
@@ -201,10 +204,11 @@ class RenderObject : public Object {
   // Lefttop of content_rect should be added when calculated children's offset.
   virtual void OnLayoutContent(const Rect& content_rect) = 0;
 
-  virtual void OnAfterLayout();
+  virtual void OnAttachedControlChanged(controls::Control* control) {
+    CRU_UNUSED(control)
+  }
 
-  virtual Rect GetPaddingRect() const;
-  virtual Rect GetContentRect() const;
+  virtual void OnAfterLayout();
 
  private:
   void SetParent(RenderObject* new_parent);
diff --git a/include/cru/ui/render/ScrollBarDelegate.hpp b/include/cru/ui/render/ScrollBarDelegate.hpp
new file mode 100644
index 00000000..e5c63f6d
--- /dev/null
+++ b/include/cru/ui/render/ScrollBarDelegate.hpp
@@ -0,0 +1,142 @@
+#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/controls/Control.hpp"
+
+#include <gsl/pointers>
+#include <memory>
+#include <optional>
+
+namespace cru::ui::render {
+class ScrollRenderObject;
+
+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<float>* 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<float> 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;
+};
+
+struct ScrollBarScrollAttemptArgs {
+  float x_offset;
+  float y_offset;
+};
+
+// 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<ScrollBarScrollAttemptArgs>* 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<ScrollBarScrollAttemptArgs> scroll_attempt_event_;
+};
+}  // namespace cru::ui::render
diff --git a/include/cru/ui/render/ScrollRenderObject.hpp b/include/cru/ui/render/ScrollRenderObject.hpp
index 3cc0e4c4..5a431527 100644
--- a/include/cru/ui/render/ScrollRenderObject.hpp
+++ b/include/cru/ui/render/ScrollRenderObject.hpp
@@ -2,7 +2,9 @@
 #include "RenderObject.hpp"
 
 #include "cru/platform/graphics/util/Painter.hpp"
+#include "cru/ui/render/ScrollBarDelegate.hpp"
 
+#include <memory>
 #include <optional>
 
 namespace cru::ui::render {
@@ -16,7 +18,7 @@ namespace cru::ui::render {
 // Or layout by scroll state.
 class ScrollRenderObject : public RenderObject {
  public:
-  ScrollRenderObject() : RenderObject(ChildMode::Single) {}
+  ScrollRenderObject();
 
   CRU_DELETE_COPY(ScrollRenderObject)
   CRU_DELETE_MOVE(ScrollRenderObject)
@@ -54,7 +56,11 @@ class ScrollRenderObject : public RenderObject {
                         const MeasureSize& preferred_size) override;
   void OnLayoutContent(const Rect& content_rect) override;
 
+  void OnAttachedControlChanged(controls::Control* control) override;
+
  private:
   Point scroll_offset_;
+
+  std::unique_ptr<ScrollBarDelegate> scroll_bar_delegate_;
 };
 }  // namespace cru::ui::render
diff --git a/src/ui/CMakeLists.txt b/src/ui/CMakeLists.txt
index d1c1e830..6153bc07 100644
--- a/src/ui/CMakeLists.txt
+++ b/src/ui/CMakeLists.txt
@@ -33,6 +33,7 @@ add_library(cru_ui STATIC
 	render/FlexLayoutRenderObject.cpp
 	render/LayoutHelper.cpp
 	render/RenderObject.cpp
+	render/ScrollBarDelegate.cpp
 	render/ScrollRenderObject.cpp
 	render/StackLayoutRenderObject.cpp
 	render/TextRenderObject.cpp
@@ -77,6 +78,7 @@ target_sources(cru_ui PUBLIC
 	${CRU_UI_INCLUDE_DIR}/render/LayoutRenderObject.hpp
 	${CRU_UI_INCLUDE_DIR}/render/MeasureRequirement.hpp
 	${CRU_UI_INCLUDE_DIR}/render/RenderObject.hpp
+	${CRU_UI_INCLUDE_DIR}/render/ScrollBarDelegate.hpp
 	${CRU_UI_INCLUDE_DIR}/render/ScrollRenderObject.hpp
 	${CRU_UI_INCLUDE_DIR}/render/StackLayoutRenderObject.hpp
 	${CRU_UI_INCLUDE_DIR}/render/TextRenderObject.hpp
diff --git a/src/ui/render/RenderObject.cpp b/src/ui/render/RenderObject.cpp
index a40ce9b8..7cf750cd 100644
--- a/src/ui/render/RenderObject.cpp
+++ b/src/ui/render/RenderObject.cpp
@@ -11,6 +11,11 @@
 #include <vector>
 
 namespace cru::ui::render {
+void RenderObject::SetAttachedControl(controls::Control* new_control) {
+  control_ = new_control;
+  OnAttachedControlChanged(new_control);
+}
+
 void RenderObject::AddChild(RenderObject* render_object, const Index position) {
   Expects(child_mode_ != ChildMode::None);
   Expects(!(child_mode_ == ChildMode::Single && children_.size() > 0));
@@ -41,6 +46,15 @@ void RenderObject::RemoveChild(const Index position) {
   OnRemoveChild(removed_child, position);
 }
 
+RenderObject* RenderObject::GetFirstChild() const {
+  const auto& children = GetChildren();
+  if (children.empty()) {
+    return nullptr;
+  } else {
+    return children.front();
+  }
+}
+
 void RenderObject::TraverseDescendants(
     const std::function<void(RenderObject*)>& action) {
   action(this);
diff --git a/src/ui/render/ScrollBarDelegate.cpp b/src/ui/render/ScrollBarDelegate.cpp
new file mode 100644
index 00000000..2814c567
--- /dev/null
+++ b/src/ui/render/ScrollBarDelegate.cpp
@@ -0,0 +1,145 @@
+#include "cru/ui/render/ScrollBarDelegate.hpp"
+
+#include "../Helper.hpp"
+#include "cru/common/Base.hpp"
+#include "cru/platform/GraphBase.hpp"
+#include "cru/platform/graphics/Factory.hpp"
+#include "cru/platform/graphics/Painter.hpp"
+#include "cru/ui/render/ScrollRenderObject.hpp"
+
+#include <gsl/pointers>
+#include <optional>
+
+namespace cru::ui::render {
+constexpr float kScrollBarCollapseThumbWidth = 2;
+
+ScrollBar::ScrollBar(gsl::not_null<ScrollRenderObject*> render_object)
+    : render_object_(render_object) {
+  // TODO: Use theme resource and delete this.
+  auto collapse_thumb_brush = GetUiApplication()
+                                  ->GetInstance()
+                                  ->GetGraphFactory()
+                                  ->CreateSolidColorBrush();
+  collapse_thumb_brush->SetColor(colors::gray.WithAlpha(128));
+  collapse_thumb_brush_ = std::move(collapse_thumb_brush);
+}
+
+void ScrollBar::SetEnabled(bool value) {
+  CRU_UNUSED(value)
+  // TODO: Implement this.
+}
+
+void ScrollBar::Draw(platform::graphics::IPainter* painter) {
+  if (is_enabled_) {
+    OnDraw(painter, is_expanded_);
+  }
+}
+
+void ScrollBar::InstallHandlers(controls::Control* control) {
+  CRU_UNUSED(control);
+  // TODO: Implement this.
+}
+
+gsl::not_null<std::shared_ptr<platform::graphics::IBrush>>
+ScrollBar::GetCollapseThumbBrush() const {
+  // TODO: Read theme resource.
+  return collapse_thumb_brush_;
+}
+
+HorizontalScrollBar::HorizontalScrollBar(
+    gsl::not_null<ScrollRenderObject*> render_object)
+    : ScrollBar(render_object) {}
+
+std::optional<ScrollBarAreaKind> HorizontalScrollBar::HitTest(
+    const Point& point) {
+  // TODO: Implement this.
+  CRU_UNUSED(point);
+  return std::nullopt;
+}
+
+void HorizontalScrollBar::OnDraw(platform::graphics::IPainter* painter,
+                                 bool expand) {
+  const auto child = render_object_->GetFirstChild();
+  if (child == nullptr) return;
+
+  const auto view_rect = render_object_->GetViewRect();
+  const auto padding_rect = render_object_->GetPaddingRect();
+  const auto child_size = child->GetSize();
+
+  if (view_rect.width >= child_size.width) return;
+
+  const float start_percentage = view_rect.left / child_size.width;
+  const float length_percentage = view_rect.width / child_size.width;
+  // const float end_percentage = start_percentage + length_percentage;
+
+  if (expand) {
+    // TODO: Implement this.
+  } else {
+    Rect thumb_rect{padding_rect.left + padding_rect.width * start_percentage,
+                    padding_rect.GetBottom() - kScrollBarCollapseThumbWidth,
+                    padding_rect.width * length_percentage,
+                    kScrollBarCollapseThumbWidth};
+    painter->FillRectangle(thumb_rect, GetCollapseThumbBrush().get().get());
+  }
+}
+
+VerticalScrollBar::VerticalScrollBar(
+    gsl::not_null<ScrollRenderObject*> render_object)
+    : ScrollBar(render_object) {}
+
+std::optional<ScrollBarAreaKind> VerticalScrollBar::HitTest(
+    const Point& point) {
+  // TODO: Implement this.
+  CRU_UNUSED(point);
+  return std::nullopt;
+}
+
+void VerticalScrollBar::OnDraw(platform::graphics::IPainter* painter,
+                               bool expand) {
+  const auto child = render_object_->GetFirstChild();
+  if (child == nullptr) return;
+
+  const auto view_rect = render_object_->GetViewRect();
+  const auto padding_rect = render_object_->GetPaddingRect();
+  const auto child_size = child->GetSize();
+
+  if (view_rect.height >= child_size.height) return;
+
+  const float start_percentage = view_rect.top / child_size.height;
+  const float length_percentage = view_rect.height / child_size.height;
+  // const float end_percentage = start_percentage + length_percentage;
+
+  if (expand) {
+    // TODO: Implement this.
+  } else {
+    Rect thumb_rect{padding_rect.GetRight() - kScrollBarCollapseThumbWidth,
+                    padding_rect.top + padding_rect.height * start_percentage,
+                    kScrollBarCollapseThumbWidth,
+                    padding_rect.height * length_percentage};
+    painter->FillRectangle(thumb_rect, GetCollapseThumbBrush().get().get());
+  }
+}
+
+ScrollBarDelegate::ScrollBarDelegate(
+    gsl::not_null<ScrollRenderObject*> render_object)
+    : render_object_(render_object),
+      horizontal_bar_(render_object),
+      vertical_bar_(render_object) {
+  horizontal_bar_.ScrollAttemptEvent()->AddHandler([this](float offset) {
+    this->scroll_attempt_event_.Raise({offset, 0});
+  });
+  vertical_bar_.ScrollAttemptEvent()->AddHandler([this](float offset) {
+    this->scroll_attempt_event_.Raise({0, offset});
+  });
+}
+
+void ScrollBarDelegate::DrawScrollBar(platform::graphics::IPainter* painter) {
+  horizontal_bar_.Draw(painter);
+  vertical_bar_.Draw(painter);
+}
+
+void ScrollBarDelegate::InstallHandlers(controls::Control* control) {
+  horizontal_bar_.InstallHandlers(control);
+  vertical_bar_.InstallHandlers(control);
+}
+}  // namespace cru::ui::render
diff --git a/src/ui/render/ScrollRenderObject.cpp b/src/ui/render/ScrollRenderObject.cpp
index 5b9cb627..18b0adbf 100644
--- a/src/ui/render/ScrollRenderObject.cpp
+++ b/src/ui/render/ScrollRenderObject.cpp
@@ -2,8 +2,11 @@
 
 #include "cru/platform/graphics/Painter.hpp"
 #include "cru/platform/graphics/util/Painter.hpp"
+#include "cru/ui/controls/Control.hpp"
+#include "cru/ui/render/ScrollBarDelegate.hpp"
 
 #include <algorithm>
+#include <memory>
 
 namespace cru::ui::render {
 namespace {
@@ -31,6 +34,10 @@ Point CoerceScroll(const Point& scroll_offset, const Size& content_size,
 }
 }  // namespace
 
+ScrollRenderObject::ScrollRenderObject() : RenderObject(ChildMode::Single) {
+  scroll_bar_delegate_ = std::make_unique<ScrollBarDelegate>(this);
+}
+
 RenderObject* ScrollRenderObject::HitTest(const Point& point) {
   if (const auto child = GetSingleChild()) {
     const auto offset = child->GetOffset();
@@ -52,6 +59,7 @@ void ScrollRenderObject::OnDrawCore(platform::graphics::IPainter* painter) {
         [child](platform::graphics::IPainter* p) { child->Draw(p); });
     painter->PopLayer();
   }
+  scroll_bar_delegate_->DrawScrollBar(painter);
 }
 
 Point ScrollRenderObject::GetScrollOffset() {
@@ -141,4 +149,12 @@ void ScrollRenderObject::OnLayoutContent(const Rect& content_rect) {
     child->Layout(content_rect.GetLeftTop() - GetScrollOffset());
   }
 }
+
+void ScrollRenderObject::OnAttachedControlChanged(controls::Control* control) {
+  if (control) {
+    scroll_bar_delegate_->InstallHandlers(control);
+  } else {
+    scroll_bar_delegate_->UninstallHandlers();
+  }
+}
 }  // namespace cru::ui::render