feat: Scroll bar. Only collapse state.

3 files changed, 175 insertions, 0 deletions

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