From 7ccb08ac09a83e81a822712b712dc0473c9b23cf Mon Sep 17 00:00:00 2001
From: crupest <crupest@outlook.com>
Date: Tue, 27 Nov 2018 17:53:21 +0800
Subject: Add mouse wheel support.

---
 src/ui/controls/scroll_control.cpp | 23 +++++++++++++++++++++++
 src/ui/controls/scroll_control.hpp |  4 +++-
 2 files changed, 26 insertions(+), 1 deletion(-)

(limited to 'src/ui/controls')

diff --git a/src/ui/controls/scroll_control.cpp b/src/ui/controls/scroll_control.cpp
index 103a5c20..aa5403d4 100644
--- a/src/ui/controls/scroll_control.cpp
+++ b/src/ui/controls/scroll_control.cpp
@@ -308,6 +308,29 @@ namespace cru::ui::controls
         }
     }
 
+    void ScrollControl::OnMouseWheelCore(events::MouseWheelEventArgs& args)
+    {
+        Control::OnMouseWheelCore(args);
+
+        constexpr const auto view_delta = 30.0f;
+
+        if (args.GetDelta() == 0.0f)
+            return;
+
+        const auto content_rect = GetRect(RectRange::Content);
+        if (IsVerticalScrollEnabled() && GetScrollOffsetY() != (args.GetDelta() > 0.0f ? 0.0f : AtLeast0(GetViewHeight() - content_rect.height)))
+        {
+            SetScrollOffset(std::nullopt, GetScrollOffsetY() - args.GetDelta() / WHEEL_DELTA * view_delta);
+            return;
+        }
+
+        if (IsHorizontalScrollEnabled() && GetScrollOffsetX() != (args.GetDelta() > 0.0f ? 0.0f : AtLeast0(GetViewWidth() - content_rect.width)))
+        {
+            SetScrollOffset(GetScrollOffsetX() - args.GetDelta() / WHEEL_DELTA * view_delta, std::nullopt);
+            return;
+        }
+    }
+
     void ScrollControl::CoerceAndSetOffsets(const float offset_x, const float offset_y, const bool update_children)
     {
         const auto old_offset_x = offset_x_;
diff --git a/src/ui/controls/scroll_control.hpp b/src/ui/controls/scroll_control.hpp
index 76762f21..0541a010 100644
--- a/src/ui/controls/scroll_control.hpp
+++ b/src/ui/controls/scroll_control.hpp
@@ -16,7 +16,7 @@ namespace cru::ui::controls
     // Done: Draw(no need)
     // Done: API
     // Done: ScrollBar
-    // TODO: MouseEvent
+    // Done: MouseEvent
     class ScrollControl : public Control
     {
     private:
@@ -128,6 +128,8 @@ namespace cru::ui::controls
         void OnMouseMoveCore(events::MouseEventArgs& args) override final;
         void OnMouseUpCore(events::MouseButtonEventArgs& args) override final;
 
+        void OnMouseWheelCore(events::MouseWheelEventArgs& args) override;
+
     private:
         void CoerceAndSetOffsets(float offset_x, float offset_y, bool update_children = true);
         void UpdateScrollBarVisibility();
-- 
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