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1 files changed, 87 insertions, 0 deletions

diff --git a/include/cru/ui/click_detector.hpp b/include/cru/ui/click_detector.hpp
new file mode 100644
index 00000000..e7d5e417
--- /dev/null
+++ b/include/cru/ui/click_detector.hpp
@@ -0,0 +1,87 @@
+#pragma once
+#include "control.hpp"
+
+#include <cstdlib>
+#include <forward_list>
+#include <optional>
+
+namespace cru::ui {
+class ClickEventArgs : Object {
+ public:
+  ClickEventArgs(Control* sender, const Point& down_point,
+                 const Point& up_point, MouseButton button)
+      : sender_(sender),
+        down_point_(down_point),
+        up_point_(up_point),
+        button_(button) {}
+
+  CRU_DEFAULT_COPY(ClickEventArgs)
+  CRU_DEFAULT_MOVE(ClickEventArgs)
+
+  ~ClickEventArgs() override = default;
+
+  Control* GetSender() const { return sender_; }
+  Point GetDownPoint() const { return down_point_; }
+  Point GetUpPoint() const { return up_point_; }
+  MouseButton GetButton() const { return button_; }
+
+ private:
+  Control* sender_;
+  Point down_point_;
+  Point up_point_;
+  MouseButton button_;
+};
+
+class ClickDetector : public Object {
+ public:
+  explicit ClickDetector(Control* control);
+
+  ClickDetector(const ClickDetector& other) = delete;
+  ClickDetector& operator=(const ClickDetector& other) = delete;
+  ClickDetector(ClickDetector&& other) = delete;
+  ClickDetector& operator=(ClickDetector&& other) = delete;
+
+  ~ClickDetector() override = default;
+
+  Control* GetControl() const { return control_; }
+
+  // Return a union of buttons being pressed. Return 0 if no button is being
+  // pressed.
+  MouseButton IsPressing() const {
+    unsigned result = 0;
+    if (click_map_.left.has_value()) result |= MouseButton::Left;
+    if (click_map_.middle.has_value()) result |= MouseButton::Middle;
+    if (click_map_.right.has_value()) result |= MouseButton::Right;
+    return static_cast<MouseButton>(result);
+  }
+
+  IEvent<ClickEventArgs>* ClickEvent() { return &event_; }
+
+ private:
+  std::optional<Point>& FromButton(MouseButton button) {
+    switch (button) {
+      case MouseButton::Left:
+        return click_map_.left;
+      case MouseButton::Middle:
+        return click_map_.middle;
+      case MouseButton::Right:
+        return click_map_.right;
+      default:
+        std::abort();
+    }
+  }
+
+ private:
+  Control* control_;
+
+  Event<ClickEventArgs> event_;
+
+  std::forward_list<EventRevokerGuard> event_rovoker_guards_;
+
+  struct {
+    std::optional<Point> left = std::nullopt;
+    std::optional<Point> middle = std::nullopt;
+    std::optional<Point> right = std::nullopt;
+  } click_map_;
+};
+}  // namespace cru::ui