Added support for Twitch's Chat Replies (#3722)

Co-authored-by: Rasmus Karlsson <rasmus.karlsson@pajlada.com>

src/widgets/DraggablePopup.hpp

@@ -0,0 +1,47 @@
+#pragma once
+
+#include "widgets/BaseWindow.hpp"
+
+#include <QPoint>
+#include <QTimer>
+
+#include <memory>
+
+namespace chatterino {
+
+class DraggablePopup : public BaseWindow
+{
+    Q_OBJECT
+
+public:
+    /// DraggablePopup implements the automatic dragging behavior when clicking
+    /// anywhere in the window (that doesn't have some other widget).
+    ///
+    /// If closeAutomatically is set, the window will close when losing focus,
+    /// and the window will be frameless.
+    DraggablePopup(bool closeAutomatically, QWidget *parent);
+
+protected:
+    void mousePressEvent(QMouseEvent *event) override;
+    void mouseReleaseEvent(QMouseEvent *event) override;
+    void mouseMoveEvent(QMouseEvent *event) override;
+
+    // lifetimeHack_ is used to check that the window hasn't been destroyed yet
+    std::shared_ptr<bool> lifetimeHack_;
+
+private:
+    // isMoving_ is set to true if the user is holding the left mouse button down and has moved the mouse a small amount away from the original click point (startPosDrag_)
+    bool isMoving_ = false;
+
+    // startPosDrag_ is the coordinates where the user originally pressed the mouse button down to start dragging
+    QPoint startPosDrag_;
+
+    // requestDragPos_ is the final screen coordinates where the widget should be moved to.
+    // Takes the relative position of where the user originally clicked the widget into account
+    QPoint requestedDragPos_;
+
+    // dragTimer_ is called ~60 times per second once the user has initiated dragging
+    QTimer dragTimer_;
+};
+
+}  // namespace chatterino