Add transparent overlay window (#4746)

src/widgets/helper/OverlayInteraction.hpp

@@ -0,0 +1,47 @@
+#pragma once
+
+#include "widgets/helper/TitlebarButton.hpp"
+
+#include <QPropertyAnimation>
+#include <QWidget>
+
+class QGridLayout;
+
+namespace chatterino {
+
+class OverlayWindow;
+class OverlayInteraction : public QWidget
+{
+    Q_OBJECT
+public:
+    OverlayInteraction(OverlayWindow *parent);
+
+    void attach(QGridLayout *layout);
+
+    QWidget *closeButton();
+
+    void startInteraction();
+    void endInteraction();
+
+    bool isInteracting() const;
+
+protected:
+    void paintEvent(QPaintEvent *event) override;
+
+private:
+    Q_PROPERTY(double interactionProgress READ interactionProgress WRITE
+                   setInteractionProgress)
+
+    TitleBarButton closeButton_;
+
+    double interactionProgress() const;
+    void setInteractionProgress(double progress);
+
+    bool interacting_ = false;
+    double interactionProgress_ = 0.0;
+    QPropertyAnimation interactAnimation_;
+
+    OverlayWindow *window_;
+};
+
+}  // namespace chatterino