chore: adjusted the project directory structure

app/toolbutton.cpp

@@ -0,0 +1,28 @@
+#include "toolbutton.h"
+
+#include "opacityhelper.h"
+
+#include <QPainter>
+#include <QGraphicsOpacityEffect>
+#include <QPropertyAnimation>
+
+ToolButton::ToolButton(bool hoverColor, QWidget *parent)
+    : QPushButton(parent)
+    , m_opacityHelper(new OpacityHelper(this))
+{
+    setFlat(true);
+    QString qss = "QPushButton {"
+                  "background: transparent;"
+                  "}";
+    if (hoverColor) {
+        qss += "QPushButton:hover {"
+               "background: red;"
+               "}";
+    }
+    setStyleSheet(qss);
+}
+
+void ToolButton::setOpacity(qreal opacity, bool animated)
+{
+    m_opacityHelper->setOpacity(opacity, animated);
+}