chore: adjusted the project directory structure

app/opacityhelper.cpp

@@ -0,0 +1,27 @@
+#include "opacityhelper.h"
+
+#include <QGraphicsOpacityEffect>
+#include <QPropertyAnimation>
+
+OpacityHelper::OpacityHelper(QWidget *parent)
+    : QObject(parent)
+    , m_opacityFx(new QGraphicsOpacityEffect(parent))
+    , m_opacityAnimation(new QPropertyAnimation(m_opacityFx, "opacity"))
+{
+    parent->setGraphicsEffect(m_opacityFx);
+
+    m_opacityAnimation->setDuration(300);
+}
+
+void OpacityHelper::setOpacity(qreal opacity, bool animated)
+{
+    if (!animated) {
+        m_opacityFx->setOpacity(opacity);
+        return;
+    }
+
+    m_opacityAnimation->stop();
+    m_opacityAnimation->setStartValue(m_opacityFx->opacity());
+    m_opacityAnimation->setEndValue(opacity);
+    m_opacityAnimation->start();
+}