perf: improve animation smoothness on Wayland

src/qEmbyApp/components/slidingstackedwidget.h

@@ -2,11 +2,13 @@
 #define SLIDINGSTACKEDWIDGET_H
 
 #include <QStackedWidget>
-#include <QPropertyAnimation>
-#include <QParallelAnimationGroup>
 #include <QEasingCurve>
+#include <QElapsedTimer>
 #include <QList>
+#include <QPoint>
 #include <QPointer>
+#include <QRect>
+#include <QTimer>
 
 class QLabel;
 
@@ -42,15 +44,31 @@ private Q_SLOTS:
     void animationDoneSlot();
 
 private:
+    QLabel *createSnapshotLabel(QWidget *source, const QRect &geometry);
+    void clearSnapshotLabels();
+    void startSlideAnimation(QWidget *widgetNow, const QPoint &nowStart,
+                             const QPoint &nowEnd, QWidget *widgetNext,
+                             const QPoint &nextStart,
+                             const QPoint &nextEnd);
+    void updateSlideAnimation();
+    int animationFrameIntervalMs() const;
     void flushPendingWidgetDisposals();
 
     int m_speed;
     QEasingCurve::Type m_animationType;
-    QParallelAnimationGroup *m_animGroup;
+    QTimer m_slideTimer;
+    QElapsedTimer m_slideClock;
+    QPointer<QWidget> m_animWidgetNow;
+    QPointer<QWidget> m_animWidgetNext;
+    QPoint m_animNowStart;
+    QPoint m_animNowEnd;
+    QPoint m_animNextStart;
+    QPoint m_animNextEnd;
     bool m_isAnimating;
     int m_nextIndex;
     QList<QPointer<QWidget>> m_pendingWidgetDisposals;
-    QLabel* m_snapshotLabel = nullptr; 
+    QLabel* m_currentSnapshotLabel = nullptr;
+    QLabel* m_nextSnapshotLabel = nullptr;
 };
 
 #endif