Fixed main popup positions under Wayland

… for bottom and right panels.

The problem was that some Wayland compositors returned global coordinates when anchors were applied, while some others (perhaps KWin) didn't. So, the patch uses local coordinates and changes them to the global ones in the end.

panel/lxqtpanel.cpp

@@ -1416,28 +1416,35 @@ Plugin* LXQtPanel::findPlugin(const ILXQtPanelPlugin* iPlugin) const
  ************************************************/
 QRect LXQtPanel::calculatePopupWindowPos(QPoint const & absolutePos, QSize const & windowSize) const
 {
-    int x = absolutePos.x(), y = absolutePos.y();
+    // Using of anchors makes coordinates be absolute under some Wayland compositors.
+    // Therefore, to cover both X11 and Wayland, we first use the local coordinates
+    // and then map them to the global coordinates.
+    QPoint localPos = mapFromGlobal(absolutePos);
+    int x = localPos.x(), y = localPos.y();
 
     switch (position())
     {
     case ILXQtPanel::PositionTop:
-        y = mGeometry.bottom();
+        y = mGeometry.height();
         break;
 
     case ILXQtPanel::PositionBottom:
-        y = mGeometry.top() - windowSize.height();
+        y = -windowSize.height();
         break;
 
     case ILXQtPanel::PositionLeft:
-        x = mGeometry.right();
+        x = mGeometry.width();
         break;
 
     case ILXQtPanel::PositionRight:
-        x = mGeometry.left() - windowSize.width();
+        x = -windowSize.width();
         break;
     }
 
-    QRect res(QPoint(x, y), windowSize);
+    QRect res(mapToGlobal(QPoint(x, y)), windowSize);
+
+    if (qGuiApp->nativeInterface<QNativeInterface::QWaylandApplication>())
+        return res;
 
     QRect panelScreen;
     const auto screens = QApplication::screens();