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QWindow::startSystemMove()
On platforms that support it, this method of moving windows is preferred over setPosition, because it allows a more native look-and-feel of moving windows, e.g. letting the window manager snap this window against other windows, or special tiling or resizing behavior with animations when dragged to the edge of the screen. Furthermore, on some platforms such as Wayland, setPosition is not supported, so this is the only way the application can influence its position.
Вкратце - из wayland не работает setX (и просто назначение x).
