systemGestureInsets property Null safety
The number of physical pixels on each side of the display rectangle into which the view can render, but where the operating system will consume input gestures for the sake of system navigation.
For example, an operating system might use the vertical edges of the screen, where swiping inwards from the edges takes users backward through the history of screens they previously visited.
When this property changes,
onMetricsChanged is called.
WindowPadding get systemGestureInsets => viewConfiguration.systemGestureInsets;