The input source is a pointing device associated with a display. Examples: InputDevice.SourceTouchscreen, InputDevice.SourceMouse. A Android.Views.MotionEvent should be interpreted as absolute coordinates in display units according to the Android.Views.View hierarchy. Pointer down/up indicated when the finger touches the display or when the selection button is pressed/released. Use InputDevice.GetMotionRange(Axis) to query the range of the pointing device. Some devices permit touches outside the display area so the effective range may be somewhat smaller or larger than the actual display size.

[Android Documentation]