Abstract base class for touch gestures.
InputEventGestures are sent when a user performs a supported gesture on a touch screen. Gestures can't be emulated using mouse, because they typically require multi-touch.
$DOCS_URL/tutorials/inputs/inputevent.html
- The local gesture position relative to the [Viewport]. If used in [method Control._gui_input], the position is relative to the current [Control] that received this gesture.