Base input event type for mouse events. Stores general information about mouse events. $DOCS_URL/tutorials/inputs/inputevent.html The mouse button mask identifier, one of or a bitwise combination of the [enum MouseButton] button masks. When received in [method Node._input] or [method Node._unhandled_input], returns the mouse's position in the root [Viewport] using the coordinate system of the root [Viewport]. When received in [method Control._gui_input], returns the mouse's position in the [CanvasLayer] that the [Control] is in using the coordinate system of the [CanvasLayer]. When received in [method Node._input] or [method Node._unhandled_input], returns the mouse's position in the [Viewport] this [Node] is in using the coordinate system of this [Viewport]. When received in [method Control._gui_input], returns the mouse's position in the [Control] using the local coordinate system of the [Control].