XGetDeviceButtonMapping returns the number of physical buttons actually on the device. XGetDeviceButtonMapping can generate BadDevice or BadMatch errors. An invalid device was specified. The speci fied device does not exist or has not been opened by this client via XOpenInputDevice. This error may also occur if the specified device is the X keyboard or X pointer device.
Some numeric value falls outside the range of values accepted by the request.
Unless a spe cific range is specified for an argument, the full range defined by the argument's type is accepted. Any argument defined as a set of alternatives can generate this error.