Filtering Input Streams in a Multi-Touch System

Once a first touch has been initiated on a multi-touch input device, the device ignores any additional touches which are initiated on the device while the first touch is still occurring. For example, although hardware in the device may detect such additional touches, the hardware may opt not to provide input representing such additional touches to software (such as device drivers) executing on the device. Alternatively, the hardware may provide input representing such additional touches to software executing on the device, but such software may ignore such input, such as by not associating the input with any touch input streams maintained by the software. In summary, although the device has the inherent ability to process multiple simultaneous touches, the device may be configured to operate in a "first come, first served" mode, in which the device acts only on touches initiated while no other touch is still occurring.