## Pen for OS/2 Device Driver Reference

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### Event Rate Controls

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The Pen for OS/2 system extension controls the rate of events with IOCtls in two ways. First, the sample rate IOCtl requests that the driver control the total number of sample events. Most pen hardware products support this , but if your hardware product does not, the pen device driver would discard locator events to reduce the sample rate as seen by the Pen for OS/ 2 system. The sample rate is set with the category 91 Set Locator Sample Rate IOCtl.

Second, a pass rate filter is used to control the rate of OS/2 events. Every locator event is passed to the Pen for OS/2 system, but only some of those are passed to the OS/2 operating system as standard mouse events. The pass rate is set with the category 91 Set Locator Pass Rate IOCtl.

The Pen for OS/2 Device Driver Services attempt to set the pass rate automatically based on the device's sample rate as reported during registration. Automatic pass rate is requested by setting the pass rate to 0 in the locator capabilities packet. The pen device driver's pass rate variable is set with the category 91 Set Locator Pass Rate IOCtl.

The automatic pass rate can be overridden by setting the pass rate field in the capabilities packet to a positive value. This value determines how many locator events are passed to the Pen for OS/2 system for every one mouse event passed to the OS/2 operating system. For example, if the pass rate is set to 2, then for every 2 locator events only one is passed as a standard OS/2 mouse event.

Events which contain changes in button events will not be discarded.