## Virtual Device Driver Reference for OS/2

[prev][next][parent][TOC]

### Virtual Touch Device Driver

The virtual touch device driver (VTOUCH) provides support for the INT 7Fh in multiple DOS sessions. This virtual device driver is limited (by default ) to making actual touch XYZ data available only to full-screen DOS programs because the physical device driver, which handles the touch data interrupts, cannot determine which window to send the touch data to when running with the Presentation Manager session in the foreground.

In contrast, the physical mouse device driver can determine which window to send the mouse data to because it is able to feed the single queue of the Presentation Manager. The Presentation Manager can then determine, based upon the event XYZ data, which window is to receive the event. If the window is a DOS window, it calls the virtual device driver.

For those DOS applications that receive full screen XYZ touch data while running in a window, the DOS setting TOUCH_EXCLUSIVE_ACCESS is provided. This DOS setting effectively turns off mouse emulation and directs all touch data to that window. The (now device-independent) INT 7Fh continues to function in a window. However, touch data is not available to the application until it is switched to full screen. In all other respects, the application functions exactly as before.

DOS mouse applications are not subject to this restriction because they can run in a windowed or full screen DOS session with touch input in the form of emulated mouse data.