Specifications

Chapter 7 - CTKERN CARROLL TOUCH
7-2 Touch System Programmer’s Guide
Overview
The CTKERN driver communicates with the touch system using the
TAPI driver appropriate for the touch system, and with the application
program using the CTKERN functions, which are accessed via a
software interrupt.
CTKERN is a DOS driver that offers the following features:
• Calibration support, including multiple calibrations to allow for
monitors that do not maintain a constant image size when
displaying multiple video modes.
• Touch coordinate scaling support, including multiple sets of
scaling parameters to automatically support multiple video modes.
• Easy-to-use touch state reporting.
• Support for user-installable touch event handlers for
interrupt-driven applications.
• Uninstall capability.
The application software may not issue TAPI function calls while
CTKERN is loaded. In fact, when CTKERN loads, it reads the TAPI
software interrupt vector, saves it, and uses it to call the TAPI driver
instead of the software interrupt. The TAPI software interrupt is
replaced by a pointer to a return from interrupt instruction within
CTKERN, blocking any calls to TAPI. The return from interrupt
instruction is followed by a NOP and the CT DRIVER - string, so that
the driver detection mechanism continues to indicate an installed TAPI
driver at the TAPI software interrupt. When CTKERN is unloaded, it
replaces the TAPI software interrupt vector with the value that was
saved, re-enabling calls to TAPI.
The overall relationship between the touch hardware, the TAPI drivers,
the CTKERN driver, and the application software is illustrated in
Figure 7-1.
Calibration
CTKERN allows up to ten sets of video mode specific calibration
parameters. By using multiple calibrations, CTKERN can allow for
monitors that do not maintain a constant image size when displaying
multiple video modes. One of these sets is designated as the default
calibration.
There are three options for calibration: disabled, fixed, and automatic.
If calibration is disabled, the touch coordinates reported by CTKERN