The driver must submit points while the user"s finger or stylus is touching the touch screen. When the user"s finger or stylus is removed from the screen, the driver must submit at least one final event indicating that the user"s finger or stylus tip was removed. The calibrated coordinates must be reported to the nearest one-quarter of a pixel.
The following steps detail the basic algorithm for using the touch screen:
Call TouchPanelEnable to start the screen sampling.
Call TouchPanelGetDeviceCaps to request the number of sampling points.
For every calibration point, perform the following steps:
Call TouchPanelGetDeviceCaps to get a calibration coordinate.
Draw a crosshair at the returned coordinate.
Call TouchPanelReadCalibrationPoint to get calibration data.
Call TouchPanelSetCalibration to calculate the calibration coefficients.
After executing this sequence, any finger or stylus samples generated for the screen are passed to the callback function specified in TouchPanelEnable. The driver may pass either calibrated or uncalibrated points to the callback. If the driver has an efficient calibration algorithm, it can return calibrated points. However, if the calibration is computationally intensive, the driver may choose to return uncalibrated points, rather than perform extensive calculations in the high-priority driver thread. The lower priority thread processing points from the callback can then perform the calibration.
You can calibrate your touch screen without the ENTER key. The GWES keyboard code opens HKEY_LOCAL_MACHINEHARDWAREDEVICEMAPKEYBD and looks for a DWORD value called Status. This is a bit mask combining the KBDI_KEYBOARD_XXX values from %_WINCEROOT%PublicCommonSDKINCKeybd.h. If it is not found, GWES assumes KBDI_KEYBOARD_PRESENT | KBDI_KEYBOARD_ENTER_ESC | KBDI_KEYBOARD_ALPHA_NUM. This registry access only occurs once, when the keyboard driver is loaded. This value is the basis for what you get when you call GetKeyboardStatus. GWES will add or subtract the KBDI_KEYBOARD_ENABLED bit based on EnableHardwareKeyboard calls. The KBDI_KEYBOARD_ENABLED bit is set when the keyboard driver is loaded. The UseEnterEsc behavior can be controlled by a registry key.
The following table shows the touch screen driver functions.
Function Des cription
DdsiTouchPanelAttach Called when the MDD"s DLL entry point gets a DLL_PROCESS_ATTACH message.
DdsiTouchPanelDetach Called when the MDD"s DLL entry point gets a DLL_PROCESS_DETACH message.
DdsiTouchPanelDisable Disables the touch screen device.
DdsiTouchPanelEnable Applies power to the touch screen device and initializes it for operation.
DdsiTouchPanelGetDeviceCaps Queries for capabilities of the touch screen device.
DdsiTouchPanelGetPoint Returns the most recently acquired point and its associated tip-state information.
DdsiTouchPanelPowerHandler Indicates to the driver that the system is entering or leaving the suspend state.
DdsiTouchPanelSetMode Sets information about the touch screen device.
ErrorAnalysis Provides information on the accuracy of the touch screen calibration.
TouchPanelCalibrateAPoint Converts uncalibrated points to calibrated points.
TouchPanelDisable Disables the touch screen.
TouchPanelEnable Enables and re-enables the touch screen.
TouchPanelGetDeviceCaps Returns information about the capabilities of the touch screen.
TouchPanelPowerHandler Handles power-state change notifications.
TouchPanelReadCalibrationAbort Aborts the currently active call to the TouchPanelCalibrateAPoint function
TouchPanelReadCalibrationPoint Initiates the process of getting a calibration point.
TouchPanelSetCalibration Initializes calibration information in the vCalcParam global parameter.
TouchPanelSetMode Sets mode information for a touch screen device.
