优化触摸屏驱动程序：实时更新与配置指南

> 
> /************************ Touch Screen Update Task **************************/
> /*--------------------------------------------------------------------------*/
> // TouchTask- A continuous, very low priority task to update the touch
> //  position. This task sends mouse messages (PM_LBUTTONDOWN, PM_LBUTTONUP,
> //  and/or PM_POINTERMOVE) into PegMessageQueue, where PEG routes them
> //  to wherever they need to go.
> //
> //  This task is started by the InitializeTouchScreen function if the
> //  calibration completes OK.
> /*--------------------------------------------------------------------------*/
> void PegTouchTask(void)
> {
>     PegMessage TouchMesg;
>     PEGINT XPos, YPos, OldXPos, OldYPos;
>     PEGUINT wLastState;
>     PEGBOOL IsTouched;
> 
>     TouchMesg.pTarget = NULL;
> 
>     XPos = YPos = OldXPos = OldYPos = wLastState = 0;
> 
>     // First configure the hardware registers:
> 
>     TouchConfigureHardware();
> 
>     // Next run the calibration sequence:
> 
>     CalibrateTouchScreen();
> 

>     // Now continuously read and post touch screen messages:
> 
>     while(1)
>     {
>         TOUCH_DELAY(TOUCH_POLLING_PERIOD);
> 
>         IsTouched = GetScaledTouchPos(&XPos, &YPos);
> 
>         if (IsTouched)
>         {
>             if (wLastState & TS_TOUCH_SENT) // already sent a touch message?
>             {
>                 // check for a move message:
> 
>                 if (OldXPos != XPos || OldYPos != YPos)
>                 {
>                     // The screen is still touched, but the position
>                     // changed. Send a PointerMove message to PEG
> 
> 
>                     TouchMesg.wType = PM_POINTER_MOVE;
>                     TouchMesg.Point.x = XPos;
>                     TouchMesg.Point.y = YPos;
>                     PegThing::MessageQueue()->Fold(&TouchMesg);
>                     OldXPos = XPos;
>                     OldYPos = YPos;
>                 }
>             }
>             else
>             {