触摸屏绝对轴范围

如何解决触摸屏绝对轴范围

我需要获得触摸屏的绝对MAX轴值。我查看 xinput_calibrator 源，并执行以下功能：

void Xget_absoluteMax (XDeviceInfoPtr devInfo,int * absMAX)
{
XAnyClassPtr any = (XAnyClassPtr) (devInfo->inputclassinfo);
for (int j=0; j<devInfo->num_classes; j++)
        {

            if (any->class == ValuatorClass)
            {
                XValuatorInfoPtr V = (XValuatorInfoPtr) any;
                XAxisInfoPtr ax = (XAxisInfoPtr) V->axes;

                if (V->mode != Absolute) {

                        printf("DEBUG: Skipping device '%s' id=%i,does not report Absolute events.\n",devInfo->name,(int)devInfo->id);
                } else if (V->num_axes < 2 ||
                    (ax[0].min_value == -1 && ax[0].max_value == -1) ||
                    (ax[1].min_value == -1 && ax[1].max_value == -1)) {
                    printf("DEBUG: Skipping device '%s' id=%i,does not have two calibratable axes.\n",(int)devInfo->id);
                } else {



                    absMAX[ABS_MAX_X] = ax[0].max_value;

                    absMAX[ABS_MAX_Y] = ax[1].max_value;

                printf("DEBUG: Setup ABS_MAX X Y: %d %d\r\n",ax[0].max_value,ax[1].max_value);
                }

            }

            /*
             * Increment 'any' to point to the next item in the linked
             * list.  The length is in bytes,so 'any' must be cast to
             * a character pointer before being incremented.
             */
            any = (XAnyClassPtr) ((char *) any + any->length);
        }

    }

它可以在Ubuntu 16上很好地工作，给我2047x2047，这是真实值

但是在Ubuntu 20中，它给了我一些假值65535x65535

所以，我开始挖掘并发现一些东西...

在Ubuntu 20上， evtest 给我真正的价值

evtest /dev/input/event8
Input driver version is 1.0.1
Input device ID: bus 0x3 vendor 0xeef product 0x1 version 0x100
Input device name: "eGalax Inc."
Supported events:
  Event type 0 (EV_SYN)
  Event type 1 (EV_KEY)
    Event code 330 (BTN_TOUCH)
  Event type 3 (EV_ABS)
    Event code 0 (ABS_X)
      Value      0
      Min        0
      Max     2047
    Event code 1 (ABS_Y)
      Value      0
      Min        0
      Max     2047
Properties:
Testing ... (interrupt to exit)

然后我发现错误的价值观存在何处...

 xinput  list --long 9
eGalax Inc.                                     id=9    [slave  pointer  (2)]
        Reporting 6 classes:
                Class originated from: 9. Type: XIButtonClass
                Buttons supported: 7
                Button labels: "Button Left" "Button Middle" "Button Right" "Button Wheel Up" "Button Wheel Down" "Button Horiz Wheel Left" "Button Horiz Wheel Right"
                Button state:
                Class originated from: 9. Type: XIValuatorClass
                Detail for Valuator 0:
                  Label: Abs MT Position X
                  Range: 0.000000 - 65535.000000
                  Resolution: 0 units/m
                  Mode: absolute
                  Current value: 0.000000
                Class originated from: 9. Type: XIValuatorClass
                Detail for Valuator 1:
                  Label: Abs MT Position Y
                  Range: 0.000000 - 65535.000000
                  Resolution: 0 units/m
                  Mode: absolute
                  Current value: 0.000000
                Class originated from: 9. Type: XIValuatorClass
                Detail for Valuator 2:
                  Label: Rel Horiz Scroll
                  Range: -1.000000 - -1.000000
                  Resolution: 0 units/m
                  Mode: relative
                Class originated from: 9. Type: XIValuatorClass
                Detail for Valuator 3:
                  Label: Rel Vert Scroll
                  Range: -1.000000 - -1.000000
                  Resolution: 0 units/m
                  Mode: relative
                Class originated from: 9. Type: XITouchClass
                Touch mode: direct
                Max number of touches: 1

那么如何使用 Xorg 东西获得真实的范围值？

P.S。我已经有了计划B。使用 evtest 代码...但是它需要在/ dev / input / event *设备上打开和ioctl，这意味着我需要root权限。