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Qt/Embedded Pointer Handling

Pointer handling in Qt/Embedded works for any mouse-like device such as a touchpanel, a trackball, or real mouse.

In a real device, only a small number of pointer devices (usually one) would be supported, but for demonstration purposes, Qt/Embedded includes a large number of supported devices.

Mouse Protocols

Qt/Embedded normally auto-detects the mouse type and device if it is one of the supported types on /dev/psaux or one of the /dev/ttyS? serial lines. If multiple mice are detected, all may be used simultaneously.

Alternatively, you may set the environment variable QWS_MOUSE_PROTO to determine which mouse to use. This environment variable may be set to:

<protocol>:<device>

• MouseMan
• IntelliMouse
• Microsoft

To add another protocol, new subclasses of QAutoMouseSubHandler or QMouseHandler can be written in kernel/qwsmouse_qws.cpp.

Touch Panels

Qt/Embedded ships with support for the NEC Vr41XX touchpanel and the iPAQ touchpanel. These are subclasses of QCalibratedMouseHandler which is in turn a subclass of QMouseHandler in kernel/qwsmouse_qws.cpp.

Writing a custom touch panel handler for Qt/Embedded is not as hard as the QVrTPanelHandlerPrivate class makes it look. The Vr41XX touch panel handler is complex; it handles filtering of noisy input data, and it generates mouse release events by using a timer.

Many touch panel devices have a much simpler interface, so a port to Qt/Embedded can be written in a few minutes, without expert knowledge of Qt/Embedded.

The Qt/Embedded release contains an example touch panel handler in the class QCustomTPanelHandlerPrivate, located in the file $QTDIR/src/kernel/qwsmouse_qws.cpp. It is protected by#ifdef QWS_CUSTOMTOUCHPANEL.

The example reads data from /dev/ts with the following format: Each packet consists of 5 bytes.

• Byte 0 gives status information, in particular, bit 6 (0x40) is 1 when the stylus is down, 0 if it is released.
• Bytes 1 and 2 give the x position;
• Bytes 3 and 4 give the y position;

To enable this driver, uncomment the line #define QWS_CUSTOMTOUCHPANEL in the file qwsmouse_qws.cpp.

Chances are, your touch panel device will not match exactly the example device. As an example, take a hypothetical device located at /dev/touchpanel. This device uses 6-byte packets. Byte 0 and 1 give status and pressure information. In particular, bit 5 (0x20) of byte 1 tells whether the stylus is down or up. Bytes 2 and 3 give x position and bytes 4 and 5 give y position.

Pressure information is not necessary for basic Qt/Embedded operation, so we will ignore that for now. The following shows the modified touch panel handler for the hypothetical device, with comments marked with //*** indicating the changes made. You can also see some printf calls left over from the (hypothetical) debugging.

//*** Modified Trolltech's example handler to handle the
//*** hypothetical touch panel.
QCustomTPanelHandlerPrivate::QCustomTPanelHandlerPrivate( MouseProtocol, QString )
{
    //*** changed device name to /dev/touchpanel

    if ((mouseFD = open( "/dev/touchpanel", O_RDONLY)) < 0) {
        qWarning( "Cannot open /dev/touchpanel (%s)", strerror(errno));
        return;
    } 
    //*** removed the delay since our device does not need it.
    //else {
    //    sleep(1);
    //}

    QSocketNotifier *mouseNotifier;
    mouseNotifier = new QSocketNotifier( mouseFD, QSocketNotifier::Read,
                                         this );
    connect(mouseNotifier, SIGNAL(activated(int)),this, SLOT(readMouseData()));
}

QCustomTPanelHandlerPrivate::~QCustomTPanelHandlerPrivate()
{
    if (mouseFD >= 0)
        close(mouseFD);
}

struct CustomTPdata {

  unsigned char status;
  unsigned short xpos;
  unsigned short ypos;

};

void QCustomTPanelHandlerPrivate::readMouseData()
{
    if(!qt_screen)
        return;
    CustomTPdata data;

    //*** changed size to 6 bytes
    unsigned char data2[6];

    int ret;

    //*** read 6 bytes
    ret=read(mouseFD,data2,6);

    if(ret==6) { //*** change to 6
        //*** all the indexes changed:
        data.status=data2[1]; 
        data.xpos=(data2[2] << 8) | data2[3];
        data.ypos=(data2[4] << 8) | data2[5];
        QPoint q;
        q.setX(data.xpos);
        q.setY(data.ypos);
        mousePos=q;
        if(data.status & 0x20) { //*** Changed to 0x20 (bit 5)
          emit mouseChanged(mousePos,Qt::LeftButton);
          //printf( "Stylus press/move %d,%d\n", data.xpos, data.ypos );
        } else {
          emit mouseChanged(mousePos,0);
          //printf( "Stylus release %d,%d\n", data.xpos, data.ypos );
        }
    }
    if(ret<0) { 
        qDebug("Error %s",strerror(errno));
    }
}