Add: absolute touch screen handling in evdevmouse

Some touch screen drivers present themselves as mice with absolute
coordinates. Setting QT_QPA_EVDEV_MOUSE_PARAMETERS=abs will force
qevdevmousehandler to use absolute coordinates, mapped to the screen
from the hardware maximums. These maximum values are read from the
driver using ioctls.
This feature can be safely used with mice, as the features checks will
fail and qevdevmouse will revert back to using relative coordinates.
This way touch screens and mice can work together.

Change-Id: Ic27bda02aa2199f008bac26db75c1f896696f9f5
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>

src/platformsupport/input/evdevmouse/qevdevmousehandler.cpp

@@ -60,6 +60,8 @@
 
 //#define QT_QPA_MOUSE_HANDLER_DEBUG
 
+#define TEST_BIT(array, bit)    (array[bit/8] & (1<<(bit%8)))
+
 QT_BEGIN_NAMESPACE
 
 QEvdevMouseHandler *QEvdevMouseHandler::create(const QString &device, const QString &specification)
@@ -71,6 +73,7 @@ QEvdevMouseHandler *QEvdevMouseHandler::create(const QString &device, const QStr
     bool compression = true;
     int jitterLimit = 0;
     int grab = 0;
+    bool abs = false;
 
     QStringList args = specification.split(QLatin1Char(':'));
     foreach (const QString &arg, args) {
@@ -80,27 +83,37 @@ QEvdevMouseHandler *QEvdevMouseHandler::create(const QString &device, const QStr
             jitterLimit = arg.mid(9).toInt();
         else if (arg.startsWith(QLatin1String("grab=")))
             grab = arg.mid(5).toInt();
+        else if (arg == QLatin1String("abs"))
+            abs = true;
     }
 
     int fd;
     fd = qt_safe_open(device.toLocal8Bit().constData(), O_RDONLY | O_NDELAY, 0);
     if (fd >= 0) {
         ::ioctl(fd, EVIOCGRAB, grab);
-        return new QEvdevMouseHandler(device, fd, compression, jitterLimit);
+        return new QEvdevMouseHandler(device, fd, abs, compression, jitterLimit);
     } else {
         qWarning("Cannot open mouse input device '%s': %s", qPrintable(device), strerror(errno));
         return 0;
     }
 }
 
-QEvdevMouseHandler::QEvdevMouseHandler(const QString &device, int fd, bool compression, int jitterLimit)
+QEvdevMouseHandler::QEvdevMouseHandler(const QString &device, int fd, bool abs, bool compression, int jitterLimit)
     : m_device(device), m_fd(fd), m_notify(0), m_x(0), m_y(0), m_prevx(0), m_prevy(0),
-      m_compression(compression), m_buttons(0), m_prevInvalid(true)
+      m_abs(abs), m_compression(compression), m_buttons(0), m_prevInvalid(true)
 {
     setObjectName(QLatin1String("Evdev Mouse Handler"));
 
     m_jitterLimitSquared = jitterLimit * jitterLimit;
 
+    // Some touch screens present as mice with absolute coordinates.
+    // These can not be differentiated from touchpads, so supplying abs to QT_QPA_EVDEV_MOUSE_PARAMETERS
+    // will force qevdevmousehandler to treat the coordinates as absolute, scaled to the hardware maximums.
+    // Turning this on will not affect mice as these do not report in absolute coordinates
+    // but will make touchpads act like touch screens
+    if (m_abs)
+        m_abs = getHardwareMaximum();
+
     // socket notifier for events on the mouse device
     QSocketNotifier *notifier;
     notifier = new QSocketNotifier(m_fd, QSocketNotifier::Read, this);
@@ -113,16 +126,66 @@ QEvdevMouseHandler::~QEvdevMouseHandler()
         qt_safe_close(m_fd);
 }
 
+// Ask touch screen hardware for information on coordinate maximums
+// If any ioctls fail, revert to non abs mode
+bool QEvdevMouseHandler::getHardwareMaximum()
+{
+    unsigned char absFeatures[(ABS_MAX / 8) + 1];
+    memset(absFeatures, '\0', sizeof (absFeatures));
+
+    // test if ABS_X, ABS_Y are available
+    if (ioctl(m_fd, EVIOCGBIT(EV_ABS, sizeof (absFeatures)), absFeatures) == -1)
+        return false;
+
+    if ((!TEST_BIT(absFeatures, ABS_X)) || (!TEST_BIT(absFeatures, ABS_Y)))
+        return false;
+
+    // ask hardware for minimum and maximum values
+    struct input_absinfo absInfo;
+    if (ioctl(m_fd, EVIOCGABS(ABS_X), &absInfo) == -1)
+        return false;
+
+    m_hardwareWidth = absInfo.maximum - absInfo.minimum;
+
+    if (ioctl(m_fd, EVIOCGABS(ABS_Y), &absInfo) == -1)
+        return false;
+
+    m_hardwareHeight = absInfo.maximum - absInfo.minimum;
+
+    QRect g = QGuiApplication::primaryScreen()->virtualGeometry();
+    m_hardwareScalerX = static_cast<qreal>(m_hardwareWidth) / (g.right() - g.left());
+    m_hardwareScalerY = static_cast<qreal>(m_hardwareHeight) / (g.bottom() - g.top());
+
+#ifdef QT_QPA_MOUSE_HANDLER_DEBUG
+    qDebug() << "Absolute pointing device";
+    qDebug() << "hardware max x" << m_hardwareWidth;
+    qDebug() << "hardware max y" << m_hardwareHeight;
+    qDebug() << "hardware scalers x" << m_hardwareScalerX << "y" << m_hardwareScalerY;
+#endif
+
+    return true;
+}
+
 void QEvdevMouseHandler::sendMouseEvent()
 {
-    int x = m_x - m_prevx;
-    int y = m_y - m_prevy;
+    int x;
+    int y;
+
+    if (!m_abs) {
+        x = m_x - m_prevx;
+        y = m_y - m_prevy;
+    }
+    else {
+        x = m_x / m_hardwareScalerX;
+        y = m_y / m_hardwareScalerY;
+    }
+
     if (m_prevInvalid) {
         x = y = 0;
         m_prevInvalid = false;
     }
 
-    emit handleMouseEvent(x, y, m_buttons);
+    emit handleMouseEvent(x, y, m_abs, m_buttons);
 
     m_prevx = m_x;
     m_prevy = m_y;

src/platformsupport/input/evdevmouse/qevdevmousehandler_p.h

@@ -57,26 +57,32 @@ public:
     ~QEvdevMouseHandler();
 
 signals:
-    void handleMouseEvent(int x, int y, Qt::MouseButtons buttons);
+    void handleMouseEvent(int x, int y, bool abs, Qt::MouseButtons buttons);
     void handleWheelEvent(int delta, Qt::Orientation orientation);
 
 private slots:
     void readMouseData();
 
 private:
-    QEvdevMouseHandler(const QString &device, int fd, bool compression, int jitterLimit);
+    QEvdevMouseHandler(const QString &device, int fd, bool abs, bool compression, int jitterLimit);
 
     void sendMouseEvent();
+    bool getHardwareMaximum();
 
     QString m_device;
     int m_fd;
     QSocketNotifier *m_notify;
     int m_x, m_y;
     int m_prevx, m_prevy;
+    bool m_abs;
     bool m_compression;
     Qt::MouseButtons m_buttons;
     int m_jitterLimitSquared;
     bool m_prevInvalid;
+    int m_hardwareWidth;
+    int m_hardwareHeight;
+    qreal m_hardwareScalerY;
+    qreal m_hardwareScalerX;
 };
 
 QT_END_NAMESPACE

src/platformsupport/input/evdevmouse/qevdevmousemanager.cpp

@@ -111,11 +111,16 @@ QEvdevMouseManager::~QEvdevMouseManager()
     m_mice.clear();
 }
 
-void QEvdevMouseManager::handleMouseEvent(int x, int y, Qt::MouseButtons buttons)
+void QEvdevMouseManager::handleMouseEvent(int x, int y, bool abs, Qt::MouseButtons buttons)
 {
     // update current absolute coordinates
-    m_x += x;
-    m_y += y;
+    if (!abs) {
+        m_x += x;
+        m_y += y;
+    } else {
+        m_x = x;
+        m_y = y;
+    }
 
     // clamp to screen geometry
     QRect g = QGuiApplication::primaryScreen()->virtualGeometry();
@@ -156,7 +161,7 @@ void QEvdevMouseManager::addMouse(const QString &deviceNode)
     QEvdevMouseHandler *handler;
     handler = QEvdevMouseHandler::create(deviceNode, m_spec);
     if (handler) {
-        connect(handler, SIGNAL(handleMouseEvent(int,int,Qt::MouseButtons)), this, SLOT(handleMouseEvent(int,int,Qt::MouseButtons)));
+        connect(handler, SIGNAL(handleMouseEvent(int,int,bool,Qt::MouseButtons)), this, SLOT(handleMouseEvent(int,int,bool,Qt::MouseButtons)));
         connect(handler, SIGNAL(handleWheelEvent(int,Qt::Orientation)), this, SLOT(handleWheelEvent(int,Qt::Orientation)));
         m_mice.insert(deviceNode, handler);
     } else {

src/platformsupport/input/evdevmouse/qevdevmousemanager_p.h

@@ -62,7 +62,7 @@ public:
     QDeviceDiscovery *deviceDiscovery() { return m_deviceDiscovery; }
 
 public slots:
-    void handleMouseEvent(int x, int y, Qt::MouseButtons buttons);
+    void handleMouseEvent(int x, int y, bool abs, Qt::MouseButtons buttons);
     void handleWheelEvent(int delta, Qt::Orientation orientation);
 
 private slots: