QGestures on ios - c++

Question

i am trying to use gestures on ios with qt like this:
#ifndef SWIPESTACKWIDGET_H
#define SWIPESTACKWIDGET_H
#include <QStackedWidget>
#include <QSwipeGesture>
class SwipeStackWidget : public QStackedWidget
{
Q_OBJECT
public:
explicit SwipeStackWidget(QWidget *parent = 0);
bool event(QEvent *event);
bool gestureEvent(QGestureEvent *event);
void swipeTriggered(QSwipeGesture *gesture);
signals:
public slots:
};
#endif // SWIPESTACKWIDGET_H
and
#include "swipestackwidget.h"
#include <QDebug>
SwipeStackWidget::SwipeStackWidget(QWidget *parent) :
QStackedWidget(parent)
{
setAttribute(Qt::WA_AcceptTouchEvents);
grabGesture(Qt::TapGesture);
grabGesture(Qt::TapAndHoldGesture);
grabGesture(Qt::PanGesture);
grabGesture(Qt::PinchGesture);
grabGesture(Qt::SwipeGesture);
}
bool SwipeStackWidget::event(QEvent *event)
{
if (event->type() == QEvent::Gesture)
return gestureEvent(static_cast<QGestureEvent*>(event));
return QWidget::event(event);
}
bool SwipeStackWidget::gestureEvent(QGestureEvent *event)
{
qDebug() << "gestureEvent():" << event->gestures().size();
if (QGesture *swipe = event->gesture(Qt::SwipeGesture))
swipeTriggered(static_cast<QSwipeGesture *>(swipe));
if (QGesture *pan = event->gesture(Qt::PanGesture))
qDebug() << "Pan";
if (QGesture *pinch = event->gesture(Qt::PinchGesture))
qDebug() << "Pinch";
if (QGesture *pinch = event->gesture(Qt::TapGesture))
qDebug() << "Tap";
if (QGesture *pinch = event->gesture(Qt::TapAndHoldGesture))
qDebug() << "Tapandhold";
return true;
}
void SwipeStackWidget::swipeTriggered(QSwipeGesture *gesture)
{
qDebug() << "swipeTriggered()";
if (gesture->state() == Qt::GestureFinished) {
if (gesture->horizontalDirection() == QSwipeGesture::Left) {
qDebug() << "swipeTriggered(): swipe to previous";
setCurrentIndex( std::max( 0, currentIndex()-1) );
} else if (gesture->horizontalDirection() == QSwipeGesture::Right) {
qDebug() << "swipeTriggered(): swipe to next";
setCurrentIndex( std::min( count()-1, currentIndex()+1) );
}
update();
}
}
I can compile the code and execute it on the iphone. I do recieve tab gestures and tabAndHold reliably. Pan and Pimch do occur sometimes. Swipe is a big problem:
It only appears with 3 fingers
It appears only when swiping to bottom or to the right
It appears only sometimes
Swiping to the bottom is sometime recognized as next, sometimes as left
Does anyone have experience with QGestures on ios an can help me?
My test class is directly used in the main window and i use the grabGestures command in the main window as well but i do not handle the gestures there.

Answer 1

I can confirm that it requires three fingers. I tested with PyQt, Qt5.3.1, on an iPad. (Also, pan requires two fingers.)
I suspect that Qt designed it that way, so it is the same across platforms (choosing the finger count that is common on Ubuntu, since Canonical may have contributed much of the code?)
In the iOS SDK, some of the base gesture classes are configurable for number of fingers and directions. Read more. Thats only relevant since it means Qt could easily have configured the native gestures Qt subscribes to, if they are subscribing to native gestures. You could look at Qt's code (for the iOS platform abstraction QPA and in their other gesture related code) to verify that they designed 3 fingers for a swipe (that it is not a bug.)
But the 3-finger swipe physical gesture in the upward direction on the iOS platforms should mean "hide the app and show the system tray"? (That's my experience, I can't quote the iOS HIG, and don't know what the App Store requires.) If so, then an app should subscribe to Qt's swipe gesture and follow the guidelines.
But you could also implement a recognizer in Qt for a one-finger swipe?