How to add swipe gesture on QScrollArea widget ?

[Qt embedded developer]

i want to add swipe gesture on QScrollArea. i want to catch event also. if any body know how to add swipe gesture on QScrollArea then let me know . i also want to know how to catch event of swipe up and down.

[raven-worx]

@Qt-embedded-developer
Are you on a touchscreen? If yes, are you sure it's driver delivers really touch events to the OS. Cheap touch screens rather simulate "single-touch" mouse events.

https://doc.qt.io/qt-5/gestures-overview.html

If using mouse events you might want to check QScroller

[JoeCFD]

QScrollArea * scroll_area = new QScrollArea( this );
scroll_area->setHorizontalScrollBarPolicy( Qt::ScrollBarAlwaysOff );
scroll_area->horizontalScrollBar()->setEnabled( false );

QScroller::grabGesture( scroll_area, QScroller::LeftMouseButtonGesture );
QScrollerProperties properties = QScroller::scroller( scroll_area )->scrollerProperties();
QVariant overshoot_policy = QVariant::fromValue< QScrollerProperties::OvershootPolicy >( QScrollerProperties::OvershootAlwaysOff );
properties.setScrollMetric( QScrollerProperties::VerticalOvershootPolicy, overshoot_policy );
properties.setScrollMetric( QScrollerProperties::HorizontalOvershootPolicy, overshoot_policy );
QScroller::scroller( scroll_area )->setScrollerProperties( properties );

[Qt embedded developer]

@JoeCFD how to catch event of QScroller::LeftMouseButtonGesture on swipe up and down ?

[JoeCFD]

@Qt-embedded-developer you create an instance of QScroller::scroller and connect it to QScroller::stateChanged

[Qt embedded developer]

@JoeCFD if possible can you provide example code for it

[JoeCFD]

@Qt-embedded-developer
QScroller * scroller = QScroller::scroller( scroll_area );
scroller->setScrollerProperties( properties );

connect( scroller, &QScroller:: stateChanged, this, &yourFuncSlot );

[Qt embedded developer]

@JoeCFD As per your suggestion i have used below code but in my case on scrolling the slot DisplayImageList1() is not getting called.

why stateChanged does not call my slot DisplayImageList1() ?

where is mistake done in below code to get desired slot call on scrolling using QScroller::LeftMouseButtonGesture ?

 QScrollerProperties qScrollerProperties;

 QVariant overshootPolicy = QVariant::fromValue<QScrollerProperties::OvershootPolicy>(QScrollerProperties::OvershootAlwaysOff);

 qScrollerProperties.setScrollMetric(QScrollerProperties::VerticalOvershootPolicy, overshootPolicy);

    QScroller* qScroller = QScroller::scroller(ui->scrollArea);

    qScroller->grabGesture(ui->scrollArea, QScroller::LeftMouseButtonGesture);

    qScroller->setScrollerProperties(qScrollerProperties);


    QObject::connect(qScroller, SIGNAL(stateChanged(QScroller::State)),
                     this,  SLOT(DisplayImageList1()));

Note: Above question i asked because on scrolling inside QScrollArea i need to call DisplayImageList1().

[JoeCFD]

@Qt-embedded-developer I think you are doing swipe of pictures. Check this example out:
https://code.qt.io/cgit/qt/qtbase.git/tree/examples/widgets/gestures/imagegestures?h=5.15