QScroller speed and touch screen

[Talei]

Hello,
I have problem with the touch screen (Win 8.1 - full win - 10' tablet) and touch events.

1. QScroller - basically everything working fine, except that when placing scroller on i.e. viewport for the QTreeView I can't resize rows when content exceed visible area - QScroller kick in and move view - probably subclass and event propagation would fix that. But what I cant figure out is speed for scroller.
Question - how to slow dont scroller? My code for scroller:

QScroller *scroller = QScroller::scroller(ui_->treeView->viewport());
 
    QScrollerProperties prop = scroller->scrollerProperties();
 
    prop.setScrollMetric(QScrollerProperties::AxisLockThreshold, 0.66);
    prop.setScrollMetric(QScrollerProperties::ScrollingCurve, QEasingCurve(QEasingCurve::OutExpo));
    prop.setScrollMetric(QScrollerProperties::DecelerationFactor, 0.05);
    prop.setScrollMetric(QScrollerProperties::MaximumVelocity, 0.635);
    prop.setScrollMetric(QScrollerProperties::OvershootDragResistanceFactor, 0.33);
    prop.setScrollMetric(QScrollerProperties::OvershootScrollDistanceFactor, 0.33);
    prop.setScrollMetric(QScrollerProperties::SnapPositionRatio, 0.93);
    prop.setScrollMetric(QScrollerProperties::DragStartDistance, 0.001);
 
    scroller->setScrollerProperties(prop);
 
    scroller->grabGesture(ui_->treeView, QScroller::TouchGesture);
    scroller->grabGesture(ui_->treeView, QScroller::LeftMouseButtonGesture);

QScroller *scroller = QScroller::scroller(ui_->treeView->viewport());

    QScrollerProperties prop = scroller->scrollerProperties();

    prop.setScrollMetric(QScrollerProperties::AxisLockThreshold, 0.66);
    prop.setScrollMetric(QScrollerProperties::ScrollingCurve, QEasingCurve(QEasingCurve::OutExpo));
    prop.setScrollMetric(QScrollerProperties::DecelerationFactor, 0.05);
    prop.setScrollMetric(QScrollerProperties::MaximumVelocity, 0.635);
    prop.setScrollMetric(QScrollerProperties::OvershootDragResistanceFactor, 0.33);
    prop.setScrollMetric(QScrollerProperties::OvershootScrollDistanceFactor, 0.33);
    prop.setScrollMetric(QScrollerProperties::SnapPositionRatio, 0.93);
    prop.setScrollMetric(QScrollerProperties::DragStartDistance, 0.001);

    scroller->setScrollerProperties(prop);

    scroller->grabGesture(ui_->treeView, QScroller::TouchGesture);
    scroller->grabGesture(ui_->treeView, QScroller::LeftMouseButtonGesture);

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Basically when I move by mouse it's work fast but when I use touch screen then its "ultra" fast. Tree contains file model so there is a lot of items and I can move to bottom with single touch move.

2. Touch events wrong values:

I want to move widget by touch event. So I do accept touch event on the widget and then on events I do calculate delta and move my widget. It's working fine when using mouse, but when using touch I got big delta.

void MainWindow::mousePressEvent(QMouseEvent *e)
{
    mPos_ = e->pos();
}
 
void MainWindow::mouseMoveEvent(QMouseEvent *e)
{
    if (e->buttons() & Qt::LeftButton && !this->isFullScreen()) {
 
        QPoint mP = e->pos() - mPos_;
        this->move(mapToParent(mP));
    }

void MainWindow::mousePressEvent(QMouseEvent *e)
{
    mPos_ = e->pos();
}

void MainWindow::mouseMoveEvent(QMouseEvent *e)
{
    if (e->buttons() & Qt::LeftButton && !this->isFullScreen()) {

        QPoint mP = e->pos() - mPos_;
        this->move(mapToParent(mP));
    }

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Delta sometimes is 200x100 pix etc. Why? This happens only on touch screen. Also what's strange is that mouse press event is registered twice and what I do is touch screen and slowly move. It's not always but sometimes.

Any suggestions are more then welcome.

PS. Tested on Win 8 / Win 8.1 with Qt 5.1.1 and 5.2 with MSVC2010 and MinGW. 32 bit all.

[sedi]

Try setting the verticalScrollMode of your view to ScrollPerPixel
http://doc.qt.io/qt-4.8/http://doc.qt.digia.com/qt-maemo/qabstractitemview.html#verticalScrollMode-prop

[Talei]

Thanks for the info.

So maybe some one knows about 2 - large delta on touch screen.

[pliniofernando]

You are a genius!!! Your clue is the solution for a lot of opened posts related to QScroller not smooth. I was looking for a answer about it for days. When you do

setHorizontalScrollMode(QAbstractItemView::ScrollPerPixel);

setHorizontalScrollMode(QAbstractItemView::ScrollPerPixel);

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everything works good. Thank you!

Try setting the verticalScrollMode of your view to ScrollPerPixel
http://doc.qt.io/qt-4.8/http://doc.qt.digia.com/qt-maemo/qabstractitemview.html#verticalScrollMode-prop

[smegy]

Note that in your code

scroller->grabGesture(ui_->treeView, QScroller::TouchGesture);

scroller->grabGesture(ui_->treeView, QScroller::TouchGesture);

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is useless as the next line, replace the grab :

scroller->grabGesture(ui_->treeView, QScroller::LeftMouseButtonGesture);

scroller->grabGesture(ui_->treeView, QScroller::LeftMouseButtonGesture);

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