PinchArea do not work well in Qt 5.4

benlau

Hi all,

I am using Flickable +PinchArea to provide pinching gesture for a photo . However, I found that the PinchArea do not work well in Qt 5.4. Here is an example code :

@
import QtQuick 2.4
import QtQuick.Window 2.2

Window {
id : window
visible: true

Flickable {
    id : flickable
    anchors.fill: parent
    interactive: true
    contentWidth: container.width
    contentHeight: container.height
    flickableDirection: Flickable.HorizontalAndVerticalFlick

    PinchArea {
        pinch.target : container
        pinch.maximumScale: 8
        pinch.minimumScale: 0.5

        anchors.fill: parent
        onPinchStarted: {
            console.log("pinch started");
            flickable.interactive = false
        }

        onPinchFinished: {
            flickable.interactive = true;
        }
    }


    Item {
        id: container

        width: window.width
        height: window.height
        Rectangle {
            anchors.centerIn: parent
            width: window.width * 0.5
            height: window.height * 0.5
            color : "red"
        }
    }
}

}
@

It shows a red rectangle in the center and you may use two fingers to zoom in / out. In Qt 5.3.2 , the PinchArea is working fine.

But in Qt 5.4, the pinch area's PinchStarted signal is triggered only if both of the fingers touch on the screen at the SAME time. It don't fulfill the common practise for pinching gesture.

The code has been tested in Android and iOS.

That is a bug or I should use another component for handling pinching gesture?

Thanks for any advise.

Johan_R28

Hi !

Consider examples provide from Qtcreator :
"PhotoSurface":http://doc.qt.io/qt-5/qtquick-demos-photosurface-example.html in this case

It's a good way to resolve quickly your issue.

Regards.

benlau

Hi Johan,

Thank for your reply. However, the PhotoSurface code do not work with my case. Since I need to integrate Flickable and PinchArea together , but the PhotoSurface just show how PinchArea work.

Since my example code is copied from another project , it is not pretty/simple enough to show the problem. I have reposted another version.

As Qt 5.4.1 is launched already , I have tested but still has same problem.

benlau

The reason I need Flickable is because I would like to let user to drag the photo and it will continues to move slightly after released the finger and return to bound afterward.

May be it is not the problem of PInchArea, but there has something wrong with Flickable that steal the mouse event from PinchArea

benlau

I have reported it as a bug already and it is marked as P2.

[QTBUG-44645] Flickable and PinchArea are not working well together - Qt Bug Tracker
https://bugreports.qt.io/browse/QTBUG-44645