[Development] Issues with QApplication::startDragDistance

Gianluca gmaxera at gmail.com
Thu Nov 13 11:18:28 CET 2014

Dear Jeremias,
I use a lot of ListView and Flickable in my apps, and I test them on iOS iPhone and iPad with Retina display and on Android Samsung with 320 DPI and an Android tablet with about 100 DPI.
During my test with Qt 5.3.2, I’ve never experienced what you are saying.
I was able to perfectly click without any problem on the Items into the ListView with the default Qt settings on both high and low DPI devices.
So, I’m wondering if your problem is really correlated to the startDragDistance.


Il giorno 13/nov/2014, alle ore 11:11, Jeremias Bosch <jeremias.bosch at basyskom.com> ha scritto:

> Dear all,
> I was looking into deploying a simple QML App on a wide range of devices. The App consists basically of two QML Lists which are used for horizontal and vertical page navigation. The ranges of Display DPI differ a lot between those devices.
> Now there are two issues I ran into.
> On High DPI cases the sensitivity of the lists is very high, basically touching the screen is already registered as a drag and pressing buttons is pretty hard. On Low DPI its fine. Of course you can tweak the startDragDistance with QApplication::startDragDistance, or the corresponding value in your Platform Style. However, this would mean that you need to adjust for each target device to get the expected behavior, which might not be possible and preferable - I think that the default value should respect the screen DPI.
> I would like to have the vertical page navigation list to be less sensitive than the horizontal page navigation list and the horizontal page navigation list even less sensitive than all other "normal" content lists. 
> I couldn't find a way to adjust the sensitivity on a case by case situation. All I found was a feature request https://bugreports.qt-project.org/browse/QTBUG-18792, but it was closed invalid back in 2011, without any comment.
> Maybe I overlook a feature and this is already possible?
> What do you think?
> Wouldn't it make sense to make the default start drag distance respecting screen dpi?
> What do you think about to add a property on the QML Flickable in order to customize startDragDistance for this one QML Flickable? Are there any concerns about having such a property?
> Thanks for your opinion,
>  Jeremias
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