[Interest] How can i animate Layout.preferredWidth and friends?

[Mark]

On Fri, Oct 11, 2013 at 5:08 PM, Mark <markg85 at gmail.com> wrote:

>
>
> On Fri, Oct 11, 2013 at 2:37 PM, Saether Jan-Arve <
> Jan-Arve.Saether at digia.com> wrote:
>
>> > > Of course it should not crash.
>> > > I get an ASSERT: "mo" in file qml\qqmlvme.cpp, line 849 (this is with
>> current stable branch though).
>> > >
>> > > I'm a bit curious to know why do you want to animate that property?
>> > > What do you want to achieve?
>> > >
>> > > Jan Arve
>> > >
>> > > From: interest-bounces+jan-arve.saether=digia.com at qt-project.org[mailto:
>> interest-bounces+jan-arve.saether=digia.com at qt-project.org] On Behalf Of
>> Mark
>> > > > Sent: 30. september 2013 01:40
>> > > > To: Qt Interest
>> > > > Subject: [Interest] How can i animate Layout.preferredWidth and
>> friends?
>> > > >
>> > > > Hi,
>> > > >
>> > > > I thought something as simple as:
>> > > >
>> > > >            Behavior on Layout.preferredWidth {
>> > > >                NumberAnimation { duration: 1000 }
>> > > >            }
>> > > >
>> > > > would do.. Apparently not since it crashes qmlscene..
>> > > > Do i need to do it differently or did i just hit a bug?
>> > > >
>> > > > Version details:
>> > > > Qt 5.1.0 x64 (i know, 5.1.1 is out)
>> > > > Mac Mountain Lion fully updated
>> > > >
>> > > > Cheers,
>> > > > Mark
>> >  Hi Jan,
>> >
>> > What i try to do is animate the (in this case) width. In a simple
>> > description that would be it. However, i try to animate the with of a
>> > component that is within a Layout. In this case a RowLayout. If i use
>> > the width, the RowLayout itself doesn't update, you can see that in
>> > this snippet [1]. Just press the nice orange square :) What i want
>> > for that is to work. I tried animating the Layout.preferredWidth
>> > property because changing the width using that does update the
>> > RowLayout, but then the animation doesn't work.
>> >
>> > That's all i'm trying to do.
>> >
>> > [1] http://pastebin.kde.org/pxgjxhtza
>>
>> Your example code works exactly how I would expect it to work.
>> You are only animating the width of the red rectangle, and the layout
>> doesn't rely on the width property for rearranging its items.
>> Therefore, the layout and the other children are not affected by this.
>> (Try to set opacity: 0.5 on the green item, then you will better see
>> what's going on :-)
>>
>
> I actually didn't do that before. Tried it out just now and it indeed does
> exactly what i would expect :) Only issue is that the layout itself doesn't
> do what i expect..
> I was about to create a bug report, but the qt-project site is currently
> extremely slow with the occasional timeout errors... So i will do that
> later.
>
>>
>> However, I would expect changing togglePreferredWidth to actually
>> toggle Layout.preferredWidth (while keeping the Behavior on width) to
>> do what you want, but I think that Behaviors are only applied if the
>> property
>> is changed in QML. (The width property is changed in the C++ backend of
>> the layout engine, which then wouldn't apply the behavior)
>>
>
> I actually tried that initially but that didn't work.
>
>>
>> This modified example demonstrates the issue, and AFAIK it's a limitation
>> of the
>> Behavior element:
>>
>> http://pastebin.com/bcD9wRu5
>>
>> Jan Arve
>>
>>
> Bug report created: https://bugreports.qt-project.org/browse/QTBUG-34045
I hope i explained it well.
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