[SailfishDevel] Delegate creation on demand

[Hendrik Borghorst]

Sure,

This example I've just created and it does exactly what I want to show.

greetings and thanks for your support

There are 2 buttons, one populates the model with 25000 simple items. 

The second one pushes a page above the page with listview. After the
push you can see the ListView creating lots of delegates in console.log

PS.: I've not tested it with qmlscene but as an application
(modeltext.tar.xz) on real device.


Am Sonntag, den 15.12.2013, 20:25 +0000 schrieb Robin Burchell:
> Can you please provide a minimal test case (i.e. ideally a single QML file, usable with qmlscene) demonstrating your problem?
> 
> Please see http://sscce.org/
> 
> On 15 Dec 2013, at 21:03, Hendrik Borghorst <hendrikborghorst at gmail.com> wrote:
> 
> > Hello,
> > 
> > the problem isn't my delegate. It is quite minimal. 
> > 
> > The problem is I think a bug in QML Listview. It goes absolutly crazy if
> > it is invisible and starts making delegate for around 50% of all items.
> > This causes the memory to run full.
> > 
> > A workaround I added is
> > 
> > model: visible ? modelVar : null
> > 
> > which works quite nicely. I think this bug could be an upstream qt bug?
> 
> > 
> > greetings
> > 
> > Am Sonntag, den 15.12.2013, 10:01 +0100 schrieb
> > christopher.lamb at thurweb.ch:
> >> Hi Hendrik
> >> 
> >> Have you seen this? http://qt-project.org/wiki/Performance_tip_Lists
> >> 
> >> The general advice is to keep the delegates is lightweight as  
> >> possible, and to use Loaders for anything needed later (e.g. onClick)
> >> 
> >> Chris
> >> 
> >> Zitat von "Hendrik Borghorst" <hendrikborghorst at gmail.com>:
> >> 
> >>> Hello folks,
> >>> 
> >>> I've got a problem with long lists (~25000 elements). All delegates are
> >>> created at once which causes the memory usage to explode beyond the
> >>> devices capability.
> >>> 
> >>> I already tried setting "cacheBuffer: 0" in SiliciaListView but  it
> >>> doesn't change it.
> >>> 
> >>> Is the something I'm doing wrong.
> >>> 
> >>> You can see the actual page code here:
> >>> 
> >>> https://github.com/djselbeck/smpc/blob/master/pages/CurrentPlaylistPage.qml
> >>> 
> >>> Shouldn't the delegates be constructed on demand? It is weird because my
> >>> old n8 wasn't struggling with qml lists with this size.
> >>> 
> >>> greetings and congrats on getting the devices to your customers (I'm
> >>> very pleased)
> >>> 
> >> 
> >> 
> >> 
> >> 
> > 
> > _______________________________________________
> > SailfishOS.org Devel mailing list
> 
> _______________________________________________
> SailfishOS.org Devel mailing list

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