[Interest] Improve ListView scrolling performance (many pictures)

[Bernhard B]

Hi Vlad,

you mean the QQuickAsyncImageProvider? That one sounds really promising.
Will definitely try that out. Many thanks for the suggestion!

Bernhard

Am Donnerstag, 10. August 2017 schrieb Vlad Stelmahovsky :

> threaded image provider might help
>
> On Thu, Aug 10, 2017 at 12:36 PM, Bernhard B <schluchti at gmail.com
> <javascript:_e(%7B%7D,'cvml','schluchti at gmail.com');>> wrote:
>
>> Hi,
>>
>> yesterday, I also tried to replace the Base64ImageProvider approach with
>> a subclassed QQuickPaintedItem which paints the image in it's paint method.
>> I imagined that this approach might be faster es no bade64 decoding needs
>> to be done. But unfortunately it looks like as it's performing even worse
>> that way.
>>
>> Bernhard
>>
>> Am Mittwoch, 9. August 2017 schrieb Bernhard B :
>>
>>> Hi,
>>>
>>> I would need some help from you guys on how to improve the ListView's
>>> performance. The problem is, that scrolling through my ListView sometimes
>>> feels a little bit sluggish.
>>>
>>> If I only display some text in the ListView's delegate I can scroll
>>> smoothly through my list. But as soon as there is a picture in the
>>> ListView's delegate I notice that I can't scroll smoothly through my list
>>> anymore. That's especially noticable if I try to scroll fast through my
>>> list. Every time I hit a picture while scrolling through the list I can see
>>> that there is a noticable delay until the picture is fully loaded. My
>>> assumption is, that those pictures are the reason why he scrolling feels so
>>> sluggish.
>>>
>>> My application currently works like this:
>>>
>>> * load 20 pictures via REST (pictures are base64 encoded)
>>> * populate list model
>>> * the Image component in the delegate uses a Base64ImageProvider (self
>>> written) to access the model's base64 encoded content and displays the image
>>> * if the user scrolls past a threshold another batch of base64 encoded
>>> pictures is fetched from the server
>>>
>>> I also found this document: http://doc.qt.io/qt-
>>> 5/qtquick-performance.html#rendering and tried to apply as much as
>>> possible. In detail I applied the following changes:
>>>
>>> * removed complex bindings from delegate
>>> * set sourceSize property for Image
>>> * increased cacheBuffer a bit
>>> * profiled with QML profiler and improved a few things
>>>
>>> But still, the ListView feels a bit sluggish. The strange thing is, that
>>> it's most noticable on Android whereas on Windows and iOs it is better.
>>>
>>> Does anyone have an idea on how to improve that?
>>>
>>>
>>> Any help is really appreciated.
>>> Thanks a lot!
>>>
>>
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>>
>
>
> --
> Best regards,
> Vlad
>
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