Hi Andy, many thanks for your response! I am also using a QAbstractListModel-derived class that gets exposed to the QML world which contains the images.
Yesterday I started to resize the images before feeding them to the ListModel. According to the QML Profiler the delegate gets now created a little bit faster, but fast scrolling is still a little bit sluggish. Today I probably will play a little bit with different image codecs to see if those have an impact. Currently I am using *.png files often which is probably not the best choice. Thanks a lot for your input, really appreciated! Bernhard Am Freitag, 11. August 2017 schrieb Andy : > Bernhard: > > I don't use QML, but in my application I use a QAbstractItemModel-derived > class and a QTreeView-derived class to display image thumbnails in the > view. The way I make it speedy is to save the image as a thumbnail so the > view items don't need to resize the image data at all. > > Maybe you could save a thumbnail of an appropriate size when you're adding > them to your model? > > --- > Andy Maloney // https://asmaloney.com > twitter ~ @asmaloney <https://twitter.com/asmaloney> > > > On Fri, Aug 11, 2017 at 3:33 AM, Bernhard B <schluc...@gmail.com > <javascript:_e(%7B%7D,'cvml','schluc...@gmail.com');>> wrote: > >> 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 <schluc...@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! >>>>> >>>> >>>> _______________________________________________ >>>> Interest mailing list >>>> Interest@qt-project.org >>>> http://lists.qt-project.org/mailman/listinfo/interest >>>> >>>> >>> >>> >>> -- >>> Best regards, >>> Vlad >>> >> >> _______________________________________________ >> Interest mailing list >> Interest@qt-project.org >> <javascript:_e(%7B%7D,'cvml','Interest@qt-project.org');> >> http://lists.qt-project.org/mailman/listinfo/interest >> >> >
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