mobile: not smooth scrolling from dive-detail to dive-detail

[Sebastian Kügler]

On Wednesday, February 10, 2016 03:59:52 PM Jan Mulder wrote:
> On 10-02-16 15:28, Sebastian Kügler wrote:
> > On Wednesday, February 10, 2016 03:24:38 PM Jan Mulder wrote:
> >> As has been noticed by a number of people that are active in the android
> >> mobile development, the scrolling/swiping from dive-detail to
> >> dive-detail is not "smooth". It stops and moves forward at (lets say)
> >> 80% of the width of the profile window, and up to now it is unclear if
> >> it is a QML/Qt thing or something in our code.
> > 
> > This is most likely the profile being rendered, which is quite slow. Ideas
> > to make it faster:
> > 
> > - cache the dive profiles, so only render them one for a given size,
> > re-read>
> >    from disk; this would of course only help after a dive has been shown
> >at least once
> >
> > - use an imageprovider *1 for the dive profile; this allows to load them
> >
> >    asynchronous, could be combined with the above cache idea
> >
> > *1 http://doc.qt.io/qt-5/qquickimageprovider.html
> 
> Tempted by the hypothesis of the slow profile rendering being the the 
> issue of the "strange scrolling behavior", I did the following 
> experiment. Commented the entire QMLProfile block (and the references to 
> it) from the DiveDetails.qml. This does result in a page without the 
> profile, so, with knowing much about the internals of QML, I assume that 
> this suppresses any dive profile rendering related computations.
> 
> This does not change the strange scrolling behavior.
> 
> I agree that the profile rendering is an computational serious effort, 
> and that asynchronous computation, and caching are very relevant ideas 
> to tackle this, but I doubt that it touches the "80% scrolling" behavior.

Hm, I tried this a while ago myself, and back then it had a noticeable 
effect... I wonder what changed. (It's of course awesome that the profile 
rendering doesn't seem the culprit anymore.)

Next thing I can think of is a too complex details page.
-- 
sebas

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