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

[Jan Mulder]

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.

best,

--jan