[Qt-qml] SmoothedAnimation Soul Searching

[Alan Alpert]

I'm looking for some feedback on what people think the real use case for 
SmoothedAnimation is. There's currently two different cases that I'm looking 
into.

A) Move from point C to point D, smoothly, where point D doesn't change 
(much).
B) Move from point C to point D, smoothly, where point D is an animating or 
constantly changing value.

We don't have SmoothFollow anymore so as to have a separate element for these 
cases. My feeling is that you need a separate element due to the velocity 
requirements. 

For movement A you want the set velocity to be the average, so that you can 
actually work out in your head how long it will take to get there. 

For movement B you want the set velocity to be the maximum, as it will never 
get 'there' unless either the target stops or it reaches the same velocity as 
the target. Only setting the maximum velocity gives you the control you need 
here. The duration means very little in this case as well, as the animation is 
always being 'restarted' when the value changes. It's not quite the same as 
doing movement A to the target of the animating value, because in that case 
you could get ahead of that value and in this case you cannot.

Where I need some help is not only in verifying the reasoning I just threw out 
there. I'm not yet convinced that option B is common enough to be a valid use 
case. Does anyone know of a non-contrived example where you genuinely want 
behavior B and not A? 

-- 
Alan Alpert
Software Engineer
Nokia, Qt Development Frameworks