[Development] Scalable UIs in QtQuick (take 2)

[Sorvig Morten]

> On 19 Feb 2016, at 10:44, Gunnar Sletta <gunnar at sletta.org> wrote:
> 
> Now every piece of code needs to also know about device pixel ratio and that needs to passed down to image loaders, icon generators


This is essential complexity, not accidental complexity. With
high-DPI displays in use raster images now vary across two
dimensions: amount of content and amount of detail.

Consider a map tile provider: starting with a 50x50 base tile
there are two ways to render a 100x100 tile: More map content
or finer content detail.

The inputs to the image provider is either (logical pixels, scale)
or (actual pixels, scale). In both cases you have to carry the
scale factor.

The only way out is to reject the extra dimensionality (as I did
initially with the QML image providers), but I think Qt will be 
better off if we support it. 

- Morten