[Development] Scalable UIs in QtQuick (take 2)

[Konstantin Ritt]

Yet another question: when we write Item { id: item; width: 5cm }, what
would item.width return? value expressed in logical pixels?


Konstantin

2016-02-18 15:05 GMT+03:00 Sorvig Morten <Morten.Sorvig at theqtcompany.com>:

>
> > On 18 Feb 2016, at 12:35, Nikita Krupenko <krnekit at gmail.com> wrote:
> >
> > 2016-02-18 12:50 GMT+02:00 Hausmann Simon <
> Simon.Hausmann at theqtcompany.com>:
> >> (1) In order to make it really easy to scale "logical" pixels without
> having to introduce your own context property or factor in a .qml file that
> you multiply everywhere, we could turn the regular "pixels" in QtQuick into
> truly logical pixels that scale with an application wide (or window wide)
> factor. So Image { width: 100 ... } will scale automatically from 100
> logical pixels to maybe 200 physical pixels on a x2 display. This assumes
> the availability of API to change this mapping.
> >>
> >> (2) In the events where you still _want_ to use physical pixels, you
> could use "px" units.
> >>
> >> So at first nothing would change for app developers at all because we
> map logical pixels to physical pixels. But
> >> if you'd like to, you could opt into changing this mapping and having a
> relatively easy fallback to physical pixels using for example the "px"
> unit. We might as well offer the other physical units anyway, that probably
> causes little to no harm.
> >
> > Isn't (1) already done with Qt::AA_EnableHighDpiScaling? Though
> > disabling this feature for some items would be useful, like for
> > Canvas, which is broken now with this scaling.
>
> This is indeed what is done for that flag and on OS X and iOS. In that
> sense logical pixels are already supported.
>
> “px” could be added, but what are the use cases? You almost never want to
> have small content on high-DPI display. I see doing custom scaling in the
> application as a possible one.
>
> As a minor platform note, “px” would not be guaranteed to be physical
> pixels
> on Apple operating systems. There can be further resolution virtualization,
> for example when setting a scaled resolution for the display.
>
> Morten
>
>
>
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