[Development] Scalable UIs in QtQuick (take 2)

[Rutledge Shawn]

> On 2 Mar 2016, at 09:37, Welbourne Edward <edward.welbourne at theqtcompany.com> wrote:
> 
> Andreas Hartmetz said:
>> Arcminutes are a really good idea. The size of screen elements isn't
>> really about physical dimensions, it's about size on retina (the
>> actual biological thing ;) really, or legibility.
> [...]
>> If the system had "known" that the typical user to screen distance was
>> 2-3 meters and acted accordingly, that wouldn't have happened.  Of
>> course, you need to know the "typical viewing distance" for a screen,
> 
> So perhaps what we should be using to configure UI scaling isn't a scale
> factor but this typical viewing distance; as long as the system has some
> way to discover the physical dimensions of the screen and its pixels, it
> then know everything it needs to scale the UI sensibly.

But some devices tell lies in their EDID data, and some don’t.  And with a projector you don’t know the physical size either.  So we can’t always discover the physical dimensions without user intervention.  (At least xorg.conf provides a way to override it.)

We could have some kind of calibration tool to help close the loop: a wizard that detects all possible settings, tries some tweaks, asks you to measure some calibration rects and text (rendered with both QtQuick and widgets) with a ruler, and then suggests settings that you probably need to adjust manually.  Kindof like using a colorimeter to calibrate color.  Except other software and hardware would keep changing out of our control, so this tool would never be “done”.  And really the desktop environment should have a sufficiently powerful control panel that we don’t need to write that.  But maybe it’s worth a try anyhow.