High DPI issues

[Teo Mrnjavac]

On Tuesday, May 20, 2014 14:55:16 David Edmundson wrote:
> On Tue, May 20, 2014 at 2:28 PM, Teo Mrnjavac <teo at kde.org> wrote:
> > Hello,
> > 
> > I've had a chat with Morten Johan Sørvig, the person behind the high DPI
> > effort in Qt. What follows is a status report.
> > 
> > The work on high DPI support that's already merged is focused on OS X and
> > iOS, but it's mostly cross-platform code. There's also some unmerged work
> > on other platforms.
> > The X11 implementation of the scaling feature would rely on an environment
> > variable QT_HIGHDPI_SCALE_FACTOR, leaving it to the workspace to set this
> > value to something sensible (also described in [1]).
> 
> That means it's fixed as one global scale factor instead of one per screen.
> Given the API is all there that's a bit rubbish.

The QT_HIGHDPI_SCALE_FACTOR could also be per-screen, we can arrange that, but 
it makes our heuristics and/or settings more complicated. I'm guessing we'd 
have to at least move the DPI override setting from the Fonts KCM to KScreen.

> 
> I'm not sure how else one could do it in a X-platform way. Maybe this
> is worth a talk with Gnome, Ubuntu and whoever else pretty soon.

It seems like Xorg people don't even want to talk about this, judging from 
those bug reports I linked earlier.
Based on a quick search and skim through [1], Gnome 3 seems to go the X way, 
i.e. hardcoding 96ppi and using its own scaling factor set in dconf 
(org.gnome.desktop.interface text-scaling-factor). I don't know if they have 
heuristics to try to come up with that number automatically.
Ubuntu/Unity, no clue.
Sure, we can try to talk to people.

> 
> > Another important issue is that currently the only tested and nicely
> > working values for QT_HIGHDPI_SCALE_FACTOR are 1.0 and 2.0, i.e. Mac OS
> > style scaling.
> I can't imagine it being too big a problem; things only look bad once
> they're past a certain point.
> 
> > produce decent results and minimize glitches, but the only way to be sure
> > of that is trying it out. I'll try to give his branch a spin when I get
> > the chance.
> 
> Please do, and report back.

Will do.

[1] https://bugzilla.gnome.org/show_bug.cgi?id=643704

Cheers,
-- 
Teo Mrnjavac
http://teom.org | teo at kde.org