Re: Debian with HiDPI / 4K displays
On 2015-08-09 18:02:05 +0200, Vincent Bernat wrote:
> While it is possible to derive the true DPI setting from the resolution
> and the dimension, I don't think that's what users would be
> expecting. On a laptop, you'll want smaller fonts than on a desktop
> because the screen is usually nearer from your eyes.
>
> For example, on my laptop, the screen is 310mm x 174mm for 2560 x
> 1440. Strictly speaking, DPI is 210. However, I am setting it to 144
> because at 210, everything is far too big.
>
> On my desktop station, I am using 23" monitors (510mm x 290mm). It's 96
> DPI and it is just fine.
The best choice really depends on the user, but what's important is
that the default is not too small, otherwise the machine is hardly
usable just after installation. One needs to have some time to be
able to configure it (see below).
> What could be a goal is to only have one universal setting. This setting
> could be Xft.dpi since most applications work just fine with
> that. However, this hijacks the original purpose of this setting, but I
> think most people would like to have a bigger interface if they need
> bigger fonts.
This makes sense at least for icons attached to text (e.g. in menus).
There could (should) also be separate configuration, but it would be
nice if the global size of the UI followed the default font size.
Hardcoded icon size is unacceptable.
For instance, see
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=789273
concerning lightdm-gtk-greeter (one can change the font size, but not
the size of the icons, which are tiny on high-dpi screens).
On 2015-08-10 11:49:03 +0200, Daniel Pocock wrote:
> On 10/08/15 00:17, Simon McVittie wrote:
> > On 09/08/15 17:02, Vincent Bernat wrote:
> >> While it is possible to derive the true DPI setting from the resolution
> >> and the dimension
> >
> > ... except for when the stated dimensions in the display's EDID are full
> > of lies and claim that it is 4cm x 3cm, or 16cm x 9cm, or even 0cm x
> > 0cm. See also
> > <https://lists.fedoraproject.org/pipermail/devel/2011-October/157760.html>
> > and its surrounding thread - admittedly that was a few years ago. I'd be
> > delighted to be proved wrong, but I suspect hardware manufacturers
> > haven't got a whole lot better at this since then.
Unfortunately the default dpi setting to 96 is also completely wrong:
text is hardly readable on high-dpi screens. The screen definition
(WxH in pixels) is at least correct, so that the default dpi could be
based on that. For instance, if one has a 4K (3840×2160) screen, then
probably either this is a high-dpi screen or the physical dimensions
are large (e.g. 32"), but in which case the screen may also be far
from the user. So, choosing a large dpi value (e.g. 192) makes sense
in both cases.
> This brings a few thoughts to mind - I realize opinions may differ and
> there would be some work involved in any of these:
>
> - could there be some prompt on the first X startup or the first time a
> new screen is detected, asking the user to confirm DPI or dimensions?
There's still the problem that you need to display the prompt with
large enough font. One probably doesn't need a prompt. Just a sane
default and an easy way to change it.
> - could X use detected values that are in some range considered to be
> sane and if some users are unhappy, encourage them to complain to the
> monitor vendor? To put this another way, isn't it better to favor those
> monitors that do things correctly?
IMHO, the screen definition should be OK to choose a default dpi value
(as said above).
--
Vincent Lefèvre <vincent@vinc17.net> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)
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