Debian with HiDPI / 4K displays

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Debian with HiDPI / 4K displays

Daniel Pocock-4


I recently started using a 4K display with Debian jessie and GNOME shell

The hardware setup was quite straightforward as I chose to buy a new
graphics card with 4K support and a relatively new monitor.  The
graphics card and monitor both support DisplayPort 1.2 so I just hook
them up with the standard cable.

The graphics card vendor supplies a proprietary driver but everything
else is currently running using the packages from jessie.

However, I've come up against the DPI issues.

The actual DPI is about 131x137 on a 32" display.

xdpyinfo reports 96x96

It looks like there has been a history of bug reports about DPI in both
the Xorg server itself and some individual applications.

Some web sites suggested using gnome-tweak-tool to change the window
scaling factor.  It only appears to accept integer values and changing
it from the default of 1 to 2 makes the fonts too big.

So, is there any strategy for HiDPI with Debian?  Is a BTS tag needed to
track such issues perhaps?  Or is it already dealt with in unstable and
people just have to wait for it?

My general feeling is that the 32" 4K display was a worthwhile purchase
and it definitely lets me improve my workflow.  For example, I can now
have all my communication tools (Icedove, IRC and others) arranged in a
single virtual desktop, none of them overlap each other and I don't have
to use alt-tab to switch between them.  In another virtual desktop I no
longer need to run Eclipse at full screen, I can just give it two thirds
of the screen and use the rest for testing things.  However, all fonts
are really tiny, they are readable and even pleasant to look at but I
would probably like to see them just a little bigger.

Regards,

Daniel


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Re: Debian with HiDPI / 4K displays

Vincent Bernat-3
 ❦  8 août 2015 20:58 +0200, Daniel Pocock <[hidden email]> :

> The hardware setup was quite straightforward as I chose to buy a new
> graphics card with 4K support and a relatively new monitor.  The
> graphics card and monitor both support DisplayPort 1.2 so I just hook
> them up with the standard cable.
>
> The graphics card vendor supplies a proprietary driver but everything
> else is currently running using the packages from jessie.
>
> However, I've come up against the DPI issues.
>
> The actual DPI is about 131x137 on a 32" display.
>
> xdpyinfo reports 96x96
>
> It looks like there has been a history of bug reports about DPI in both
> the Xorg server itself and some individual applications.
>
> Some web sites suggested using gnome-tweak-tool to change the window
> scaling factor.  It only appears to accept integer values and changing
> it from the default of 1 to 2 makes the fonts too big.
>
> So, is there any strategy for HiDPI with Debian?  Is a BTS tag needed to
> track such issues perhaps?  Or is it already dealt with in unstable and
> people just have to wait for it?
>
> My general feeling is that the 32" 4K display was a worthwhile purchase
> and it definitely lets me improve my workflow.  For example, I can now
> have all my communication tools (Icedove, IRC and others) arranged in a
> single virtual desktop, none of them overlap each other and I don't have
> to use alt-tab to switch between them.  In another virtual desktop I no
> longer need to run Eclipse at full screen, I can just give it two thirds
> of the screen and use the rest for testing things.  However, all fonts
> are really tiny, they are readable and even pleasant to look at but I
> would probably like to see them just a little bigger.
The support of HiDPI in Debian is pretty good with a few
exceptions. Which DE are you using? I don't know exactly how this work
with Gnome, but the solution is to keep X.org at 96dpi (most apps don't
care, but some "I know better than everyone" needs that, for example
Chromium) and to change Xft DPI to an appropriate value (I suggest 144
in your case, better try to round a bit).

You can either set Xft.dpi with xrdb. Any new application should now be
scaled correctly (most apps will scale fonts _and_ the interface).

You can also set Xft/DPI in XSETTING. The advantage of doing that is
that all applications will notice the change. In this case, this depends
of your DE. If you don't have a big one, you can use xsettingsd with the
following line:

Xft/DPI 147456

(it's 144*1024)

The best resource is ArchLinux wiki:
 https://wiki.archlinux.org/index.php/HiDPI
However, don't try to apply everything.
--
Make the coupling between modules visible.
            - The Elements of Programming Style (Kernighan & Plauger)

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Re: Debian with HiDPI / 4K displays

Josh Triplett-9
In reply to this post by Daniel Pocock-4
Daniel Pocock wrote:
> The actual DPI is about 131x137 on a 32" display.
[...]
> Some web sites suggested using gnome-tweak-tool to change the window
> scaling factor.  It only appears to accept integer values and changing
> it from the default of 1 to 2 makes the fonts too big.
>
> So, is there any strategy for HiDPI with Debian?  Is a BTS tag needed to
> track such issues perhaps?  Or is it already dealt with in unstable and
> people just have to wait for it?

I have a similar experience with a 2560x1440 14" screen (210 DPI).
Using a scale factor of 2 would make it act like a 720p screen, making
everything far too large.  However, I find that GNOME's font-based
scaling works fine for me: in gnome-tweak-tool, I changed Fonts ->
Scaling Factor to 1.4.  That also sets the X property Xft.dpi to 144
(see xrdb -query), which many non-GNOME programs look at too.  Firefox
doesn't, but it has its own setting that even supports non-integer
scaling of the entire UI, so I changed its layout.css.devPixelsPerPx to
1.4 as well.

This handles the majority of programs I use.  A few notable exceptions:
gitk scales up some but not all of its fonts (reported as a bug),
Celestia's and stellarium's in-rendering text (reported as bugs), old X
utilities like xcalc/xconsole/xedit/xdvi/xmag/xman/xmessage (not really
worth reporting, better to replace them with modern tools), and anything
that relies heavily on toolbars like gimp/inkscape/audacity (tools and
other UI elements not scaled up, since they don't use text; unfortunate
but expected, as they don't have non-integer scaling).

- Josh Triplett


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Re: Debian with HiDPI / 4K displays

Vincent Bernat-3
 ❦  8 août 2015 18:11 -0700, Josh Triplett <[hidden email]> :

> This handles the majority of programs I use.  A few notable exceptions:
> gitk scales up some but not all of its fonts (reported as a bug),
> Celestia's and stellarium's in-rendering text (reported as bugs), old X
> utilities like xcalc/xconsole/xedit/xdvi/xmag/xman/xmessage (not really
> worth reporting, better to replace them with modern tools), and anything
> that relies heavily on toolbars like gimp/inkscape/audacity (tools and
> other UI elements not scaled up, since they don't use text; unfortunate
> but expected, as they don't have non-integer scaling).

I don't have any such problems with Gimp and Inkscape and Xft/DPI set to
144 (both through xrdb and XSETTINGS). All GTK apps are behaving
correctly, notably Gimp and Inkscape. It seems GTK is doing complex
stuff to determine the scaling to be applied, so many things may
influence it. Other apps fail to understand how GTK works and try to
emulate it by piling hacks together (notably Chromium).

I could show you at Debconf to spot a configuration difference.
--
No group of professionals meets except to conspire against the public at large.
                -- Mark Twain

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Re: Debian with HiDPI / 4K displays

Vincent Lefevre-10
In reply to this post by Daniel Pocock-4
On 2015-08-08 20:58:37 +0200, Daniel Pocock wrote:
> So, is there any strategy for HiDPI with Debian?  Is a BTS tag needed to
> track such issues perhaps?  Or is it already dealt with in unstable and
> people just have to wait for it?

I have similar problems with a 3200x1800 15" screen. Here's my
Xresources file for high DPI:

! X resources for high-definition screens

! This will define the unit for the font sizes below.
Xft.dpi: 132

Emacs*font: Monospace 10
Emacs*geometry: 80x48

! With the following, the width should be $((11*COLUMNS+13)) pixels;
! in contrast, the fixed = 6x13 bitmap font is typically used on a
! low-definition screen, giving a width of $((6*COLUMNS+13)) pixels.
XTerm*faceName: Monospace
XTerm*faceSize: 10
! For xterm menus. This font is large enough, but a bit ugly.
XTerm*font: -adobe-helvetica-bold-r-normal--0-0-0-0-p-0-iso8859-1

! The fontList resource is not documented, but found in "xpdf/XPDFApp.cc".
Xpdf*fontList: -adobe-helvetica-bold-r-normal--0-0-0-0-p-0-iso8859-1
Xpdf.initialZoom: 200

--------

and my firefox.cfg file:

// IMPORTANT: Start your code on the 2nd line
var hdef = getenv("X11_HDEF");
if (hdef >= 2400) {
  pref("layout.css.devPixelsPerPx", "1.77");
} else {
  pref("layout.css.devPixelsPerPx", "-1.0");
}

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Re: Debian with HiDPI / 4K displays

Thorsten Glaser-6
In reply to this post by Daniel Pocock-4
Daniel Pocock <daniel <at> pocock.pro> writes:

> However, I've come up against the DPI issues.
>
> The actual DPI is about 131x137 on a 32" display.
>
> xdpyinfo reports 96x96

I've recently had the problem that some applications like Kontact/KDEPIM
suddenly use the wrong fixedmisc font for eMail displaying, and tracked
it down to X reporting 91 dpi (IIRC, not sure, could have been 96), but
my actual dpi is closer to 72/75 than to 96/100.

I added a line…
    xrandr --dpi 80
… to my ~/.xsessionrc after interactively trying out the value in which
things come out “right”. Note that this, interestingly enough, does not
match my real dpi value either, but it's the one causing fonts not to
go haywire.

YMMV, and this is probably the wrong fix, but I thought to share anyway,
as it's new (we used to specify display size in XF86Config to fix this,
some time ago).

Maybe keithp has got some insight on this?

bye,
//mirabilos

PS: the fixedmisc font I intend to use for all my non-proportional font
    needs is the 9x18/18x18ko one (amended with many more glyphs), in
    case this matters.
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Re: Debian with HiDPI / 4K displays

Daniel Pocock-4
In reply to this post by Vincent Bernat-3
On 09/08/15 09:22, Vincent Bernat wrote:

>  ❦  8 août 2015 18:11 -0700, Josh Triplett <[hidden email]> :
>
>> This handles the majority of programs I use.  A few notable exceptions:
>> gitk scales up some but not all of its fonts (reported as a bug),
>> Celestia's and stellarium's in-rendering text (reported as bugs), old X
>> utilities like xcalc/xconsole/xedit/xdvi/xmag/xman/xmessage (not really
>> worth reporting, better to replace them with modern tools), and anything
>> that relies heavily on toolbars like gimp/inkscape/audacity (tools and
>> other UI elements not scaled up, since they don't use text; unfortunate
>> but expected, as they don't have non-integer scaling).
> I don't have any such problems with Gimp and Inkscape and Xft/DPI set to
> 144 (both through xrdb and XSETTINGS). All GTK apps are behaving
> correctly, notably Gimp and Inkscape. It seems GTK is doing complex
> stuff to determine the scaling to be applied, so many things may
> influence it. Other apps fail to understand how GTK works and try to
> emulate it by piling hacks together (notably Chromium).
>
> I could show you at Debconf to spot a configuration difference.

Thanks for all this feedback

Looking through the feedback and comments elsewhere,

a) most people are using some manual configuration to deal with this

b) it needs to be tweaked in more than one place (e.g. xrdb + Iceweasel
+ other places)

c) there is at least some stuff that is video-card specific, e.g. NVIDIA
offers some driver options[1] for it and it is not clear if these simply
supplement the Xorg options like DisplaySize or if the NVIDIA driver
breaks DisplaySize functionality in some way such that an alternative
has to be provided

d) there is some concern that not all displays report DPI accurately and
so it wasn't considered safe to trust the value from the display and so
people started using the hard-coded values in GNOME at some point in the
past - is that still a valid argument today though?

Does anybody feel strongly enough that manual DPI configuration
shouldn't be necessary any more, just as it is no longer necessary to
manually create X ModeLines for most monitors?  Would this be a
worthwhile goal for stretch?

It would appear that having a consistent approach to this is not just
useful for the newer range of UHD and laptop displays, but also for any
Debian derivatives or blends that are interested in more exotic displays
such as mobile screens or smart TVs.

1.
http://us.download.nvidia.com/XFree86/Linux-x86/173.14.12/README/appendix-b.html#UseEdidDpi




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Re: Debian with HiDPI / 4K displays

Vincent Bernat-3
 ❦  9 août 2015 16:28 +0200, Daniel Pocock <[hidden email]> :

> b) it needs to be tweaked in more than one place (e.g. xrdb + Iceweasel
> + other places)

Yes, that's unfortunate. If GTK people could explain Iceweasel and
Chromium people how they should handle it, it would lessen the amount of
manual configuration needed. Using only XSETTINGS (or XSETTINGS + xrdb)
would unify the configuration and allow automatic change when switching
From one DPI settings to another.

I don't know the Iceweasel case, but for Chromium, it seems they are
pretty clueless and just add more hacks until people stop complaining.

> d) there is some concern that not all displays report DPI accurately and
> so it wasn't considered safe to trust the value from the display and so
> people started using the hard-coded values in GNOME at some point in the
> past - is that still a valid argument today though?

The hard coding is done in X at 96 dpi and it is still true today. If you
change DPI settings in X (with -dpi), you can check that the display
dimensions is adjusted appropriately, making your change useless. XRANDR
reports the appropriate values and applications wishing to use it should
use that instead.

See:
 https://bugs.freedesktop.org/show_bug.cgi?id=23705
 https://bugs.freedesktop.org/show_bug.cgi?id=41115
 http://pastebin.com/vtzyBK6e

As you said, Nvidia is special here.

> Does anybody feel strongly enough that manual DPI configuration
> shouldn't be necessary any more, just as it is no longer necessary to
> manually create X ModeLines for most monitors?  Would this be a
> worthwhile goal for stretch?

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.

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.
--
Habit is habit, and not to be flung out of the window by any man, but coaxed
down-stairs a step at a time.
                -- Mark Twain, "Pudd'nhead Wilson's Calendar

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Re: Debian with HiDPI / 4K displays

Simon McVittie-7
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.

As has been noted elsewhere in this thread, there are actually two
values that desktop environments are trying to use: taking GNOME as an
example because that's the one I know best, it will happily scale fonts
to any  "dpi" value of your choice (even if it isn't an integer multiple
of 96), because fonts are designed to be scalable anyway; but it will
only apply integer numbers of real pixels per "density-independent
pixel", because non-integer ratios there would make all the widgets,
window decoration, icons, etc. blurry, and I think there are some more
technical reasons to prefer integer ratios. Qt 5 similarly only supports
integer numbers of real pixels per dp.

I believe Android supports arbitrary multiples of 0.5 real pixels per
dp, although I don't know how commonly-used those are in practice.

Density-independent pixels (dp) are the Android term; I don't know
whether there's a different conventional name is elsewhere. "CSS pixels"
are basically the same thing as Android's dp.

    S


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Re: Debian with HiDPI / 4K displays

Daniel Pocock-4


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.
>

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?

- 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?

- is there any Linux recommended monitor list or would there be value in
such a list?  Correct EDID data could be a criteria for inclusion on the
list?

- could people crowdsource a database of monitor specs, maybe combined
with some setup wizard?

Some of this is obviously not Debian-specific either.  Does any other OS
keep a list of known monitor dimensions for example?

Regards,

Daniel


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Re: Debian with HiDPI / 4K displays

Vincent Lefevre-10
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).

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Re: Debian with HiDPI / 4K displays

Simon Kainz-3
In reply to this post by Vincent Bernat-3
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512



Am 2015-08-09 um 09:22 schrieb Vincent Bernat:

> ❦  8 août 2015 18:11 -0700, Josh Triplett <[hidden email]>
> :
>
>> This handles the majority of programs I use.  A few notable
>> exceptions: gitk scales up some but not all of its fonts
>> (reported as a bug), Celestia's and stellarium's in-rendering
>> text (reported as bugs), old X utilities like
>> xcalc/xconsole/xedit/xdvi/xmag/xman/xmessage (not really worth
>> reporting, better to replace them with modern tools), and
>> anything that relies heavily on toolbars like
>> gimp/inkscape/audacity (tools and other UI elements not scaled
>> up, since they don't use text; unfortunate but expected, as they
>> don't have non-integer scaling).
>
> I don't have any such problems with Gimp and Inkscape and Xft/DPI
> set to 144 (both through xrdb and XSETTINGS). All GTK apps are
> behaving correctly, notably Gimp and Inkscape. It seems GTK is
> doing complex stuff to determine the scaling to be applied, so many
> things may influence it. Other apps fail to understand how GTK
> works and try to emulate it by piling hacks together (notably
> Chromium).
>
> I could show you at Debconf to spot a configuration difference.
>
I am also very interested in this (at Debconf), as i own a MacBook Pro
running Jessie with no problems so far, except some very tiny
checkboxes/radiobuttons in firefox and tiny buttons in gimp/inkscape.

Is there probably a Debian/HiDPI wiki/website with information about
how to set up specific apps under specific Desktop Environments?

Simon.
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Re: Debian with HiDPI / 4K displays

Vincent Bernat-3
 ❦ 10 août 2015 23:29 +0200, Simon Kainz <[hidden email]> :

>>> This handles the majority of programs I use.  A few notable
>>> exceptions: gitk scales up some but not all of its fonts
>>> (reported as a bug), Celestia's and stellarium's in-rendering
>>> text (reported as bugs), old X utilities like
>>> xcalc/xconsole/xedit/xdvi/xmag/xman/xmessage (not really worth
>>> reporting, better to replace them with modern tools), and
>>> anything that relies heavily on toolbars like
>>> gimp/inkscape/audacity (tools and other UI elements not scaled
>>> up, since they don't use text; unfortunate but expected, as they
>>> don't have non-integer scaling).
>>
>> I don't have any such problems with Gimp and Inkscape and Xft/DPI
>> set to 144 (both through xrdb and XSETTINGS). All GTK apps are
>> behaving correctly, notably Gimp and Inkscape. It seems GTK is
>> doing complex stuff to determine the scaling to be applied, so many
>> things may influence it. Other apps fail to understand how GTK
>> works and try to emulate it by piling hacks together (notably
>> Chromium).
>>
>> I could show you at Debconf to spot a configuration difference.
>>
> I am also very interested in this (at Debconf), as i own a MacBook Pro
> running Jessie with no problems so far, except some very tiny
> checkboxes/radiobuttons in firefox and tiny buttons in gimp/inkscape.
I may have been overly enthusiastic. Since I am only at 1.5 scale, tiny
icons are not really my concern:

See Gimp and Inkscape:
 http://postimg.org/image/g5i6rfgsz/

So, there are more stuff than Xft/DPI to adjust. I suppose that setting
org.gnome.desktop.interface scaling-factor to 2 may help. However, I am
unable to test as it is not based on XSETTINGS but it's just a
gnome-control-center property.
--
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Re: Debian with HiDPI / 4K displays

Daniel Pocock-4
In reply to this post by Simon Kainz-3
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256



On 10/08/15 23:29, Simon Kainz wrote:

>
>
> Am 2015-08-09 um 09:22 schrieb Vincent Bernat:
>> ❦  8 août 2015 18:11 -0700, Josh Triplett
>> <[hidden email]> :
>
>>> This handles the majority of programs I use.  A few notable
>>> exceptions: gitk scales up some but not all of its fonts
>>> (reported as a bug), Celestia's and stellarium's in-rendering
>>> text (reported as bugs), old X utilities like
>>> xcalc/xconsole/xedit/xdvi/xmag/xman/xmessage (not really worth
>>> reporting, better to replace them with modern tools), and
>>> anything that relies heavily on toolbars like
>>> gimp/inkscape/audacity (tools and other UI elements not scaled
>>> up, since they don't use text; unfortunate but expected, as
>>> they don't have non-integer scaling).
>
>> I don't have any such problems with Gimp and Inkscape and
>> Xft/DPI set to 144 (both through xrdb and XSETTINGS). All GTK
>> apps are behaving correctly, notably Gimp and Inkscape. It seems
>> GTK is doing complex stuff to determine the scaling to be
>> applied, so many things may influence it. Other apps fail to
>> understand how GTK works and try to emulate it by piling hacks
>> together (notably Chromium).
>
>> I could show you at Debconf to spot a configuration difference.
>
> I am also very interested in this (at Debconf), as i own a MacBook
> Pro running Jessie with no problems so far, except some very tiny
> checkboxes/radiobuttons in firefox and tiny buttons in
> gimp/inkscape.
>
> Is there probably a Debian/HiDPI wiki/website with information
> about how to set up specific apps under specific Desktop
> Environments?
>

I just created a page where people could copy in some of the details
from this thread:

https://wiki.debian.org/MonitorDPI


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Re: Debian with HiDPI / 4K displays

John Goerzen-3
In reply to this post by Daniel Pocock-4
On 08/08/2015 01:58 PM, Daniel Pocock wrote:

I recently started using a 4K display with Debian jessie and GNOME shell

The hardware setup was quite straightforward as I chose to buy a new

There is also an understated problem - DPI changing during a session, or even different monitors having different DPI in a multihead situation.

This seems to be particularly poorly supported, but is rather common.  My laptop is 1920x1080 in a 12.5" display, with approximately 176DPI.  The external monitor on its docking station is a more conventional DPI.

There are many questions here:

  • Simplest: When I use one monitor at the time, does the OS do the right thing with the only enabled display device changes to a device with a different DPI?  (No, it doesn't; there is no automatic DPI changing.)
  • Then: Does the OS do the right thing when there are two non-mirrored devices with differing DPIs?  (Not really)
  • Does the OS do the right thing when a connected device changes configured resolution, changing DPI?
  • Finally: Does the OS do the right thing when a display is mirrored across two devices with diverging DPIs?  What even IS the right thing here?  Probably stick with the DPI of the device that got in "first".  But what is that device when both an internal and external display are connected at boot?
(Note: DE here is XFCE)

There are many things that seem to not handle differences in DPI.  Fonts are just the start.  What about taskbars and taskbar icons, which become tiny at certain DPIs?  We seem to be using pixel heights in these a lot.

John

graphics card with 4K support and a relatively new monitor.  The
graphics card and monitor both support DisplayPort 1.2 so I just hook
them up with the standard cable.

The graphics card vendor supplies a proprietary driver but everything
else is currently running using the packages from jessie.

However, I've come up against the DPI issues.

The actual DPI is about 131x137 on a 32" display.

xdpyinfo reports 96x96

It looks like there has been a history of bug reports about DPI in both
the Xorg server itself and some individual applications.

Some web sites suggested using gnome-tweak-tool to change the window
scaling factor.  It only appears to accept integer values and changing
it from the default of 1 to 2 makes the fonts too big.

So, is there any strategy for HiDPI with Debian?  Is a BTS tag needed to
track such issues perhaps?  Or is it already dealt with in unstable and
people just have to wait for it?

My general feeling is that the 32" 4K display was a worthwhile purchase
and it definitely lets me improve my workflow.  For example, I can now
have all my communication tools (Icedove, IRC and others) arranged in a
single virtual desktop, none of them overlap each other and I don't have
to use alt-tab to switch between them.  In another virtual desktop I no
longer need to run Eclipse at full screen, I can just give it two thirds
of the screen and use the rest for testing things.  However, all fonts
are really tiny, they are readable and even pleasant to look at but I
would probably like to see them just a little bigger.

Regards,

Daniel



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Re: Debian with HiDPI / 4K displays

Simon McVittie-7
On 11/08/15 23:17, John Goerzen wrote:
> There are many things that seem to not handle differences in DPI.  Fonts
> are just the start.  What about taskbars and taskbar icons, which become
> tiny at certain DPIs?  We seem to be using pixel heights in these a lot.

I think we're going in circles now, but to recap, the state-of-the-art
here seems to be the same approach as Apple's "Retina displays": the
desktop environment or runtime chooses a scaling factor (usually an
integer) for "real pixels per logical pixel", and considers most
application-requested pixel sizes to be measured in logical pixels, not
real pixels. Icon rendering, widget rendering with Cairo and so on can
use the real pixels to get sub-logical-pixel resolution, but the layout
is done in terms of logical pixels (and because the scale factor is an
integer, everything is whole-pixel-aligned, so widgets aren't blurred).
CSS has a similar approach, defining a "CSS pixel" (the px unit) to be
one or more real pixels.

I know Gtk and Qt support this; Gtk can do non-integer scale factors
(although they are probably a bad idea), Qt only does integer scale
factors. In the case of Gtk, the scale factor is exposed as a setting in
gnome-tweak-tool.

Font sizes are relative to the scale factor, so if your laptop is really
176dpi and you're using a 2x scale factor, you might set X's DPI value
to around 88 (96 might be close enough).

    S


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Re: Debian with HiDPI / 4K displays

Nikolaus Rath
In reply to this post by Daniel Pocock-4
On Aug 09 2015, Daniel Pocock <[hidden email]> wrote:
> d) there is some concern that not all displays report DPI accurately and
> so it wasn't considered safe to trust the value from the display and so
> people started using the hard-coded values in GNOME at some point in the
> past - is that still a valid argument today though?

No, the argument (at least from the Gnome people) is that DPI (as
reported by xrandr) is a useless metric to determine the proper font
rendering size. Their main argument is that their is no API to report
different DPIs for different screens, and it doesn't factor in things
like the distance of the user from the screen, or simply a user's
preference to have bigger/smaller fonts.

Therefore, they started ignoring X11 dpi completely and added their own
Gnome DPI (which, as far as I know, still doesn't support different DPI
values for different displays).

There is a truly gigantic bugzilla issue about this, but I don't
have the exact URL anymore.

(At some point I suggested to drop the Gnome DPI and instead use a Gnome
DPI scale factor that's applied on top of the X11 DPI but there was
never a response. Most likely the issue is a lot more complicated, or
the bug has become completely useless to because of its size).


Best,
-Nikolaus

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Re: Debian with HiDPI / 4K displays

Ondřej Surý-4
In reply to this post by Daniel Pocock-4
On Sun, Aug 9, 2015, at 16:28, Daniel Pocock wrote:
> Thanks for all this feedback
>
> Looking through the feedback and comments elsewhere,
>
> a) most people are using some manual configuration to deal with this
>
> b) it needs to be tweaked in more than one place (e.g. xrdb + Iceweasel
> + other places)

Try Debian stretch - it mostly works out of the box with GNOME 3.16
without tweaking anything. I am running on:

  dimensions:    3200x1800 pixels (846x476 millimeters)

with internal display and simple FullHD on external and the only thing
that needs restarts between switches are browsers (both Firefox and
Chromium), the rest of the GNOME switches automatically based on the
plugged-in monitor.

O.
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Re: Debian with HiDPI / 4K displays

Vincent Bernat-3
 ❦ 12 août 2015 15:30 +0200, Ondřej Surý <[hidden email]> :

> Try Debian stretch - it mostly works out of the box with GNOME 3.16
> without tweaking anything. I am running on:
>
>   dimensions:    3200x1800 pixels (846x476 millimeters)
>
> with internal display and simple FullHD on external and the only thing
> that needs restarts between switches are browsers (both Firefox and
> Chromium), the rest of the GNOME switches automatically based on the
> plugged-in monitor.

Chromium triggers a change when it detects a RandR event (while all
other apps are listening to the appropriate GTK or Gnome property). In
my case, it seems that Chrome is slow enough to handle that when all
other properties to be up-to-date, so it adapts automatically on DPI
change. But maybe this is not your case.
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