304946 - X11: system wide DPI change ramifications not regarded in document

Status: RESOLVED WONTFIX

(www.mozilla.org :: General, defect)

Description

[Daniel Kabs, reporting bugs since 2002]

The page "Mozilla DPI-related Font Size Issues on Unix" is about the text size
of the Mozilla UI font (not the HTML content of displayed pages).

The first approach is to set the X-Servers DPI resolution correctly.

While this approach is fine, one should not fiddle with the correct 
screen dimensions in order to get Mozillas UI displayed satisfactory, because
changing the X-Servers DPI resolution affects other applications, too.

This is fact is not reflected in the documentation.

Comment 1

[Daniel Kabs, reporting bugs since 2002]

Suggestion: Add the following lines to mozilla-org/html/unix/dpi.html (or
something to this effect)

<p>
<b>Hint:</b>
Changing the display resolution does also affect the appearance
of text in other applications. While fiddling with DisplaySize, make sure to 
check the impact on other applications. If other applications display
satisfactory and only the size of the Mozilla UI is unsatisfactory use the CSS
solution below.
</p>

Comment 2

[Felix Miata]

My initial inclination is to WONTFIX this as redundant:

The very first paragraph under the heading "DPI Problem Solving" is about
getting the DPI correctly set at the system level (X server), so it naturally
follows that the impact of any tweaks one makes is a systemwide impact, and that
tweaking the setting toward or away from literal correctness will impact more
than just Mozilla.

However, I'm leaving open now for others' input and possible language tweaking,
and changing owner to default to prevent anyone from thinking I'm the only one
who could change the page.

Comment 3

[Daniel Kabs, reporting bugs since 2002]

It might seem naturally to you that tweaking the DPI settings at the X Server
level affects the appearance of other programs, too, but it might not for the
"average user".

Thus I think a small hint is warranted. Just to make sure, readers set the DPI
*accurately* and do not tweak and bend the dimensions until Mozilla looks good
(succeeding with a dpi value far off the accurate resolution).

As suggested in http://en.tldp.org/HOWTO/FDU/x-config.html#AEN185
 "It is important that the dpi resolution be accurate"


So "DPI Problem Solving" should stress to set *accurate* dpi values and not a
values that make (just) Mozilla look good.

Consequently, the following paragraphs including the "brute force" methods
should be moved somewhere else (or removed altogether) because these settings
are not system wide but affect mozilla only. Having said that, for me these
methods do not work. Did your Mozilla change anything when you change
"Appearance->Fonts->Display resolution"? Mine does not.

Comment 4

[Daniel Kabs, reporting bugs since 2002]

To make a long story short :-) The document should maintain the following workflow:
1. Set accurate DPI resolution
2. Change fonts sizes using CSS.

By the way: For step #2 it would be nice to change some *global* css files so
that the changes do not have to be done in every provile using /userChrome.css/ .
Otherwise, every user has do install /userChrome.css/ into every profile he/she
uses.

Comment 5

[Felix Miata]

Regarding "It is important that the dpi resolution be accurate":

Setting DPI "accurately" is very often counter productive. It is well known
among web page authors that the most widely used operating systems by default
rarely use an accurate DPI setting. Those systems are set by default by the OS
producer to 96 DPI regardless what the actual hardware configuration and
resolution are. Only recently have some OEMs begun setting some of their higher
resolution systems to anything else, in almost every case 120 DPI. Both 96 and
120 thus set nearly always render text objects larger than the size an accurate
DPI would render. Note on http://members.ij.net/mrmazda/auth/dpi.html the two
most common resolutions (800 wide & 1024 wide) on the two most common display
sizes (15" nominal/14" actual and 17" nominal/16" actual) produce DPI values as
low as 62.5 only up to 91.4.

It is in this context of erroneous DPIs that most web page authors produce their
web pages, with most expecting cross-platform standards-compliant browsers to
render their pages "the same" regardless of OS. By setting DPI accurately, fewer
pages will render as their authors expect or intend.

Regarding: 'Did your Mozilla change anything when you change
"Appearance->Fonts->Display resolution"? Mine does not.':

Whether changing this setting changes anything depends on your OS and build
type. Bug 114270 applies to most Mozilla users. On these Linux builds:
  mozilla.org:
    Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8b4) Gecko/20050811 SeaMonkey/1.0a
    Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8b3) Gecko/20050712 Firefox/1.0+
  Mandriva:
    Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.11) Gecko/20050730
    Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.10) Gecko/20050719
Firefox/1.0.6 Mandriva/1.0.6-5mdk (2006.0)

changing Appearance->Fonts->Display resolution has no effect on the browser UI,
but does affect web content using DPI based sizing methods (e.g.
http://members.ij.net/mrmazda/auth/PointsDemo.html ). If you want to use DPI to
change Mozilla controls on GTK2 Linux, you'll need to set DPI at the system
level, where it generally works as expected, depending on your distro version's
X server implementation. If that is unacceptable to you, you'll just have to not
adjust Mozilla by tweaking DPI, unless and until such time as Mozilla is changed
to apply browser.display.screen_resolution to the UI as well as content.

The subject page is not intended to be a full-fledged HOWTO on fixing problems
on Linux, but only to list common issues involved, and to offer some suggestions
for coping with them. Note the page title.

Comment 6

[Justin Wood (:Callek)]

As far as "a global CSS file for every user" I disagree with this document even
talking about it.

For one simple fact, once the dpi is correct, defaults are generally good as the
default. and thusly, not every user will have the same eyesight as you, and may
want smaller or need larger font to work professionally.

I agree with MrMazda on this, personally.

Comment 7

[Daniel Kabs, reporting bugs since 2002]

(In reply to comment #6)
> As far as "a global CSS file for every user" I disagree with this document 
> even talking about it. 

The reasoning behind the idea of manipulation a *global default* comes from an
administrator's point of view: If you set up Mozilla on a desktop machine and
find out that - after setting DPI correctly - the default does not look good, it
would be easier to modify the defaults globally than to teach every user to use
userChrome.css in *every* profile.

> For one simple fact, once the dpi is correct,
> defaults are generally good as the default.

This brings us back to the question, to what values one should set the DPI
resolution to: accurate to reflect the correct display dimensions or to make
Mozilla look good?

> ... not every user will have the same eyesight as you...

That's true. If you care about "visually impaired people", don't you agree that
Mozilla should offer an easy way to change UI font size? Fiddling with
userChrome.css does not count as "easy", I guess :-) Something like
Preferences->Fonts->DisplayResolution. But that does not work, as MrMazda
explained. :-/

Comment 8

[Daniel Kabs, reporting bugs since 2002]

Hello Felix.

> Regarding "Setting DPI accurately is very often counter productive."

Thanks for introducing me into the world of DPI issues. I did not know the
ramifications of setting DPIs correctly. Sounds like I opened pandora's box.

Maybe that's a good point to tell you why I am interested in that topic:
I just installed Debian Linux (replacing SuSE) and feel that the Mozilla UI
fonts are rendered too big. Searching for a solution, I came to the "Mozilla
DPI-related Font Size Issues on Unix" document. As I've already set the fonts
sizes for KDE applications through it's "Control Center" (10 pt. for Konsole and
11 pt. for general), changing the X-Server DPI setting away from it's "correct"
value to make Mozilla UI fonts look satisfactory would render the fonts in KDE
(and other applications) smaller. I was trapped.

I was looking for a "reference" to set up my system correctly. And starting with
"set accurate DPI resolution" sounded reasonable.

On the other hand, I understand your arguments against "setting DPI accurately".
As you can see from my other bug reports in bugzilla, I also create web pages
and thus need Mozilla (which runs on Linux) to render pages "the same" as on
Windows.

So what to do now?

> Regarding: "Appearance->Fonts->Display Resolution"

Thanks for pointing me to bug #114270. I also checked your page
http://members.ij.net/mrmazda/auth/PointsDemo.html using Mozilla on Windows.
Even on Windows, setting Display Resolution in Mozilla Preferences does not
change the rendering of your page. If this setting is disregarded by Mozilla,
why is it there in the first place (mh, I see, that question belongs to bug
#114270, let me try again :-) If this setting is disregarded by Mozilla, why
does dpi.html refer to it?

Comment 9

[Daniel Kabs, reporting bugs since 2002]

(In reply to my comment #8)
> > Regarding: "Appearance->Fonts->Display Resolution"

Looking at http://members.ij.net/mrmazda/auth/dpi-screen-window.html I just
learned that this setting DOES change the appearance of the contents of the
page. My fault, sorry. 

I also figured, that this setting affects not only the content but also the user
interface ONLY when userChrome.css is used. Have a look at my screenshots:
http://www.mobotix-service.de/~daniel/DisplayResolutionAndUI.gif 

Bug or feature?

Comment 10

[Daniel Kabs, reporting bugs since 2002]

I learned, DPI settings involves a lot of issues. And it's rather an expert
topic. Still beginners might read that document.

Thus I'd like to sustain my suggestion, that the section "DPI Problem Solving"
should be amended to explicitely mention that setting DPI has system wide impact
and affects the appearance of other applications. For the expert it might
"naturally follow" that fiddling with DPI settings at the X Server level affects
global rendering but I think, it would be a good idea to write that down.

He, it's just costs a few words more. Just to make sure, everybody understands
that if they tweak X-Server's DPI settings too much, Mozilla might look good,
but Konqueror not any more :-)

My second motion was to introduce a kind of workflow (1. set DPIs correctly, 2.
fiddle with userChrome.css) but I understand that "setting DPIs correctly" is
not without issues. So I see this motion overruled. Still for me, it's just
logical to start with setting an "accurate DPI resolution". Shouldn't we try to
be better than windoze? :-)

Comment 11

[Daniel Kabs, reporting bugs since 2002]

Resolved as I WONTFIX it. :-)

Comment 12

[Felix Miata]

For those not aware of the origin of the 96 DPI assumption: http://blogs.msdn.com/fontblog/archive/2005/11/08/490490.aspx