553136 - text looks slightly worse due to increased or decreased text spacing

Status: RESOLVED FIXED

(Core :: Graphics, defect)

Description

[Timothy Nikkel (:tnikkel)]

Text looks slightly worse in recent nightlies. I noticed this on Wikipedia with fullzoom one step larger. Will attach good/bad screenshots.

Regression range
http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=17a3e86d5ec5&tochange=050887c64183
Looks like probably bug 502906.

Comment 1

[Timothy Nikkel (:tnikkel)]

Attachment: good screenshot

Screenshot of http://en.wikipedia.org/wiki/Mil_Millington where the text looks good to me.

Comment 2

[Timothy Nikkel (:tnikkel)]

Attachment: bad screenshot

Screenshot of http://en.wikipedia.org/wiki/Mil_Millington where the text looks bad to me.

Comment 3

[Jonathan Kew [:jfkthame]]

It looks like we're getting tighter character spacing for some reason. Does this happen with all text sizes and all fonts? Are you able to compare behavior on newer versions of Windows as well?

Comment 4

[Dão Gottwald [:dao]]

I see the same on XP.

Comment 5

[Jo Hermans]

This is probably the issue I mentioned yesterday on IRC, although I saw the opposite - some texts were more widely spaced. I'm on Windows XP.

Comment 6

[Timothy Nikkel (:tnikkel)]

Some texts look more widely spaced for me as well (for example the label name when looking at a message in gmail). So this is probably all the same issue.

Only some fonts and/or sizes seem to be affected. For example, Wikipedia at default zoom looks the same.

Comment 7

[Jo Hermans]

Attachment: example of wide spacing

left: Firefox 3.7a4pre (20100318)
right: Firefox 3.6

This is an example of wide spacing, but in my case it's also visible on Wikipedia (default zoom, not a single font preference changed). It looks to me that the sans-serif font is suddenly monospaced or something.

Comment 8

[Jo Hermans]

Today (Gecko/20100321), it seems to be fixed for me (comment 7), although I don't see any obvious reason why.

Comment 9

[Dão Gottwald [:dao]]

I still see this with the 20100321 nightly.

Comment 10

[Timothy Nikkel (:tnikkel)]

Whether I got too wide or too narrow spacing, and which places I saw the problem has changed, but the problem is still there for me with 2010-03-21 nightly as well.

Comment 11

[Jonathan Kew [:jfkthame]]

My guess (without having investigated properly yet) is that the issue is a difference between hinted/grid-fitted and "ideal" glyph metrics. Perhaps the issue depends on some characteristics of the device context at the point when the glyphs get measured and stored into the textruns, or how we set up the cairo font. We should be controlling this properly so that the results are consistent, of course, but something may have been missed in the restructuring of the font code.

Comment 12

[Alistair Vining]

This is certainly much more common in the last few days, but there has been a hard-to-reproduce bug with font metrics for years; it's often triggered by non-western characters in western text, but also crops up in bits of the gmail UI, e.g. the "Search, add or invite" box.  I have a bunch of screenshots from mid-2008 and it may go back further, see bug 237438 or bug 384025.  So maybe the recent changes just make it show up more.

Comment 13

[Jonathan Kew [:jfkthame]]

Interesting - yes, the screenshot in bug 237438 does look like it could be the same underlying issue, though clearly it's become more frequent since the patch in bug 502906 (part 3) landed.

Comment 15

[Joe Drew (not getting mail)]

John, I'm assigning this to you because I know you'll make sure it gets taken care of, even if you're not the one doing the taking-care-of :)

Comment 16

[earlpiggot]

It's still here, and it's on every build, and all the time at random... so annoying.
http://forums.mozillazine.org/viewtopic.php?f=23&t=1850415

Comment 18

[Sergey Sokoloff]

That's a heizenbug, very hard to reproduce reliably.

I've seen it at http://forums.kuban.ru/forum/viewforum_new.php?f=5 a number of times, sometimes only for bold font of the same family (or so I remember).

Windows XP SP3.

The bug generally disappears after I restart Firefox once or twice or thrice.

Update Notifier extension suddenly becomes very handy: it provides a toolbar button with a context menu item that restarts Firefox.

Comment 19

[Larry Snow]

FWIW, it is always reproducible at CNN.com.  Most of links produce bad looking text.  XP SP3.

Comment 20

[Justin Lebar (not reading bugmail)]

(In reply to comment #19)
> FWIW, it is always reproducible at CNN.com.  Most of links produce bad looking
> text.  XP SP3.

Not for me, at least.  All the text and links on cnn.com look the same in FF and Chrome on my machine.  Also XP SP3.

Comment 21

[WildcatRay]

Installing and/or updating an add-on--also enabling/disabling an add-on--can (often?) trigger this bug for me. However, enabling/disabling an add-on rarely untriggers it. Where I see it most often, though, is Gmail, Gmail login page, and Google Reader.

Comment 22

[Jonathan Kew [:jfkthame]]

As an experiment: Those who are able to easily reproduce this bug, I'd appreciate hearing whether the test build at

http://ftp.mozilla.org/pub/mozilla.org/firefox/tryserver-builds/[e-mail]-61ddbf901689/tryserver-win32/

behaves any differently for you. This includes one small change borrowed from bug 449292 that could potentially affect the font system, so I'm curious if it might have any impact here.

Comment 23

[Warner Young]

Jonathan, I just tested the tryserver build, but I still see this problem.  The problem doesn't seem to be completely deterministic normally, so I don't know if it's occuring with the same frequency, but I definitely saw looser character spacing on www.thedigitalbits.com and also Slashdot.

Comment 24

[John Daggett (:jtd)]

Attachment: testcase, Arial rendered at different sizes

The cause of this is bug 561304, a regression bug caused by the restructuring work done for bug 502906.  Prior to these changes, Windows font code always used GDI shaping at smaller font sizes and Uniscribe shaping for larger sizes to get kerning and ligatures.  But there's a bug in Uniscribe shaping under XP, it does weird glyph placement at some smaller sizes.  In the attached testcase note how the text for 14px Arial is smushed under XP, it renders with the same positions as 13px text.  The "weird" sizes vary by font.

Comment 25

[John Daggett (:jtd)]

More extensive waterfall test:
http://people.mozilla.org/~jdaggett/tests/decimalfontwaterfalls-default.html

Comment 26

[John Daggett (:jtd)]

Attachment: screenshot, winxp vs. win7 rendering with cleartype off

Trunk renderings on Windows XP and Windows 7, both with Cleartype disabled.  Note the funky rendering on XP with Arial at 14px.  God I love Windows...

Comment 27

[Larry Snow]

Jonathan, I too tried your build in a pristine state and still have the same problem on most links at CNN.com.

Comment 28

[Warner Young]

If this is caused by bug 561304, then zooming a problem page and increasing the font size should make the problem go away.  I just tried it on a page that had loose spacing, and it does seem to improve the character spacing when I zoom the text.

Comment 29

[Sergey Sokoloff]

I have just noticed that _decreasing_ the font size (e.g. Ctrl+minus) reliably makes the problem go away. You are very likely to be right about this bug connected with bug 561304 some way.

Comment 30

[Stanimir Stamenkov]

(In reply to comment #22)
Using the test build I don't see any difference, i.e. the problem is still visible.

Comment 31

[Jonathan Kew [:jfkthame]]

(In reply to comment #30)
> (In reply to comment #22)
> Using the test build I don't see any difference, i.e. the problem is still
> visible.

Yes, that doesn't appear to be relevant; thanks to those who confirmed this.

It seems that John's diagnosis in bug 561304 is a key to this; I still don't understand the intermittent nature of the problem, though.

Comment 32

[WildcatRay]

(In reply to comment #28)
> If this is caused by bug 561304, then zooming a problem page and increasing the
> font size should make the problem go away.  I just tried it on a page that had
> loose spacing, and it does seem to improve the character spacing when I zoom
> the text.

Is the zoom and reset to "correct" this for the test builds only? I tried on the regular nightly builds, but did not see things return to expected.

Comment 33

[Stanimir Stamenkov]

Attachment: [Screenshot] WinXP, SeaMonkey 2.0.5/Gecko 1.9.1.10

FWIW, I'm seeing the weird spacing effects happening in random places and at random times using older Gecko like SeaMonkey 2.0.5 (my primary browser).  Usually when I restart the application I'm no longer seeing the effect at the same place I've just seen.  I use a default sans-serif (Arial) font at 14px size.  The shot is taken from <http://www.w3.org/TR/html401/> - look at the sentences starting with "Public discussion" and "Please report errors".

Comment 34

[Sergey Sokoloff]

> Is the zoom and reset to "correct" this for the test builds only? I tried on
> the regular nightly builds, but did not see things return to expected.

Zoom and reset does not correct anything.

When you just zoom out (Ctrl+Minus without further Ctrl+0 resetting), you are likely to correct some spacing in the main block of text, if it was broken (however, some other text, previously rendered correctly, may become broken, e.g. headings or navigation links).

Comment 35

[Sergey Sokoloff]

(In reply to comment #33)

> FWIW, I'm seeing the weird spacing effects happening in random places and at
> random times using older Gecko like SeaMonkey 2.0.5 (my primary browser). 
> Usually when I restart the application I'm no longer seeing the effect at the
> same place I've just seen.

In Firefox 3.7 alpha 4 and nightlies that's far worse (i.e. more often), and does not automagically disappear after restart.

Comment 36

[John Daggett (:jtd)]

Try server build with bug 561304 patch v.0.1a
http://bit.ly/9GFdIO

If folks who are seeing this problem could test with this build I'd appreciate it.  If there are specific zoom settings that still produce rendering that is worse than 3.6, please try and isolate it down to a specific font family / size combination if at all possible, that would be a huge help.

Comment 37

[Larry Snow]

John, I just tried your test build and it works!  At least it does on the CNN.com links, which is where I have usually observed it.  Text looks find again just like in 3.6.

Comment 38

[Larry Snow]

I meant text looks fine again.  Is there a way to edit a post?

Comment 39

[John Daggett (:jtd)]

Problem fonts/sizes:
Arial 14px
Georgia 16px
Times New Roman 13px
Trebuchet MS 14px

Testcase showing problem fonts/sizes:

http://people.mozilla.org/~jdaggett/tests/bug553136-extended.html

Comment 40

[Stanimir Stamenkov]

Attachment: Sylfaen narrower at 18px than 17px

(In reply to comment #36)
> Try server build with bug 561304 patch v.0.1a
> http://bit.ly/9GFdIO

Looks o.k. - same as 3.6.

(In reply to comment #39)
> Problem fonts/sizes:

Using attachment 448444 [details] from Bug 561304 I'm also observing similar symptom with the Sylfaen font at 18px, but then it looks the same with 3.6, also.

Comment 41

[Stanimir Stamenkov]

(In reply to comment #40)
> Sylfaen narrower at 18px than 17px

Just to point out - font sizes 10px, 11px and 12px look the same as I have 12px minimum font size set.

Comment 42

[Warner Young]

The tryserver build works for me.  I didn't see any instances of the spacing problem on sites I commonly visit.

Comment 43

[Sergey Sokoloff]

Please land some patch (even if not final) in Firefox 3.7 alpha 5.

Comment 44

[John Daggett (:jtd)]

(In reply to comment #43)
> Please land some patch (even if not final) in Firefox 3.7 alpha 5.

The patch on 561304 is under review, that should fix this.

Comment 45

[John Daggett (:jtd)]

Fixed in bug 561304.  If you're still seeing problems, reopen.