386606 - char ​ (zero width space) now rendered incorrectly

Status: RESOLVED FIXED

(Core :: Layout: Text and Fonts, defect)

Description

[p.ernst]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.2) Gecko/20070222 SeaMonkey/1.1.1
Build Identifier: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9a6pre) Gecko/20070702 Minefield/3.0a6pre

After Bug 9101 "(shy) – Break lines at soft hyphens (­)..." was reported to be fixed, I found the following behavior:

Yes, ­ is working now.

But the character ​ (zero width space) is rendered now incorrectly (which used to be fine before the fix). The line breaking behavior is correct, but a square is rendered for this character instead of just nothing.

Reproducible: Always

Steps to Reproduce:
1.TestText​TestText​TestText
2.
3.

Comment 1

[Ryan VanderMeulen [:RyanVM]]

The tests at the bottom of that page WFM on XPSP2.

Comment 2

[j.j.]

(In reply to comment #1)
> The tests at the bottom of that page WFM on XPSP2.

Yes, works on Windows XP
Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9a6pre) Gecko/20070630 Minefield/3.0a6pre

Comment 3

[Magnus Melin [:mkmelin]]

Seems WFM on Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9a6pre) Gecko/20070702 Minefield/3.0a6pre ID:2007070204 too

Comment 4

[p.ernst]

Attachment: screenshot of new bahavior

This is how ­ and ​ are rendered on my display.

Comment 5

[p.ernst]

Attachment: screenshot with firefox-2.0.0.4 (same display/profile) Mozilla/5.0 (X11; U; Linux i686; en-GB; rv:1.8.1.4) Gecko/20070515 Firefox/2.0.0.4

This screenshot was taken on the same computer with firefox-2.0.0.4.

Comment 6

[j.j.]

(In reply to comment #4)
> This is how ­ and ​ are rendered on my display.

Probably a problem with some fonts?
http://www.quirksmode.org/quirksmode.css uses "georgia,times,serif".

Your font doesn't look like georgia. Which font is used?

Comment 7

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Please check your testcase in a build from, say, last week. I think you'll find that the soft hyphen changes I just landed were not responsible for this regression, that it happened earlier.

This is probably a bad font. We can work around it, but I'd like to verify that it's a font issue first.

Comment 8

[p.ernst]

> Your font doesn't look like georgia. Which font is used?

I created a simple HTML page with 
"TestText​TestText​TestText&#8203..."
and tried different font settings in Firefox Preferences.

Fonts are influencing the problem, however I see this problem with most of the
fonts.

With these fonts the problem remains, e.g.
Adobe Courier, Adobe Helvetica, Adobe Times, Arial, Georgia, cmr10, 
SUSE Serif, Courier New, etc.

A few fonts don't show anything wrong: .e.g. Courier

With "Gnu Unifont", a small glyph saying "NUL" is displayed at the positions
of ​.

I tested the situation again with the binary release granparadiso/alpha5
(Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9a5) Gecko/20070605 GranParadiso/3.0a5):

It is as you expected: the problem with the squares at the 8203 positions is already visible in this version, and therefore does not seem to be related with the soft hyphen fix.

I tested it also with granparadiso/alpha1, and already here I see the small squares.

Comment 9

[Robert O'Callahan (:roc) (email my personal email if necessary)]

OK. Does anyone else see the problem with those fonts?

What version of Pango do you have?

Comment 10

[p.ernst]

(In reply to comment #9)
> What version of Pango do you have?

pango-1.8.1-4 SuSE Linux 9.3 (i586)

Comment 11

[j.j.]

Attachment: testcase using some different fonts

Comment 12

[philippe (part-time)]

On OS X  10.4.10, ppc - and using the testcase mentioned in comment 8, I see what looks like a full space (U+0020) where the zero-width space is. This happens with most of the default OS X fonts, except Lucida Grande. That includes the MS fonts shipped with the OS (Arial, Trebuchet MS, Georgia, Times New Roman).
Some mono-space fonts work correctly: Monaco, Courier.

I can go back quite a long time - so far 'till the 20070524 Minefield build.

(I double checked the test file using the latest WebKit build and Opera 9.2 - both where correct for all fonts).

Comment 13

[j.j.]

Attachment: testcase using more fonts

Comment 14

[p.ernst]

I compiled different versions of Pango and tested them with a current
build (changing LD_LIBRARY_PATH).

I get
broken "zero width space" display with Pango versions <= 1.10.4.

I get 
correct "zero width space" display with Pango versions >= 1.12.0.

(tested with glib-2.12.12)


Firefox-2.0.0.4 always shows a correct display, independent of the
version of Pango (tested with 1.8.1, 1.10.4, 1.12.0).

Comment 15

[Adam Guthrie]

Thanks for that information, p.ernst! I just thought I'd point out that per the (tentative) Linux runtime requirements for Firefox 3, we'll require versions of Pango 1.14.x and greater. http://wiki.mozilla.org/Linux/Runtime_Requirements

Comment 16

[Robert O'Callahan (:roc) (email my personal email if necessary)]

This should be fixed, even for old Pangos, by the patch I just checked in (associated with bug 385423).

Comment 17

[p.ernst]

Attachment: reftests for soft-hyphen and zero-width-space

Comment 18

[p.ernst]

Attachment: reftests for soft-hyphen

Comment 19

[p.ernst]

Attachment: reftests for soft-hyphen

Comment 20

[p.ernst]

Attachment: reftests for soft-hyphen

Comment 21

[p.ernst]

Attachment: reftests for soft-hyphen

Comment 22

[p.ernst]

Attachment: reftests for zero-width-space

Comment 23

[p.ernst]

Attachment: reftests for zero-width-space

Comment 24

[p.ernst]

Attachment: reftests for zero-width-space

Comment 25

[p.ernst]

Attachment: reftests for zero-width-space

Comment 26

[Robert O'Callahan (:roc) (email my personal email if necessary)]

I'd make the container width little bigger, maybe 100em, just in case there are really bad fonts out there. Also the reference testcase is usually called "-ref.html". Other than that, these look good and could be put under layout/reftests/text. Thanks!