Test results: Webfonts, font linking

Summary & conclusions

See the results below for user agents tested. This section summarizes the results of those tests.

It is important to note that support for webfonts is work in progress at the time of writing. Upcoming versions of Safari, Opera and Firefox are expected to perform better against these tests.

Of the browsers tested, only Safari currently supports webfont linking at all.

Support in Safari is slightly different for Windows and the Mac. On Windows none of the text that used OpenType features was supported in the webfont text, although the text styled with the installed font worked well in all but two cases (small rendering issues for one Arabic font, and complete failure for the Urdu Nastaliq font). The version of Uniscribe used for the test was the same as that used for the reference graphics, and quite recent. Note that rendering difficulties appear in some scripts if an older (more commonly installed) version of Uniscribe is used.

On the Mac, the situation is a little more complicated. With one exception, the font linked text was the same as the installed font text. It is not currently clear what is the baseline regarding operating system support for these scripts, so we cannot be clear about why the complex script text didn't render like the reference graphic, but it is likely (since the installed font exhibited the same problems) that operating system support is the issue.

One Windows test was run with an older version of Uniscribe and this made a difference to the rendering of the installed text in Khmer. This clearly illustrates the importance of operating system support as well as the font.

As a general summary, out of the user agents tested, font linking is only supported on Safari, but even then support for complex scripts is not available on Windows. The availability of the underlying operating system to render OpenType features is clearly an additional important factor in the successful production of complex script text, and probably a particular issue for interoperable solutions in this area.

Latest results

These are results for the latest versions of each browser tested. A green background (yes) means the browser displayed the text using the linked font in the same way as the text using the installed font; orange background (partially) means that the browser was obviously attempting to use the linked font, but some of the rendering was not correct; red (no) means that the browser did not use the linked font.

The check and cross marks are used to indicate the following: green means that the installed font text was the same as the reference graphic; orange means that there were some differences of rendering, but the same font was used. A red cross means that the installed font text was substantially different from the reference graphic. If a check mark is the same color as the background it is omitted.

A red cross on a green background signals that it appeared that the installed font was not being used, at least for portions of the text.

An orange check mark on a green background points to rendering issues that may be produced because the font relies on the operating system for such rendering.

A green check mark on a red background clearly indicates that the font linking mechanism has failed to produce the right result.

Most XP tests were run using a very recent Uniscribe version, 1.626.5756.0. Unless you have this version installed, your results may differ. One test was also reported with everything the same except for the version of Uniscribe used (1.420.2600.5512 - the version that came with XP SP3); this version of Uniscribe doesn't support Khmer, and you can see the difference.

UA	IE	Firefox	Firefox	Chrome	Opera	Safari	Safari	IE
version	7	3.0.1	3.0.1	0.2.149.30	9.51	3.1.2	3.1.2	8 Beta
OS	XP, SP3	XP, SP3	XP, SP3	XP, SP3	XP, SP3	Mac OS 10.4.11	XP, SP3	XP, SP3
Uniscribe version	1.626.5756.0	1.626.5756.0	1.420.2600.5512	1.626.5756.0	1.626.5756.0	n/a	1.626.5756.0	1.626.5756.0
date	20080907	20080907	20080923	20080907	20080907	20080918	20080907	20080907
1 Alphabetic script (Georgian)	no	no	no	no	no	yes	yes	no
2 Alphabetic script (Armenian)	no	no	no	no	no	yes	yes	no
3 Complex scripts (Khmer 1)	no	no	no 6	no	no	yes 6	no 1	no
4 Complex scripts (Khmer 2)	no	no	no 6	no	no	yes 6	no 2	no
5 Complex scripts (Hindi 1)	no	no	no	no	no	yes 7	no 3	no
6 Complex scripts (Hindi 2)	no	no	no	no	no	yes 7	no 3	no
7 Shaping scripts (Arabic 1)	no	no	no	no	no	yes 8	no 4	no
8 Shaping scripts (Arabic 2)	no	no	no	no	no	partially 9	no 3	no
9 Shaping scripts (Urdu)	no	no	no	no	no	yes 10	no 5	no
10a Mixed scripts (Thai)	no	no	no	no	no	yes 11	no 3	no
10b Mixed scripts (Tibetan)	no	no	no	no	no	yes 12	no 3	no
10c Mixed scripts (Myanmar)	no	no	no	no	no	yes 13	no 3	no

Notes:

1. Linked font text was blank. System default font text was blank. The installed font text was exactly the same as the reference graphic except that the KHMER VOWEL SIGN I was rendered slightly higher.
2. Linked font text was blank. System default font text was blank.
3. Linked font text was blank. System default font text was not blank.
4. Linked font text was blank. System default font text was not blank. A few small discrepancies in glyph advance spacing between installed font text and reference graphic that need to be fixed.
5. Linked font text and installed font text blank.
6. Though the linked and installed font texts were identical, they exhibited the following differences from the reference graphic: subjoined consonants were not subjoined and the virama was visible; KHMER LETTER PHO and KHMER VOWEL SIGN AA were not correctly ligated; KHMER VOWEL SIGN I was rendered too high; KHMER VOWEL SIGN OO does not surround its base character.
7. Though the linked and installed font texts were identical, they exhibited the following differences from the reference graphic: conjuncts were not formed and viramas were visible; left-side vowel signs appeared to the right of the base character.
8. Though the linked and installed font texts were identical, they exhibited significant differences from the reference graphic, and the results are unusable. The installed font appears to use the correct font for only a few letters, and a different font for the others. Diacritics are displayed over a baseline extension. Contextual forms and ligatures are not displayed the same, even if in apparently the same font.
9. Linked and installed font texts use the same font, but not the same font as the reference graphic. The linked font differs from the installed font in that it displays certain combining characters (shadda and anything following the shadda) over a baseline extension character.
10. Linked and installed font texts use the same font, but it is not a Nastaliq-style font. It is not the default system font either (though similar).
11. Positioning of tone marks is not context-sensitive in the installed font.
12. Stacking of subjoined consonants is not correct in the installed font.
13. No combining characters combined, nor positioned to left of base character.