Status

()

3 years ago
3 years ago

People

(Reporter: netrolller.3d, Unassigned)

Tracking

38 Branch
x86_64
Windows 7
Points:
---

Firefox Tracking Flags

(Not tracked)

Details

(Whiteboard: [gfx-noted], URL)

(Reporter)

Description

3 years ago
Some types of diacritics appear to cause kerning pairs to be drawn incorrectly.

The following two lines should have the same width when rendered in a variable-width font (e.g. Times):
SZILVASVARAD
SZILVÁSVÁRAD
(name of a town in Hungary, without accents, then correctly spelled)

In the correctly accented versions, there is excessive space between V and Á.

A more aggressive test case is available at the URL. For maximum visibility, enter this in the right box:
VAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVA
VAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVA
VAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVA
VAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVA
VAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVA
Each line will have different lengths after diacritics are added. (Page uses Unicode combining diacritics, but also reproducible using precomposed characters.)

The bug is not confined to uppercase letters; anything with kerning pairs in it will cause problems. E.g. the following renders wrong when pasted into the referenced page:
rdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrd
rdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrd
rdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrd
rdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrd
rdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrd
rdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrdrd
This sounds like a font limitation rather than a browser bug. If the font you're using (e.g. Times New Roman) has a kerning pair for <V, A> but does not have one for <V, Á> (for example), then clearly you won't get kerning between those characters.

In the case of the http://www.marlborotech.com/Zalgo.html page, there's the added issue that it's quite likely some of the combining diacritics it's using will not be available in the main font, and therefore will cause fallback to some other font; and this will interrupt the text run for the purposes of glyph shaping (such as kerning).
Whiteboard: [gfx-noted]
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