[webkit-dev] 48459: Glyphs in vertical text tests are rotated 90 degrees clockwise on Windows

Koji Ishii kojiishi at gluesoft.co.jp
Fri Feb 24 12:14:37 PST 2012

Hi webkit-dev,

I was looking into bug 48459: "Glyphs in vertical text tests are rotated 90 degrees clockwise on Windows"

and found that it has two issues:

1. It does not support text-orientation[1] property as OS X does.

2. It uses @-font, which lets Windows do a magic to rotate some code points and apply 'vert' automatically. But that means WebKit has no control over the glyph orientations, and therefore orientation of some code points don't match to the one on OS X.

I think the correct fix for the bug is to port showGlyphsWithAdvances from FontMac.mm to FontCGWin.cpp.

But I then encounter an issue that WebKitLibraries does not support CTFontGetVerticalTranslationsForGlyphs API.

Since Windows doesn't have such API, possible options I can think of are:

1. Bring the CTFontGetVerticalTranslationsForGlyphs API to WebKitLibraries.
2. Use other libraries such as FreeType[2] to read related OpenType tables.
3. Read raw tables using GetFontData Win32 API and parse vhea/vorg/vmtx tables etc.

I have no idea how I can make option 1 happen.

Any suggestions?

[1] http://dev.w3.org/csswg/css3-writing-modes/#text-orientation
[2] http://freetype.sourceforge.net/license.html


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