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[ft-devel] last bugs before 2.2 release

From: David Turner
Subject: [ft-devel] last bugs before 2.2 release
Date: Thu, 16 Mar 2006 10:17:14 +0100
User-agent: Thunderbird 1.5 (Windows/20051201)

Hello everyone,

I've been trying to get rid of the last annoying bugs before the 2.2 release, and it's not
really an easy task. The bugs are the following:

A/ When RGB hinting mode is used, the advance of certain fonts is broken.
For example, when selecting Vera Serif at 12 points / 96 dpi on my desktop,
    the word "at" appears with its two letters completely stuck

B/ When RGB hinting mode is also used, some fonts appear larger than usual
    (e.g. Vera Sans at 10 points / 96 dpi on my desktop)

I also discovered a new one:

C/ When selecting a size that corresponds to an embedded bitmap strike in a TrueType font, the rendering of hinted outlines is also different from what we had in previous

It turns out that bug A/ is rather old, and is a consequence of the hinting algorithm that we've not spotted yet. It is at least present in 2.1.9, and not something that can be easily fixed at the moment. I guess we'll release 2.2 with it; trying to fix it for 2.2.1

Bugs B/ and C/ come from the changes to the code introduced with the new FT_Size_Request functions. They come from subtle differences in the way some computations are performed (especially in the TrueType driver). Basically, when libXft/Cairo asks for 10points/96 dpi though FT_Set_Char_Size, this creates 'x_scale' and 'y_scale' values that are slightly different from the ones computed in previous releases (which were all consistent), even though the 'x_ppem' and
'y_ppem' are the same

I don't know at the moment if I'll be able to correct this quickly. If not, I'll simply remove the new FT_Size_Request functions and bring back the old implementation throughout the engine.

More news in a few days,


- David Turner
- The FreeType Project  (

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