[cairo-bugs] [Bug 20779] text improperly positioned - scaled font glyph device transform misapplied

[bugzilla-daemon at freedesktop.org]

http://bugs.freedesktop.org/show_bug.cgi?id=20779





--- Comment #2 from Tony Garland <tony3 at GarlandConsulting.us>  2009-03-21 15:29:55 PST ---
Hello Behdad,

Being a novice at cairo, I am not in a position to understand all the
subtleties of the description which you helpfully posted.  But I did want to
clarify that I don't think the operation I'm seeing is related to the patch--at
least it isn't at all intuitive that it would be.

I've carefully looked through all the differences introduced by the patch. The
patch creates some new files, but makes only very minor modifications to
existing cairo files--none of them related to the use of the device_transform
or glyph rendering.

The purpose of the patch is to make it easier to make use of freetype fonts
without having fontconfig available to correlate font characteristics to a
specific font file.  I think this idea is mentioned in the roadmap:

    cairo 1.12 (2010?)
    • David Turner's cairo-ft rewrite. (behdad)

The particular file in question (cairo-scaled-font.c) is not affected by the
patch I referred to.  Thus, it is the unmodified file from version 1.8.6 of
cairo-scaled-font.c that I had to modify to correct the problem.

Perhaps there are some subtleties that go beyond my meager knowledge of cairo
that would explain why I had to modify the code. But, as I say, the patch
differences are extremely minor and have no direct bearing on the
device_transform use for glyphs.  It simply uses cairo with freetype to open
and read a truetype file and the resulting glyph origins wind up being applied
in the reverse direction than they should so the text outside of the clip
region.

So, in summary: a) I don't see how the patch would cause the problem I'm
seeing; b) the change had to be made in the latest version of
cairo-scaled-font.c which was not modified by the patch.


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