Re: [ft-devel] A few bugs

[David Turner]

On Tue, 20 Mar 2007 10:25:14 -0300, "Charles A. Landemaine" <address@hidden> 
said:
> Hello, I don't know if this the right place to report bugs, but on
> your web site I haven't found any bug-reporting tool.
> 
> There are several fonts that look nice on Windows but with freetype,
> they are not drawn properly, for instance letters like "w", "v", and
> the letter "3" or "6" are dirty.
> 
> In this screenshot:
> http://home.comcast.net/~ddamian/ubuntu/howto/firefox_nonaa_ubuntu.png
> look at the 'v' in 'privacy' and 'advanced', the W in 'Web features',
> the 'x' and 'm' in 'Linux Forums'.
> 
> This has been discussed in this thread:
> http://ubuntuforums.org/showthread.php?t=20976&page=14
> 
> The same page looks perfect in Windows and the aforementioned letters
> don't have these issues in Windows.
> Thanks,
> 

Sadly, this is not very informative. There is no detail about which version
of FreeType is being used, or even which version of the Arial font file is
being used (yes, there are several ones), or the screen DPI being used by
this user's configuration. I assure you that the text is not 9pt Arial at either
72 or 96 dpi, the most common values.

I cannot reproduce any of these problems on my workstation with the current CVS,
or with 2.3.1. I've been hacking the bytecode interpreter lately to try to get
rid of some regression introduced in 2.3.2 as well as get rid with some 
differences
with the Windows rasterizer, but I'd like to remark that:

- the problem is not simple. There are various ambiguities in the TrueType spec
  as to how to perform various computations. Moreover, some bytecode programs
  unfortunately depend on the way the engine performs rounding and 
approximations
  for subtle operations like interpolation and intersections.

  we even found bytecode programs that were specifically designed to work around
  computational bugs in the Windows engine

- there are several TrueType engines from Microsoft, and each one of them has
  subtle differences from the other ones. This is generally hard to see, but I
  guarantee you that some new fonts would hardly render properly on a Windows 
3.1
  machine, or even a Windows 95 one.

  that also explains why there are so many versions of Arial or Times.

- if you think you have a solution to this problem, we'll be able to consider it
  for inclusion in the source code.

- also, you might be experiencing a bug that only appears at some weird DPI
  setting (e.g. 92 or 95 dpi). Try to set Windows to the same setting and see
  if it still renders everything perfectly. You might be surprised :-)

Regards,

- David Turner
- The FreeType Project  (www.freetype.org)


> -- 
> Charles A. Landemaine.
> 
> 
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