Re: [Devel] bug with MSung-Light-Acro

[David Turner]

Hello Edward,

"Edward G.J. Lee" a écrit :
> 
> Hello,
> 
> On Thu, Dec 20, 2001, Werner LEMBERG wrote:
> >
> > I've found an interesting bug in the font MSung-Light-Acro (CJK
> > extension for Acroread; copyrighted 1998; I think I have version
> > 3.001; size 6665200 Bytes).
> >
> > Using `ftview -f 2027 48 MSung-Light-Acro', look at glyph 2027.  It is
> > displayed two times!  Reducing the size, the doublette vanishes.
> > Switching AA off, you even get corrupted glyph images while zooming
> > in...
> 
>   If I display via pfaedit or old version ftview(use CVS libfreetype),
>   CNS1_2027 display one time only.
> 
>   Maybe it's not the problem of MSung-Light-Acro?
>

It's definitely a problem with the library. I just looked at the code
for ftview, and the function "get_glyph_bitmap" (in ftcommon.i) didn't
check the error result of FT_Glyph_ToBitmap at all..

The "double" glyph could come from having glyph 2028 not being properly
rendered (for a yet-to-be-determined reason), and the code using a dangling
pointer to a previously rendered glyph (i.e. 2027). I wouldn't be surprised
if the garbage that appears was due to heap allocated data accessed through
the pointer, overwriting freed memory..

It's just an hypothesis but it's the best I can come with for now. Does
someone knows where to find this font, __please__ (and do not send it to
me via e-mail)..

I've added error checks to "ftview", could someone test the new code to
see if the doublet and garbage still appear ??


Thanks,

- David