nanogui: Thread: Re: utf8 to utf16 in nanox

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Subject: Re: utf8 to utf16 in nanox
From: "Greg Haerr" ####@####.####
Date: 29 Apr 2010 03:53:41 -0000
Message-Id: <036801cae74f$874ddca0$6564a8c0@winXP>

YuTao - 

The logic sounds correct, I believe that twice the input string
character count should work.  However, it appears that both
the buffer in GdGetTextSize, as well as the buffer in 
GdConvertEncoding will have to be auto-allocated.  This
is also complicated by the fact that the cc count can be
set to -1, and the string length is checked after the
call in GdGetTextSize, so that strlen() code may have
to be moved up.  Thus your patch directly as written
will need more code, and cc to be calculated in the
case it is -1.

I would jump into this but don't have good test data.
Also, use the ALLOCA macro, and call FREEA 
when done, as not all systems support alloca.

Another solution would be to increase the size of the
first char buf[2048] in GdGetTextSize and char buf16[1024]
in GdConvertEncoding.  GdConvertEncoding should
count space and not overfill the buffer, there's a comment
in that routine to this effect.

Let me know how you'd like to proceed.


  ----- Original Message ----- 
  From: YuTao 
  To: Greg Haerr ; kavedai 
  Cc: ####@####.#### ; ####@####.#### 
  Sent: Wednesday, April 28, 2010 4:58 AM
  Subject: utf8 to utf16 in nanox

  Hi Greg:

  In GdGetTextSize (src/engine/devfont.c), it will use GdConvertEncoding to convert the input string (utf8) to utf16 (utf8_to_utf16, when the input is utf8), then get text size in the font (pfont->fontprocs->GetTextSize).

  You have added a FIXME in it:
  /*FIXME: if buf is not big enough, buf overflow may cause exceptions!!!!*/
  src/engine/devfont.c, line 986

  It is really a critical issue.

  It will crash when input string is large than 520 for a certain ttf font.

  - unsigned long  buf[256];
  + unsigned long *buf = (unsigned long *)alloca(2*cc);

  could you check this patch ?
  the max of utf8 is 4 bytes, the utf16 is 2 bytes. so the twice of input string should be enough?

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