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[libpng17] Changed user chunk callback API to respect global and per chunk

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defaults.  Previously a return of 0 from a user chunk callback would result in
the chunk being saved (if this was safe, even if the chunk was unsafe-to-copy);
this change respects the defaults set by the application, so unknown chunks
can be discarded by default and known-safe ones preserved.
This commit is contained in:
John Bowler
2013-03-02 21:39:44 -06:00
committed by Glenn Randers-Pehrson
parent 6152dbd424
commit ec89aefb44
6 changed files with 68 additions and 63 deletions
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34
pngrutil.c
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@@ -2801,37 +2801,19 @@ png_handle_unknown(png_structrp png_ptr, png_inforp info_ptr,
if (ret < 0)
png_chunk_error(png_ptr, "error in user chunk");
else if (ret == 0)
{
/* If the keep value is 'default' or 'never' override it, but
* still error out on critical chunks unless the keep value is
* 'always' While this is weird it is the behavior in 1.4.12.
* A possible improvement would be to obey the value set for the
* chunk, but this would be an API change that would probably
* damage some applications.
*
* The png_app_warning below catches the case that matters, where
* the application has not set specific save or ignore for this
* chunk or global save or ignore.
*/
if (keep < PNG_HANDLE_CHUNK_NEVER)
{
# ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
if (png_ptr->unknown_default < PNG_HANDLE_CHUNK_IF_SAFE)
png_app_warning(png_ptr,
"forcing save of an unhandled chunk;"
" please call png_set_keep_unknown_chunks");
# endif
keep = PNG_HANDLE_CHUNK_IF_SAFE;
}
}
else /* chunk was handled */
else if (ret > 0) /* chunk was handled */
{
handled = 1;
/* Critical chunks can be safely discarded at this point. */
keep = PNG_HANDLE_CHUNK_NEVER;
}
/* else: use the default handling.
* NOTE: this is an API change in 1.7.0, prior to 1.7.0 libpng would
* force keep to PNG_HANDLE_CHUNK_IF_SAFE at this point, and 1.6.0
* would issue a warning if this caused a default of discarding the
* chunk to be changed.
*/
}
else