NAME¶
Imager::Threads - Imager and threads
SYNOPSIS¶
use Imager;
use threads;
Imager->preload;
threads->create(...);
DESCRIPTION¶
Starting from version 0.94 Imager attempts to work safely with perl's
"ithreads".
Previous versions stored some state in global variables, in particular the
internal error stack.
However there are some limitations:
- •
- Imager's debug malloc isn't thread safe and will never be. Imager's debug
malloc is disabled by default.
- •
- "libtiff", which Imager uses for TIFF file support is not thread
safe, "Imager::File::TIFF" works around this by single-threading
its access to "libtiff".
- •
- "giflib", which Imager uses for GIF support is not thread safe
before version 5. "Imager::File::GIF" works around this by
single threading its access to "giflib".
- •
- "T1Lib", used by one of Imager's font drivers, is not thread
safe. "Imager::Font::T1" works around this by single threading
access.
- •
- killing a thread reading or writing TIFF or GIF files, or using T1 fonts
through "Imager::Font::T1" may deadlock other threads when they
attempt to read or write TIFF or GIF files, or work with Type 1
fonts.
- •
- Fill, font, color or I/O layer objects created in one thread are not valid
for use in child threads. If you manage to duplicate such an object in
another thread, you get to keep both pieces when it breaks.
Note that if you have another module using "libtiff",
"giflib" or "t1lib" it may interact with Imager's use of
those libraries in a threaded environment, since there's no way to co-ordinate
access to the global information "libtiff", "giflib" and
"t1lib" maintain.
Imager currently doesn't use threads itself, except for testing its threads
support.
SEE ALSO¶
Imager, "threads"
AUTHOR¶
Tony Cook <tony@cpan.org>