Imager::Threads - Imager and threads
use Imager;
use threads;
Imager->preload;
threads->create(...);
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.
Tony Cook <tony@cpan.org>