In gimp_parallel_run_async(), lower the priority of threads
executing independent async operations. Independent operations
are generally potentially long-standing background tasks, which we
don't want to bog down the rest of the program.
This is currently only implemented on Linux and Windows.
In gimp_parallel_run_async(), when aborting a GimpAsync operation
in reponse to its "cancel" signal, properly clean up internal data
attached to the object, to avoid use-after-free if the signal is
emitted again.
(cherry picked from commit 3fa4c01bcf)
Add a boolean "independent" parameter to gimp_parallel_run_async().
When FALSE, the passed function is run in the shared async thread
pool; when TRUE, the passed function is run in an independent
thread.
Generally, async operations should run in the async pool, however,
it might be desirable to run long-standing operations, especially
ones that can't be canceled, in independent threads. This avoids
stalling quicker operations, and shutdown.
Adapt the rest of the code for the change. In particular,
initialize the font cache in an independent thread.
(cherry picked from commit ad8add6808)
In gimp_parallel_run_async(), connect to the returned GimpAsync's
"cancel" signal, and abort the operation in response if it's still
enqueued, i.e., if its execution hasn't started yet.
(cherry picked from commit 3958ffbe50)
... which runs a user-provided function asynchronously, returning a
corresponding GimpAsync object. This can be used to execute code
off the main thread, using the GimpAsync object to synchronize as
necessary.
Note that while the code allows for running multiple asynchronous
functions in parallel in a thread pool, we currently limit the pool
to a single thread, queueing overlapping async function, since we
have no use for parallel asynchronous functions at the moment.
Add gimp-parallel.[cc,h], which provides a set of parallel
algorithms.
These currently include:
- gimp_parallel_distribute(): Calls a callback function in
parallel on multiple threads, passing it the current thread
index, and the total number of threads. Allows specifying the
maximal number of threads used.
- gimp_parallel_distribute_range(): Splits a range of integers
between multiple threads, passing the sub-range to a callback
function. Allows specifying the minimal sub-range size.
- gimp_parallel_distribute_area(): Splits a rectangular area
between multiple threads, passing the sub-area to a callback
function. Allows specifying the minimal sub-area.
The callback function is passed using an appropriately-typed
function pointer, and a user-data pointer. Additionally, when used
in a C++ file, each of the above functions has an overloaded
template version, taking the callback through a generic parameter,
without a user-data pointer, which allows using function objects.
