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<GMainContext>
The GMainContext
struct is an opaque data
type representing a set of sources to be handled in a main loop.
(define-values (%return) (main-context:acquire? self))
Tries to become the owner of the specified context.
If some other thread is the owner of the context,
returns FALSE
immediately. Ownership is properly
recursive: the owner can require ownership again
and will release ownership when g_main_context_release()
is called as many times as g_main_context_acquire()
.
You must be the owner of a context before you
can call g_main_context_prepare()
, g_main_context_query()
,
g_main_context_check()
, g_main_context_dispatch()
.
(define-values () (main-context:add-poll self fd priority))
Adds a file descriptor to the set of file descriptors polled for
this context. This will very seldom be used directly. Instead
a typical event source will use g_source_add_unix_fd()
instead.
context |
a GMainContext (or Passed as |
fd |
a GPollFD structure holding information about a file descriptor to watch. Passed as |
priority |
the priority for this file descriptor which should be
the same as the priority used for Passed as |
(define-values (%return) (main-context:check? self max-priority fds))
Passes the results of polling back to the main loop.
You must have successfully acquired the context with
g_main_context_acquire()
before you may call this function.
(define-values () (main-context:dispatch self))
Dispatches all pending sources.
You must have successfully acquired the context with
g_main_context_acquire()
before you may call this function.
(define-values (%return) (main-context:find-source-by-id self source-id))
Finds a GSource given a pair of context and ID.
It is a programmer error to attempt to look up a non-existent source.
More specifically: source IDs can be reissued after a source has been
destroyed and therefore it is never valid to use this function with a
source ID which may have already been removed. An example is when
scheduling an idle to run in another thread with g_idle_add()
: the
idle may already have run and been removed by the time this function
is called on its (now invalid) source ID. This source ID may have
been reissued, leading to the operation being performed against the
wrong source.
(define-values (%return) (main-context:find-source-by-user-data self user-data))
Finds a source with the given user data for the callback. If multiple sources exist with the same user data, the first one found will be returned.
(define-values () (main-context:invoke-full self priority function data notify))
Invokes a function in such a way that context
is owned during the
invocation of function
.
This function is the same as g_main_context_invoke()
except that it
lets you specify the priority in case function
ends up being
scheduled as an idle and also lets you give a GDestroyNotify for data
.
notify
should not assume that it is called from any particular
thread or with any particular context acquired.
(define-values (%return) (main-context:is-owner? self))
Determines whether this thread holds the (recursive)
ownership of this GMainContext. This is useful to
know before waiting on another thread that may be
blocking to get ownership of context
.
(define-values (%return) (main-context:iteration? self may-block))
Runs a single iteration for the given main loop. This involves
checking to see if any event sources are ready to be processed,
then if no events sources are ready and may_block
is TRUE
, waiting
for a source to become ready, then dispatching the highest priority
events sources that are ready. Otherwise, if may_block
is FALSE
sources are not waited to become ready, only those highest priority
events sources will be dispatched (if any), that are ready at this
given moment without further waiting.
Note that even when may_block
is TRUE
, it is still possible for
g_main_context_iteration()
to return FALSE
, since the wait may
be interrupted for other reasons than an event source becoming ready.
(define-values (%return) (main-context:pending? self))
Checks if any sources have pending events for the given context.
(define-values () (main-context:pop-thread-default self))
Pops context
off the thread-default context stack (verifying that
it was on the top of the stack).
(define-values (%return priority) (main-context:prepare self))
Prepares to poll sources within a main loop. The resulting information for polling is determined by calling g_main_context_query ().
You must have successfully acquired the context with
g_main_context_acquire()
before you may call this function.
(define-values () (main-context:push-thread-default self))
Acquires context
and sets it as the thread-default context for the
current thread. This will cause certain asynchronous operations
(such as most [gio][gio]-based I/O) which are
started in this thread to run under context
and deliver their
results to its main loop, rather than running under the global
default context in the main thread. Note that calling this function
changes the context returned by g_main_context_get_thread_default()
,
not the one returned by g_main_context_default()
, so it does not affect
the context used by functions like g_idle_add()
.
Normally you would call this function shortly after creating a new
thread, passing it a GMainContext which will be run by a
GMainLoop in that thread, to set a new default context for all
async operations in that thread. In this case you may not need to
ever call g_main_context_pop_thread_default()
, assuming you want the
new GMainContext to be the default for the whole lifecycle of the
thread.
If you don't have control over how the new thread was created (e.g.
in the new thread isn't newly created, or if the thread life
cycle is managed by a GThreadPool), it is always suggested to wrap
the logic that needs to use the new GMainContext inside a
g_main_context_push_thread_default()
/ g_main_context_pop_thread_default()
pair, otherwise threads that are re-used will end up never explicitly
releasing the GMainContext reference they hold.
In some cases you may want to schedule a single operation in a
non-default context, or temporarily use a non-default context in
the main thread. In that case, you can wrap the call to the
asynchronous operation inside a
g_main_context_push_thread_default()
/
g_main_context_pop_thread_default()
pair, but it is up to you to
ensure that no other asynchronous operations accidentally get
started while the non-default context is active.
Beware that libraries that predate this function may not correctly
handle being used from a thread with a thread-default context. Eg,
see g_file_supports_thread_contexts()
.
(define-values (%return timeout- fds) (main-context:query! self max-priority fds))
Determines information necessary to poll this main loop.
You must have successfully acquired the context with
g_main_context_acquire()
before you may call this function.
context |
a GMainContext Passed as |
max_priority |
maximum priority source to check Passed as |
timeout_ |
location to store timeout to be used in polling Passed as |
fds |
location to store GPollFD records that need to be polled. Passed as |
n_fds |
length of Inferred from |
(define-values (%return) (main-context:ref self))
Increases the reference count on a GMainContext object by one.
(define-values () (main-context:release self))
Releases ownership of a context previously acquired by this thread
with g_main_context_acquire()
. If the context was acquired multiple
times, the ownership will be released only when g_main_context_release()
is called as many times as it was acquired.
(define-values () (main-context:remove-poll self fd))
Removes file descriptor from the set of file descriptors to be polled for a particular context.
(define-values () (main-context:unref self))
Decreases the reference count on a GMainContext object by one. If the result is zero, free the context and free all associated memory.
(define-values () (main-context:wakeup self))
If context
is currently blocking in g_main_context_iteration()
waiting for a source to become ready, cause it to stop blocking
and return. Otherwise, cause the next invocation of
g_main_context_iteration()
to return without blocking.
This API is useful for low-level control over GMainContext; for example, integrating it with main loop implementations such as GMainLoop.
Another related use for this function is when implementing a main loop with a termination condition, computed from multiple threads:
#define NUM_TASKS 10 static volatile gint tasks_remaining = NUM_TASKS; ... while (g_atomic_int_get (&tasks_remaining) != 0) g_main_context_iteration (NULL, TRUE);
Then in a thread:
perform_work(); if (g_atomic_int_dec_and_test (&tasks_remaining)) g_main_context_wakeup (NULL);
(define-values (%return) (main-context:default))
Returns the global default main context. This is the main context
used for main loop functions when a main loop is not explicitly
specified, and corresponds to the "main" main loop. See also
g_main_context_get_thread_default()
.
(define-values (%return) (main-context:get-thread-default))
Gets the thread-default GMainContext for this thread. Asynchronous
operations that want to be able to be run in contexts other than
the default one should call this method or
g_main_context_ref_thread_default()
to get a GMainContext to add
their GSources to. (Note that even in single-threaded
programs applications may sometimes want to temporarily push a
non-default context, so it is not safe to assume that this will
always return NULL
if you are running in the default thread.)
If you need to hold a reference on the context, use
g_main_context_ref_thread_default()
instead.
(define-values (%return) (main-context:ref-thread-default))
Gets the thread-default GMainContext for this thread, as with
g_main_context_get_thread_default()
, but also adds a reference to
it with g_main_context_ref()
. In addition, unlike
g_main_context_get_thread_default()
, if the thread-default context
is the global default context, this will return that GMainContext
(with a ref added to it) rather than returning NULL
.