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Gnome::Glib::N-MainContext

Description

The Gnome::Glib::N-MainContext struct is an opaque data type representing a set of sources to be handled in a main loop.

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Class initialization

new

:native-object

Create an object using a native object from elsewhere. See also Gnome::N::TopLevelSupportClass.

multi method new ( N-Object :$native-object! )

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new-maincontext

Creates a new Gnome::Glib::N-MainContext structure.

method new-maincontext ( --> Gnome::Glib::MainContext \)

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new-with-flags

Creates a new Gnome::Glib::N-MainContext structure.

method new-with-flags ( UInt $flags --> Gnome::Glib::MainContext \)

• $flags; a bitwise-OR combination of Gnome::Glib::T-main flags that can only be set at creation time..

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Methods

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acquire

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 .release() is called as many times as .acquire().

You must be the owner of a context before you can call .prepare(), .query(), .check(), .dispatch().

method acquire (--> Bool )

Return value; True if the operation succeeded, and this thread is now the owner of $context..

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add-poll

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.

method add-poll ( N-Object $fd, Int() $priority )

• $fd; a Gnome::Glib::N-PollFD structure holding information about a file descriptor to watch.

• $priority; the priority for this file descriptor which should be the same as the priority used for g_source_attach() to ensure that the file descriptor is polled whenever the results may be needed..

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check

Passes the results of polling back to the main loop. You should be careful to pass $fds and its length $n-fds as received from .query(), as this functions relies on assumptions on how $fds is filled.

You must have successfully acquired the context with .acquire() before you may call this function.

method check ( Int() $max-priority, N-Object $fds, Int() $n-fds --> Bool )

• $max-priority; the maximum numerical priority of sources to check.

• $fds; array of Gnome::Glib::N-PollFD's that was passed to the last call to .query()

• $n-fds; return value of .query().

Return value; True if some sources are ready to be dispatched..

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dispatch

Dispatches all pending sources.

You must have successfully acquired the context with .acquire() before you may call this function.

method dispatch ( )

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find-source-by-funcs-user-data

Finds a source with the given source functions and user data. If multiple sources exist with the same source function and user data, the first one found will be returned.

method find-source-by-funcs-user-data ( N-Object $funcs, gpointer $user-data --> N-Object )

• $funcs; the $source-funcs passed to g_source_new().

• $user-data; the user data from the callback..

Return value; the source, if one was found, otherwise undefined.

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find-source-by-id

Finds a Gnome::Glib::N-Source 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.

method find-source-by-id ( UInt() $source-id --> N-Object )

• $source-id; the source ID, as returned by g_source_get_id()..

Return value; the Gnome::Glib::N-Source.

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find-source-by-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.

method find-source-by-user-data ( gpointer $user-data --> N-Object )

• $user-data; the user_data for the callback..

Return value; the source, if one was found, otherwise undefined.

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get-poll-func

Gets the poll function set by .set-poll-func().

method get-poll-func (-->  )

Return value; the poll function.

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invoke

Invokes a function in such a way that $context is owned during the invocation of $function.

If $context is undefined then the global default main context — as returned by .default() — is used.

If $context is owned by the current thread, $function is called directly. Otherwise, if $context is the thread-default main context of the current thread and .acquire() succeeds, then $function is called and .release() is called afterwards.

In any other case, an idle source is created to call $function and that source is attached to $context (presumably to be run in another thread). The idle source is attached with G_PRIORITY_DEFAULT priority. If you want a different priority, use .invoke-full().

Note that, as with normal idle functions, $function should probably return False. If it returns True, it will be continuously run in a loop (and may prevent this call from returning).

method invoke ( &function, gpointer $data )

• &function; function to call. Tthe function must be specified with following signature; :( gpointer $user-data -- gboolean )>.

• $data; data to pass to $function.

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invoke-full

Invokes a function in such a way that $context is owned during the invocation of $function.

This function is the same as .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 Gnome::Glib::T-types for $data. $notify should not assume that it is called from any particular thread or with any particular context acquired.

method invoke-full ( Int() $priority, &function, gpointer $data, &notify )

• $priority; the priority at which to run $function.

• &function; function to call. Tthe function must be specified with following signature; :( gpointer $user-data -- gboolean )>.

• $data; data to pass to $function.

• &notify; a function to call when $data is no longer in use, or undefined.. Tthe function must be specified with following signature; :( gpointer $data ).

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is-owner

Determines whether this thread holds the (recursive) ownership of this Gnome::Glib::N-MainContext. This is useful to know before waiting on another thread that may be blocking to get ownership of $context.

method is-owner (--> Bool )

Return value; True if current thread is owner of $context..

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iteration

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 .iteration() to return False, since the wait may be interrupted for other reasons than an event source becoming ready.

method iteration ( Bool() $may-block --> Bool )

• $may-block; whether the call may block..

Return value; True if events were dispatched..

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pending

Checks if any sources have pending events for the given context.

method pending (--> Bool )

Return value; True if events are pending..

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pop-thread-default

Pops $context off the thread-default context stack (verifying that it was on the top of the stack).

method pop-thread-default ( )

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prepare

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 .acquire() before you may call this function.

method prepare ( Array[Int] $priority --> Bool )

• $priority; (transfer ownership: full) location to store priority of highest priority source already ready..

Return value; True if some source is ready to be dispatched prior to polling..

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push-thread-default

Acquires $context and sets it as the thread-default context for the current thread. This will cause certain asynchronous operations (such as most 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 .get-thread-default(), not the one returned by .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 Gnome::Glib::N-MainContext which will be run by a Gnome::Glib::N-MainLoop 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 .pop-thread-default(), assuming you want the new Gnome::Glib::N-MainContext 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 Gnome::Glib::N-ThreadPool), it is always suggested to wrap the logic that needs to use the new Gnome::Glib::N-MainContext inside a .push-thread-default() / .pop-thread-default() pair, otherwise threads that are re-used will end up never explicitly releasing the Gnome::Glib::N-MainContext 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 .push-thread-default() / .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().

method push-thread-default ( )

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query

Determines information necessary to poll this main loop. You should be careful to pass the resulting $fds array and its length $n-fds as is when calling .check(), as this function relies on assumptions made when the array is filled.

You must have successfully acquired the context with .acquire() before you may call this function.

method query ( Int() $max-priority, Array[Int] $timeout, N-Object $fds, Int() $n-fds --> Int )

• $max-priority; maximum priority source to check.

• $timeout; (transfer ownership: full) location to store timeout to be used in polling.

• $fds; location to store Gnome::Glib::N-PollFD records that need to be polled.

• $n-fds; length of $fds..

Return value; the number of records actually stored in $fds, or, if more than $n-fds records need to be stored, the number of records that need to be stored..

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ref

Increases the reference count on a Gnome::Glib::N-MainContext object by one.

method ref (--> N-Object )

Return value; the $context that was passed in (since 2.6).

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release

Releases ownership of a context previously acquired by this thread with .acquire(). If the context was acquired multiple times, the ownership will be released only when .release() is called as many times as it was acquired.

method release ( )

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remove-poll

Removes file descriptor from the set of file descriptors to be polled for a particular context.

method remove-poll ( N-Object $fd )

• $fd; a Gnome::Glib::N-PollFD descriptor previously added with .add-poll()

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set-poll-func

Sets the function to use to handle polling of file descriptors. It will be used instead of the poll() system call (or GLib's replacement function, which is used where poll() isn't available).

This function could possibly be used to integrate the GLib event loop with an external event loop.

method set-poll-func ( &func )

• &func; the function to call to poll all file descriptors. Tthe function must be specified with following signature; :( N-Object $ufds, guint $nfsd, gint $timeout -- gint )>.

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unref

Decreases the reference count on a Gnome::Glib::N-MainContext object by one. If the result is zero, free the context and free all associated memory.

method unref ( )

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wakeup

If $context is currently blocking in .iteration() waiting for a source to become ready, cause it to stop blocking and return. Otherwise, cause the next invocation of .iteration() to return without blocking.

This API is useful for low-level control over Gnome::Glib::N-MainContext; for example, integrating it with main loop implementations such as Gnome::Glib::N-MainLoop.

Another related use for this function is when implementing a main loop with a termination condition, computed from multiple threads:

Then in a thread:

method wakeup ( )

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Functions

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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 .get-thread-default().

method default (--> N-Object )

Return value; the global default main context..

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get-thread-default

Gets the thread-default Gnome::Glib::N-MainContext 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 .ref-thread-default() to get a Gnome::Glib::N-MainContext 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 undefined if you are running in the default thread.)

If you need to hold a reference on the context, use .ref-thread-default() instead.

method get-thread-default (--> N-Object )

Return value; the thread-default Gnome::Glib::N-MainContext, or undefined if the thread-default context is the global default context..

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ref-thread-default

Gets the thread-default Gnome::Glib::N-MainContext for this thread, as with .get-thread-default(), but also adds a reference to it with .ref(). In addition, unlike .get-thread-default(), if the thread-default context is the global default context, this will return that Gnome::Glib::N-MainContext (with a ref added to it) rather than returning undefined.

method ref-thread-default (--> N-Object )

Return value; the thread-default Gnome::Glib::N-MainContext. Unref with .unref() when you are done with it..