GI.GLib.Structs.Source

The GSource struct is an opaque data type representing an event source.

Exported types

newtype Source

Memory-managed wrapper type.

Constructors

Source (ManagedPtr Source)

Instances

BoxedObject Source

Defined in GI.GLib.Structs.Source

Methods

boxedType :: Source -> IO GType

tag ~ AttrSet => Constructible Source tag

Defined in GI.GLib.Structs.Source

Methods

new :: MonadIO m => (ManagedPtr Source -> Source) -> [AttrOp Source tag] -> m Source

newZeroSource :: MonadIO m => m Source

Construct a Source struct initialized to zero.

noSource :: Maybe Source

A convenience alias for Nothing :: Maybe Source.

Methods

addChildSource

sourceAddChildSource

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: a Source

-> Source

childSource: a second Source that source should "poll"

-> m ()

Adds childSource to source as a "polled" source; when source is added to a MainContext, childSource will be automatically added with the same priority, when childSource is triggered, it will cause source to dispatch (in addition to calling its own callback), and when source is destroyed, it will destroy childSource as well. (source will also still be dispatched if its own prepare/check functions indicate that it is ready.)

If you don't need childSource to do anything on its own when it triggers, you can call g_source_set_dummy_callback() on it to set a callback that does nothing (except return True if appropriate).

source will hold a reference on childSource while childSource is attached to it.

This API is only intended to be used by implementations of Source. Do not call this API on a Source that you did not create.

Since: 2.28

addPoll

sourceAddPoll

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: a Source

-> PollFD

fd: a PollFD structure holding information about a file descriptor to watch.

-> m ()

Adds a file descriptor to the set of file descriptors polled for this source. This is usually combined with sourceNew to add an event source. The event source's check function will typically test the revents field in the PollFD struct and return True if events need to be processed.

This API is only intended to be used by implementations of Source. Do not call this API on a Source that you did not create.

Using this API forces the linear scanning of event sources on each main loop iteration. Newly-written event sources should try to use sourceAddUnixFd instead of this API.

addUnixFd

sourceAddUnixFd

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: a Source

-> Int32

fd: the fd to monitor

-> [IOCondition]

events: an event mask

-> m (Ptr ())

Returns: an opaque tag

Monitors fd for the IO events in events.

The tag returned by this function can be used to remove or modify the monitoring of the fd using sourceRemoveUnixFd or sourceModifyUnixFd.

It is not necessary to remove the fd before destroying the source; it will be cleaned up automatically.

This API is only intended to be used by implementations of Source. Do not call this API on a Source that you did not create.

As the name suggests, this function is not available on Windows.

Since: 2.36

attach

sourceAttach

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: a Source

-> Maybe MainContext

context: a MainContext (if Nothing, the default context will be used)

-> m Word32

Returns: the ID (greater than 0) for the source within the MainContext.

Adds a Source to a context so that it will be executed within that context. Remove it by calling sourceDestroy.

destroy

sourceDestroy

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: a Source

-> m ()

Removes a source from its MainContext, if any, and mark it as destroyed. The source cannot be subsequently added to another context. It is safe to call this on sources which have already been removed from their context.

getCanRecurse

sourceGetCanRecurse

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: a Source

-> m Bool

Returns: whether recursion is allowed.

Checks whether a source is allowed to be called recursively. see sourceSetCanRecurse.

getContext

sourceGetContext

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: a Source

-> m (Maybe MainContext)

Returns: the MainContext with which the source is associated, or Nothing if the context has not yet been added to a source.

Gets the MainContext with which the source is associated.

You can call this on a source that has been destroyed, provided that the MainContext it was attached to still exists (in which case it will return that MainContext). In particular, you can always call this function on the source returned from mainCurrentSource. But calling this function on a source whose MainContext has been destroyed is an error.

getCurrentTime

sourceGetCurrentTime

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: a Source

-> TimeVal

timeval: TimeVal structure in which to store current time.

-> m ()

Deprecated: (Since version 2.28)use sourceGetTime instead

This function ignores source and is otherwise the same as getCurrentTime.

getId

sourceGetId

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: a Source

-> m Word32

Returns: the ID (greater than 0) for the source

Returns the numeric ID for a particular source. The ID of a source is a positive integer which is unique within a particular main loop context. The reverse mapping from ID to source is done by mainContextFindSourceById.

You can only call this function while the source is associated to a MainContext instance; calling this function before sourceAttach or after sourceDestroy yields undefined behavior. The ID returned is unique within the MainContext instance passed to sourceAttach.

getName

sourceGetName

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: a Source

-> m Text

Returns: the name of the source

Gets a name for the source, used in debugging and profiling. The name may be NULL if it has never been set with sourceSetName.

Since: 2.26

getPriority

sourceGetPriority

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: a Source

-> m Int32

Returns: the priority of the source

Gets the priority of a source.

getReadyTime

sourceGetReadyTime

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: a Source

-> m Int64

Returns: the monotonic ready time, -1 for "never"

Gets the "ready time" of source, as set by sourceSetReadyTime.

Any time before the current monotonic time (including 0) is an indication that the source will fire immediately.

getTime

sourceGetTime

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: a Source

-> m Int64

Returns: the monotonic time in microseconds

Gets the time to be used when checking this source. The advantage of calling this function over calling getMonotonicTime directly is that when checking multiple sources, GLib can cache a single value instead of having to repeatedly get the system monotonic time.

The time here is the system monotonic time, if available, or some other reasonable alternative otherwise. See getMonotonicTime.

Since: 2.28

isDestroyed

sourceIsDestroyed

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: a Source

-> m Bool

Returns: True if the source has been destroyed

Returns whether source has been destroyed.

This is important when you operate upon your objects from within idle handlers, but may have freed the object before the dispatch of your idle handler.

C code

static gboolean
idle_callback (gpointer data)
{
  SomeWidget *self = data;
   
  GDK_THREADS_ENTER ();
  // do stuff with self
  self->idle_id = 0;
  GDK_THREADS_LEAVE ();
   
  return G_SOURCE_REMOVE;
}
 
static void
some_widget_do_stuff_later (SomeWidget *self)
{
  self->idle_id = g_idle_add (idle_callback, self);
}
 
static void
some_widget_finalize (GObject *object)
{
  SomeWidget *self = SOME_WIDGET (object);
   
  if (self->idle_id)
    g_source_remove (self->idle_id);
   
  G_OBJECT_CLASS (parent_class)->finalize (object);
}

This will fail in a multi-threaded application if the widget is destroyed before the idle handler fires due to the use after free in the callback. A solution, to this particular problem, is to check to if the source has already been destroy within the callback.

C code

static gboolean
idle_callback (gpointer data)
{
  SomeWidget *self = data;
  
  GDK_THREADS_ENTER ();
  if (!g_source_is_destroyed (g_main_current_source ()))
    {
      // do stuff with self
    }
  GDK_THREADS_LEAVE ();
  
  return FALSE;
}

Calls to this function from a thread other than the one acquired by the MainContext the Source is attached to are typically redundant, as the source could be destroyed immediately after this function returns. However, once a source is destroyed it cannot be un-destroyed, so this function can be used for opportunistic checks from any thread.

Since: 2.12

modifyUnixFd

sourceModifyUnixFd

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: a Source

-> Ptr ()

tag: the tag from sourceAddUnixFd

-> [IOCondition]

newEvents: the new event mask to watch

-> m ()

Updates the event mask to watch for the fd identified by tag.

tag is the tag returned from sourceAddUnixFd.

If you want to remove a fd, don't set its event mask to zero. Instead, call sourceRemoveUnixFd.

This API is only intended to be used by implementations of Source. Do not call this API on a Source that you did not create.

As the name suggests, this function is not available on Windows.

Since: 2.36

new

sourceNew

Arguments

:: (HasCallStack, MonadIO m)

=> SourceFuncs

sourceFuncs: structure containing functions that implement the sources behavior.

-> Word32

structSize: size of the Source structure to create.

-> m Source

Returns: the newly-created Source.

Creates a new Source structure. The size is specified to allow creating structures derived from Source that contain additional data. The size passed in must be at least sizeof (GSource).

The source will not initially be associated with any MainContext and must be added to one with sourceAttach before it will be executed.

queryUnixFd

sourceQueryUnixFd

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: a Source

-> Ptr ()

tag: the tag from sourceAddUnixFd

-> m [IOCondition]

Returns: the conditions reported on the fd

Queries the events reported for the fd corresponding to tag on source during the last poll.

The return value of this function is only defined when the function is called from the check or dispatch functions for source.

This API is only intended to be used by implementations of Source. Do not call this API on a Source that you did not create.

As the name suggests, this function is not available on Windows.

Since: 2.36

ref

sourceRef

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: a Source

-> m Source

Returns: source

Increases the reference count on a source by one.

remove

sourceRemove

Arguments

:: (HasCallStack, MonadIO m)

=> Word32

tag: the ID of the source to remove.

-> m Bool

Returns: For historical reasons, this function always returns True

Removes the source with the given ID from the default main context. You must use sourceDestroy for sources added to a non-default main context.

The ID of a Source is given by sourceGetId, or will be returned by the functions sourceAttach, g_idle_add(), idleAdd, g_timeout_add(), timeoutAdd, g_child_watch_add(), childWatchAdd, g_io_add_watch(), and ioAddWatch.

It is a programmer error to attempt to remove 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.

removeByFuncsUserData

sourceRemoveByFuncsUserData

Arguments

:: (HasCallStack, MonadIO m)

=> SourceFuncs

funcs: The sourceFuncs passed to sourceNew

-> Ptr ()

userData: the user data for the callback

-> m Bool

Returns: True if a source was found and removed.

Removes a source from the default main loop context given the source functions and user data. If multiple sources exist with the same source functions and user data, only one will be destroyed.

removeByUserData

sourceRemoveByUserData

Arguments

:: (HasCallStack, MonadIO m)

=> Ptr ()

userData: the user_data for the callback.

-> m Bool

Returns: True if a source was found and removed.

Removes a source from the default main loop context given the user data for the callback. If multiple sources exist with the same user data, only one will be destroyed.

removeChildSource

sourceRemoveChildSource

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: a Source

-> Source

childSource: a Source previously passed to sourceAddChildSource.

-> m ()

Detaches childSource from source and destroys it.

This API is only intended to be used by implementations of Source. Do not call this API on a Source that you did not create.

Since: 2.28

removePoll

sourceRemovePoll

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: a Source

-> PollFD

fd: a PollFD structure previously passed to sourceAddPoll.

-> m ()

Removes a file descriptor from the set of file descriptors polled for this source.

This API is only intended to be used by implementations of Source. Do not call this API on a Source that you did not create.

removeUnixFd

sourceRemoveUnixFd

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: a Source

-> Ptr ()

tag: the tag from sourceAddUnixFd

-> m ()

Reverses the effect of a previous call to sourceAddUnixFd.

You only need to call this if you want to remove an fd from being watched while keeping the same source around. In the normal case you will just want to destroy the source.

This API is only intended to be used by implementations of Source. Do not call this API on a Source that you did not create.

As the name suggests, this function is not available on Windows.

Since: 2.36

setCallback

sourceSetCallback

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: the source

-> SourceFunc

func: a callback function

-> m ()

Sets the callback function for a source. The callback for a source is called from the source's dispatch function.

The exact type of func depends on the type of source; ie. you should not count on func being called with data as its first parameter. Cast func with G_SOURCE_FUNC() to avoid warnings about incompatible function types.

See [memory management of sources][mainloop-memory-management] for details on how to handle memory management of data.

Typically, you won't use this function. Instead use functions specific to the type of source you are using, such as g_idle_add() or g_timeout_add().

It is safe to call this function multiple times on a source which has already been attached to a context. The changes will take effect for the next time the source is dispatched after this call returns.

setCallbackIndirect

sourceSetCallbackIndirect

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: the source

-> Ptr ()

callbackData: pointer to callback data "object"

-> SourceCallbackFuncs

callbackFuncs: functions for reference counting callbackData and getting the callback and data

-> m ()

Sets the callback function storing the data as a refcounted callback "object". This is used internally. Note that calling sourceSetCallbackIndirect assumes an initial reference count on callbackData, and thus callbackFuncs->unref will eventually be called once more than callbackFuncs->ref.

It is safe to call this function multiple times on a source which has already been attached to a context. The changes will take effect for the next time the source is dispatched after this call returns.

setCanRecurse

sourceSetCanRecurse

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: a Source

-> Bool

canRecurse: whether recursion is allowed for this source

-> m ()

Sets whether a source can be called recursively. If canRecurse is True, then while the source is being dispatched then this source will be processed normally. Otherwise, all processing of this source is blocked until the dispatch function returns.

setFuncs

sourceSetFuncs

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: a Source

-> SourceFuncs

funcs: the new SourceFuncs

-> m ()

Sets the source functions (can be used to override default implementations) of an unattached source.

Since: 2.12

setName

sourceSetName

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: a Source

-> Text

name: debug name for the source

-> m ()

Sets a name for the source, used in debugging and profiling. The name defaults to NULL.

The source name should describe in a human-readable way what the source does. For example, "X11 event queue" or "GTK+ repaint idle handler" or whatever it is.

It is permitted to call this function multiple times, but is not recommended due to the potential performance impact. For example, one could change the name in the "check" function of a SourceFuncs to include details like the event type in the source name.

Use caution if changing the name while another thread may be accessing it with sourceGetName; that function does not copy the value, and changing the value will free it while the other thread may be attempting to use it.

Since: 2.26

setNameById

sourceSetNameById

Arguments

:: (HasCallStack, MonadIO m)

=> Word32

tag: a Source ID

-> Text

name: debug name for the source

-> m ()

Sets the name of a source using its ID.

This is a convenience utility to set source names from the return value of g_idle_add(), g_timeout_add(), etc.

It is a programmer error to attempt to set the name of 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.

Since: 2.26

setPriority

sourceSetPriority

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: a Source

-> Int32

priority: the new priority.

-> m ()

Sets the priority of a source. While the main loop is being run, a source will be dispatched if it is ready to be dispatched and no sources at a higher (numerically smaller) priority are ready to be dispatched.

A child source always has the same priority as its parent. It is not permitted to change the priority of a source once it has been added as a child of another source.

setReadyTime

sourceSetReadyTime

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: a Source

-> Int64

readyTime: the monotonic time at which the source will be ready, 0 for "immediately", -1 for "never"

-> m ()

Sets a Source to be dispatched when the given monotonic time is reached (or passed). If the monotonic time is in the past (as it always will be if readyTime is 0) then the source will be dispatched immediately.

If readyTime is -1 then the source is never woken up on the basis of the passage of time.

Dispatching the source does not reset the ready time. You should do so yourself, from the source dispatch function.

Note that if you have a pair of sources where the ready time of one suggests that it will be delivered first but the priority for the other suggests that it would be delivered first, and the ready time for both sources is reached during the same main context iteration, then the order of dispatch is undefined.

It is a no-op to call this function on a Source which has already been destroyed with sourceDestroy.

This API is only intended to be used by implementations of Source. Do not call this API on a Source that you did not create.

Since: 2.36

unref

sourceUnref

Arguments

:: (HasCallStack, MonadIO m)

=> Source

source: a Source

-> m ()

Decreases the reference count of a source by one. If the resulting reference count is zero the source and associated memory will be destroyed.