package Glib.Cancellable is

type Gcallback is access procedure;

The type used for callback functions in structure definitions and function signatures. This doesn't mean that all callback functions must take no parameters and return void. The required signature of a callback function is determined by the context in which is used (e.g. the signal to which it is connected). Use G_CALLBACK to cast the callback function to a Gcallback.

procedure G_New 
(
Self
: out Gcancellable);

Creates a new Glib.Cancellable.Gcancellable object. Applications that want to start one or more operations that should be cancellable should create a Glib.Cancellable.Gcancellable and pass it to the operations. One Glib.Cancellable.Gcancellable can be used in multiple consecutive operations or in multiple concurrent operations.

procedure Initialize 
(
Self
: not null access Gcancellable_Record'Class);

Creates a new Glib.Cancellable.Gcancellable object. Applications that want to start one or more operations that should be cancellable should create a Glib.Cancellable.Gcancellable and pass it to the operations. One Glib.Cancellable.Gcancellable can be used in multiple consecutive operations or in multiple concurrent operations.

function Gcancellable_New return Gcancellable;

Creates a new Glib.Cancellable.Gcancellable object. Applications that want to start one or more operations that should be cancellable should create a Glib.Cancellable.Gcancellable and pass it to the operations. One Glib.Cancellable.Gcancellable can be used in multiple consecutive operations or in multiple concurrent operations.

procedure Cancel 
(
Self
: not null access Gcancellable_Record);

Will set Cancellable to cancelled, and will emit the Glib.Cancellable.Gcancellable::cancelled signal. (However, see the warning about race conditions in the documentation for that signal if you are planning to connect to it.) This function is thread-safe. In other words, you can safely call it from a thread other than the one running the operation that was passed the Cancellable. The convention within gio is that cancelling an asynchronous operation causes it to complete asynchronously. That is, if you cancel the operation from the same thread in which it is running, then the operation's Gasync_Ready_Callback will not be invoked until the application returns to the main loop.

function Connect 
(
Self
: not null access Gcancellable_Record;
Callback
: Gcallback;
Data_Destroy_Func
: Glib.G_Destroy_Notify_Address) return Gulong;

Convenience function to connect to the Glib.Cancellable.Gcancellable::cancelled signal. Also handles the race condition that may happen if the cancellable is cancelled right before connecting. Callback is called at most once, either directly at the time of the connect if Cancellable is already cancelled, or when Cancellable is cancelled in some thread. Data_Destroy_Func will be called when the handler is disconnected, or immediately if the cancellable is already cancelled. See Glib.Cancellable.Gcancellable::cancelled for details on how to use this. Since: gtk+ 2.22 "callback": The Gcallback to connect. "data_destroy_func": Free function for Data or null.

procedure Disconnect 
(
Self
: not null access Gcancellable_Record;
Handler_Id
: Gulong);

Disconnects a handler from a cancellable instance similar to g_signal_handler_disconnect. Additionally, in the event that a signal handler is currently running, this call will block until the handler has finished. Calling this function from a Glib.Cancellable.Gcancellable::cancelled signal handler will therefore result in a deadlock. This avoids a race condition where a thread cancels at the same time as the cancellable operation is finished and the signal handler is removed. See Glib.Cancellable.Gcancellable::cancelled for details on how to use this. If Cancellable is null or Handler_Id is %0 this function does nothing. Since: gtk+ 2.22 "handler_id": Handler id of the handler to be disconnected, or %0.

function Get_Fd 
(
Self
: not null access Gcancellable_Record) return Gint;

Gets the file descriptor for a cancellable job. This can be used to implement cancellable operations on Unix systems. The returned fd will turn readable when Cancellable is cancelled. You are not supposed to read from the fd yourself, just check for readable status. Reading to unset the readable status is done with Glib.Cancellable.Reset. After a successful return from this function, you should use Glib.Cancellable.Release_Fd to free up resources allocated for the returned file descriptor. See also g_cancellable_make_pollfd.

function Is_Cancelled 
(
Self
: not null access Gcancellable_Record) return Boolean;

Checks if a cancellable job has been cancelled.

procedure Pop_Current 
(
Self
: not null access Gcancellable_Record);

Pops Cancellable off the cancellable stack (verifying that Cancellable is on the top of the stack).

procedure Push_Current 
(
Self
: not null access Gcancellable_Record);

Pushes Cancellable onto the cancellable stack. The current cancellable can then be received using Glib.Cancellable.Get_Current. This is useful when implementing cancellable operations in code that does not allow you to pass down the cancellable object. This is typically called automatically by e.g. Gfile.Gfile operations, so you rarely have to call this yourself.

procedure Release_Fd 
(
Self
: not null access Gcancellable_Record);

Releases a resources previously allocated by Glib.Cancellable.Get_Fd or g_cancellable_make_pollfd. For compatibility reasons with older releases, calling this function is not strictly required, the resources will be automatically freed when the Cancellable is finalized. However, the Cancellable will block scarce file descriptors until it is finalized if this function is not called. This can cause the application to run out of file descriptors when many GCancellables are used at the same time. Since: gtk+ 2.22

procedure Reset 
(
Self
: not null access Gcancellable_Record);

Resets Cancellable to its uncancelled state. If cancellable is currently in use by any cancellable operation then the behavior of this function is undefined.

function Set_Error_If_Cancelled 
(
Self
: not null access Gcancellable_Record) return Boolean;

If the Cancellable is cancelled, sets the error to notify that the operation was cancelled.

function Source_New 
(
Self
: not null access Gcancellable_Record) return Glib.Main.G_Source;

Creates a source that triggers if Cancellable is cancelled and calls its callback of type Gcancellable_Source_Func. This is primarily useful for attaching to another (non-cancellable) source with g_source_add_child_source to add cancellability to it. For convenience, you can call this with a null Glib.Cancellable.Gcancellable, in which case the source will never trigger. Since: gtk+ 2.28

function Get_Current return Gcancellable;

Gets the top cancellable from the stack.

procedure On_Cancelled 
(
Self
: not null access Gcancellable_Record;
Call
: Cb_GObject_Void;
Slot
: not null access Glib.Object.GObject_Record'Class;
After
: Boolean := False);

Emitted when the operation has been cancelled. Can be used by implementations of cancellable operations. If the operation is cancelled from another thread, the signal will be emitted in the thread that cancelled the operation, not the thread that is running the operation. Note that disconnecting from this signal (or any signal) in a multi-threaded program is prone to race conditions. For instance it is possible that a signal handler may be invoked even *after* a call to g_signal_handler_disconnect for that handler has already returned. There is also a problem when cancellation happen right before connecting to the signal. If this happens the signal will unexpectedly not be emitted, and checking before connecting to the signal leaves a race condition where this is still happening. In order to make it safe and easy to connect handlers there are two helper functions: Glib.Cancellable.Connect and Glib.Cancellable.Disconnect which protect against problems like this. An example of how to us this: |[ /<!-- -->* Make sure we don't do any unnecessary work if already cancelled *<!-- -->/ if (g_cancellable_set_error_if_cancelled (cancellable)) return; /<!-- -->* Set up all the data needed to be able to * handle cancellation of the operation *<!-- -->/ my_data = my_data_new (...); id = 0; if (cancellable) id = g_cancellable_connect (cancellable, G_CALLBACK (cancelled_handler) data, NULL); /<!-- -->* cancellable operation here... *<!-- -->/ g_cancellable_disconnect (cancellable, id); /<!-- -->* cancelled_handler is never called after this, it * is now safe to free the data *<!-- -->/ my_data_free (my_data); ]| Note that the cancelled signal is emitted in the thread that the user cancelled from, which may be the main thread. So, the cancellable signal should not do something that can block.