Package ch.bailu.gtk.gio

Class Cancellable

java.lang.Object
ch.bailu.gtk.type.Type
ch.bailu.gtk.type.Pointer
ch.bailu.gtk.gobject.Object
ch.bailu.gtk.gio.Cancellable
All Implemented Interfaces:
PointerInterface
public class Cancellable extends Object
GCancellable is a thread-safe operation cancellation stack used
throughout GIO to allow for cancellation of synchronous and
asynchronous operations.

https://docs.gtk.org/gio/class.Cancellable.html

  • Field Details

  • Constructor Details

    • Cancellable

      public Cancellable(PointerContainer pointer)

    • Cancellable

      public Cancellable()
      Creates a new #GCancellable object.

      Applications that want to start one or more operations
      that should be cancellable should create a #GCancellable
      and pass it to the operations.

      One #GCancellable can be used in multiple consecutive
      operations or in multiple concurrent operations.

  • Method Details

    • getClassHandler

      public static ClassHandler getClassHandler()

    • cancel

      public void cancel()
      Will set @cancellable to cancelled, and will emit the
      #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.

      If @cancellable is %NULL, this function returns immediately for convenience.

      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 #GAsyncReadyCallback will not be invoked until
      the application returns to the main loop.

    • connect

      public long connect(Cancellable.OnCallback callback, @Nullable Pointer data, Cancellable.OnDestroyNotify data_destroy_func)
      Convenience function to connect to the #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 #GCancellable::cancelled for details on how to use this.

      Since GLib 2.40, the lock protecting @cancellable is not held when
      @callback is invoked. This lifts a restriction in place for
      earlier GLib versions which now makes it easier to write cleanup
      code that unconditionally invokes e.g. g_cancellable_cancel().
      Parameters:
      callback - The #GCallback to connect.
      data - Data to pass to @callback.
      data_destroy_func - Free function for @data or %NULL.
      Returns:
      The id of the signal handler or 0 if @cancellable has already been cancelled.

    • disconnect

      public void disconnect(long handler_id)
      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
      #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 #GCancellable::cancelled for
      details on how to use this.

      If @cancellable is %NULL or @handler_id is `0` this function does
      nothing.
      Parameters:
      handler_id - Handler id of the handler to be disconnected, or `0`.

    • getFd

      public int getFd()
      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 g_cancellable_reset().

      After a successful return from this function, you should use
      g_cancellable_release_fd() to free up resources allocated for
      the returned file descriptor.

      See also g_cancellable_make_pollfd().
      Returns:
      A valid file descriptor. `-1` if the file descriptor is not supported, or on errors.

    • isCancelled

      public boolean isCancelled()
      Checks if a cancellable job has been cancelled.
      Returns:
      %TRUE if @cancellable is cancelled, FALSE if called with %NULL or if item is not cancelled.

    • makePollfd

      public boolean makePollfd(@Nonnull PollFD pollfd)
      Creates a #GPollFD corresponding to @cancellable; this can be passed
      to g_poll() and used to poll for cancellation. This is useful both
      for unix systems without a native poll and for portability to
      windows.

      When this function returns %TRUE, you should use
      g_cancellable_release_fd() to free up resources allocated for the
      @pollfd. After a %FALSE return, do not call g_cancellable_release_fd().

      If this function returns %FALSE, either no @cancellable was given or
      resource limits prevent this function from allocating the necessary
      structures for polling. (On Linux, you will likely have reached
      the maximum number of file descriptors.) The suggested way to handle
      these cases is to ignore the @cancellable.

      You are not supposed to read from the fd yourself, just check for
      readable status. Reading to unset the readable status is done
      with g_cancellable_reset().
      Parameters:
      pollfd - a pointer to a #GPollFD
      Returns:
      %TRUE if @pollfd was successfully initialized, %FALSE on failure to prepare the cancellable.

    • popCurrent

      public void popCurrent()
      Pops @cancellable off the cancellable stack (verifying that @cancellable
      is on the top of the stack).

    • pushCurrent

      public void pushCurrent()
      Pushes @cancellable onto the cancellable stack. The current
      cancellable can then be received using g_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 operations,
      so you rarely have to call this yourself.

    • releaseFd

      public void releaseFd()
      Releases a resources previously allocated by g_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.

    • reset

      public void reset()
      Resets @cancellable to its uncancelled state.

      If cancellable is currently in use by any cancellable operation
      then the behavior of this function is undefined.

      Note that it is generally not a good idea to reuse an existing
      cancellable for more operations after it has been cancelled once,
      as this function might tempt you to do. The recommended practice
      is to drop the reference to a cancellable after cancelling it,
      and let it die with the outstanding async operations. You should
      create a fresh cancellable for further async operations.

    • setErrorIfCancelled

      public boolean setErrorIfCancelled() throws AllocationError
      If the @cancellable is cancelled, sets the error to notify
      that the operation was cancelled.
      Returns:
      %TRUE if @cancellable was cancelled, %FALSE if it was not
      Throws:
      AllocationError

    • sourceNew

      public Source sourceNew()
      Creates a source that triggers if @cancellable is cancelled and
      calls its callback of type #GCancellableSourceFunc. 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 #GCancellable,
      in which case the source will never trigger.

      The new #GSource will hold a reference to the #GCancellable.
      Returns:
      the new #GSource.

    • onCancelled

      public SignalHandler onCancelled(Cancellable.OnCancelled signal)
      Connect to signal "cancelled".
      See Cancellable.OnCancelled.onCancelled() for signal description.
      Field SIGNAL_ON_CANCELLED contains original signal name and can be used as resource reference.
      Parameters:
      signal - callback function (lambda).
      Returns:
      SignalHandler. Can be used to disconnect signal and to release callback function.

    • getCurrent

      public static Cancellable getCurrent()
      Gets the top cancellable from the stack.
      Returns:
      a #GCancellable from the top of the stack, or %NULL if the stack is empty.

    • getTypeID

      public static long getTypeID()

    • getParentTypeID

      public static long getParentTypeID()

    • getTypeSize

      public static TypeSystem.TypeSize getTypeSize()

    • getParentTypeSize

      public static TypeSystem.TypeSize getParentTypeSize()

    • getInstanceSize

      public static int getInstanceSize()