Possibly advances an animation to a new frame. Chooses the frame based
on the start time passed to gdk_pixbuf_animation_get_iter().
must be greater than or equal to the time passed to
gdk_pixbuf_animation_get_iter(), and must increase or remain
unchanged each time gdk_pixbuf_animation_iter_get_pixbuf() is
called. That is, you can't go backward in time; animations only
play forward.
As a shortcut, pass NULL for the current time and g_get_current_time()
will be invoked on your behalf. So you only need to explicitly pass
at double speed.
If this function returns FALSE, there's no need to update the animation
display, assuming the display had been rendered prior to advancing;
if TRUE, you need to call gdk_animation_iter_get_pixbuf() and update the
display with the new pixbuf.

Parameters:

GLib.TimeVal current_time Required (not null)

current time

Returns:

gboolean TRUE if the image may need updating

Gets the number of milliseconds the current pixbuf should be displayed,
or -1 if the current pixbuf should be displayed forever. g_timeout_add()
conveniently takes a timeout in milliseconds, so you can use a timeout
to schedule the next update.

Returns:

gint32 delay time in milliseconds (thousandths of a second)

Gets the current pixbuf which should be displayed; the pixbuf will
be the same size as the animation itself
(gdk_pixbuf_animation_get_width(), gdk_pixbuf_animation_get_height()).
This pixbuf should be displayed for
gdk_pixbuf_animation_iter_get_delay_time() milliseconds. The caller
of this function does not own a reference to the returned pixbuf;
the returned pixbuf will become invalid when the iterator advances
to the next frame, which may happen anytime you call
gdk_pixbuf_animation_iter_advance(). Copy the pixbuf to keep it
(don't just add a reference), as it may get recycled as you advance
the iterator.

Returns:

GdkPixbuf.Pixbuf the pixbuf to be displayed

Used to determine how to respond to the area_updated signal on
GdkPixbufLoader when loading an animation. area_updated is emitted
for an area of the frame currently streaming in to the loader. So if
you're on the currently loading frame, you need to redraw the screen for
the updated area.

Returns:

gboolean TRUE if the frame we're on is partially loaded, or the last frame