Used to determine how to respond to the area_updated signal on #GdkPixbufLoader when loading an animation.

The `::area_updated` signal is emitted for an area of the frame currently streaming in to the loader. So if you're on the currently loading frame, you will need to redraw the screen for the updated area.

Gets the current pixbuf which should be displayed.

The pixbuf might not 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.

Gets the number of milliseconds the current pixbuf should be displayed, or -1 if the current pixbuf should be displayed forever.

The `g_timeout_add()` function conveniently takes a timeout in milliseconds, so you can use a timeout to schedule the next update.

Note that some formats, like GIF, might clamp the timeout values in the image file to avoid updates that are just too quick. The minimum timeout for GIF images is currently 20 milliseconds.