An asynchronous update interface for receiving notifications about
Image information as the Image is constructed.
This flag in the infoflags argument to imageUpdate indicates that
an image which was being tracked asynchronously was aborted before
production was complete. No more information will become available
without further action to trigger another image production sequence.
If the ERROR flag was not also set in this image update, then
accessing any of the data in the image will restart the production
again, probably from the beginning.
This flag in the infoflags argument to imageUpdate indicates that
a static image which was previously drawn is now complete and can
be drawn again in its final form. The x, y, width, and height
arguments to the imageUpdate callback method should be ignored.
This flag in the infoflags argument to imageUpdate indicates that
an image which was being tracked asynchronously has encountered
an error. No further information will become available and
drawing the image will fail.
As a convenience, the ABORT flag will be indicated at the same
time to indicate that the image production was aborted.
This flag in the infoflags argument to imageUpdate indicates that
another complete frame of a multi-frame image which was previously
drawn is now available to be drawn again. The x, y, width, and height
arguments to the imageUpdate callback method should be ignored.
This flag in the infoflags argument to imageUpdate indicates that
the height of the base image is now available and can be taken
from the height argument to the imageUpdate callback method.
This flag in the infoflags argument to imageUpdate indicates that
the properties of the image are now available.
This flag in the infoflags argument to imageUpdate indicates that
more pixels needed for drawing a scaled variation of the image
are available. The bounding box of the new pixels can be taken
from the x, y, width, and height arguments to the imageUpdate
callback method.
This flag in the infoflags argument to imageUpdate indicates that
the width of the base image is now available and can be taken
from the width argument to the imageUpdate callback method.
This method is called when information about an image which was
previously requested using an asynchronous interface becomes
available. Asynchronous interfaces are method calls such as
getWidth(ImageObserver) and drawImage(img, x, y, ImageObserver)
which take an ImageObserver object as an argument. Those methods
register the caller as interested either in information about
the overall image itself (in the case of getWidth(ImageObserver))
or about an output version of an image (in the case of the
drawImage(img, x, y, [w, h,] ImageObserver) call).
This method
should return true if further updates are needed or false if the
required information has been acquired. The image which was being
tracked is passed in using the img argument. Various constants
are combined to form the infoflags argument which indicates what
information about the image is now available. The interpretation
of the x, y, width, and height arguments depends on the contents
of the infoflags argument.
The infoflags argument should be the bitwise inclusive
OR of the following flags: WIDTH,
HEIGHT, PROPERTIES, SOMEBITS,
FRAMEBITS, ALLBITS, ERROR,
ABORT.