Q:
When using QTNewGWorldFromPtr I'd like to know when is it
necessary to call LockPixels? Additionally, what happens
to the pixel data when a GWorld returned by QTNewGWorldFromPtr
is disposed?
A:
QTNewGWorldFromPtr requires the caller to supply a pointer
to a pixel buffer that will be available for the lifetime
of the returned GWorld and will not move in memory.
When supplying your own pointer for the buffer parameter
(baseAddr), calling LockPixels is not necessary. It is however
your responsibility to make sure this pixel buffer is available
for the lifetime of the GWorld and that it not move in memory.
When supplying a pointer to some pixel data belonging to another
GWorld, it is your responsibility to ensure the source
GWorlds pixels are locked. Therefore, you should call LockPixels
for the source GWorld's PixMap. This should
be done before calling QTNewGWorldFromPtr. Be sure to not
unlock or dispose the source GWorld's PixMap
until you're done with the GWorld created by calling QTNewGWorldFromPtr.
When a GWorld created by calling QTNewGWorldFromPtr
is disposed; its pixel data is not disposed as QuickTime does not know
how the pixel data was originally allocated. It is therefore your responsibility
to manage disposing of the pixel data.
[Feb 26 2001]
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