bhyde@inmet.UUCP (02/28/85)
Use the capture procs. The pictures are much more complex. Pictures
are encoded as a prefix byte code. This byte code is reasonably clever about
having shorter forms for things, short vectors are an example. This
byte code is also very complex, consider all the fields in a grafPort.
Dynamic clipping regions are a particularly complex issue. With out Apple
deciding to go public, or disassembling the picture interpreter it is
very hard to be confident you know all about the picture encoding.
The best reason to keep the picture secret is to save developers the
trouble of thinking about using the information. Better documentation
of the heap usage, and speed of "budget" ( of everything ) would
be a big help!
It would be nice to have an ascii form that one could ship to/from the
Mac. The encoded picture form does have some nice uses for creating
clever little drawing tools, but this use isn't very safe since Apple
might decide to change (fix) something.
The pictures form do not seem to have a subdrawing ablities, i.e. the
byte code interpreter doesn't have goto or call instructions. You can
do a lot with the comment instruction to simulate a call instruction
within an application.
Pictures are sort of complex to use for recognizing that a mouseDown
hit a part of your drawing. You end up building a lot of mechinism
into the comments to get you back to the object being hit's full
information. It maybe that it is best to use the picture as the
skeleton around which you wrap all your drawing data, embedding that
data entirely in the comments. What have other people actually built
to solve these problems?
I like to say that 98% of all secrets exist to avoid embarressment.
There doesn't appear to be anything embarressing in the picture
encoding. Nothing very unusual either given that you've seen a task
specific byte-code before. All that tense hacking is fun to pick
thru. It would be unnatural to document tense hacking. Secrets do add
another pleasing element of magic to an already magical machine.
Ben Hyde, Cambridge Mass.