mirror of https://github.com/python/cpython
Removed most of the README text since it is all about the Mac specific
examples, which no longer live here.
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Guido van Rossum
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BGEN -- An Experiment: Automatic Generation of Extension Modules
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================================================================
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BGEN -- Automatic Generation of Extension Modules
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=================================================
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This directory contains BGEN -- a package that helps in generating
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complete source code for Python extension module. It currently also
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contains a set of examples that were generated with BGEN. These
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examples are mostly interfaces to a number of important managers in
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the Macintosh toolbox.
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Overview of Subdirectories
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--------------------------
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Main subdirectories:
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bgen the code generator package
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Example subdirectories:
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ae AppleEvents
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ctl Controls
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cm Component manager
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dlg Dialogs
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evt Events
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menu Menus
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list Lists
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qd QuickDraw
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qt QuickTime
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res Resources
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snd Sound
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win Windows
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Contents of Subdirectories
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--------------------------
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The contents of each example subdirectory is similar (<Foobar> is
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for instance AppleEvents, while <foo> is ae):
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<foo>scan.py Scan the <Foobar>.h header, generating <foo>gen.py
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<foo>gen.py Output of <foo>scan.py, input for <foo>support.py
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<foo>edit.py Manually written complement of <foo>gen.py, sometimes
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<foo>support.py Generate <Foo>module.c from <foo>gen.py and <foo>edit.py
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<Foo>module.c The interface module, ready to be compiled
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<Foobar>.py Symbolic constants extracted from <Foobar.h>
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Tests and Examples
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------------------
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Other files in these subdirectories are usually examples using the
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extension. If there's a file t<foo>.py, it usually is a really
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boring test program.
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Some test programs contain pathnames that should be edited before
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trying them.
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Some of the less boring tests and examples:
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At the top level:
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test.py Application mainloop, uses most Mac extensions
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In ae:
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aetools.py Conversions between AE and Python data type
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echo.py Dummy AE server, echoes all data back
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tell.py Primitive AE client
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aete.py Decode 'aete' and 'aeut' resources (incomplete)
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gensuitemodule.py
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Read aete/aeut resources and turn them into python
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modules. The *_Suite.py modules have been generated
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with this.
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AEservertest.py A simple AE server, similar to echo but different.
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In cm:
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cmtest.py List all components in the system plus some info on them
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In qt:
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MovieInWindow.py Play a movie in a fixed-sized window, stop on mouse-press
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VerySimplePlayer.py Play a movie with the standard quicktime controller.
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In res:
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listres.py List *all* resources in current and in all res files
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copyres.py Copy a resource file
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mkerrstrres.py Read "errors.txt" and create a set of "Estr" resources
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In snd:
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playaiff.py Play an AIFF file
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morse.py Turn text into Morse code
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audiodev.py The standard audiodev.py extended with Mac support
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Audio_mac.py The Mac support for audiodev.py
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Creating new Macintosh interfaces
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---------------------------------
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These instructions were written up by Jack while he was building the
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interface to Lists.h, the macintosh list manager. they may or may not
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have a more global scope than exactly that.
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First, start by copying ...scan.py and ...support.py from another,
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preferrably similar type. I started with evt, but that was a mistake
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since evt has no "own" object. Ctl or Dlg would probably have been a
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better idea.
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Now, the first thing to do is to comment out the blacklisted types and
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functions and the transformation rules for arguments, we'll fill those
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in lateron. Also, change the various definitions at the top, so that
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the right include file is parsed, and the .py files are generated with
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the correct name. If your manager has a type that will be implemented
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as a python object you may as well now change the destination() method
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to recognize that. (List was funny in this respect, since it has the
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list as the last argument in stead of the first).
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Now run your scanner. This will probably go fine until it tries to
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execute the generated code in the ...gen.py module. Look at that file,
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it will have formalized "definitions" of all the functions and methods
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that will be generated. Look at them all (with the documentation of the
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manager you're implementing in hand). Now you'll have to fix the
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blacklists and the repair instructions. This is sort of a black art,
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but a few guidelines may be handy here:
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- If there are argument types you cannot implement (or want to leave for
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the moment) put them in blacklisttypes. Complex structures come to
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mind, or routine pointers/UPP's. You will probably also want to
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blacklist the routine that disposes of your object (since you'll do
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that in the python destruction routine).
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- Various types of buffers are available in bgenBuffer, bgenHeapBuffer
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and macsupport in the bgen directory. These'll let you handle all
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sorts of input and output parameters. You can put instructions in the
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repair list to let the C-arguments be handled by the correct type
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of buffer. Check the other bgen-generated modules for using this for
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passing raw structures and input and output buffers.
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- It appears that the parser usually guesses correctly whether a parameter
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is meant for input or output. But, check the routines to be sure.
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- Some types are pretty hard to handle but you need the functionality
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the a routine that uses them anyway. Various routines expecting ProcPtrs
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or RegionHandles come to mind. Often, you can use the FakeType class
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to provide a sensible default (i.e. NULL or a pointer to a routine you
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coded in C, or a region specifying "the whole window"). This way, python
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programmers won't get the full functionality but at least they'll get the
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common case. You put the FakeType stuff in ...support.py.
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Next you'll probably have to write the code to implement your object.
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This will probably be a subclass of GlobalObjectDefinition. This goes
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into ...support.py. Also, some types used by the manager may look
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enough like standard types that you can equate them here (there are a
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lot of 2-integer structures that look remarkably like a Point, for
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instance).
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You'll also have to define the Function() and Method() classes. The
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OSErrFunctionGenerator and its method-counterpart are particularly
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handy for a lot of mac managers.
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Finally, you'll have to try and compile your resulting C-source, and go
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through the steps above until it works. For tlist.py, the test program
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for list, I started with the application framework. This is probably a
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good idea for any manager that does something to the display, since
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ApplicationFramework takes care of all the intricacies of event
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handling and decoding (up to a point).
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complete source code for Python extension module. For examples of its
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use, see the Mac Python source distribution (available separately
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from the Python ftp archives). Note that BGEN is not Mac specific!
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