mirror of https://github.com/GNOME/gimp.git
102 lines
3.5 KiB
Plaintext
102 lines
3.5 KiB
Plaintext
Some mostly unfinished docs are here.
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-Yosh
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PDBGEN
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------------------
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What is this?
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It's a tool to automate much of the drudge work of making PDB interfaces
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to GIMP internals. Right now, it generates PDB description records,
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argument marshallers (with sanity checking) for the app side, as well
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as libgimp wrappers for C plugins. It's written so that extending it
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to provide support for CORBA and other languages suited to static
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autogeneration.
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How to invoke pdbgen from the command line:
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Change into the ./tools/pdbgen directory
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$ ./pdbgen.pl DIRNAME
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where DIRNAME is either "lib" or "app", depending on which set of
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files you want to generate. The files are written to ./app or ./lib
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in the ./tools/pdbgen directory. Up to you to diff the file you
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changed and when you're happy copy it into the actual ./app/ or ./lib/
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directory where it gets built.
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Anatomy of a PDB descriptor:
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PDB descriptors are Perl code. You define a subroutine, which corresponds
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to the PDB function you want to create. You then fill certain special
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variables to fully describe all the information pdbgen needs to generate
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code. Since it's perl, you can do practically whatever perl lets you
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do to help you do this. However, at the simplest level, you don't need
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to know perl at all to make PDB descriptors.
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Annotated description:
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For example, we will look at gimp_display_new, specified in gdisplay.pdb.
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sub display_new {
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We start with the name of our PDB function (not including the "gimp_" prefix).
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$blurb = 'Create a new display for the specified image.';
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This directly corresponds to the "blurb" field in the ProcRecord.
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$help = <<'HELP';
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Creates a new display for the specified image. If the image already has a
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display, another is added. Multiple displays are handled transparently by the
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GIMP. The newly created display is returned and can be subsequently destroyed
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with a call to 'gimp-display-delete'. This procedure only makes sense for use
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with the GIMP UI.
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HELP
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This is the help field. Notice because it is a long string, we used HERE
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document syntax to split it over multiple lines. Any extra whitespace
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in $blurb or $help, including newlines, is automatically stripped, so you
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don't have to worry about that.
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&std_pdb_misc;
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This is the "author", "copyright", and "date" fields. Since S&P are quite
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common, they get a special shortcut which fills these in for you. Stuff
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like this is defined in stddefs.pdb.
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@inargs = ( &std_image_arg );
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You specify arguments in a list. Again, your basic image is very common,
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so it gets a shortcut.
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@outargs = (
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{ name => 'display', type => 'display',
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desc => 'The new display', alias => 'gdisp', init => 1 }
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);
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This is a real argument. It has a name, type, description at a minimum.
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"alias" lets you use the alias name in your invoker code, but the real
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name is still shown in the ProcRecord. This is useful not only as a
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shorthand, but for grabbing variables defined somewhere else (or constants),
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in conjunction with the "no_declare" flag. "init" simply says initialize
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this variable to a dummy value (in this case to placate gcc warnings)
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%invoke = (
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headers => [ qw("gdisplay.h") ],
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These are the headers needed for the functions you call.
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vars => [ 'guint scale = 0x101' ],
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Extra variables can be put here for your invoker.
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code => <<'CODE'
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{
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if (gimage->layers == NULL)
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success = FALSE;
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else
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success = ((gdisp = gdisplay_new (gimage, scale)) != NULL);
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}
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CODE
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The actual invoker code. Since it's a multiline block, we put curly braces
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in the beginning.
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