I hope you don't mind that I reply to the list also - this might also be interesting to others. Daniel Carrera (dcarrera@xxxxxxxxxxxx) wrote: > On Sat, Mar 29, 2003 at 03:54:24AM +0100, Simon Budig wrote: > > > > What is a PDB function? Is that what people use to make bindings? > > > > Yes, and to write plugins etc - except that some plugin-authors are > > probably not aware of that fact. Gimp maintains a Procedural DataBase > > with various functions. Libgimp has some functions to access this > > Databasea (search, execute) plus a lot of wrappers around this > > functions. Basically for a language binding you have to use these > > pdb-access functions to map the pdb functions into the target language. > > > > http://developer.gimp.org/api/1.3/libgimp/libgimp-gimpproceduraldb.html > > I've read this page, but I don't feel any closer to understanding this. > What is a procedural database? Why would I want to touch it when I'm > trying to make language bindings? For a short explantation of the PDB have a look at http://www.home.unix-ag.org/simon/gimp/guadec2002/gimp-plugin/html/ > Shouldn't I try to make bindings around all the other libgimp functions, > like gimp_image_scale() or things like that? The point is, that this is not necessary. If you look at the libgimp implementation of gimp_image_scale() you'll see that it is a short wrapper around a PDB call: gboolean gimp_image_scale (gint32 image_ID, gint new_width, gint new_height) { GimpParam *return_vals; gint nreturn_vals; gboolean success = TRUE; return_vals = gimp_run_procedure ("gimp_image_scale", &nreturn_vals, GIMP_PDB_IMAGE, image_ID, GIMP_PDB_INT32, new_width, GIMP_PDB_INT32, new_height, GIMP_PDB_END); success = return_vals[0].data.d_status == GIMP_PDB_SUCCESS; gimp_destroy_params (return_vals, nreturn_vals); return success; } Most libgimp functions look exactly this way. So, if you want to look at it this way the libgimp is (except the PDB-access stuff) basically a C-binding. Bindings for other languages don't need to use gimp_image_scale() from libgimp, they can use their wrapper around gimp_run_procedure directly. IIRC the Perl bindings don't have fixed wrappers around all PDB functions. They dynamically search the PDB with some heuristics if a function gets called. This has the advantage that it can provide bindings to PDB functions the author (of the binding) at the time of writing did not know about. > I don't understand how PDB relates to the rest of Gimp. Basically the PDB *is* the GIMP. Ok, this is not exactly true, but as far as plugins and bindings it is. You cannot access image manipulation functions that are not entered in the PDB - fortunately most functionality is available via the PDB. > Thank you for your help. I hope this helps. Bye, Simon -- Simon.Budig@xxxxxxxxxxx http://www.home.unix-ag.org/simon/
