One more defs user

[Daniel Silva <daniel silva gmail com>]

Hello,

I'm currently writing GTK bindings by hand (to bring GTK into PLT
Scheme) and would rather use the .defs files.  However, they seem to
be missing some information.

For example, gtk_list_store_insert takes a GtkListStore input pointer
and a GtkTreeIter output pointer, but gtk.defs and gtk-types.defs
don't mention that the second pointer is just for output (a return
value).

gtk.defs says:

(define-method insert
  (of-object "GtkListStore")
  (c-name "gtk_list_store_insert")
  (return-type "none")
  (parameters
    '("GtkTreeIter*" "iter")
    '("gint" "position")
  )
)

But in Scheme (using a libffi wrapper), I have to write:

(defgtk gtk_list_store_insert
   (_fun _GtkListStorePtr (iter : (_ptr o _GtkTreeIter)) _int -> _void
-> iter)))

where _fun says gtk_list_store_insert is a function, (_ptr o
_GtkTreeIter) says iter is an output pointer, and "-> _void -> iter"
says the C function returns void but the Scheme function returns iter.

It would be nice if gtk.defs could say:

(define-method insert
  (of-object "GtkListStore")
  (c-name "gtk_list_store_insert")
  (return-type "none")
  (parameters
    '("GtkTreeIter*" "iter" output)
    '("gint" "position")
  )
)


The other part missing right now is computed parameters.  For example,
in gtk_drag_dest_set:

(define-method drag_dest_set
  (of-object "GtkWidget")
  (c-name "gtk_drag_dest_set")
  (return-type "none")
  (parameters
    '("GtkDestDefaults" "flags")
    '("const-GtkTargetEntry*" "targets")
    '("gint" "n_targets")
    '("GdkDragAction" "actions")
  )
)

targets is actually an array and n_targets is its length.  Neither
bits are specified.  Right now I write:

(defgtk gtk_drag_dest_set
  (_fun _GtkWidgetPtr
           _GtkDestDefaults
          (targets : (_list i _GtkTargetEntry))
          (_int = (length targets))
         _GdkDragAction
        -> _void))

and it would be nice if gtk.specs said something like:

(define-method drag_dest_set
  (of-object "GtkWidget")
  (c-name "gtk_drag_dest_set")
  (return-type "none")
  (parameters
    '("GtkDestDefaults" "flags")
    '("const-GtkTargetEntry*" "targets" list)
    '("gint" "n_targets" (auto (length "targets")))
    '("GdkDragAction" "actions")
  )
)

I don't think any of the additions would break existing tools,
considering the first and second elements of the type&name lists stay
the same.


Thanks,
Daniel