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Re: ffi-help: status to date

From: Matt Wette
Subject: Re: ffi-help: status to date
Date: Tue, 24 Oct 2017 17:18:29 -0700

> On Oct 22, 2017, at 11:31 AM, Matt Wette <address@hidden> wrote:
> Hi All,
> I am working on a ffi-helper (FH): a program that will read in a C dot-h file 
> and generate a Guile dot-scm file 
> which defines a module to provide hooks into the associated C library.  

> I was able to generate scm code for glib, gobject, gio, pango, and gtk2+.  
> The following demo code actually works.
> I get a GUI and click the button and it closes, though with an error message:
>    gtkdemo.scm:16:0: Wrong number of arguments to #<procedure hello (widget 
> data)>

> (define (hello widget data)
>  (display "Hello World!\n"))

>  (g_signal_connect button "clicked" hello NULL)

The reason I got error messages was that g_signal_connect uses signature `void 
(*f)(void)' for the 
callback but the semantics of GTK say use `void (*f)(void*, void*)', basically. 
 GTK handles this 
by providing casts for arguments.  I got the code working by hand generating 

  (define ~hello (ffi:procedure->pointer ffi:void hello (list '* '*)))

  (g_signal_connect button "clicked" ~hello NULL)

Doing this by hand is a bit of a mess, but ... there it is.  I am not confident 
that there is a way
to automate or make this easier.  I had to generate a couple other hand-casts 
but the result is that
the demo is now working w/o error messages.  

In case you are interested here are line counts for the text files and sizes 
for the object files.
(oops, didn't include pango; that is bigish)

mwette$ wc gobject.* glib.* gtk2+.* gdk2.*
      26      77     885 gobject.ffi
   12543   28465  426476 gobject.scm
      31      82    1006 glib.ffi
   31326   75035 1013504 glib.scm
      17      47     470 gtk2+.ffi
   92827  210107 3259549 gtk2+.scm
      18      52     534 gdk2.ffi
   18986   45046  639630 gdk2.scm

mwette$ ls -l gobject.* glib.* gtk2+.* gdk2.*
-rw-r--r--  1 mwette  staff   3619461 Oct 22 10:57 gdk2.scm.go
-rw-r--r--  1 mwette  staff   5546829 Oct 22 10:48 glib.scm.go
-rw-r--r--  1 mwette  staff   2554501 Oct 24 16:36 gobject.scm.go
-rw-r--r--  1 mwette  staff  18521997 Oct 22 11:06 gtk2+.scm.go

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