Re: [PATCH] GNOME VFS support for dia

["W. Michael Petullo" <mike flyn org>]

> > I wrote a quick patch for dia (CVS tree as of Nov 23) that adds support
> > for opening and manipulating GNOME VFS URIs.  I did this using
> > libgnomevfs, libgsf and the gsf_xml_parser_context function.  The new
> > code is enabled as long as the GNOME preprocessor variable is #define'd
> > (--enable-gnome).

> > So now "dia file:///path/to/diagram.dia" should work, with the following
> > caveats:

> > 1.  For some reason compression is not working (it only works with
> > uncompressed files).  If anyone has experience with gsf_input_gzip_new,
> > I could use your help!

> > 2.  I have not yet looked at the import and export filters, but I suspect
> > they may need modification too.
 
> Two so far:  Shouldn't Gnome fall back on normal file opening if VFS fails?

I'm of the opinion that it should not.  GNOME's VFS is a pretty
fundamental module within the desktop.  If file:///foo.dia can't be opened
then I think it should be assumed that it doesn't exist.  Falling back
to stdio seems like it would just add complexity.

> And the bit about creating a tmp file is the way it is for Win32
> compatibility. 

The new code will have to be used when GNOME is #define'd until I find
a gsf/gnomevfs-happy mkstemp.  I'll put the Win32 code back in as the
default, though.

> The import and export filters ought to be redone to call just one file
> opening function, then.  We don't want to have this complexity in 15 
> different places.

Right.  I did a quick analysis of dia's plugins and this is what I discovered:

Type            File                    Import/Export   Interface
====            ====                    =============   =========
png             export_png.c            export          libpng 
                                                (need to use png_set_read_fn)
ps              diapsrenderer.c         export          fprintf
cgm             plugins/cgm             export          putc
dxf             plugins/dxf             both            fprintf/fgets
hpgl            plugins/hpgl            export          fprintf
metapost        plugins/metapost        export          fprintf
pixbuf          plugins/pixbuf          both            gdk_pixbuf_save/
                                                        gdk_pixbuf_new_from_file
pstricks        plugins/pstricks        export          fprintf
shape           plugins/svg             export          libxml2?
svg             plugins/svg             both            libxml2?
wpg             plugins/wpg             export          fwrite
xfig            plugins/xfig            both            fprintf/fscanf
xslt            plugins/xslt            both            libxml2?

Since most plugins use stdio, I think I should write a #ifdef'ed
mini-library that provides GNOME VFS if available but falls back on
direct stdio.  All of these modules could then cleanly use that code.
And the exceptions (like export_png.c/libpng and pixbuf/gdk_pixbuf_save)
could be provided a couple of lines of wrapper to glue them in.

The result should be little or no #ifdef's in plugin code.

-- 
Mike

:wq