Re: [PATCH] GNOME VFS support for dia

[Lars Clausen <lrclause cs uiuc edu>]

On 24 Nov 2003, W. Michael Petullo wrote:
> > 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.

Not if VFS lookup fails, but if VFS itself fails to load.  The #define
GNOME area in your patch just bails out when it can't find VFS, where it
could just fall back on ordinary fopen.

> > 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.

Good.  I don't think Gnome exists under Win32, anyway.

> > 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.

Oh, it doesn't just open a FILE*?  That's annoying.  But if you can make a
clean wrapper, that'll be fine.

-Lars

-- 
Lars Clausen (http://shasta.cs.uiuc.edu/~lrclause)| HÃrdgrim of Numenor
"I do not agree with a word that you say, but I   |----------------------------
will defend to the death your right to say it."   | Where are we going, and
    --Evelyn Beatrice Hall paraphrasing Voltaire  | what's with the handbasket?