Re: XPM support for NSImage

[Richard Frith-Macdonald]

On 8 Nov 2006, at 03:27, Hubert Chan wrote:

> On Wed, 08 Nov 2006 00:47:53 +0100, Fred Kiefer <address@hidden>  
> said:
>
> > Hubert Chan schrieb:
> > > Is there any interest in including my XPM NSImage support into
> > > GNUstep GUI?  If so, I will sign the copyright form, and rework  
> > > it as
> > > a patch against GNUstep GUI, rather than as a standalone class.  If
> > > not, I'll probably get it into Etoile.
>
> > I would love to see support for XPM images and also many other  
> > format,
> > but not directly in gui.
>
> OK, that's fine.
>
> FWIW, I'm hoping to (eventually) also work on SVG support (using
> librsvg), PDF support (using PopplerKit, and implement Apple's
> NSPDFImageRep API), and DjVu support.  (Roughly in that order.)

I'd like to see a lot of image support provided with the gui library  
(though not actually in the library itsself).   As fred suggested,  
filter services are ideal for this ... allowing you to provide  
functionality for use by all applications, without forcing those  
applications to actually link the code into themselves.

> > We rather should have it as an image filter service. Of course
> > somebody will have to write supporting code for that as well, but it
> > seems like the better solution. And it should not be to hard doing
> > this via the code already in NSPasteboard. But I don't have an  
> > idea on
> > the tasks involved in writing the filter service.
>
> Hmm... I'm not sure exactly what an image filter service is, or why  
> it's
> needed.  Right now, I'm just registering my class using NSImageRep's
> +registerImageRepClass:, so if you ask NSImage to load an XPM file,
> everything works fine.  What else is needed?
>
> My current plan is to make it into a "user defined AppKit bundle",
> instead of making it a library as I'm currently doing it, so that  
> every
> app can benefit from it.

I think what Fred probably intended was  to have a lot of filter  
services available for different image file formats.  Then in the gui  
library have an NSImageRep subclass which would use any filter  
service as required.  That way, the only extra code in the gui  
library (and hence linked in to apps) would be the little bit letting  
the NSImageRep use filter services.  The gui package could install a  
set of image filters, but other packages/applications would also be  
able to supply more or better filters.  When the gui needs to convert  
from format A to B it would just ask the NSImageRep to do it, and  
that would automatically pick one of the available filters to perform  
the actual conversion.