Re: gnustep on windows

[Richard Frith-Macdonald]

On 1 Mar 2008, at 17:18, Paul Fox wrote:

> > When programming with GNUstep you will be working against the GNUstep
> > drawing API, not cairo or GDI. It is true that the implementation of
> > this API for cairo is more complete, but even that may be changed.
>
> Oh, I know, but it doesn't make a lot of sense to maintain multiple  
> backends when one will serve. Also GDI vector drawing looks ugly and  
> Cairo looks nice... so I'd prefer to use Cairo. That way, my results  
> should be pretty much the same on Windows and Linux.
> > You might be talking about [Camaelon][1] (spelling is important).
>
> I have read a bit about Camaelon, but my understanding is that it's  
> a theming engine rather than an API. I also have the impression that  
> it's a bit slow because it's pixmap-based. I was looking at the  
> Narcissus theme engine, but the developer made the comment that his  
> patch to NSScroller to enable theming of the scroller was rejected  
> because it didn't conform to the theming API that had been planned.  
> I haven't really been able to find out much about this API, however.

Look at GSTheme.[hm] in the gui library and the Thematic developer app.

The theming stuff is *very* rudimentary so far, but the core framework  
is there for themes to be loaded  and changed at runtime.

A theme is a loadable bundle with resources and (possibly) code.

The code is in the GSTheme class (or a subclass of it).

The idea is that the controls in the gui should eventually draw  
themselves entirely in terms of methods in the GSTheme class (most of  
which are yet to be defined) ... and that those methods can draw  
things in terms of pixmaps (code already in place to support tiling of  
pixmaps etc to draw frames/rectangles) or can draw directly (when the  
theme developer provides a subclass of GSTheme in their theme bundle).

So ... given that the theming API is not yet defined, anyone  
interested has a good opportunity to shape that API.
The Narcissus theme patch was not really rejected ... rather the  
author was asked to rework it to fit in with the GSTheme concept ...  
ie the drawing code should be added to GSTheme, and NSScroller  
modified to call the new methods which are added.  Any API added  
should be well designed ... so that it can easily be implemented using  
pixmaps as well as using hard-coded methods in a GSTheme subclass.

So ... the ideal way to add some theming would be ...

1. Design a new method/methods for GSTheme ... add them to the headers.
2. Alter the gui controls to use the new methods
3a. Implement them in the GSTheme base class in terms of using pixmap  
images with the existing methods
3b. Write a GSTheme subclass to implement the new methods with hard- 
coded drawing rather than pixmaps for performance
4. Modify Thematic to support the new stuff.