Re: GNUstep themeing and MacOS HITheme APIs...

[Adrian Robert]

On Nov 5, 2004, at 4:20 PM, Michael Hanni wrote:

> Hi,
>
> Just one point...
>
> --- "M. Uli Kusterer" <witness@t-online.de> wrote:
>
> >  If you want to allow that people create custom controls that match 
> > any
> > theme, you may still want to make sure you have a complete set of 
> > high-
> > and low-level theme-drawing APIs. Both a call to draw a full NSTabView
> > as well as a call to draw just a tab or just the body area of a tab
> > view, etc. Having a look at Apple's stuff (both in HITheme.h and
> > Appearance.h) is a good way to make sure nothing is overlooked.
>
> The latest NSTabView code
> (http://www.cc.utah.edu/~msh3/gnustep/NSTabView-NG-0.02.tgz) has 
> methods to
> draw the whole tab and for each side of the tab. In theory you could 
> override
> easily any of these methods to completely change the look of the tab.

I'd like to insert a general plea here that people working on theming 
support take performance into account.  From the sound of the 
discussion it seems easy to add many layers of method calls, pixmap 
composits, etc. that must be executed for every exposure and update 
operation on each widget.  An example of a bad result is Java Swing, 
which has extensive theming support but results in interfaces that even 
on fast machines can feel like molasses.  (Not all of this is the fault 
of theme support, but some is.)  I hope this does not happen for 
GNUstep, or at least can be short-circuited if you want a simple (but 
fast) GUI.

I don't know that much about this, but I imagine that the same 
approaches that work well in GTK, a pure-C library, for example, might 
not be as suitable in Objective-C with method call overhead.

(Please ignore this message if performance is already being attended 
to, but I just thought I would throw the issue out now. ;)