Re: Two gui ABI changes

[Wolfgang Lux]

Fred Kiefer wrote:

> Markus Hitter wrote:
> > Am 24.03.2009 um 09:07 schrieb Fred Kiefer:
> >
> > > The other change is to give up a special behaviour in GNUstep. Apple
> > > documents that calls to [NSView setNeedsDisplay:] (and
> > > setNeedsDisplayInRect:) only work as expected on the main thread.
> > > GNUstep has some code that lets these methods do their work on a
> > > secondary thread as well.
> >
> > Isn't this a serious enhancement over Cocoa? As far as I can see,
> > there's nothing stopping you from writing Cocoa-compatible code with
> > GNUstep, so I'm not sure wether it's wise to introduce limitations  
> > just
> > to enhance portability slightly. Any chance for a #ifdef
> > COCOA_COMPATIBILITY compile time flag or even a runtime check (global
> > flag which NSLog()'s a warning if set and this feature is used)?
>
> Yes, it is an enhancement in GNUstep, but it costs run time and will
> results in applications not being portable. What it does is to save
> programmers that make changes to gui objects the hassle of restricting
> these changes to the main thread, as only there setNeedsDisplay: will
> work properly on Cocoa. But then, any application that relies on this
> feature will fail on Apple systems.

As Markus already suggested, the gui could just NSLog a message from
-setNeedsDisplay: when it is called for the first time on a secondary
thread, saying that this feature is a GNUstep specific extension that
does not work on Cocoa. This is just the same way Apple warns developers
about the non-portable use of some APIs (in general deprecated ones).
IMHO, the only reasons for removing the ability to call - 
setNeedsDisplay:
from a secondary thread would be that it noticeably slows down the gui
or that it complicates the implementation.

Wolfgang