Re: Drawing optimization question

[Adrian Robert]

On Mar 9, 2005, at 3:14 PM, Fred Kiefer wrote:

> Adrian Robert wrote:
> > I'm drawing directly to a view, either using [NSString 
> > -drawAtPoint..]  or,
> > say, with NSRectFill() and friends.
> > I do something like:
> >     [view lockFocus]
> >       (draw comands ...)
> >     [view unlockFocus]
> >     [[view window] flushWindow]
>
> ...
>
> Even [NSWindow flushWindow] will only flush the union of the 
> rectangles it thinks some drawing was going on, but it guesses them 
> based on lockFocusInRect:, if you locked the whole window, the whole 
> window will be flushed.

Thanks, I'll try lockFocusInRect:.


> > - Alternatively, could I just cause the drawing to go directly to X,
> >   and do away with the flush completely?
> >   I thought NSBackingStoreRetained would do this, but the results I
> >   get with it are not what I'd expect.
>
> NSBackingStoreNonretained would be the one to draw directly. But I am 
> not sure if this makes much of a difference.

I'll try this as well.


> I think, you should explain first, why you want to bypass the usual 
> ways of drawing in GNUstep. Only if there really is no way to fit it 
> in there, should you go ahead with this approach.

Short answer: this is the way the Emacs code is and I don't want to 
change it since it worked efficiently and well on 25 MHz NeXT all the 
way through OS X on a G5.

Longer answer: Emacs is weird because it runs two event loops 
simultaneously (the Lisp/Emacs one being primary) and deals out draw 
requests piecemeal to the windowing code, therefore it's not easy to 
use the standard GNUstep [view drawRect:] approach for every case.


>  Even the standard GNUstep drawing may still be slow, but at least 
> there we know, we only draw what we need to draw. And of course should 
> go ahead and try to optimize this.

I don't see any problem in GNUstep, except maybe the flushWindow could 
guess the rect better.  I'm experiencing a situation where the CPU is 
limiting text rendering and cursor movement speed in Emacs, but 90% of 
the CPU is going to X, and only <10% to the GNUstep app.  I'm pretty 
sure the suggestions you made will resolve this.

Thanks!