Re: GNUstep slowness while drawing

[Andreas Höschler]

Hi Fred,

> Andreas Höschler wrote:
> > Hi all,
> > I have a view subclass with
> > - (void)mouseDown:(NSEvent *)theEvent
> > {
> >    NSPoint locA = [self convertPoint:[theEvent locationInWindow] 
> > fromView:nil];
> >    BOOL shiftPressed = (([theEvent modifierFlags] & NSShiftKeyMask) > 
> > 0);
> >    BOOL keepOn = YES;
> >    BOOL hasDragged = NO;
> >    while (keepOn)
> >      {
> >       theEvent = [[self window] 
> > nextEventMatchingMask:NSLeftMouseUpMask | NSLeftMouseDraggedMask];
> >       switch ([theEvent type])
> >         {
> >          case NSLeftMouseDragged:
> >            {
> >               NSPoint locB = [self convertPoint:[theEvent 
> > locationInWindow] fromView:nil];
> >               NSSize offset =  NSMakeSize(locB.x - locA.x, locB.y - 
> > locA.y);
> >               NSRect oldRect = _selectionRect;
> >               _selectionRect.origin = locA;
> >               if (offset.width < 0)
> >                 {
> >                  _selectionRect.origin.x = locB.x;
> >                  offset.width = -offset.width;
> >                 }
> >               if (offset.height < 0)
> >                 {
> >                  _selectionRect.origin.y = locB.y;
> >                  offset.height = -offset.height;
> >                 }
> >               _selectionRect.size = offset;
> >               _selecting = YES;
> >               [self setNeedsDisplayInRect:NSUnionRect(_selectionRect, 
> > oldRect)];
> >               hasDragged = YES;
> >            }
> >             break;
> >          case NSLeftMouseUp:
> >            {
> >               keepOn = NO;
> >            }
> >             break;
> >          default:
> >             break;
> >         }
> >      }
> > }
> > - (void)drawRect:(NSRect)rect
> > {
> >    [super drawRect:rect];
> >    if (_selecting)
> >      {
> >       [[NSColor grayColor] set];
> >       NSFrameRect(_selectionRect);
> >      }
> > }
> > This draws a rectangle following the mouse until the user releases 
> > the mouse button. On MacOSX the rectangle follows the mouse 
> > instantly. Under GNUstep I see a significant delay. Dragging 
> > rectangles makes no fun there. Any idea why this is so slow? This of 
> > course has nothing to do with rectangles in special but with slow 
> > drawing code in general. In my app I want to drag objects around with 
> > the mouse. This works under GNUstep and MacOX but on GNustep it is 
> > almost too slow to be usable. Is this a known (may be even already 
> > improved) issue? My GNUstep tree is already a year old. :-)
>
> Most likely the slow drawing speed you see in GNUstep has nothing to 
> do with the drawing itself, but with the event handling in GNUstep. 
> The window will just not get a chance to redraw itself.
> One possible reason for this may be that in
> [NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] we 
> handle an expiration date of nil different from Cocoa. There 
> distantPast is used while we use distantFuture, resulting in the loop 
> to wait until the next event happens.
>
> As I am no expert in this area, I would like to get some comments from 
> other developers before changing this code. That change may result in 
> the need to adopt a lot of places that rely on the old behaviour.

For a qick test I changed all occurances of distantFuture to 
distantPast in NSApplication.m. This had no obvious effect, neither 
good nor bad. Drawing (event handling) is still (far too) slow!? Any 
more ideas?

Thanks a lot!

Regards,

  Andreas