Re: GNUstep slowness while drawing

[Andreas Höschler]

Hi Fred,

> > 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?
>
> As this simple change isn't working, I will need a stripped down 
> version of your application to reproduce the issue.

While preparing the stripped down application I figured out that this 
has nothing to do with event handling but is indeed a drawing problem. 
The stripped down version (subclass of NSView) worked perfectly also 
under GNUstep. My ObjectBrowserView was actually a subclass or 
NSImageView since I wanted to have a background image. :-) Now this 
NSImageView was setup with  [_platformObject 
setImageScaling:NSScaleToFit]. This turned out to be the problem. After 
adding

#ifndef __APPLE__
- (void)setImageScaling:(NSImageScaling)image
{
   [super setImageScaling:NSScaleNone];
}
#endif

to my NSImageView subclass the performance problem was gone. Now I have 
a rather ugly blue frame around the image but I can at least reasonably 
select objects now which is much more important.

On MacOSX (10.2.8) I see no performance problem even with NSScaleToFit. 
However, I can live with this solution.

Thanks a lot!

Regards,

 Andreas