NSScrollView jumping to previous scroll when using scroll wheel

FROM : Chilton Webb
DATE : Mon Jan 07 16:27:33 2008

Hi,

I suspect this is a matter of just missing some particular method 
call, but I'm out of ideas.

I set up an NSScrollView object in IB containing a custom NSView. I 
want to programmatically scroll it horizontally back and forth. I can 
do this just fine (see code below), and I can scroll it using the 
scroll wheel just fine. But if I programmatically scroll it, and then 
use the scroll wheel, the scroll 'jumps' back to the place where I 
left off scrolling with the scroll wheel earlier.

If I show the scroll view's horizontal scroll bar using [[self 
enclosingScrollView] setHasHorizontalScroller:YES]; , the location of 
the scroll I set programmatically is preserved, and everything works 
beautifully. If I set that to NO, which is the desired setting, the 
jumping occurs. How can I make it not jump?

Here's my code.

- (void) scrollIt
{
   NSScrollView *scrollView = [self enclosingScrollView];
   NSPoint currentScrollPosition=[[scrollView contentView] bounds].origin;
   NSLog(@"Before: %@", NSStringFromPoint(currentScrollPosition));

// _scroll is an NSPoint that we set earlier, based on the current 
scroll plus our desired offset.
   [[scrollView documentView] scrollPoint:_scroll];

// Turning this to YES or NO will deactivate or activate the bug
   [[self enclosingScrollView] setHasHorizontalScroller:YES];
   
// This line verifies that the bug exists, and that we are actually 
jumping to the coordinates we scrolled
// to when we last used the scroll wheel
NSLog(@"After: %@", NSStringFromPoint([[[self enclosingScrollView] 
contentView] bounds].origin));


// These were suggested, but didn't help
//  [scrollView setHorizontalLineScroll:delta];
//  [scrollView reflectScrolledClipView:[scrollView documentView]]; // 
didn't help
//  [scrollView reflectScrolledClipView:[scrollView contentView]]; // 
didn't help
//  [scrollView reflectScrolledClipView]; // didn't help

}


Again, just having the scroller exist or not exist will toggle the 
bug. Is there something I'm missing?

Thank you,
-Chilton