Hi, thanks,
it works. But now I get a new trouble:
If I set setHasHorizontalScroller:NO, any scrollPoint: I call
programmatically is not seen by the next drag.
In details:
within the method endGestureWithEvent: I call
NSLog(@"endGesture %@", NSStringFromPoint([mClipView bounds].origin));
// and I get X = 50;
[NSObject cancelPreviousPerformRequestsWithTarget:self
selector:@selector(scrollToPageNum:) object:nil];
// now we go and adjust the scroll to 100.
[self performSelector:@selector(scrollToPageNum:) withObject:NumI(page)
afterDelay:0];
within the scrollToPageNum: I programmatically scroll the clipView to the
X point = 100.
[mDocView scrollPoint:newPoint];
[self reflectScrolledClipView:mClipView];
[self display];
Now I can see the page well positioned at X = 100
Also, if I check with
NSLog(@"scrollToPage %@", NSStringFromPoint([mClipView bounds].origin));
everything looks ok. I get X = 100;
Now If a drag again on the trackpad, the clipView moves suddenly to the X=50
then I can drag the page. Wrong! When setHasHorizontalScroller:YES the error
doesn't occur.
What do I miss?
Regards
-- Leonardo
> Da: Quincey Morris <quinceymor...@earthlink.net>
> Data: Thu, 16 Jun 2011 16:17:53 -0700
> A: Leonardo <mac.iphone....@gmail.com>
> Cc: <cocoa-dev@lists.apple.com>
> Oggetto: Re: pagingEnabled on NSScrollView?
>
> On Jun 16, 2011, at 14:57, Leonardo wrote:
>
>> I would like to reach the same effect as UIScrollView.pagingEnabled, but on
>> an NSScrollView. Can that be done?
>>
>> If not, which technique should I use?
>> I thought to deal with NSAnimationContext to move the scrollView's document
>> with scrollPoint: when a scrolling ends (the finger stops dragging on the
>> track-pad). Am I on the right way?
>
> NSScrollView is not designed to have this behavior, so you'll have to do the
> work.
>
> The basic approach is to have (say) your window controller monitor the scroll
> view's clip view's frame- and bounds-changed notifications. When you receive
> these notifications, you examine the relationship between the "clip" view
> bounds and the "document" (i.e. enclosed) view frame, and adjust the
> relationship to align the two views however you want.
>
> To detect when scrolling "ends", you can use a well-known trick. When you see
> a notification, don't perform the scrolling adjustment immediately, but
> schedule it for "later" using 'performSelector: ... afterDelay: 0'. Since you
> don't want multiple deferred adjustments to get queued, you first cancel any
> pending ones with one of the 'cancelPrevious...' or 'cancelPerform...'
> methods, just before invoking 'performSelector:...'. That way, the last one
> "wins".
>
> If you want to have this adjustment animate, you should be able to use the
> appropriate view's animator or NSViewAnimation to move the document view
> frame.
>
> The only difficulty I can think of is if Lion's trackpad gesture-based
> scrolling itself has some animation built into it (e.g. an iOS-like "bounce").
> In that case you might have some trouble trying to integrate your animation
> with the built-in one.
>
> However, given that all of this is not expected Mac scroll view behavior,
> unless you have a *very* compelling need for it, I'd recommend you don't do
> it. NSScrollView responds to the Page Up and Page Down keys for paging. Why
> limit the user to where you think the page boundaries are?
>
>
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