NSTextView, appending text and smooth scrolling

Question

I am trying to implement smooth scrolling in a chat history view I implemented, however if the content I append is big enough the smooth scroll will only scroll for a few lines.

My first guess was that the view did not redraw itself yet.. not the case, even when forcing immediate drawing with -display it still breaks.

- (void)scrollAnimated:(BOOL)animated
{
    if( animated )
    {
        NSClipView *clipView = [[_chatHistoryView enclosingScrollView] contentView];

        [NSAnimationContext beginGrouping];
        [[NSAnimationContext currentContext] setDuration:0.100f];
        NSPoint constrainedPoint = [clipView constrainScrollPoint:NSMakePoint(0, CGFLOAT_MAX)];
        [[clipView animator] setBoundsOrigin:constrainedPoint];
        [NSAnimationContext endGrouping];
    }
    else
    {
        NSRange range;
        range.location = [[_chatHistoryView textStorage] length];
        range.length = 1;
        [_chatHistoryView scrollRangeToVisible:range];
    }
}

What am I doing wrong?

I'm sure this won't solve your problem, but in the non-animated code your range will be out of bounds as it will end at length+1. — appmattus
Been using that code for a while, I probably would have to look in the docs why the (location+1) of the last char ( since the length is (location+1) I guess ) is being accepted. — Antwan van Houdt

Prakruti Joshi Prakruti Joshi · Accepted Answer · 2012-11-07T09:51:49

This may help you...

- (void)maybeAutoscrollForThumb:(ThumbImageView *)thumb {

autoscrollDistance = 0;

// only autoscroll if the thumb is overlapping the thumbScrollView
if (CGRectIntersectsRect([thumb frame], [thumbScrollView bounds])) {

    CGPoint touchLocation = [thumb convertPoint:[thumb touchLocation] toView:thumbScrollView];
    float distanceFromLeftEdge  = touchLocation.x - CGRectGetMinX([thumbScrollView bounds]);
    float distanceFromRightEdge = CGRectGetMaxX([thumbScrollView bounds]) - touchLocation.x;

    if (distanceFromLeftEdge < AUTOSCROLL_THRESHOLD) {
        autoscrollDistance = [self autoscrollDistanceForProximityToEdge:distanceFromLeftEdge] * -1; // if scrolling left, distance is negative
    } else if (distanceFromRightEdge < AUTOSCROLL_THRESHOLD) {
        autoscrollDistance = [self autoscrollDistanceForProximityToEdge:distanceFromRightEdge];
    }        
}

// if no autoscrolling, stop and clear timer
if (autoscrollDistance == 0) {
    [autoscrollTimer invalidate];
    autoscrollTimer = nil;
} 

// otherwise create and start timer (if we don't already have a timer going)
else if (autoscrollTimer == nil) {
    autoscrollTimer = [NSTimer scheduledTimerWithTimeInterval:(1.0 / 60.0)
                                                       target:self 
                                                     selector:@selector(autoscrollTimerFired:) 
                                                     userInfo:thumb 
                                                      repeats:YES];
}

}

NSTextView, appending text and smooth scrolling

1 Answers