How to maintain the scroll position in NSScrollView when changing scale?

Question

I\'ve got an NSView (myView) wrapped in an NSScrollView (myScrollView). Using zoom-in/out buttons, the user can alter the scale of myView. If the user is currently scrolle

Answer 1

This is an old question, but I hope someone looking for this finds my answer useful...

float zoomFactor = 1.3;

-(void)zoomIn
{
    NSRect visible = [scrollView documentVisibleRect];
    NSRect newrect = NSInsetRect(visible, NSWidth(visible)*(1 - 1/zoomFactor)/2.0, NSHeight(visible)*(1 - 1/zoomFactor)/2.0);
    NSRect frame = [scrollView.documentView frame];

    [scrollView.documentView scaleUnitSquareToSize:NSMakeSize(zoomFactor, zoomFactor)];
    [scrollView.documentView setFrame:NSMakeRect(0, 0, frame.size.width * zoomFactor, frame.size.height * zoomFactor)];

    [[scrollView documentView] scrollPoint:newrect.origin];
}

-(void)zoomOut
{
    NSRect visible = [scrollView documentVisibleRect];
    NSRect newrect = NSOffsetRect(visible, -NSWidth(visible)*(zoomFactor - 1)/2.0, -NSHeight(visible)*(zoomFactor - 1)/2.0);

    NSRect frame = [scrollView.documentView frame];

    [scrollView.documentView scaleUnitSquareToSize:NSMakeSize(1/zoomFactor, 1/zoomFactor)];
    [scrollView.documentView setFrame:NSMakeRect(0, 0, frame.size.width / zoomFactor, frame.size.height / zoomFactor)];

    [[scrollView documentView] scrollPoint:newrect.origin];
}