How to pass scroll events to parent NSScrollView

cocoa, nsevent, nsscrollview

Solution

This is really embarrassing. After weeks of putting it off, I made a first attempt to get a subclassed NSScrollView to behave passively — and it turned out to be a no brainer.

Here’s the subclass:

h file:

#import <Cocoa/Cocoa.h>

@interface ScrollViewPassive : NSScrollView {

// This property is assigned a ref to windowController’s main scrollview.
NSScrollView *svActive; 

}

@property (nonatomic, retain) NSScrollView *svActive;

@end

m file:

#import "ScrollViewPassive.h"

@implementation ScrollViewPassive

@synthesize svActive;

// Pass any gesture scrolling up to the main, active scrollview.
- (void)scrollWheel:(NSEvent *)event {
    [svActive scrollWheel:event];
}

@end

There’s no need to make outlets for these passive scrollviews; I give them their refs to the main scrollview right after their xibs are assigned as content to the NSBox:

    [self.boxDisplayingTextViews setContentView:self.subviewCtllr1.view];
    // A textview's superview's superview is its scrollview:    
    ((ScrollViewPassive *)[[self.subviewCtllr1.textview1 superview] superview]).svActive = self.scrollviewMain;

That’s it. Works like a charm.

Problem

I need fixed-size NSTextViews inside a larger scrolling window. IB requires that the textviews be inside their own NSScrollViews, even though their min/max sizes are fixed so that they won’t actually scroll. When trackpad gestures are made within the textview frames (regardless of whether they have focus), they are captured by the textviews’ scrollviews, so nothing happens. How do I tell the textviews’ scrollviews to pass scroll events up to the window’s main scrollview? (Or perhaps I should be asking how I tell the window’s main scrollview to handle these events itself and not pass them on to its child scrollviews.) The IB structure is like this: - window - window’s content view - big scrollview for window (desired target for scroll events) - box - swappable content view in separate xib - scrollview for textview - textview And, yes, the window does scroll correctly when the textviews do not have focus.

Original source