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I’m trying to create a subclassed NSSplitView for a specific need: I want a 2-subview split with one of them always keeping a specific aspect ratio (in this case, 2.5 times its width). To that end I’ve subclassed NSSplitView, and I’ve determined that I really only need to override adjustSubviews as follows

-(void)adjustSubviews { NSLog(@”adjust splitviews”); id left=self subviews] objectAtIndex:0]; id right=[[self subviews] objectAtIndex:1]; float width;

// determine if user resized the divider directly, or if this was
// from another event such as a window resize with a "springy" splitview
if([[NSMouseInRect([NSEvent mouseLocation], [self bounds], NO))
    // divider resize, calculate based on new width
    width=[right frame].size.width;
    // from elsewhere, calculate based on new height
    width=round([self frame].size.height/2.5);

// resize the subview to the correct aspect, and resize the splitview for new height
[left setFrameSize:NSMakeSize([self frame].size.width-width-[self dividerThickness],round(width * 2.5))];
[self setFrameSize:NSMakeSize([self frame].size.width,round(width * 2.5))];
[super adjustSubviews];  }

I have this subclassed splitview in a window, set to expand with the window (“springy”); it works perfectly when I resize the window, but it doesn’t work when I try to resize the splitview directly using the divider. The problem is that I don’t know how to capture a divider resize/move (adjustSubviews doesn’t fire). I’ve also tried using a notification (no go), as well as overriding mouseDragged: but it seems that only fires when the mouse is dragged in one of the subviews, not the divider.

Is there a way I can detect a divider move?

Instead of subclassing NSSplitView, set an object as its delegate and implement the delegate methods. See SplitViewBasics.

I’ve already tried this; it works, but the code is really messy, mostly due to the fact that I must disable/reenable notifications and delegates (for the splitview, windows, etc.) so that resizes work properly and isn’t jittery due to the resize codes being called twice (from delegate + notifications), and I still haven’t been able to really make that work perfectly (some notifications still occur dispite being removed), so I really think subclassing is a better solution in end, both for control of the resize, code size, and just plain simplicity.

I think you had your [super adjustSubviews] for nothing there, and the splitview tended to move up within the window when resizing the window. I did have a similar need a while back; here’s what I came up with (adapted your code above to keep it familiar to better see changes):

@interface RatioSplitView : NSSplitView { BOOL selfDrag; } -(id)init; @end

@implementation RatioSplitView -(id)init { self=[super init]; selfDrag=NO; return self; }

-(void)adjustSubviews { id right=self subviews] objectAtIndex:0]; id left=[[self subviews] objectAtIndex:1]; float width; float height;

[[NSEvent * theEvent=[NSApp currentEvent];
if( [self frame].size.height!=round([left frame].size.width * 2.5) || [theEvent deltaX] || [theEvent deltaY])
    if(!selfDrag) // dragging divider
        height=[self frame].size.height;
    else  // other resize
        width=[left frame].size.width;
        height=round(width * 2.5);
    // resize the subview to the correct aspect, and resize the splitview for new height
    [right setFrameSize:NSMakeSize([self frame].size.width-width-[self dividerThickness],height)];
    [left setFrame:NSMakeRect([self frame].size.width-width,[right frame].origin.y,width,height)];
    [self setFrame:NSMakeRect([self frame].origin.x,[self frame].origin.y,[self frame].size.width,height)];
{[super adjustSubviews];}  }


It’s smooth when resizing the window, and the splitview itself, but it could probably be optimized (don’t know if I have the setNeedsDisplay… stuff correctly in the right order). I didn’t try to see if the window could be resized automatically when the spitview is resized by hand, but I suspect it might cause a loop since the splitview would get resized too I imagine (and round and round we go).

But I agree - beats trying to implement delegates and such to make the resize happen.