Cocoa VBox

VBox.h

//
//  VBox.h
//  VBox
//
//  Created by Panupan Sriautharawong on 9/23/11.
//  Copyright 2011 Panupan.com. All rights reserved.
//

@interface WILLVBox : NSView {
    NSColor *backgroundColor;
    int spacing;
    int padding;
    BOOL mouseEnabled;
    BOOL repositionOrigin;
    NSTrackingArea* trackingArea;
}
@property (nonatomic, strong) NSColor *backgroundColor;
@property (nonatomic, assign) int spacing;
@property (nonatomic, assign) int padding;
@property (nonatomic, assign) BOOL mouseEnabled;
@property (nonatomic, assign) BOOL repositionOrigin;
- (void)updateDisplayList;

@end

VBox.m

//
//  VBox.m
//  VBox
//
//  Created by Panupan Sriautharawong on 9/23/11.
//  Copyright 2011 Panupan.com. All rights reserved.
//

#import "WILLVBox.h"

@implementation WILLVBox

@synthesize backgroundColor;
@synthesize spacing, padding, mouseEnabled, repositionOrigin;
- (void)setSpacing:(int)o {
    spacing = o;
    [self updateDisplayList];
}
- (void)setPadding:(int)o {
    padding = o;
    [self updateDisplayList];
}
- (BOOL)isFlipped { return YES; }


#pragma mark - Overrides
- (id)initWithFrame:(NSRect)frameRect
{
    self = [super initWithFrame:frameRect];
    if (self) {
        spacing          = 8;
        padding          = 20;
        mouseEnabled     = false;
        repositionOrigin = true;
        [self setAutoresizingMask: NSViewWidthSizable | NSViewMaxXMargin | NSViewMinYMargin];    
    }
    
    return self;
}

- (void)didAddSubview:(NSView *)subview 
{
    [subview addObserver:self 
              forKeyPath:@"frame" 
                 options:NSKeyValueObservingOptionNew 
                 context:nil];    
    [subview addObserver:self 
              forKeyPath:@"hidden" 
                 options:NSKeyValueObservingOptionNew 
                 context:nil];
    [self updateDisplayList];
}

- (void)willRemoveSubview:(NSView *)subview 
{
    [subview removeObserver:self 
                 forKeyPath:@"frame"]; 
    [subview removeObserver:self 
                 forKeyPath:@"hidden"];       
    [self updateDisplayList];
}

- (void)updateDisplayList
{
    //NSLog(@"updateDisplayList managedViews:%d", (int)[managedViews count]);
    
    int newHeight = padding * 2;
    int currY     = 0;
    NSView *subview;

    // Get new height
    for (subview in self.subviews) {
        if (!subview.isHidden) {
            newHeight += subview.frame.size.height + spacing;
        }
    }    
    
    // Resize and reposition VBox    
    [self setFrame:NSMakeRect(self.frame.origin.x, 
                              repositionOrigin ? self.frame.origin.y + (self.frame.size.height-newHeight) : self.frame.origin.y, 
                              self.frame.size.width,
                              newHeight)];
     
    // Rearrange subviews
    currY = padding;
    for (subview in self.subviews) {
        if (subview.isHidden) continue;
        [subview setFrameOrigin:NSMakePoint(subview.frame.origin.x, currY)];
        currY += subview.frame.size.height + (subview != [self.subviews lastObject] ? spacing : 0);
    }
    
    if (mouseEnabled) {
        [self removeTrackingArea:trackingArea];
        trackingArea = [[NSTrackingArea alloc] initWithRect:self.frame options: (NSTrackingMouseMoved |  NSTrackingMouseEnteredAndExited | NSTrackingActiveAlways) owner:self userInfo:nil];
        [self addTrackingArea:trackingArea];
    }
}

// Prevents retain cycle caused by observers
- (void)viewDidMoveToSuperview
{
    for (NSView *subview in self.subviews) 
    {
        if (self.superview) {
            [subview addObserver:self 
                      forKeyPath:@"frame" 
                         options:NSKeyValueObservingOptionNew 
                         context:nil];
        }
        else {
            [subview removeObserver:self 
                         forKeyPath:@"frame"];
        }
    }
}

- (void)drawRect:(NSRect)dirtyRect
{
    // Drawing code here.
    if ([self backgroundColor]) 
    {
        [backgroundColor setFill];
        NSRectFill(dirtyRect);
    }
}

#pragma mark - NSKeyValueObserving
- (void)observeValueForKeyPath:(NSString *)keyPath 
                      ofObject:(id)object 
                        change:(NSDictionary *)change 
                       context:(void *)context 
{
    [self updateDisplayList];
}

@end