Gap above NSMenuItem custom view

Your post is tagged "Objective-C" and "Cocoa", although your sample code is C and Carbon. I assume you'd prefer a Cocoa solution?

It's actually pretty simple in Cocoa. The only trick is learning how to draw outside the lines. :-)

@interface FullMenuItemView : NSView
@end

@implementation FullMenuItemView
- (void) drawRect:(NSRect)dirtyRect
{
    NSRect fullBounds = [self bounds];
    fullBounds.size.height += 4;
    [[NSBezierPath bezierPathWithRect:fullBounds] setClip];

    // Then do your drawing, for example...
    [[NSColor blueColor] set];
    NSRectFill( fullBounds );
}
@end

Use it like this:

CGFloat menuItemHeight = 32;

NSRect viewRect = NSMakeRect(0, 0, /* width autoresizes */ 1, menuItemHeight);
NSView *menuItemView = [[[FullMenuItemView alloc] initWithFrame:viewRect] autorelease];
menuItemView.autoresizingMask = NSViewWidthSizable;

yourMenuItem.view = menuItemView;