Mouse Enter/Exit events on partially hidden NSViews

Question

I have a problem that I think is solvable with some hackery, but I'm very curious if there is an easier way to get the job done without having to do all of that.

I have a stack of NSViews (layer-backed, if that somehow helps provides some better solution), as shown below:

The view stack/layout

The thing here is that this is essentially a menu, but is hover-sensitive. If the user hovers over one of the exposed parts of the lower-level views, I need to perform an action depending on what that view is. It is a dynamic system so the number of stacked menu items like this may change, making static calculations more difficult. As you can see, they are basically all a copy (shape-wise) of the first item, but then rotated a bit the further you go down the stack via simple transform rotation.

My question to the SO community is what do you all think the best approach to getting mouseEntered: and mouseExited: events for just the literally visible portions of these views?

What I have attempted to do is use an NSTrackingArea on the visibleRect portion of these views, which sounds much more handy than it really is in this situation. In reality, the visibleRect seems to be "visible" for all of them, all the time. Nothing is explicitly blocked or hidden by anything more than just a partially overlapping NSView. All that happens is I get a spammed console from all of the views screaming out at once that a mouse entered their rect.

Something I am considering is making sub-NSView's of each menu item and having each of those be responsible for the tracking area... each menu item having a "strip" view along the right and bottom sides that could report, but that's still a bit of a hack and is icky.

Does anyone have a better idea? Perhaps one from experience?

Thanks!

rdelmar rdelmar · Accepted Answer · 2012-04-03T02:59:43

I know you already have a solution, but I thought I would try a different approach, that didn't require getting tons of mouseMoved events. I created 3 custom views in code, added tracking rects for them and sent all mouseEntered and mouseExited messages to the same method that does a hitTest to determine which view is top most. This is the code for the content view of the window.

@implementation MainView
@synthesize oldView;

-(void)awakeFromNib {
    oldView = nil;
    Card *card1 = [[Card alloc]initWithFrame:NSMakeRect(150, 150, 200, 150) color:[NSColor redColor] name:@"Red Box"];
    NSTrackingArea *area1 = [[NSTrackingArea alloc]initWithRect:card1.frame options:NSTrackingMouseEnteredAndExited|NSTrackingActiveInActiveApp owner:self userInfo:nil];
    [self addTrackingArea:area1];
    [self addSubview:card1];

    Card *card2 = [[Card alloc]initWithFrame:NSMakeRect(180, 120, 200, 150) color:[NSColor yellowColor] name:@"Yellow Box"];
    NSTrackingArea *area2 = [[NSTrackingArea alloc]initWithRect:card2.frame options:NSTrackingMouseEnteredAndExited|NSTrackingActiveInActiveApp owner:self userInfo:nil];
    [self addTrackingArea:area2];
    [self addSubview:card2];

    Card *card3 = [[Card alloc]initWithFrame:NSMakeRect(210, 90, 200, 150) color:[NSColor greenColor] name:@"Green Box"];
    NSTrackingArea *area3 = [[NSTrackingArea alloc]initWithRect:card3.frame options:NSTrackingMouseEnteredAndExited|NSTrackingActiveInActiveApp owner:self userInfo:nil];
    [self addTrackingArea:area3];
    [self addSubview:card3];
}

-(void)mouseEntered:(NSEvent *)theEvent {
    [self reportTopView:theEvent];
}

-(void)mouseExited:(NSEvent *)theEvent {
    [self reportTopView:theEvent];
}

-(void)reportTopView:(NSEvent *)theEvent {
    id topView = [self hitTest:[theEvent locationInWindow]];
    if (![topView isEqual:oldView]) {
        oldView = topView;
        ([topView isKindOfClass:[Card class]])? NSLog(@"%@",[(Card *)topView name]):NULL;
    }
}

This is the code for what I called cards (colored rectangles):

@implementation Card
@synthesize name,fillColor;

- (id)initWithFrame:(NSRect)frame color:(NSColor *)color name:(NSString *)aName{
    self = [super initWithFrame:frame];
    if (self) {
        self.fillColor = color;
        self.name = aName;
    }
    return self;
}

- (void)drawRect:(NSRect)rect {
    [self.fillColor drawSwatchInRect:rect];

}

Mouse Enter/Exit events on partially hidden NSViews

4 Answers

Overlapping tracking-areas:

VS the default enter and exit behaviour: