- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
    // Insert code here to initialize your application
    NSScrollView *scrollView = [[NSScrollView alloc] init];
    [self.window.contentView addSubview:scrollView];
    [scrollView setFrame:NSMakeRect(0, 0, self.window.contentView.frame.size.width, self.window.contentView.frame.size.height)];
    [scrollView setHasHorizontalScroller:YES];

    NSView *documentView = [[NSView alloc] initWithFrame:NSMakeRect(0, 0, 1000, scrollView.frame.size.height)];
    [documentView setWantsLayer:YES];
    [documentView.layer setBackgroundColor:[NSColor redColor].CGColor];
    [scrollView setDocumentView:documentView];

    NSView *aView = [[NSView alloc] initWithFrame:NSMakeRect(10, 10, 30, 30)];
    aView.layer.backgroundColor = [NSColor blueColor].CGColor;
    [aView setWantsLayer:YES];
    [aView setNeedsLayout:YES];
    [aView setNeedsDisplay:YES];
    [scrollView addSubview:aView];
    //What I really want is [scrollView addFloatingSubview:aView forAxis:NSEventGestureAxisHorizontal]; but since the `addSubview` doesn't work, so the problem is not at the floating stuff.
}