-(void) buttonClick:(NSButton *)sender {
// Create view controller
    EXPopoverViewController *viewController = [[EXPopoverViewController alloc] init];
// Create popover
NSPopover *entryPopover = [[NSPopover alloc] init];
    [entryPopover setContentSize:NSMakeSize(200.0, 200.0)];
    [entryPopover setBehavior:NSPopoverBehaviorTransient];
    [entryPopover setAnimates:YES];
    [entryPopover setContentViewController:viewController];
// Convert point to main window coordinates
NSRect entryRect = [sender convertRect:sender.bounds
toView:[[NSApp mainWindow] contentView]];
// Show popover
    [entryPopover showRelativeToRect:entryRect
ofView:[[NSApp mainWindow] contentView]
preferredEdge:NSMinYEdge];
}