FocusZoom.m

- (void)tableView:(UITableView *)tableView didUpdateFocusInContext:(UITableViewFocusUpdateContext *)context withAnimationCoordinator:(UIFocusAnimationCoordinator *)coordinator {
    
    switch( tableView.tag ) {
        case InboxTable_Folders: {
            // Expand folders
            self.folderWidth.constant = FOLDERS_OPEN;
            self.threadWidth.constant = THREADS_OPEN;
            [self.view setNeedsLayout];
            [self.view setNeedsUpdateConstraints];
            
            [UIView animateWithDuration:0.35 delay:0 usingSpringWithDamping:0.75 initialSpringVelocity:0.05 options:UIViewAnimationOptionCurveLinear|UIViewAnimationOptionBeginFromCurrentState animations:^{
                [self.view layoutIfNeeded];
                [self.mailPreviewContainer zoomToRect:CGRectMake(0, 0, MIN_PREVIEW_WIDTH, 1) animated:NO];
            } completion:nil];
            break;
        }
        case InboxTable_Threads: {
            // Collapse folders
            if ( context.previouslyFocusedView != self.mailPreview ) {
                if ( context.previouslyFocusedView.superview != context.nextFocusedView.superview ) {
                    self.folderWidth.constant = FOLDERS_COLLAPSED;
                    self.threadWidth.constant = THREADS_OPEN;
                    [self.view setNeedsLayout];
                    [self.view setNeedsUpdateConstraints];
                    
                    [UIView animateWithDuration:0.35 delay:0 usingSpringWithDamping:0.75 initialSpringVelocity:0.05 options:UIViewAnimationOptionCurveLinear|UIViewAnimationOptionBeginFromCurrentState animations:^{
                        [self.view layoutIfNeeded];
                        [self.mailPreviewContainer zoomToRect:CGRectMake(0, 0, MIN_PREVIEW_WIDTH, 1) animated:NO];
                    } completion:nil];
                }
            }
            break;
        }
    }
}