if (!viewport.to.isEmpty) {
        hooks.push(`${phase}:${viewport.name}.${viewport.to.name}.binding.enter`);
        hooks.push(`${phase}:${viewport.name}.${viewport.to.name}.binding.leave`);
        hooks.push(`${phase}:${viewport.name}.${viewport.to.name}.bound.enter`);
        hooks.push(`${phase}:${viewport.name}.${viewport.to.name}.bound.leave`);