{% if sub.cancelled or sub.cancelled_for_teachers %}
{# Canceled lesson: no room #}
{% elif sub.room and sub.lesson_period.room %}
{# New and old room available #}
{{ sub.lesson_period.room.short_name }}
→
{{ sub.room.short_name }}
{% elif sub.room and not sub.lesson_period.room %}
{# Only new room available #}
{{ sub.room.short_name }}
{% elif not sub.room and not sub.lesson_period.room %}
{# Nothing to view #}
{% else %}
{# Only old room available #}
{{ sub.lesson_period.room.short_name }}
{% endif %}