Filter by subject in teacher calendar

In the daily calendar by lecturers, the lecturers who have class on the selected day are displayed.
When the checkbox is activated to display all lecturers and not just those who have classes, the subject of interest can now also be selected.

This will display only those lecturers who teach that subject.
This solution is particularly useful when a flexible lesson of a particular subject is to be scheduled, thus having the possibility to select one of the free lecturers.