Zero length ranges, such as for events without a DTEND could be
considered to overlap a range if they were at exactly the end of the
range. The end of a range however is the first date that is supposed to
not overlap, so a zero-length range on exactly this point should not be
considered overlapping.
This fixes cases where all-day events from the next month could show up
on the same day of the current month if they did not have a DTEND.
This also adds tests for all possible cases of such zero-length events
overlapping.
Fixes https://gitlab.gnome.org/GNOME/gnome-calendar/-/issues/701
The behavior of gcal_range_compare(), and the 'position' argument
of gcal_range_calculate_overlap(), should be the same. However,
because we were comparing the end dates in the wrong order, they
didn't match.
Fix that by properly comparing the end of the ranges.
Sebastian Keller