how should alpha work for self intersecting lines

[rroohhh]

There are two main possibilities

1. alpha of self intersecting lines is a no op, if a line self intersects the intersection has the same alpha at the whole line
2. it works like "real" pen / pencil and the intersection accumulates alpha

The first option is vastly more easy to implement and even if one implements the second option it is probably never as fast as the first option.
However the second option is a lot nicer for real drawing stuff, probably not so important for note taking.

I guess having the choice between the two would be nice, however the first option will probably be implemented a lot earlier then the second option.

The first option is also how most other infinite canvas drawing programs handle this (atleast Milton and Mischief)