It was causing the entire last line to be re-scanned to find the
cursor drawing position if the cursor was at the end of the buffer.
This was both slow and resulted in an incorrect position, since
all the rest of the drawing assumes line blocks.
The formatters now work on grapheme iterators instead of directly on
lines, which frees up the LineFormatter to break up long lines into
smaller blocks of text. This is partially taken advantage of right
now in various parts of the code, but more work is still needed to
get it both working properly and fast.
This is a big shift in the formatter API's. It simplifies the
responsibilities of the implementers so that pretty much all they
have to do it implement an iterator. Everything else will be
automatically derived from that. (Or, at least, that's the hope.)
This commit pulls the formatter out of the text buffer and
puts it in the editor instead. However, there is a lot of
commented code utlizing the buffer and formatter that still
needs to be updated.
In short, the editor is pretty non-functional in this commit.
The reformat code was being run on every resize event,
which chokes on most resizes which end up emitting a lot
of resize events. Now it waits and processes a bunch of
resize events until there aren't any left, and only does
the actual reformat on the last one.
The rust SDL2 bindings have changed in a way that makes the lifetimes
very strict. This is probably a good thing from a safety standpoint,
but means I'll likely need to re-architect the GUI drawing code.
For now I'm going to leave that on the back-burner and focus on getting
the console version working.
