Longer name, but it doesn't lie. We have no data structure right now for
combining multiple code points. And it makes no sense for the notion of
a grapheme to conflate its Unicode encoding.
Unix text-mode terminals transparently support utf-8 these days, and so
I treat utf-8 sequences (which I call graphemes in Mu) as fundamental.
I then blindly carried over this state of affairs to bare-metal Mu,
where it makes no sense. If you don't have a terminal handling
font-rendering for you, fonts are most often indexed by code points and
not utf-8 sequences.
I'm loading them in uncompressed ASCII format, and all streams and gap
buffers all over the place need to get massively scaled up to 256KB
capacity. But the tests don't yet run out of RAM, so I'll keep going.
Font rendering now happens off the real screen, which provides the effect
of double-buffering.
Apps can now also use convert-graphemes-to-pixels for more traditional
double-buffering.
Two interesting things:
- We don't really need double-buffering for rendering the screen on the
sandbox as a progress indicator. Everything else is untouched, and render-screen
should be doing that as well.
- Rendering just pixels of the fake screen is buttery smooth. It's the
_graphemes_ that are slowing things down. Even though there's so many
fewer of them!
As a result, drawing the fake screen less frequently in `evaluate` doesn't
actually help with flicker. Even though it'll make the debug cycle shorter.
So my current plan is to attack flicker in isolation before I mess with
the render frequency.
In this commit I optimized away the cursor handling. Still doesn't seem
to be helping. In fact it actually seems _worse_.
Rename cells containing screens to screen vars because of the ambiguity
that each grapheme in fake screens is represented by a type screen-cell.
While we're at it, we also analogously rename keyboard vars.
I wrote a comment about how some code was not covered by tests, and then
promptly forgot what it was for. This is why we need tests.
Now the hack is gone.
Kartik K. Agaram