They uncovered one bug: in edit/003-shortcuts.mu
<scroll-down> was returning 0 for an address in one place where I
thought it was returning 0 for a boolean.
Now we've eliminated this bad interaction between tangling and punning
literals.
Improvement on fix 3957: rather than put a band-aid over a slow
operation, eliminate the slowdown entirely.
In this case it turns out we're unnecessarily saving files to disk when
they could never be modified. Are we doing this on F4 as well?!
As a blanket rule, down-arrow now stops scrolling once the bottom margin
comes on screen.
Now that we have page-wise scrolling with ctrl-f/b and line-wise
scrolling with ctrl-s/x, we don't need to conflate scroll positioning
with the arrow keys. And as a result, early students no longer have to
struggle with accidentally scrolling part of the sandbox off the screen
when there's tons of empty space available.
`move-to-next-line` is still super messy and will need further
rethinking, but this commit simplifies the codebase as a whole by
eliminating a couple of historical accidents:
a) We only introduced scrolling past the bottom of the screen to allow
more sandboxes to come into view before we had scrolling for the
sandbox side.
b) We undid scrolling past the bottom in just the recipe side to allow
errors to come into view.
Since these historical details are now irrelevant, we no longer need
separate logic for the recipe and sandbox sides, and we don't need to
keep track of the recipe-bottom separate from the bottom margin of
arbitrary editors.
Bugfix: when you hit `enter`, the cursor-row does not increment in *one*
special situation: when the line wraps and the cursor is right at the
start of one of the wrapped lines.
This change is interesting because I only updated one test to gain confidence
that F4 will never redraw the recipe side. (Most of the changes are to
explicitly render-all before each scenario.)
Yet another bugfix, this time in just the sandbox/ app:
open sandbox/ with empty lesson/ directory
type 'a'
press backspace
cursor was not moving left
Now fixed.
Turns out the sandbox/ app hadn't been working right since commit 3854.
(Which ironically was a revert but clearly didn't revert enough; the last
truly good commit was 3823, and we're still clawing our way back to the
sunlight.)
The issue in this case was that commit 3853 disabled update-cursor in some
situations when it shouldn't have. To be safe, just always update-cursor
one very event. I should probably reorganize this in edit/ as well, but
it's not necessary for this particular bug.
---
Incidentally, as part of my git bisecting I realized that the bug fixed
in the trace browser as part of commit 3862 was very old:
press '/'
press some key
press ctrl-u to erase
press some key
= out of bounds string access
To achieve this we have to switch to a model of the screen in termbox that
is closer to the underlying terminal.
Before:
a screen is a grid of characters
writing out of bounds does nothing
After:
a screen is a scrolling raster of characters
writing out of bounds wraps to next line and scrolls if necessary
To move to the new model, it was essential that I migrate my fake screen
at the same time to mimic it. This is why the first attempt (commit 3824)
failed (commit 3858). This is also why this commit can't be split into
smaller pieces.
The fake screen now 'scrolls' by rotating screen lines from top to bottom.
There's still no notion of a scrollback buffer.
The newer model is richer; it permits repl-like apps that upstream termbox
can't do easily. It also permits us to simply use `printf` or `cout` to
write to the screen, and everything mostly works as you would expect. Exceptions:
a) '\n' won't do what you expect. You need to explicitly print both '\n'
and '\r'.
b) backspace won't do what you expect. It only moves the cursor back,
without erasing the previous character. It does not wrap.
Both behaviors exactly mimic my existing terminal's emulation of vt100.
The catch: it's easy to accidentally scroll in apps. Out-of-bounds prints
didn't matter before, but they're bugs now. To help track them down, use
the `save-top-idx`, `assert-no-scroll` pair of helpers.
An important trick is to wrap the cursor before rather after printing
a character. Otherwise we end up scrolling every time we print to the
bottom-right character. This means that the cursor position can be invalid
at the start of a print, and we need to handle that.
In the process we also lose the ability to hide and show the screen. We
have to show the prints happening. Seems apt for a "white-box" platform
like Mu.
Kartik Agaram