Steps to reproduce:
* Run teliva with some app.
* Press ctrl-e to edit the app.
* Select some function.
* Press ctrl-g and type in some Lua keyword like 'function' or 'while'
(Since the first word in a function is often 'function', it becomes
the default if you press ctrl-g immediately after entering the editor
for a function.)
* Type nothing. Run the app.
Desired behavior: app continues to run. The definition for the keyword
is silently ignored (in future we may want to provide an error message)
Behavior before this commit: app silently exited with non-zero status,
and refused to restart thereafter until the .tlv file was manually
edited to delete the definition for the Lua keyword.
Behavior after this commit: app throws an error message like these:
* For `function`:
```
src/teliva: x.tlv:99: '(' expected near '='
sorry, you'll need to edit the image directly. press any key to exit.
```
* For `while`:
```
src/teliva: x.tlv:99: unexpected symbol near 'while'
sorry, you'll need to edit the image directly. press any key to exit.
```
You still need to edit the .tlv file manually, but the steps for
recovery are a bit more discoverable.
To fix this properly I also need to fix a looming security hole I've
been thinking about for some time. The long-term goal of Teliva is to
put the human running apps in control of what they do, by sandboxing
accesses to the file system, network and so on. However, even after we
build gates on all of Lua's standard libraries, we're still parsing .tlv
files as Lua, with all of its power available.
Solution: load .tlv files as some sort of JSON-like subset of Lua. Maybe
I should just use JSON, and rely on code that's already in Teliva, even
if I'm introducing a new notation in the process.
It turns out Lua has been providing us this information all along! I'd
just not created the space on screen to show it. Make it persist better.
Kilo now no longer tracks its own status messages, which is a regression
in a rare condition.
^/ works on Linux but not on Mac
^- emits the same character code on Mac
^_ seems to be the underlying character code, and works on both
ctrl-7 also emits the same character code
On a Thinkpad X13, the `delete` key emits `^[[3~` outside of Teliva.
Within Teliva, ncurses converts it to character code 330 (0x14a), which
it fails to recognize as KEY_BACKSPACE. Why?
My backspace is converted to character code 263, which ncurses does
recognize as KEY_BACKSPACE.
ctrl-h is character code 8.
Both 330 and 263 are valid Unicode code points, which feels really ugly
and ambiguous.
I still don't understand the entire state space here, so I'm trying to
err on the side of improving discoverability of the `ctrl-h` escape
hatch. Without requiring too wide a window to show all hotkeys on the
menu.
So far I've been trying to make Teliva follow the default colorscheme of
the terminal, but that easily ends up with illegible color combinations.
New plan: always start with a light background within Teliva. People who
want a dark background will currently need to mess with C sources.
This should somewhat fix https://github.com/akkartik/teliva/issues/1.
It's still not clear whether the default should be a dark or light
background. While dark background is more common in terminals, I believe
newcomers to terminals will prefer a light background. Then again, I'm
biased since I use a light background in my terminals.
I wish I could just hide KEY_BACKSPACE and prevent myself from using it
by accident.
Then again, I'm not making this smarts available in Teliva programs
themselves. Just for the Teliva environment.
