This makes a `ghostty-vt` Zig module available from our `build.zig` that
contains a reusable Zig API version of our core terminal emulation layer
including escape sequence parsing, terminal state, and screen state.
This is the groundwork for phase one of my "libghostty" vision.
With SIMD disabled, `ghostty-vt` has no dependencies -- not even on libc
-- and can produce fully static standalone binaries. With SIMD enabled,
`ghostty-vt` only depends on libc.
The point of this PR is primarily to get the bug fixes I found in and to
get this running in CI on every commit so that we don't regress it. In
the future we'll do more (see the future section below).
> [!WARNING]
> **The API is extremely not stable and will definitely change in the
future.** The _functionality/logic_ is very stable, because it's the
same core logic used by Ghostty, but the API itself is not at all. For
this PR, we mostly just expose everything and we'll reshape the API
later.
## What is `libghostty-vt`?
I've stated my vision for a `libghostty` for some time. You can find
background on that. Recently, I've realized that the _scope_ of
`libghostty` is way too large to ship as a single unit. To that end,
`libghostty` will be split into smaller scoped sub-libraries (that may
depend on each other for higher level functionality). The exact mapping
is being worked out.
**The first library I'm extracting is `libghostty-vt` (both Zig and C,
this PR starts with Zig).** This will be a library focused only on core
terminal emulation, terminal state, and screen state. It lacks rendering
support and input handling.
**But why?** The core terminal emulation is the primary source of both
missing functionality and bugs within terminal emulators. Look at this
[simple bug in jediterm](https://github.com/JetBrains/jediterm/pull/311)
that fails to parse a trivially common sequence resulting in horrendous
misrenders. Jediterm is used by every JetBrains IDE! Literally the core
terminal in a many-millions-of-dollars business!
`libghostty-vt` is a _zero dependency_ terminal emulation layer that
exposes a C API which will let any popular language build bindings so
that we can stop reinventing the terminal emulation layer and get best
in class (or near it) terminal emulation capabilities everywhere.
## In This PR
- `ghostty-vt` Zig module
- Example usage of it in `example/zig-vt`
- CI to run Zig module tests, test that our examples build, and test
SIMD on/off
- New feature build flag `-Dsimd` (default on) that turns SIMD on or off
- Unexposed feature flag that allows building the core terminal logic
without regex support (default on right now jus for the ghostty-vt
module as I figure out what our future regex story is in a post-oni
world).
- Fixes for non-SIMD builds
## Future
There's a lot to do in the future outside of this PR:
- Define a more stable Zig API
- Define a C API at all
- Figure out our regex engine story
- Documentation improvements
This fixes test failures when Ghostty's core is run without libc.
Ghostty in the real world (all built executables) require libc so this
bug has never been hit before, but I'm working on a libc-less core and
this caused real test failures (so its already tested, as well).
