Re: Consideration for Rust contributions in Emacs

[John Yates]

On Mon, Jan 23, 2023 at 12:06 PM Eli Zaretskii <eliz@gnu.org> wrote:
>
> Quite a few new features are still being implemented in C.  Consider
> just the recent innovations: native-compilation, tree-sitter, support
> for XInput2 and touch devices, to name just a few.

Of these four, only tree-sitter seems to be implemented in C solely
for performance reasons.  IIANM, there is nothing fundamental about
what tree-sitter is doing that *could not* be done in lisp.  The
only issue is performance.

By contrast, the three other features that you list (native-
compilation, XInput2 and touch screen support) need to interact
with the host environment.  From what I have observed, developers
typically partition such features into a C component and a lisp
component.  The impetus seems to be to find a natural partition:
to do in C what must (which may still include some performance
considerations) and then to expose a nice, clean interface to lisp.

Part of what went unsaid in my previous post is that there have been
multiple occasions where code migrated from C to lisp, often to make
it easier to maintain and/or extend.  I am sure that there must have
been instances of migration in the other direction, but none come
immediately to mind.

> Moreover, familiarity with the internals implemented in C is IME quite
> necessary even for Emacs developers who almost never touch that layer.

For some definition of Emacs developer, I do agree.  (Though, as a
C++ developer who, decades ago, left ancient C behind, and having
recently spent time noodling on the periphery of the display engine,
I can tell you that wading into that code is "bracing". :-)

/john



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John Yates
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