Re: cc-mode fontification feels random

[Jim Porter]

On 6/10/2021 8:16 AM, Ergus wrote:
> 1) What is finally the most desirable/long path/future feature? I mean,,
> finally what is preferred by the developers to support in the future?
>
> lsp or tree-sitter?

Elsewhere in the thread, I and a few others discussed this briefly. The 
solution other editors use (and which I think is ideal) is to start with 
a base that does its best purely by looking at the syntax of the file, 
and then augment that with LSP. For Emacs and CC-mode, this could mean 
continuing to use the current implementation, or switching to something 
built on tree-sitter. Then on top of that, Emacs can consult LSP for 
more-accurate information. I'm not sure whether this means LSP would 
take over entirely or if it would merely augment the base-level 
syntactic highlighting. Figuring that out would probably require doing 
some experiments to see what the best solution for Emacs would look like.

One of the main benefits of continuing to have some form of (non-LSP) 
syntactic highlighting is that it works for everyone. Even if you don't 
have an LSP server installed, you may want to edit a source file in a 
particular language. Your LSP server of choice may also lack full 
semantic highlighting support (it's a pretty new feature, as I 
understand it). Having a reasonably-correct baseline that works 
everywhere is nice, and hopefully there are no plans to get rid of that.

LSP *may* also be too slow in some situations (though this is just a 
guess). For example, when editing a file over TRAMP, the LSP server runs 
on the remote side; if the network is slow, this could result in delayed 
fontification while editing, which reduces the usefulness of 
fontification. In addition, a new checkout of a large project won't have 
any cached LSP information, so analyzing the code enough to generate 
semantic highlighting may take some time. These might not actually be 
problems, but they do make me a bit skeptical about the performance of a 
purely LSP-based fontification system.

- Jim