Possible to theme individual operators?

[edmonds]

Hi,

I'd like to be able to theme the ! operator in Rust so that it's easier to spot (basically for the same reason as https://toot.liw.fi/@liw/114187527572249038 but without adding whitespace).

It looks like all operators have to be themed the same way, though. Is that what this means?

helix/runtime/queries/rust/highlights.scm

Lines 12 to 55 in b7d735f

	; -------
	; Operators
	; -------
	[
	"*"
	"'"
	"->"
	"=>"
	"<="
	"="
	"=="
	"!"
	"!="
	"%"
	"%="
	"&"
	"&="
	"&&"
	"|"
	"|="
	"||"
	"^"
	"^="
	"*"
	"*="
	"-"
	"-="
	"+"
	"+="
	"/"
	"/="
	">"
	"<"
	">="
	">>"
	"<<"
	">>="
	"<<="
	"@"
	".."
	"..="
	"'"
	] @operator

Is it possible to theme just the ! operator or would this require an enhancement to the rust highlights.scm file?

[supersurviveur]

Hi,
You need to create a custom highlight.scm file to set a custom style on !.

You can use an existing highlight name with "!" @constant for example, or use a custom highlight name with "!" @my.custom.attribute and then change its style in your theme :

"my.custom.attribute" = { fg = "base7", modifiers = ["italic"] }

Both must be placed after all operators, or you must remove "!" from the list of operators, otherwise the list will take precedence.

[edmonds]

Does this capture all instances of ! or just when ! is used as the unary logical negation operator? I only want to highlight ! when it's the unary operator and not when it's e.g. part of a macro name.

Do I have to edit the runtime/queries/rust/highlights.scm file that gets installed on the system or is there a way to extend that from ~/.config/helix/ somehow?

Thanks!

[supersurviveur]

You can create a file in .config/helix/runtime/queries/{Lang}/highlight.scm without creating other scm files.
However you need to copy the entire content of the initial highlight.scm file, since extending it seems impossible (that's my question here #13150).

Then, the effects of your modification will depend of the lines where you put it. The highest precedence will be at the end of the file. You can use the :tree-sitter-scopes command in helix to override style only for the unary operator.

Since you need to copy the entire scm file, I advise you to add your modification at the end of the file if possible.