Strip font-faces not used

If you run ./bin/minimalcss.js -o /tmp/peterbe.css https://www.peterbe.com/search\?q\=css that CSS will contain this:

@font-face {
    font-family: 'Rating';
    src: url(data:application/x-font-ttf;charset=utf-8;base64,AAEAAAALAIAAAwAwT1MvMggjCBsAAAC8AAAAYGNtYXCj2pm8AAABHAAAAKRnYXNwAAAAEAAAAcAAAAAIZ[   ...15,330 bytes snipped... ]AAAAAAAAAAAAAAAAAA==) format('woff');
    font-weight: 400;
    font-style: normal
}

But there is NO selector that contains something like font-family: Rating;

So this font-face can be removed.

[lahmatiy]

@peterbe Thanks for mention of me!

Yep, new CSSTree version is coming (very soon, I believe) and it will bring a changes for the walk API. Instead of several walk methods, there will be just one – walk() with notation walk(ast, options) (current notation walk(ast, fn) continues to work). By options you can set enter and/or leave handlers, which allows you to organise a stack or any other context needed structures (to figure out “where we came” from and so on).

Btw, currently walk handlers get a context (via this) that points at some node types like Atrule, Rule and so on (some details can be found in docs). Unfortunately, it doesn’t work well (as expected) and probably will be removed or replaced for better solution.

[stereobooster]

Some additional inspiration https://github.com/Munter/subfont