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QSS - Simple Query Syntax

The goal of QSS is to define a simple syntax for specifying element queries by adding a new ending part between a CSS selector list and the block of rules that help define the breakpoints when those rules are to apply.

Normally in CSS you have something like this:

selectorList { block }

We are going to add a new part for our query between the selector list and the block where we will store instructions for when the rule should apply.

selectorList <query> { block }

Because this exists as a new part between the selector list and the block of rules, if you have a list of selectors like h1, h2, h3, h4, h5, h6 {} you only need to add the query once after the selector list is complete, like h1, h2, h3, h4, h5, h6 <query> {} rather than h1 <query>, h2 <query>, h3 <query>, ….

This document describes two different formats for expressing element queries for individual CSS rules, one using an if-based structure, and another that uses the @ symbol to declare when it should apply.

Phrase Formats

1) if <condition> <comparator> <breakpoint>

  • operator: if
  • condition: width | height | characters | children | xscroll | yscroll
  • comparator: < | below | under | <= | max | == | equals | >= | min | > | above | over
  • breakpoint: number

If-formatted Examples

div if width above 500 {}
input if characters under 1 {}

2) @ <comparator> <breakpoint> <condition>

  • operator: @
  • comparator: < | below | under | <= | max | == | equals | >= | min | > | above | over
  • breakpoint: number
  • condition: width | height | characters | children | xscroll | yscroll

At-formatted Examples

div @ above 500 width {}
input @ under 1 characters {}

In both phrase formats the whitespace between tokens is optional, this means that if you prefer to think about these as @above or @min you can express them that way. The following should all equivalent:

div if width >= 500 {}
div if width >=500 {}
div if width min 500 {}
div @min 500 width {}
div@min500width{}
div @ >=500 width {}

How it works

The queries parsed by QSS would be split into the following pieces:

  • selector list
  • rule block (or stylesheet?)
  • comparator
  • condition
  • breakpoint

And these could be used to construct Element Queries in syntaxes like:

Essentially QSS acts as a syntax to abstract away writing these: Useful Tests for JS-powered Styling

Demo

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