wiki/notebook/cookbook.css.implementing-numbered-headings.org
Gabriel Arazas b088086b06 Merge evergreen notes into the notebook
Now, it's all under the notebook umbrella. Seems to be appropriate as it
is just my notes after all.

I also updated some notes from there. I didn't keep track of what it is
this time. Something about more learning notes extracted from my
"Learning how to learn" course notes and then some. Lack of time and
hurriness just makes it difficult to track but it should be under
version control already.
2021-07-21 16:28:07 +08:00

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Implementing tiered headings with CSS

You may have seen certain documents with tiered headings. To implement this with pure CSS, we'll make heavy use of CSS counters.

Here is one rough implementation with SCSS.

article {
    // Named after the LaTeX counters after `chapter` counter.
    counter-reset: section subsection subsubsection paragraph subparagraph;
    --counter-spacing: 0.5rem;

    // <h2> is used as a section header since <h1> is the main title
    h2 {
        counter-reset: subsection;
        counter-increment: section;

        &::before {
            content: counter(section) ".";
            margin-right: var(--counter-spacing);
        }
    }

    h3 {
        counter-reset: subsubsection;
        counter-increment: subsection;

        &::before {
            content: counter(section) "." counter(subsection) ".";
            margin-right: var(--counter-spacing);
        }
    }

    h4 {
        counter-reset: paragraph;
        counter-increment: subsubsection;

        &::before {
            content: counter(section) "." counter(subsection) "." counter(subsubsection) ".";
            margin-right: var(--counter-spacing);
        }
    }

    h5 {
        counter-reset: subparagraph;
        counter-increment: paragraph;

        &::before {
            content: counter(section) "." counter(subsection) "." counter(subsubsection) "." counter(paragraph) ".";
            margin-right: var(--counter-spacing);
        }
    }

    h6 {
        counter-increment: subparagraph;

        &::before {
            content: counter(section) "." counter(subsection) "." counter(subsubsection) "." counter(paragraph) "." counter(subparagraph);
            margin-right: var(--counter-spacing);
        }
    }
}

This is enough for CSS but since we're using SCSS, we can optimize it further. You may notice that each level is similar with the difference being the content and their counter name.

@use 'sass:string';

@function tier-heading($counters) {
    $str: "";
    @for $level from 1 through $counters {
        $str: $str + 'counter(h#{$level})"."';
    }
    @return string.unquote($str);
}

article {
    --counter-spacing: 0.5rem;
    @for $level from 1 through 6 {
        counter-reset: h#{$level};

        h#{$level}{
            @if $level != 6 {
                counter-reset: h#{$level + 1};
            }
            counter-increment: h#{$level};

            &::before {
                content: tier-heading($level);
                margin-right: var(--counter-spacing);
            }
        }
    }
}