csssassunderscores-wp

Underscores font-size mixin

I'm using the underscores starter theme for wordpress.

They have this mixin which I've no idea what it's trying to do.

// Rem output with px fallback
@mixin font-size($sizeValue: 1) {
    font-size: ($sizeValue * 16) * 1px;
    font-size: $sizeValue * 1rem;
}

Can someone explain the math behind this?
How can I make use of it if I'm given font sizes in px?

Solution

  • It just outputs your font size in rem with pixel fallback ('16' is the base font size here). If you use @include font-size(1.2), it will output: 

    font-size: 19.2px; // fallback for those with no rem support
font-size: 1.2rem;

    This mixin is not suitable for converting font-size in pixels to rem.
    If you want to write your code in pixels and have them converted to rem, the mixin should look something like this:

    @mixin font-size-px-to-rem($value: 12) {
  font-size: $value * 1px;
  font-size: $value / 16 * 1rem;
}

    then use it:

    .test {
  @include font-size-px-to-rem(14);
}

    which outputs to:

    .test {
  font-size: 14px;
  font-size: 0.875rem;
}