CSS :root variables and SASS Functions

Question

in the Header of my HTML-Page i set the following CSS Variables:

:root{ 
  --data-color-primary: #ffcc00; 
  --data-color-secondary: #4b4b4b; 
}

In my SASS-File i use it as follow:

DIV.color {

   &.color-primary {
     background-color: var(--data-color-primary);
   }
   &.color-secondary {
     background-color: var(--data-color-secondary);
   }
}

Now i try to set the font-color depending on the brightness of the background-color:

@function set-notification-text-color($color) {
  @if (lightness($color) > 60) {
     @return #000000;
  } @else {
     @return #ffffff;
  }
}

DIV.color{
   &.color-primary {
      background-color: var(--data-color-primary);
      color: set-notification-text-color(var(--data-color-primary));
   }
}

But in my SASS-compliler i get the following i get the following Error:

Error: argument $color of lightness($color) must be a color

How is ist possible to hand over der CSS variable to the function.

---

My Problem is, the CSS Variables are set in the Backend of my CMS by User (Liferay 7) an will be rendered in a *.FTL-File and is printed in the HTML-Code.

$primary: ${clr_primary};
$secondary: ${clr_primary};

and then i cant use the SASS-Variable $primary in my SASS-File.

Answer 1

Use SASS variables in your CSS variables.

$primary: #ffcc00;
$secondary: #4b4b4b;

:root{ 
  --data-color-primary: #{$primary};
  --data-color-secondary: #{$secondary};
}

Now call your mixin

DIV.color{
   &.color-primary {
      background-color: $primary;
      color: set-notification-text-color($primary);
   }
}

---

Another options would be to create a mixin which retrieves the CSS variable

@function color($color-name) {
  @return var(--data-color-#{$color-name});
}

Now call that function like so

DIV.color {
   &.color-primary {
      background-color: color(primary);
      color: set-notification-text-color(color(primary));
   }
}

Check out this link for usefull information about combining CSS and SASS variables

https://codepen.io/jakealbaugh/post/css4-variables-and-sass

Answer 2

If you need to change CSS variables outside of :root you can do the following

.class {
  // sass-lint:disable no-duplicate-properties
  #{--background}: transparent;      
  #{--background-focused}: transparent;
  // sass-lint:enable no-duplicate-properties
}

and this compiles to

.class {
  --background: transparent;      
  --background-focused: transparent;
}