Create angular material theme with CSS variables

Question

I'm working on a project that requires to be themeable at runtime. So I created a theme system that combines SCSS variable with CSS Variables. This is how it looks.

:root {
  --primary-color: 196;
}


// Primary
$primary-100: hsl(var(--primary-color), 90%, 98%);
$primary-400: hsl(var(--primary-color), 90%, 65%);
$primary-main: hsl(var(--primary-color), 90%, 50%);
$primary-700: hsl(var(--primary-color), 90%, 30%);
$primary-900: hsl(var(--primary-color), 90%, 10%);

While this works amazingly with my custom components, I'm having a hard time making it work with the Material design theme system.

My thinking was that I will create the theme as explained in the Angular material docs, and instead of using static colors, I will use my SCSS variables. this is how my theme.scss file looks like.

@import '~@angular/material/theming';
@import 'var.scss';

@include mat-core();

$shop-primary: (
  50: $primary-100,
  100: $primary-100,
  200: $primary-200,
  300: $primary-300,
  400: $primary-400,
 // ..... all other colors
  contrast: (
    50: $black-87-opacity,
    100: $black-87-opacity,
    200: $black-87-opacity,
     // ..... all other colors
  )
);


$shop-app-primary: mat-palette($shop-primary);
$shop-app-accent:  mat-palette($shop-primary);
$shop-app-warn: mat-palette($shop-primary);


$shop-app-theme: mat-light-theme($shop-app-primary, $shop-app-accent, $shop-app-warn);

@include angular-material-theme($shop-app-theme);

And I'm getting an error:

 Argument `$color` of `rgba($color, $alpha)` must be a color

Presumingly because the Angular Material mixin is expecting a color and not a hsl() value.

So my question is how would I be able to create a custom material theme with runtime CSS variables?

Answer 1

I created a little library to make this a little easier.

You can use it like so:

1. Install:

   npm i angular-material-css-vars -S
   

2. Then remove any existing @import '~@angular/material/theming'; from your main stylesheet file.

3. Add this to your main stylesheet instead:

   @import '~angular-material-css-vars/main';
   @include initMaterialCssVars();
   

4. Change the main theme color like so:

   import {MaterialCssVarsService} from 'angular-material-css-vars';
   
   export class SomeComponentOrService {
     constructor(public materialCssVarsService: MaterialCssVarsService) {
       const hex = '#3f51b5';
       this.materialCssVarsService.changePrimaryColor(hex);
     }
   }
   

Answer 2

If you upgrade to @angular/material 7.3.4 CSS Variables will mostly work. Only riples and other stuff that uses opacity will need a little fix. I use rgba() for my project, but it should also work for hsla()

Include this:

@function mat-color($palette, $hue: default, $opacity: null) {
    @if type-of($hue) == number and $hue >= 0 and $hue <= 1 {
        @return mat-color($palette, default, $hue);
    }

    $color: map-get($palette, $hue);

    @if (type-of($color) != color) {
        @if ($opacity == null){
            @return $color;
        }

        // Here is the change from the original function:
        // If the $color resolved to something different from a color, we assume it is a CSS variable
        // in the form of rgba(var(--rgba-css-var),a) and replace the 'a' value.
        @return #{str-slice($color, 0, str-index($color, ',')) + $opacity + ')'};
    }

    @return rgba($color, if($opacity == null, opacity($color), $opacity));
}

directly after:

@import '~@angular/material/theming';

and define your colors like this:

--primary-color-50-parts: 0,158,224;
// ... all other colors

$color-primary: (
    50: rgba(var(--primary-color-50-parts), 1),
    // ... all other colors
);

if you define your colors in the map like this:

50: hsla(var(--primary-color), 90%, 98%, 1);

then you need to change str-index($color, ',') in the sass function to something that finds the last ',' in the string. Unfortunatelly my sass knowledge covers only the bare minimum and I don't know how to do that :/

Answer 3

I created a little library - material-theme-creator

You can theming your angular-application or use this approach to create themes

NPM: https://www.npmjs.com/package/material-theme-creator

DOCS: https://artik-man.github.io/material-theme-creator/

npm i material-theme-creator

@import "~material-theme-creator/ngx-mtc";
@import '~@angular/material/theming';

@include mat-core();
@include ngx-mtc-init();

$primary-map: ngx-mtc-create-theme-map('primary');
$accent-map: ngx-mtc-create-theme-map('accent');
$warn-map: ngx-mtc-create-theme-map('warn');

:root {
  --is-dark-theme: 1; // Is dark theme? 1 or 0;
  @include ngx-mtc-theme-base(); // Creates base colors

  // Creates theme colors
  @include ngx-mtc-create-variables-from-color('primary', #009688, 38%);
  @include ngx-mtc-create-variables-from-color('accent', #2196f3, 57%);
  @include ngx-mtc-create-variables-from-color('warn', #f44336, 62%);
}

// Creates Angular Material Theme
@include angular-material-theme(
  ngx-mtc-custom-theme(
    mat-palette($primary-map),
    mat-palette($accent-map),
    mat-palette($warn-map)
  )
);
 

The second theme code:

.second-theme {
  --is-dark-theme: 0;
  @include ngx-mtc-update-theme('primary', #142148, 45%);
  @include ngx-mtc-update-theme('accent', #658e14, 50%);
  @include ngx-mtc-update-theme('warn', #750101, 50%);
}

You can use it with Angular Material or SCSS or pure CSS

Answer 4

Sooo... css variables are runtime, not compile time. SASS doesn't know what to do with them. You should be able to refactor your css vars using the ${} interpolation of SCSS and have everything still work the same. http://sass-lang.com/documentation/file.SASS_REFERENCE.html#interpolation_

$primary-color: 196;

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

$primary-100: hsl($primary-color, 90%, 98%);