Angular 7 Material and Theming

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A theme is the set of colors that will be applied to the Angular Material components. The library’s approach to theming is based on the guidance from the Material Design spec.

In Angular Material, a theme is created by composing multiple palettes. In particular, a theme consists of:

A primary palette: colors most widely used across all screens and components.
An accent palette: colors used for the floating action button and interactive elements.
A warn palette: colors used to convey error state.
A foreground palette: colors for text and icons.
A background palette: colors used for element backgrounds.

In Angular Material, all theme styles are generated statically at build-time so that your app doesn’t have to spend cycles generating theme styles on startup.

Using a pre-built theme

Angular Material comes prepackaged with several pre-built theme css files. These theme files also include all of the styles for core (styles common to all components), so you only have to include a single css file for Angular Material in your app.

You can include a theme file directly into your application from @angular/material/prebuilt-themes. Available pre-built themes, are

deeppurple-amber.css
indigo-pink.css
pink-bluegrey.css
purple-green.css

If you’re using Angular CLI, this is as simple as including one line in your styles.css file:

@import ‘~@angular/material/prebuilt-themes/deeppurple-amber.css’;

Alternatively, you can just reference the file directly. This would look something like:

The actual path will depend on your server setup.

You can also concatenate the file with the rest of your application’s css.

Finally, if your app’s content is not placed inside of a mat-sidenav-container element, you need to add the mat-app-background class to your wrapper element (for example the body). This ensures that the proper theme background is applied to your page.

Defining a custom theme

When you want more customization than a pre-built theme offers, you can create your own theme file.

A custom theme file does two things:

Imports the mat-core() sass mixin. This includes all common styles that are used by multiple components. This should only be included once in your application. If this mixin is included multiple times, your application will end up with multiple copies of these common styles.
Defines a theme data structure as the composition of multiple palettes. This object can be created with either the mat-light-theme function or the mat-dark-theme function. The output of this function is then passed to the angular-material-theme mixin, which will output all of the corresponding styles for the theme.

A typical theme file will look something like this:

@import ‘~@angular/material/theming’;

// Plus imports for other components in your app.

// Include the common styles for Angular Material. We include this here so that you only

// have to load a single css file for Angular Material in your app.

// Be sure that you only ever include this mixin once!

@include mat-core();

// Define the palettes for your theme using the Material Design palettes available in palette.scss

// (imported above). For each palette, you can optionally specify a default, lighter, and darker

// hue. Available color palettes: https://material.io/design/color/

$candy-app-primary: mat-palette($mat-indigo);

$candy-app-accent: mat-palette($mat-pink, A200, A100, A400);

// The warn palette is optional (defaults to red).

$candy-app-warn: mat-palette($mat-red);

// Create the theme object (a Sass map containing all of the palettes).

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

// Include theme styles for core and each component used in your app.

// Alternatively, you can import and @include the theme mixins for each component

// that you are using.

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

You only need this single Sass file; you do not need to use Sass to style the rest of your app. If you are using the Angular CLI, support for compiling Sass to css is built-in; you only have to add a new entry to the “styles” list in angular.json pointing to the theme file (e.g., unicorn-app-theme.scss).

If you’re not using the Angular CLI, you can use any existing Sass tooling to build the file (such as gulp-sass or grunt-sass). The simplest approach is to use the node-sass CLI; you simply run:

node-sass src/unicorn-app-theme.scss dist/unicorn-app-theme.css

and then include the output file in your index.html.

The theme file should not be imported into other SCSS files. This will cause duplicate styles to be written into your CSS output. If you want to consume the theme definition object (e.g., $candy-app-theme) in other SCSS files, then the definition of the theme object should be broken into its own file, separate from the inclusion of the mat-core and angular-material-theme mixins.

The theme file can be concatenated and minified with the rest of the application’s css. Note that if you include the generated theme file in the styleUrls of an Angular component, those styles will be subject to that component’s view encapsulation.

Multiple Themes

You can create multiple themes for your application by including the angular-material-theme mixin multiple times, where each inclusion is gated by an additional CSS class.

Remember to only ever include the @mat-core mixin only once; it should not be included for each theme.

Example of defining multiple themes:

@import ‘~@angular/material/theming’;

// Plus imports for other components in your app.

// Include the common styles for Angular Material. We include this here so that you only

// have to load a single css file for Angular Material in your app.

// **Be sure that you only ever include this mixin once!**

@include mat-core();

// Define the default theme (same as the example above).

$candy-app-primary: mat-palette($mat-indigo);

$candy-app-accent: mat-palette($mat-pink, A200, A100, A400);

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

// Include the default theme styles.

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

// Define an alternate dark theme.

$dark-primary: mat-palette($mat-blue-grey);

$dark-accent: mat-palette($mat-amber, A200, A100, A400);

$dark-warn: mat-palette($mat-deep-orange);

$dark-theme: mat-dark-theme($dark-primary, $dark-accent, $dark-warn);

// Include the alternative theme styles inside of a block with a CSS class. You can make this

// CSS class whatever you want. In this example, any component inside of an element with

// `.unicorn-dark-theme` will be affected by this alternate dark theme instead of the default theme.

.unicorn-dark-theme {

@include angular-material-theme($dark-theme);

}

In the above example, any component inside of a parent with the unicorn-dark-theme class will use the dark theme, while other components will fall back to the default $candy-app-theme.

You can include as many themes as you like in this manner. You can also @include the angular-material-theme in separate files and then lazily load them based on an end-user interaction (how to lazily load the CSS assets will vary based on your application).

It’s important to remember, however, that the mat-core mixin should only ever be included once.

Multiple themes and overlay-based components

Since certain components (e.g. menu, select, dialog, etc.) are inside of a global overlay container, an additional step is required for those components to be affected by the theme’s css class selector (.unicorn-dark-theme in the example above).

To do this, you can add the appropriate class to the global overlay container. For the example above, this would look like:

import {OverlayContainer} from ‘@angular/cdk/overlay’;

@NgModule({

// …

})

export class UnicornCandyAppModule {

constructor(overlayContainer: OverlayContainer) {

overlayContainer.getContainerElement().classList.add(‘unicorn-dark-theme’);

}

Theming only certain components

The angular-material-theme mixin will output styles for all components in the library. If you are only using a subset of the components (or if you want to change the theme for specific components), you can include component-specific theme mixins. You also will need to include the mat-core-theme mixin as well, which contains theme-specific styles for common behaviors (such as ripples).

@import ‘~@angular/material/theming’;

// Plus imports for other components in your app.

// Include the common styles for Angular Material. We include this here so that you only

// have to load a single css file for Angular Material in your app.

// **Be sure that you only ever include this mixin once!**

@include mat-core();

// Define the theme.

$candy-app-primary: mat-palette($mat-indigo);

$candy-app-accent: mat-palette($mat-pink, A200, A100, A400);

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

// Include the theme styles for only specified components.

@include mat-core-theme($candy-app-theme);

@include mat-button-theme($candy-app-theme);

@include mat-checkbox-theme($candy-app-theme);

Theming your custom components

In order to style your own components with Angular Material’s tooling, the component’s styles must be defined with Sass.

Step 1. Define all color and typography styles in a “theme file” for the component

First, create a Sass mixin that accepts an Angular Material theme and outputs the color-specific styles for the component. An Angular Material theme definition is a Sass map.

For example, if building a custom carousel component:

// Import library functions for theme creation.

@import ‘~@angular/material/theming’;

// Define a mixin that accepts a theme and outputs the theme-specific styles.

@mixin candy-carousel-theme($theme) {

// Extract the palettes you need from the theme definition.

$primary: map-get($theme, primary);

$accent: map-get($theme, accent);

// Define any styles affected by the theme.

.candy-carousel {

// Use mat-color to extract individual colors from a palette.

background-color: mat-color($primary);

border-color: mat-color($accent, A400);

}

Second, create another Sass mixin that accepts an Angular Material typography definition and outputs typographic styles. For example:

@mixin candy-carousel-typography($config) {

.candy-carousel {

font: {

family: mat-font-family($config, body-1);

size: mat-font-size($config, body-1);

weight: mat-font-weight($config, body-1);

}

Step 2. Define all remaining styles in a normal component stylesheet.

Define all styles unaffected by the theme in a separate file referenced directly in the component’s styleUrl. This generally includes everything except for color and typography styles.

Step 3. Include the theme mixin in your application

Use the Sass @include keyword to include a component’s theme mixin wherever you’re already including Angular Material’s built-in theme mixins.

// Import library functions for theme creation.

@import ‘~@angular/material/theming’;

// Include non-theme styles for core.

@include mat-core();

// Define your application’s custom theme.

$primary: mat-palette($mat-indigo);

$accent: mat-palette($mat-pink, A200, A100, A400);

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

// Include theme styles for Angular Material components.

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