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devonfw-core edited this page Jan 5, 2022 · 4 revisions

Angular Material Theming

Angular Material library offers UI components for developers, those components follows Google Material design baselines but characteristics like colors can be modified in order to adapt them to the needs of the client: corporative colors, corporative identity, dark themes, …​

Theming basics

In Angular Material, a theme is created mixing multiple colors. Colors and its light and dark variants conform a palette. In general, a theme consists of the following palettes:

  • primary: Most used across screens and components.

  • accent: Floating action button and interactive elements.

  • warn: Error state.

  • foreground: Text and icons.

  • background: Element backgrounds.

Theme palette
Figure 1. Palettes and variants.

In angular material, a palette is represented as a SCSS map.

SCSS map
Figure 2. SCSS map and palettes.
💡
 Some components can be forced to use primary, accent or warn palettes using the attribute color, for example: <mat-toolbar color="primary">.

Pre-built themes

Available pre-built themes:

  • deeppurple-amber.css

`deeppurple-amber theme`
Figure 3. deeppurple-amber theme.

  • indigo-pink.css

indigo-pink theme
Figure 4. indigo-pink theme.

  • pink-bluegrey.css

` pink-bluegrey theme`
Figure 5. ink-bluegrey theme.

  • purple-green.css

purple-green theme
Figure 6. purple-green theme.

The pre-built themes can be added using @import.

@import '@angular/material/prebuilt-themes/deeppurple-amber.css';

Custom themes

Sometimes pre-built themes do not meet the needs of a project, because color schemas are too specific or do not incorporate branding colors, in those situations custom themes can be built to offer a better solution to the client.

For this topic, we are going to use a basic layout project that can be found in devon4ts-samples repository.

Basics

Before starting writing custom themes, there are some necessary things that have to be mentioned:

  • Add a default theme: The project mentioned before has just one global SCSS style sheet styles.scss that includes indigo-pink.scss which will be the default theme.

  • Add @import '~@angular/material/theming'; at the beginning of the every style sheet to be able to use angular material pre-built color palettes and functions.

  • Add @include mat-core(); once per project, so if you are writing multiple themes in multiple files you could import those files from a 'central' one (for example styles.scss). This includes all common styles that are used by multiple components.

Theme files structure
Figure 7. Theme files structure.

Basic custom theme

To create a new custom theme, the .scss file containing it has to have imported the angular _theming.scss file (angular/material/theming) file and mat-core included. _theming.scss includes multiple color palettes and some functions that we are going to see below. The file for this basic theme is going to be named styles-custom-dark.scss.

First, declare new variables for primary, accent and warn palettes. Those variables are going to store the result of the function mat-palette.

mat-palette accepts four arguments: base color palette, main, lighter and darker variants (See Palettes and variants.) and returns a new palette including some additional map values: default, lighter and darker ([id_scss_map]). Only the first argument is mandatory.

Listing 1. File styles-custom-dark.scss.
$custom-dark-theme-primary: mat-palette($mat-pink);
$custom-dark-theme-accent: mat-palette($mat-blue);
$custom-dark-theme-warn: mat-palette($mat-red);
);

In this example we are using colors available in _theming.scss: mat-pink, mat-blue, mat-red. If you want to use a custom color you need to define a new map, for instance:

Listing 2. File styles-custom-dark.scss custom pink.
$my-pink: (
    50 : #fcf3f3,
    100 : #f9e0e0,
    200 : #f5cccc,
    300 : #f0b8b8,
    500 : #ea9999,
    900 : #db6b6b,
    A100 : #ffffff,
    A200 : #ffffff,
    A400 : #ffeaea,
    A700 : #ffd0d0,
    contrast: (
        50 : #000000,
        100 : #000000,
        200 : #000000,
        300 : #000000,
        900 : #000000,
        A100 : #000000,
        A200 : #000000,
        A400 : #000000,
        A700 : #000000,
    )
);

$custom-dark-theme-primary: mat-palette($my-pink);
...
💡
 Some pages allows to create these palettes easily, for instance: http://mcg.mbitson.com

Until now, we just have defined primary, accent and warn palettes but what about foreground and background? Angular material has two functions to change both:

  • mat-light-theme: Receives as arguments primary, accent and warn palettes and return a theme whose foreground is basically black (texts, icons, …​), the background is white and the other palettes are the received ones.

`deeppurple-amber theme`
Figure 8. Custom light theme.

  • mat-dark-theme: Similar to mat-light-theme but returns a theme whose foreground is basically white and background black.

`deeppurple-amber theme`
Figure 9. Custom dark theme.

For this example we are going to use mat-dark-theme and save its result in $custom-dark-theme.

Listing 3. File styles-custom-dark.scss updated with mat-dark-theme.
...

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

To apply the saved theme, we have to go to styles.scss and import our styles-custom-dark.scss and include a function called angular-material-theme using the theme variable as argument.

Listing 4. File styles.scss.
...
@import 'styles-custom-dark.scss';
@include angular-material-theme($custom-dark-theme);

If we have multiple themes it is necessary to add the include statement inside a css class and use it in src/index.html → app-root component.

Listing 5. File styles.scss updated with custom-dark-theme class.
...
@import 'styles-custom-dark.scss';

.custom-dark-theme {
  @include angular-material-theme($custom-dark-theme);
}
Listing 6. File src/index.html.
...
<app-root class="custom-dark-theme"></app-root>
...

This will apply $custom-dark-theme theme for the entire application.

Full custom theme

Sometimes it is needed to custom different elements from background and foreground, in those situations we have to create a new function similar to mat-light-theme and mat-dark-theme. Let’s focus con mat-light-theme:

Listing 7. Source code of mat-light-theme
@function mat-light-theme($primary, $accent, $warn: mat-palette($mat-red)) {
  @return (
    primary: $primary,
    accent: $accent,
    warn: $warn,
    is-dark: false,
    foreground: $mat-light-theme-foreground,
    background: $mat-light-theme-background,
  );
}

As we can see, mat-light-theme takes three arguments and returns a map including them as primary, accent and warn color; but there are three more keys in that map: is-dark, foreground and background.

  • is-dark: Boolean true if it is a dark theme, false otherwise.

  • background: Map that stores the color for multiple background elements.

  • foreground: Map that stores the color for multiple foreground elements.

To show which elements can be colored lets create a new theme in a file styles-custom-cap.scss:

Listing 8. File styles-custom-cap.scss: Background and foreground variables.
@import '~@angular/material/theming';

// custom background and foreground palettes
$my-cap-theme-background: (
  status-bar: #0070ad,
  app-bar: map_get($mat-blue, 900),
  background: #12abdb,
  hover: rgba(white, 0.04),
  card: map_get($mat-red, 800),
  dialog: map_get($mat-grey, 800),
  disabled-button: $white-12-opacity,
  raised-button: map-get($mat-grey, 800),
  focused-button: $white-6-opacity,
  selected-button: map_get($mat-grey, 900),
  selected-disabled-button: map_get($mat-grey, 800),
  disabled-button-toggle: black,
  unselected-chip: map_get($mat-grey, 700),
  disabled-list-option: black,
);

$my-cap-theme-foreground: (
  base: yellow,
  divider: $white-12-opacity,
  dividers: $white-12-opacity,
  disabled: rgba(white, 0.3),
  disabled-button: rgba(white, 0.3),
  disabled-text: rgba(white, 0.3),
  hint-text: rgba(white, 0.3),
  secondary-text: rgba(white, 0.7),
  icon: white,
  icons: white,
  text: white,
  slider-min: white,
  slider-off: rgba(white, 0.3),
  slider-off-active: rgba(white, 0.3),
);

Function which uses the variables defined before to create a new theme:

Listing 9. File styles-custom-cap.scss: Creating a new theme function.
// instead of creating a theme with mat-light-theme or mat-dark-theme,
// we will create our own theme-creating function that lets us apply our own foreground and background palettes.
@function create-my-cap-theme($primary, $accent, $warn: mat-palette($mat-red)) {
  @return (
    primary: $primary,
    accent: $accent,
    warn: $warn,
    is-dark: false,
    foreground: $my-cap-theme-foreground,
    background: $my-cap-theme-background
  );
}

Calling the new function and storing its value in $custom-cap-theme.

Listing 10. File styles-custom-cap.scss: Storing the new theme.
// We use create-my-cap-theme instead of mat-light-theme or mat-dark-theme
$custom-cap-theme-primary: mat-palette($mat-green);
$custom-cap-theme-accent: mat-palette($mat-blue);
$custom-cap-theme-warn: mat-palette($mat-red);

$custom-cap-theme: create-my-cap-theme(
  $custom-cap-theme-primary,
  $custom-cap-theme-accent,
  $custom-cap-theme-warn
);

After defining our new theme, we can import it from styles.scss.

Listing 11. File styles.scss updated with custom-cap-theme class.
...
@import 'styles-custom-cap.scss';
.custom-cap-theme {
  @include angular-material-theme($custom-cap-theme);
}

Multiple themes and overlay-based components

Certain components (e.g. menu, select, dialog, etc.) that are inside of a global overlay container,require an additional step to be affected by the theme’s css class selector.

Listing 12. File app.module.ts
import {OverlayContainer} from '@angular/cdk/overlay';

@NgModule({
  // ...
})
export class AppModule {
  constructor(overlayContainer: OverlayContainer) {
    overlayContainer.getContainerElement().classList.add('custom-cap-theme');
  }
}

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