feat(theme-generator): Add possibility to force custom color @angular/material:theme-color

[zygarios]

Feature Description

My problem is that I still can't understand how @angular/material:theme-color works. In the terminal, I need to provide colors for primary, secondary, and tertiary. For each one, I specify a single color, like #ff9500, because that's what I want.

What HEX color should be used to generate the M3 theme? It will represent your primary color palette. (ex. #ffffff) **#005dba** What HEX color should be used represent the secondary color palette? (Leave blank to use generated colors from Material) **#005dba** What HEX color should be used represent the tertiary color palette? (Leave blank to use generated colors from Material) **#005dba**

However, when generating the theme, I see that it creates color palettes, but when I try to get just my color, I use --mat-sys-primary. Unfortunately, it appears significantly darker (#8c5000), and I don't know which variable the color is actually hidden under. I have the impression that due to the low contrast, it is being artificially darkened. However, I selected the option not to generate mixins with high contrast. I would like to be able to use exactly that color without worrying about contrast. Currently, I am forced to manually change all the system token colors because the generated palette still interferes too much with what I want to achieve, taking away the flexibility I need in this case.

Use Case

It would be great to be able to specify in the terminal that I want exactly the colors I mention, without any interference.

[jimivdw]

Very big +1. The fact that you cannot provide exact colors to an M3 theme is a deal breaker for me. Not being able to use my company's brand colors just because they aren't "up to Material's standards" just feels wrong.

I know I can manually override every color variable, and I will do so when support for M2 gets dropped eventually, but this is just very annoying and I really hope there will be an easier way to use exact colors for a theme.

[amysorto]

@zygarios For each color specified, those colors are used directly to create color palettes of tones that match that color's hue and chroma. If you only specify a single color or a subset, the other colors get created in relation to each other. So there shouldn't be much adjusting happening if you specify everything and aren't requesting high contrast.

Although, Material defines --mat-sys-primary as tone 40 in your primary palette. Typically the color used to create the color palette usually closest to tone 50 in the color palette, which is why it is slightly off to what you are expecting.

Although I do see what you are saying, it would be ideal if you can specify maybe the primary color and then the color palette gets extracted from that to get more color accuracy and be more intuitive. I'll leave this issue open so this can be looked into.

In the meantime, overriding colors is your best option for complete customization: https://material.angular.io/guide/theming#system-tokens

[richardsengers]

This is a very blocking issue right now.
It's beautifull having all kinds of colors, but our customers want at least a toolbar with their brand color.

An example (a very ugly primary color but just to let you see the difference):

in the new M3

@amysorto overriding the colors isn't the best option, because we don't know the text contrast colors

An example for changing the mat-toolbar

@use '@angular/material' as mat;
:root {
  @include mat.toolbar-overrides((
    container-background-color: var(--primary-color), // instead of using a palette color, since the brand collor is not within the palette
    container-text-color: var(--mat-sys-on-primary), // then we don't know what the contrast color of var(--primary-color) is
  ));
}

we should have someting like this #30070 so we can use

@use '@angular/material' as mat;
:root {
  @include mat.toolbar-overrides((
    container-background-color: var(--mat-sys-primary-40),
    container-text-color: var(--mat-sys-on-primary-40), 
  ));
}

But then I'm still missing my brand color

[richardsengers]

For those interested, I've created a small function which sets all theme tones to css vars, which you can use in your own color palette

import { argbFromHex, hexFromArgb, themeFromSourceColor } from '@material/material-color-utilities';

const hueTones = [0, 10, 20, 25, 30, 35, 40, 50, 60, 70, 80, 90, 95, 98, 99, 100];
// Map of neutral hues to the previous/next hues that
// can be used to estimate them, in case they're missing.
const neutralHues = new Map<number, { prev: number; next: number }>([
  [4, { prev: 0, next: 10 }],
  [6, { prev: 0, next: 10 }],
  [12, { prev: 10, next: 20 }],
  [17, { prev: 10, next: 20 }],
  [22, { prev: 20, next: 25 }],
  [24, { prev: 20, next: 25 }],
  [87, { prev: 80, next: 90 }],
  [92, { prev: 90, next: 95 }],
  [94, { prev: 90, next: 95 }],
  [96, { prev: 95, next: 98 }],
]);

const neutralHueTones = [...hueTones, ...neutralHues.keys()];
export function setCSSVariablesFromM3Theme(hex: string) {
  const m3ThemeColorsJSON = themeFromSourceColor(argbFromHex(hex));
  for (const [variant, palette] of Object.entries(m3ThemeColorsJSON.palettes)) {
    const paletteKey = variant.replace(/([a-z])([A-Z])/g, '$1-$2').toLowerCase();
    const tones = paletteKey === 'neutral' ? neutralHueTones : hueTones;
    for (const tone of tones) {
      const color = tone === 40 && paletteKey === 'primary' ? hex : hexFromArgb(palette.tone(tone));
      document.documentElement.style.setProperty(`--m3-${paletteKey}-color-${tone}`, color);
    }
  }
}

First you need to pnpm i @material/material-color-utilities which is used internally by the theme-color scheme.

My code is just a little change from what the scheme does
node_modules/@angular/material/schematics/ng-generate/theme-color/index_bundled.js (getColorPalettesSCSS(colorPalettes) function)

Offcourse not an ideal thing to do, but now I can set a brand color to tone 40 and I have all tones as css variables from one hex value.