ember-theme-changer

This Ember-Addon will help you to switch CSS style files on runtime.

For example, let's say you want to support multiple themes in your app and each of the theme styles is defined in its own CSS file (I'll show you how easy is to accomplish this on Ember). Ember-theme-changer addon provides an easy mechanism to change themes and subscribe to theme changes in your different components to handle those styles that you couldn't define using stylesheet.

Installation

ember install ember-theme-changer

Configuration

In this example we want to support Dark and Light themes. To accomplish it you must define all available themes in your config/environment.js file:

// config/environment.js

module.exports = function(environment) {
  var ENV = {
    /* ... */
    theme: {
      themes: [ 'light', 'dark'], // MANDATORY
      defaultTheme: 'dark', // OPTIONAL
      eventName: 'name of the event to be trigger when the theme changes', // OPTIONAL
      cookieName: 'name of cookie used to save the current theme value', // OPTIONAL
      useAssetMap: [default to true in Prod environment] boolean value to indicate if the assets were fingerprinted and an assetMap.json file is available // OPTIONAL
    }
  };
  return ENV;
};

Fingerprinting assets

If your app is fingerprinting your CSS files with Broccoli (which is default to true in prod environment), you could tell the Addon to use the generated /assets/assetMap.json to load the correct asset.

Enable the asset-map generation in your ember-cli-build file:

fingerprint: {
  enabled: Default: app.env === 'production' - Boolean. Enables fingerprinting if true. True by default if current environment is production.
  generateAssetMap: true
}

More info: https://ember-cli.com/asset-compilation#fingerprinting-and-cdn-urls & https://github.com/rickharrison/broccoli-asset-rev

Pre-requisites

Since v0.3.0 ember-theme-changer relies in ember-cli-head v0.4.0 addon to load the theme in runtime and provide Fastboot compatibility.

If you are not already using ember-cli-head (or another addon that requires it) you must follow these 2 simple steps:

Create a file head.hbs in your app/template folder with this content:

// app/template/head.hbs
<link rel="stylesheet" href="{{model.themeHref}}">

(If you already have a head.hbs file, just add the line: <link rel="stylesheet" href="{{model.themeHref}}">)

Add {{head-layout}} to the top of your application template.

Check ember-cli-head for more info.

Defining themes on Ember.

There are many mechanism to define themes in your application. In the following example I'll be defining style variables but you can use any mechanism that works better for you. Also, I'll be using Sass preprocessor, but the same solution applies with Less:

1st) Writing multiple theme files

// app.scss

// In your app.scss file you can define styles that are dependent on the current theme, or import external styles too
@import "ember-modal-dialog/ember-modal-structure";
@import "ember-modal-dialog/ember-modal-appearance";

body {
  width: 100%
}

// main.scss

// here is where you define styles that depends on the current theme. All the theme dependent values are referenced with variables. eg:
body {
  background-color: $bodyBackgroundColor;
}

// dark.scss

// 1) define all the variables you need
$bodyBackgroundColor: '#fff';
...

// 2) Import your style fle where the variables will be consumed.
@import 'main';

And do the same for the rest of the themes. eg:

// light.scss

// 1) Define variables
$bodyBackgroundColor: '#000';
...
// 2) import style file
@import 'main';

2nd) Generating theme files.

By default, Ember only generates 1 css file based on your app.scss content (or app.less, app.css depending in your your style preprocessor), in this case we want to generate 2 extra files (dark.css & light.css). This is accomplish easily by telling Ember about the extra output files in the ember-cli-build.js file:

// ember-cli-build.js
    outputPaths: {
      app: {
        css: {
          'light': '/assets/light.css',
          'dark': '/assets/dark.css'
        }
      }
    },

As a result, ember will generate 3 css files (app.css, light.css & dark.css).

For more info, please read the official Ember-CLI doc: https://ember-cli.com/user-guide/#configuring-output-paths

Usage

All interaction with the addon is though the themeChanger service.

Change themes

You can circle through the themes invoking the service toggleTheme method, or set an specific value with the theme property.

// your_component.js:

themeChanger: service(),
....

action: {
  switchTheme() {
    this.get('themeSwitcher').toggleTheme();
  },
  setDarkTheme() {
    this.get('themeSwitcher').set('theme', 'dark');
  }
}

Theme-change Event

In some situation you could have some styles defined outside of the CSS boundaries, this addon provides an event you can subscribe to detect changes int he current theme allowing you to execute any code.

// your_component.js:
themeChanger: service(),
chartColor,
....

  didReceiveAttrs() {
    this._super(...arguments);

    // subscribe to the theme changes event
    this.get('themeChanger').onThemeChanged((theme) => {

      // your code to handle theme changes:
      if (theme === 'light') {
        this.set('chartColor', 'black');
      } else {
        this.set('chartColor', 'white');
      }
      ...
    });

  },


  // Its important to unsubscribe to the event when your component will be destroyed
  willDestroyElement() {
    this.get('themeChanger').offThemeChanged();
    this._super(...arguments);
  }

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