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                <h1>Theming UI Components</h1>

<h2>Using BEM naming</h2>
<button class="btn btn--primary">Primary Button</button>
<hr class="rule rule-t-info"/>
<h2>Introducing First Class Theme Support</h2>
<p>Each component needs to be aware that it may be used within a colour scheme so it needs to own the process of creating the various classes required to support different uses. Sometimes semantic classes are the way forward, but perhaps we should just allow the use of names to describe the particular style (think Solarized & Darcula, not Primary, Secondary, Success, etc.)</p>

<blockquote class="note note-t-info">Names such as Primary, Secondary, etc. could and should be used to set other theme properties, such as size or font</blockquote>

<p>Here we create a themes map, which contains the colour definitions for a variety of named themes. This makes it easier to re-use a colour scheme across components and removes the cases where two component madifier classes (with different names) confusingly implement the same colour scheme. e.g. no <code>.btn--primary</code> and <code>.panel--brand</code> which actually use the same colours</p>

<p>How we use this in practise:</p>

<button class="btn btn-t-sassmeister">I'm a button</button>
<button class="btn btn-t-codepen">I'm a button</button>
<button class="btn btn-t-codepen-light">I'm a button</button>
<button class="btn btn-t-info">I'm a button</button>

<p>Read more about this approach in my blog post - <a href="" class="link-t-sassmeister-dark">A Sassy Approach To Theming Components</a></p>


                $color-primary: #fff;
$color-primary-background: #E86EA4;

.btn {
  display: block;
  width: 100%;
  padding: 0.8em 1em;
  margin-bottom: 0.8em;
  font-family: "Open Sans", "Helvetica Neue", Helvetica, Arial;
  font-size: 1.2em;
  border-width: 1px;
  border-style: solid;
  &:after {
    content: attr(class);
    margin-left: 6px;
    font-style: italic;
    opacity: 0.5;

.btn--primary {
  //arguably, all the styles in here are theme related
  color: $color-primary;
  background-color: $color-primary-background;
  border: 1px solid darken($color-primary-background, 10);
  &:hover {
    color: $color-primary;
    background-color: lighten($color-primary-background, 10);

Themes are all stored in a map data-structure which gives flexibilty
when traversing based on keys and also looking up values based on strings

$themes: (
  sassmeister: (
    foreground: #fff,
    background: #E86EA4,
    border: darken(#E86EA4, 10),
    emphasis: darken(#FFFFFF, 10),
    subtle: lighten(#E86EA4, 10),
    highlight: lighten(#E86EA4, 10),
    radius: 0
  sassmeister-dark: (
    foreground: #E86EA4,
    background: #fff,
    border: darken(#fff, 10),
    emphasis: darken(#E86EA4, 10),
    subtle: lighten(#E86EA4, 10),
    highlight: darken(#fff, 10),
    radius: 0
  codepen: (
    foreground: #CCCCCC,
    background: #1D1F20,
    border: #000000,
    emphasis: darken(#999999, 10),
    subtle: lighten(#999999, 10),
    highlight: lighten(#1D1F20, 10),
    radius: 3px
  codepen-light: (
    foreground: #1D1F20,
    background: #F2F2F2,
    border: darken(#F2F2F2, 15),
    emphasis: lighten(#1D1F20, 10),
    subtle: darken(#1D1F20, 10),
    highlight: darken(#F2F2F2, 10),
    radius: 3px
  info: (
    foreground: #FFFFFF,
    background: #809BBD,
    border: darken(#809BBD, 15),
    subtle: darken(#FFFFFF, 10),
    highlight: lighten(#809BBD, 10),
    radius: 6px,
    font-style: italic

@function get-theme($name) {
  @return map-get($themes, $name);

 * This function should warn if a theme requirement isn't met, 
 * helping to catch any issues at compile time in development
@function requires($themeName, $props) {
  $theme: get-theme($themeName);
  @each $key in $props {
    @if (map-has-key($theme, $key) == false) {
      @warn "To use this theme requires #{$key} to be set in the map";
      @return false;
  @return true;

.note {
  padding: 2em;
  font-size: 1.2rem;
  font-weight: 300;

  margin: 2em 0 2em 4em;
  width: 50%;

.note--small {
  font-size: 0.8rem;
  padding: 0.5em 1em;
  margin: 1em 0;

.note--inline {
  display: inline-block;

.rule {
  border: 0;
  margin: 2em 0;
  width: 100%;
  height: 1px;
  background-color: #ccc;

  font-weight: bold;

@mixin link-theme($name) {
  $theme: get-theme($name);
  .link-t-#{$name} {
    color: map-get($theme, foreground);
    &:hover, &:active {
      color: map-get($theme, emphasis);

$link-requirements: foreground emphasis;

@mixin button-theme($name) {
  $theme: map-get($themes, $name);
  .btn-t-#{$name} {
    color: map-get($theme, "foreground");
    background-color: map-get($theme, "background");
    border-color: map-get($theme, "border");
    border-radius: map-get($theme, "radius");
    &:hover {
      background-color: map-get($theme, "highlight");

$button-requirements: foreground background border radius highlight;

@mixin note-theme($name) {
  $theme: map-get($themes, $name);
  .note-t-#{$name} {
    background: map-get($theme, "background");
    color: map-get($theme, "foreground");
    @if map-has-key($theme, "font-style") {
      font-style: map-get($theme, "font-style");

$note-requirements: background foreground; // font-style is optional

@mixin rule-theme($name) {
  $theme: map-get($themes, $name);
    background-color: map-get($theme, "background");    

$rule-requirements: background;

@each $themeName in map-keys($themes) {
  @if (requires($themeName, $button-requirements)) {
      @include button-theme($themeName);      

  @if (requires($themeName, $note-requirements)) {
      @include note-theme($themeName);    
  @if (requires($themeName, $rule-requirements)) {
    @include rule-theme($themeName);  
  @if (requires($themeName, $link-requirements)) {
    @include link-theme($themeName);  

// Boilerplate code to get the pen setup

body {
  line-height: 1.5;
  padding: 2% 10%;
  color: #5B5B5B;