How to implement switchable themes in scss? - css

I have an existing project with a scss file that uses semantic variables:
$background-color: white;
body {
background-color: $background-color;
}
I would like to change the background to black when I add a theming class to the body:
<body class="theme-dark">...</body>
and back to white if I remove the class (or switch to a theme-light).
I haven't found any light-weight methods to do this in scss (parametrizing a class for each theme seems like a very hard to maintain approach).
I've found a hybrid scss/css-custom properties solution:
original:
.theme-light {
--background-color: white;
}
update (based on Amar's answer):
:root {
--background-color: white;
}
.theme-dark {
--background-color: black;
}
$background-color: var(--background-color);
body {
background-color: $background-color;
}
Defining the scss variable as having a css-variable expansion as the value, i.e. (from above):
$background-color: var(--background-color);
generates the following css:
:root { --background-color: white; }
.theme-dark { --background-color: black; }
body { background-color: var(--background-color); }
which seems to be what we want...?
I like it since it only requires changing the definition of $background-color (not every usage in a very large scss file), but I'm unsure if this is a reasonable solution? I'm pretty new to scss, so maybe I've missed some feature..?

Doing this with SCSS is possible but you would have to add styles to all elements you want to theme. That is because SCSS is compiled at build-time and you can't toggle the variables with classes. An example would be:
$background-color-white: white;
$background-color-black: black;
body {
background-color: $background-color-white;
}
.something-else {
background-color: $background-color-white;
}
// Dark theme
body.theme-dark {
background-color: $background-color-black;
.something-else {
background-color: $background-color-black;
}
}
The best way to currently do it is by using CSS variables. You would define the default variables like this:
:root {
--background-color: white;
--text-color: black;
}
.theme-dark {
--background-color: black;
--text-color: white;
}
Then, you would use these variables in your elements like this:
body {
background-color: var(--background-color);
color: var(--text-color);
}
If the body element has the theme-dark class, it will use the variables defined for that class. Otherwise, it will use the default root variables.

All credit goes to Dmitry Borody
I would recommend an approach like what is mentioned in this Medium article. With this approach, you can assign what classes need to be themed without specifically mentioning the theme name so multiple themes can be applied at once.
First, you set up a SASS map containing your themes. The keys can be whatever makes sense to you, just make sure that each theme is using the same name for the same thing.
$themes: (
light: (
backgroundColor: #fff,
textColor: #408bbd,
buttonTextColor: #408bbd,
buttonTextTransform: none,
buttonTextHoverColor: #61b0e7,
buttonColor: #fff,
buttonBorder: 2px solid #fff,
),
dark: (
backgroundColor: #222,
textColor: #ddd,
buttonTextColor: #aaa,
buttonTextTransform: uppercase,
buttonTextHoverColor: #ddd,
buttonColor: #333,
buttonBorder: 1px solid #aaa,
),
);
Then use the mixin and function pair to add theme support.
body {
background-color: white;
#include themify {
background-color: theme( 'backgroundColor' );
}
}
.button {
background-color: lightgray;
color: black;
#include themify {
background-color: theme( 'buttonBackgrounColor' );
color: theme( 'buttonTextColor' );
}
&:focus,
&:hover {
background-color: gray;
#include themify {
background-color: theme( 'buttonBackgroundHoverColor' );
color: theme( 'buttonTextHoverColor' );
}
}
}
If you're going to be adding a lot of themes or a theme will be touching a lot of stuff, you might want to set up your SCSS files a little differently so that all the theming doesn't bloat your main CSS file (like the example above would do). One way to do this might be to create a themes.scss file and replicate any selector paths that need theming and have a second build script that outputs just the themes.scss file.
The Mixin
#mixin themify( $themes: $themes ) {
#each $theme, $map in $themes {
.theme-#{$theme} & {
$theme-map: () !global;
#each $key, $submap in $map {
$value: map-get(map-get($themes, $theme), '#{$key}');
$theme-map: map-merge($theme-map, ($key: $value)) !global;
}
#content;
$theme-map: null !global;
}
}
}
The Function
#function themed( $key ) {
#return map-get( $theme-map, $key );
}

Related

How to generate classes using SASS?

I'm using bootstrap 4 with sass in my application. Bootstrap provides a custom input checkbox but only for the primary theme color.
I've read some things about generating classes with sass using #each and #mixin, but none of them were clear to me. As you can se in the code bellow i did it by hand typing every class and color.
.custom-checkbox-primary{
.custom-control-input:checked ~ .custom-control-label::before {
color: $primary;
border-color: $primary;
background-color: $primary;
}
}
.custom-checkbox-secondary{
.custom-control-input:checked ~ .custom-control-label::before {
color: $secondary;
border-color: $secondary;
background-color: $secondary;
}
}
.custom-checkbox-danger{
.custom-control-input:checked ~ .custom-control-label::before {
color: $danger;
border-color: $danger;
background-color: $danger;
}
}
I want sass to generate these 'custom-checkbox-{{theme-color}}' dynamically for me.
You can use #each to iterate the theme-colors like this..
#each $color, $value in $theme-colors {
.custom-checkbox-#{$color}{
.custom-control-input:checked ~ .custom-control-label::before {
color: $value;
border-color: $value;
background-color: $value;
}
}
}
Demo: https://codeply.com/go/imgvc0X9l0
Related: Extending Bootstrap 4 and SASS

CSS :root variables and SASS Functions

in the Header of my HTML-Page i set the following CSS Variables:
:root{
--data-color-primary: #ffcc00;
--data-color-secondary: #4b4b4b;
}
In my SASS-File i use it as follow:
DIV.color {
&.color-primary {
background-color: var(--data-color-primary);
}
&.color-secondary {
background-color: var(--data-color-secondary);
}
}
Now i try to set the font-color depending on the brightness of the background-color:
#function set-notification-text-color($color) {
#if (lightness($color) > 60) {
#return #000000;
} #else {
#return #ffffff;
}
}
DIV.color{
&.color-primary {
background-color: var(--data-color-primary);
color: set-notification-text-color(var(--data-color-primary));
}
}
But in my SASS-compliler i get the following i get the following Error:
Error: argument $color of lightness($color) must be a color
How is ist possible to hand over der CSS variable to the function.
My Problem is, the CSS Variables are set in the Backend of my CMS by User (Liferay 7) an will be rendered in a *.FTL-File and is printed in the HTML-Code.
$primary: ${clr_primary};
$secondary: ${clr_primary};
and then i cant use the SASS-Variable $primary in my SASS-File.
Use SASS variables in your CSS variables.
$primary: #ffcc00;
$secondary: #4b4b4b;
:root{
--data-color-primary: #{$primary};
--data-color-secondary: #{$secondary};
}
Now call your mixin
DIV.color{
&.color-primary {
background-color: $primary;
color: set-notification-text-color($primary);
}
}
Another options would be to create a mixin which retrieves the CSS variable
#function color($color-name) {
#return var(--data-color-#{$color-name});
}
Now call that function like so
DIV.color {
&.color-primary {
background-color: color(primary);
color: set-notification-text-color(color(primary));
}
}
Check out this link for usefull information about combining CSS and SASS variables
https://codepen.io/jakealbaugh/post/css4-variables-and-sass
If you need to change CSS variables outside of :root you can do the following
.class {
// sass-lint:disable no-duplicate-properties
#{--background}: transparent;
#{--background-focused}: transparent;
// sass-lint:enable no-duplicate-properties
}
and this compiles to
.class {
--background: transparent;
--background-focused: transparent;
}

Sass ampersand and two parents together in mixin?

I'm faced with the task of theming the site. I found a suitable mixin. Everything would work well, if not for the mixin for events. It turns out that I need to do something, so that if the topic's mixin is invoked in the mixin of events, then the class did not go cascade, but substituted for the topic class, the .no-touchevents class on the html tag.
Ideally, that would be so on the output:
.card {
color: #fff;
}
.t-dark .card {
color: #000;
}
.no-touchevents .card:hover {
color: #000;
}
.t-dark.no-touchevents .card:hover {
color: #fff;
}
It's a little hacky (or maybe a lot hacky) but by adding an additional parameter to the themify mixin and building our selector manually, you can achieve the output you're looking for.
$themes: (
dark: (
colorDark: #000,
colorLight: #fff
)
);
#mixin on-event() {
.no-touchevents &:hover {
#content;
}
}
#mixin themify($themes, $flat: ' ') { // Add a parameter to separate by default
#each $theme, $map in $themes {
#at-root .t-#{$theme}#{$flat}#{&} { // Build our selector manually
$theme-map: () !global;
#each $key, $submap in $map {
$value: map-get(map-get($themes, $theme), '#{$key}');
$theme-map: map-merge($theme-map, ($key: $value)) !global;
}
#content;
$theme-map: null !global;
}
}
}
#function themed($key) {
#return map-get($theme-map, $key);
}
.card {
color: #fff;
#include themify($themes) {
color: themed('colorDark')
}
#include on-event() {
color: #000;
#include themify($themes, '') { // Tell themify not to separate selectors
color: themed('colorLight')
}
}
}

Sass - What's the difference between map-get and simple variable?

I'm new with Sass stuff and I've been reading about different ways to use variables, this principle I'm trying to apply is just for colors, some of the solutions I've found were something like this (map-get):
$colors: (
lighestGray: #F8F8FA,
lightGray: #A5ACBA,
light: #FFFFFF,
dark: #000000,
link: #428bca,
linkHover: #555,
navBlue: #7AC243,
navGreen: #009CDC,
);
Then you use it on your class like this:
.my-class {
color: map-get($colors, dark);
}
And the other way is to use:
$color-black: #000000;
Then you use it like this:
.my-class {
color: $color-black;
}
My question is, which option is better? or map-getfunction has another purpose?, has Sass a pattern for this or it depends on each web-developer?.
Thanks for helping me out!.
Regards.
The differences is that when you use $map variables, they are best designed for using through iterations or using #each.
Sample case:
SCSS
// Map variable
$icons: (
facebook : "\f0c4",
twitter : "\f0c5",
googleplus : "\f0c6",
youtube : "\f0c7"
);
// Mixin doing the magic
#mixin icons-list($map) {
#each $icon-name, $icon in $map {
#if not map-has-key($map, $icon-name) {
#warn "'#{$icon-name}' is not a valid icon name";
}
#else {
&--#{$icon-name}::before {
content: $icon;
}
}
}
}
// How to use it
.social-link {
background-color: grey;
#include icons-list($icons);
}
CSS
// CSS Output
.social-link {
background-color: grey;
}
.social-link--facebook::before {
content: "";
}
.social-link--twitter::before {
content: "";
}
.social-link--googleplus::before {
content: "";
}
.social-link--youtube::before {
content: "";
}
This code was taken from my own answer in the following post but the answer is a case use of #each :)
Hope this help you
Example making a theme with css variables with fallback color
see codepen css variables
// VARS (FOR FALLBACK)
// -------------------
$theme-base: #70c1ac;
$theme-base-aa: adjust-color($theme-base, $blue: 125);
// PROCESSED THEME
$theme-color: $theme-base;
$theme-color-dark: darken($theme-color, 20%);
$theme-color-light: lighten($theme-color, 20%);
$theme-color-mixed: mix(#fff, $theme-color, 75%);
$theme-color-trans: transparentize($theme-color, .4);
// PROCESSED SECONDARY
$theme-color-aa: $theme-base-aa;
$theme-color-aa-dark: darken($theme-color-aa, 20%);
$theme-color-aa-light: lighten($theme-color-aa, 20%);
$theme-color-aa-mixed: mix(#fff, $theme-color-aa, 75%);
$theme-color-aa-trans: transparentize($theme-color-aa, .4);
$theme-colors: (
"aa-dark": $theme-color-aa-dark,
"aa-light": $theme-color-aa-light,
"aa-mixed": $theme-color-aa-mixed,
"aa-trans": $theme-color-aa-trans,
aa: $theme-color-aa,
dark: $theme-color-dark,
light: $theme-color-light,
mixed: $theme-color-mixed,
theme: $theme-color,
trans: $theme-color-trans,
);
#mixin themeColor ($prop, $color: null) {
#if ($color) {
#{$prop}: map-get($theme-colors, $color);
#{$prop}: var(--theme-color-#{$color})
} #else {
#{$prop}: map-get($theme-colors, theme);
#{$prop}: var(--theme-color);
}
}
#mixin setThemeColors($base1: "", $base2: "") {
// BASE THEME COLORS
$color-base: $theme-base;
$color-aa: $theme-base-aa;
#if ($base1) {
$color-base: $base1;
$color-aa: $base2;
}
// PROCESSED THEME COLORS
$color-aa-dark: darken($color-aa, 20%);
$color-aa-light: lighten($color-aa, 20%);
$color-aa-mixed: mix(#fff, $color-aa, 75%);
$color-aa-trans: transparentize($color-aa, .5);
$color-aa: $color-aa;
$color-dark: darken($color-base, 20%);
$color-light: lighten($color-base, 20%);
$color-mixed: mix(#fff, $color-base, 75%);
$color-trans: transparentize($color-base, .5);
// CSS VARIABLES
--theme-color-aa-dark: #{$color-aa-dark};
--theme-color-aa-light: #{$color-aa-light};
--theme-color-aa-trans: #{$color-aa-trans};
--theme-color-aa: #{$color-aa};
--theme-color-dark: #{$color-dark};
--theme-color-light: #{$color-light};
--theme-color-mixed: #{$color-mixed};
--theme-color-trans: #{$color-trans};
--theme-color: #{$color-base};
}
:root {
#include setThemeColors($theme-base, $theme-base-aa);
}
body {
#include themeColor("background","mixed");
font-size: 2rem;
}
ul {
list-style: none; /* Remove default bullets */
}
ul li::before {
content: "\2022"; /* Add content: \2022 is the CSS Code/unicode for a bullet */
#include themeColor("color","dark");
font-weight: bold; /* If you want it to be bold */
display: inline-block; /* Needed to add space between the bullet and the text */
width: 1.2em; /* Also needed for space (tweak if needed) */
margin-left: -.8em; /* Also needed for space (tweak if needed) */
}
li {
#include themeColor("color", "light");
#include themeColor("background", "aa-dark");
}
Why pick one when you can have them both.
_variables.scss
$color0 : white;
$color1 : red;
$color2 : green;
$color3 : blue;
_lists.scss
#use "variables";
#use "sass:map";
#use "sass:meta";
#use "sass:list";
#function dynamic($variable){
$i: 0;
$list: ();
#while(variable-exists($variable + $i)){
$list: list.append($list, map.get(meta.module-variables(variables), $variable + $i));
$i: $i + 1;
}
#return $list;
}
$colors: dynamic('color'); // white red green blue
Import both into your scss files and use the list when you need to loop and the variables for shorthand when applying styles.
map-get is used for getting css value from more kind of object.
suppose you have $param where you have defined multiple properties and now you want to assign. you can use it in following ways -
color: map-get($params, "color");
Where else simple variable holds only single value
map-get to get css value from object holding multiple values whereas
variable to hold single value

How to change a class format based on body's class with SCSS?

I am making a web app that is used in three (or more) different contexts, and I want each context to have a different color scheme. However, I don't want to have to maintain three different stylesheets when all that changes is colors, typically.
For instance, suppose the themes are red, blue, and orange. One of my stylesheets describes the link colors:
a {
color: $some_color;
}
I want to split this based on the class applied to the body:
body.style1 {
a {
color: $red;
}
}
body.style2 {
a {
color: $blue;
}
}
body.style3 {
a {
color: $orange;
}
}
You can see how this gets unwieldy pretty quickly if you're changing the style for lots of elements. Is there a way to do this more like this?
a {
&closest:body.style1 {
color: $red
}
&closest:body.style2 {
color: $blue;
}
&closest:body.style3 {
color: $orange;
}
}
This way I can code my scss in a clearer, more maintainable way.
It appers you don't have to have the & first, so this works (at least in 3.2.10):
a {
body.style1 & {
color: $red
}
body.style2 & {
color: $blue;
}
body.style3 &{
color: $orange;
}
}
This is what I prefer. Define a mixin like body-style :
#mixin body-style($style, $map) {
body.#{$style} & {
#each $property, $value in $map {
#{$property}: $value;
}
}
}
Then use this for every tag by passing $style as style class of body and $map as map of css keys and values.
a {
#include body-style(style1, (
color: red,
background: white
)
);
}
It will return :
body.style1 a {
color: red;
background: white;
}

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