React Native Theme System
Overview
React Native Theme System brings functional styling to react-native. It is inspired by Tachyons and uses it's scales and naming convention. More about the advantages of this approach.
Let's see how tachyons compares to traditional styling:
1. Traditional react-native style:
import {StyleSheet} from "react-native";
const s = StyleSheet.create({
view: {
borderWidth: 1,
justifyContent: "flex-start",
padding: MAGIC_PIXEL_VALUE
},
text: {
color: "white",
textAlign: "center"
}
})
<View style={[s.view]}
<Text style={[s.text]}>Something</Text>
</View>
2. Improved with theme-system:
<View cls="ba jcfs pa2"> /* string is checked for validity */
<Text cls="white tc">
Something
</Text>
</View>
Advantages
- Less code
- No need to maintain a separate stylesheet
- No need to find a proper name for every component you want to style
- Looking at a component tells you exactly how it looks, it's all in one place.
- Flexible syntax because cls can take any number of arguments which can be string, object or array.
cls={['foo', 'bar']} // => 'foo bar'
cls={['foo', { bar: true }]} // => 'foo bar'
cls={{ 'foo-bar': true }} // => 'foo-bar'
cls={{ 'foo-bar': false }} // => ''
cls={[{ foo: true }, { bar: true }]} // => 'foo bar'
cls={{ foo: true, bar: true }} // => 'foo bar'
// lots of arguments of various types
cls={['foo', { bar: true, duck: false }, 'baz', { quux: true }]} // => 'foo bar baz quux'
// other falsy values are just ignored
cls={[null, false, 'bar', undefined, 0, 1, { baz: null }, '']} // => 'bar 1'
Arrays will be recursively flattened as per the rules above:
var arr = ['b', { c: true, d: false }];
cls={['a', arr]} // => 'a b c'
Tachyons' scale
-
Dimensions and typography build on a proven scale, which is relative to
rem, the root font-size. Instead of having to find proper values for padding (or margin, width or height), you use a simple 7-step scale.pa2gets youpaddingof0.5rem. -
The scale progresses with powers of two, so each step is twice as big as the last. This means everything will always line up, no more "off-by-one-pixel"-problems.
-
You can scale the entire design just by setting a different
rem. This is a great advantage when building a responsive app. -
The optional
fontRemparameter scales the font sizes independently of other styles.
Usage
- In the entry point of your app include:
import { StyleSheet } from "react-native";
import { buildTheme } from "./config-theme";
buildTheme({
clsPropName: "cls",
/* default is cap of clsPropName, propCls => propStyle */
clsPropNameCap: "Cls",
clsMap: {
cls: "style",
contentContainerCls: "contentContainerStyle",
containerCls: "containerStyle",
wrapperCls: "wrapperStyle"
},
/* REM parameter is optional, default is 16 */
rem: screenWidth > 340 ? 18 : 16,
/* fontRem parameter is optional to allow adjustment in font-scaling. default falls back to rem */
fontRem: 20
});
Sensible rem/fontRem values
Experience with variously sized iPhone and Android phones from 4" to 6" displays showed, that for tablets, rem values in the range of 12 - 18, depending on device resolution, work well. For phones, the same rem can be used, but fontRem should be floored at 14, to keep everything readable.
- To use the
cls=''syntax, you have to wrap your component:
import { wrap } from "./theme";
@wrap
class MyComponent extends React.Component {
...
or if you use simple functions
wrap(() => <Text cls="b">Hi there!</Text>)
If you prefer to use a different propName instead of `cls`, specify the name in the options:
buildTheme({
clsPropName: "cls"
});
Reference / Supported Properties
FlexBox
absolute position: "absolute" /* default: "relative" */
flx-i flex: 1
flx-row flexDirection: "row" /* default: "column" */
flx-row-reverse flexDirection: "row-reverse"
flx-col-reverse flexDirection: "column-reverse"
flx-wrap flexWrap: "wrap" /* default: "nowrap" */
aifs alignItems: "flex-start" /* default: "stretch" */
aic alignItems: "center"
aife alignItems: "flex-end"
jcc justifyContent: "center" /* default: "flex-start" */
jcfe justifyContent: "flex-end"
jcsb justifyContent: "space-between"
jcsa justifyContent: "space-around"
asfs alignSelf: "flex-start"
asfe alignSelf: "flex-end"
asc alignSelf: "center"
ass alignSelf: "stretch"
Margins & Paddings (Scale)
ma0 ... ma8 margin: 0|0.25|0.5|1|2|4|8|16|32 rem
ml|mr|mb|mt [0-8] marginLeft, marginRight, marginBottom, marginTop
mh [0-8] marginHorizontal
mv [0-8] marginVertical
/* Same with p for padding */
Heights & Widths
h1 ... h6 height: 1|2|4|8|16|32 rem
w1 ... w6 width: 1|2|4|8|16|32 rem
min-h1 ... min-h6 minHeight: 1|2|4|8|16|32 rem
max-h1 ... max-h6 maxHeight: 1|2|4|8|16|32 rem
Absolute
absolute position: absolute
top|right|bottom|left-0 top|right|bottom|left: 0 rem
... 1 ... 1 rem
... 2 ... 2 rem
absolute-fill position: absolute, top/left/right/bottom: 0
Borders
ba borderWidth: 1
bl|br|bt|bb borderLeftWidth: 1 | borderRightWidth: 1...
br0 ... br5 borderRadius: 0|0.125|0.25|0.5|1]2 rem
br--bottom bottom radius only
br--top top radius only
br--right right radius only
br--left left radius only
Text & Fonts (Scale)
f5 fontSize: 1 rem
f1 ... f6 fontSize: 3|2.25|1.5|1.25|1|0.875 rem
f-headline fontSize: 6 rem
f-subheadline fontSize: 5 rem
normal fontWeight: normal
b fontWeight: bold
fw1 ... fw9 fontWeight: 100 ... fontWeight: 900
i fontStyle: italic
tl|tc|tr|tj textAlign: left|center|right|justify
lh-solid lineHeight: 1 rem
lh-title lineHeight: 1.25 rem
lh-copy lineHeight: 1.5 rem
/* Letter-spacing is only supported on iOS */
tracked letterSpacing: 0.1 rem
tracked-tight letterSpacing: -0.05 rem
tracked-mega letterSpacing: 0.25 rem
Font-Families
Specify the font-families you need in the configuration to use them:
ff-iowan fontFamily: "Iowan Old Style"
/* setup: */
buildTheme({
fonts: {
iowan: 'Iowan Old Style'
}
});
Images
rm-contain resizeMode: "contain"
rm-cover resizeMode: "cover"
rm-stretch resizeMode: "stretch"
tint-$color tintColor: $color, see Colors section
Opacity
o-10|20|...|100 opacity: 0.1|0.2|...|1
o-05 opacity: 0.05
o-025 opacity: 0.025
Colors
-
When using the
cls=''syntax, colors can be specified directly in the string. Every Color supported by react-native works. If the color is prefixed withbg-thebackgroundColorwill be set. A prefix ofb--sets theborderColor.bg-green green background #232323 text color of #232323 b--rgba(255,255,255,0.5) border set to rgba(255,255,255,0.5) tint-blue tint-color set to blue -
You can also specify a palette in the options and Tachyons will generate styles for you. It will also generate variants with different opacities.
buildTheme({ colors: { green: "#00FF00", } });The same syntax with
bg-for background andb--for borderColor applies.bg-green green background b--green green border // Note: double hyphens signify a class that needs green green text // another class to work in this case a border-setting /* alpha variants (same for bg- and b--) */ green-10, green-20 ... green-90 green text with 10%, 20%, ... , 90% alpha
Raw Values
To access the actual computed sizes:
import { options, sizes } from "./themes"
const s = options.rem * sizes.ma2 /* sizes.w4, ... */
Magic Functions
We can map cls attribute to defined function:
import { options } from ".themes"
buildTheme({
fn: {
myFn:(val)=>({
green: "#00FF00",
})
}
});
<View cls="myFn-12"> /* format is function-param1-param2 */
...
</View>