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Igor Demin
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README.md |
README.md
Style DSL
In this tutorial we have a look at how to style the components using the Style DSL. It’s a typesafe DSL for style sheets, which you can use to express CSS rules in your Kotlin code, and even modify styles based on the state of your Compose application.
Inline Style
You can declare inline styles via the style
block of a component
Div({
style {
display(DisplayStyle.Flex)
padding(20.px)
// custom property (or not supported out of a box)
property("font-family", "Arial, Helvetica, sans-serif")
}
}) { /* content goes here */ }
In HTML, it will look like this:
<div style="display: flex; padding: 20px; font-family: Arial, Helvetica, sans-serif;"></div>
Stylesheet
An alternative way is to define a Stylesheet that contains rules:
object AppStylesheet : StyleSheet() {
val container by style { // container is a class
display(DisplayStyle.Flex)
padding(20.px)
// custom property (or not supported out of a box)
property("font-family", "Arial, Helvetica, sans-serif")
}
}
// Stylesheet needs to be mounted:
renderComposable("root") {
Style(AppStylesheet)
Container {
Text("Content")
}
}
@Composable
fun Container(content: @Composable () -> Unit) {
Div(
attrs = { classes(AppStylesheet.container) }
) {
content()
}
}
In HTML, it will look like this:
<style></style>
<div class="AppStylesheet-container">Content</div>
Selectors examples
The Style DSL also provides a way to combine and unify selectors:
object AppStylesheet : StyleSheet() {
init {
// `universal` can be used instead of "*": `universal style {}`
"*" style {
fontSize(15.px)
padding(0.px)
}
// raw selector
"h1, h2, h3, h4, h5, h6" style {
property("font-family", "Arial, Helvetica, sans-serif")
}
// combined selector
type("A") + attr( // selects all tags <a> with href containing 'jetbrains'
name = "href",
value = "jetbrains",
operator = CSSSelector.Attribute.Operator.Equals
) style {
fontSize(25.px)
}
}
// A convenient way to create a class selector
// AppStylesheet.container can be used as a class in component attrs
val container by style {
color(Color.red)
// hover selector for a class
self + hover() style { // self is a selector for `container`
color(Color.green)
}
}
}
Media query example
To specify media queries, you can use the media
function, which takes the related query, and a block of styles:
object AppStylesheet : StyleSheet() {
val container by style {
padding(48.px)
media(maxWidth(640.px)) {
self style {
padding(12.px)
}
}
}
}
CSS Variables
The style DSL also provides support for CSS variables.
object MyVariables {
// declare a variable
val contentBackgroundColor by variable<CSSColorValue>()
}
object MyStyleSheet: StyleSheet() {
val container by style {
//set variable's value for the `container` scope
MyVariables.contentBackgroundColor(Color("blue"))
}
val content by style {
// get the value
backgroundColor(MyVariables.contentBackgroundColor.value())
}
val contentWithDefaultBgColor by style {
// default value can be provided as well
// default value is used when the value is not previously set
backgroundColor(MyVariables.contentBackgroundColor.value(Color("#333")))
}
}
Runnable example
import androidx.compose.runtime.Composable
import org.jetbrains.compose.web.css.*
import org.jetbrains.compose.web.dom.*
import org.jetbrains.compose.web.renderComposable
object MyVariables {
// declare a variable
val contentBackgroundColor by variable<CSSColorValue>()
}
object MyStyleSheet: StyleSheet() {
val container by style {
//set variable's value for the `container` scope
MyVariables.contentBackgroundColor(Color("blue"))
}
val content by style {
// get the value
backgroundColor(MyVariables.contentBackgroundColor.value())
}
val contentWithDefaultBgColor by style {
// default value can be provided as well
// default value is used when the value is not previously set
backgroundColor(MyVariables.contentBackgroundColor.value(Color("#333")))
}
}
object AppStylesheet : StyleSheet() {
val container by style { // container is a class
display(DisplayStyle.Flex)
padding(20.px)
// custom property (or not supported out of a box)
property("font-family", "Arial, Helvetica, sans-serif")
}
}
@Composable
fun Container(content: @Composable () -> Unit) {
Div(
attrs = { classes(AppStylesheet.container) }
) {
content()
}
}
fun main() {
renderComposable(rootElementId = "root") {
Div({
style {
display(DisplayStyle.Flex)
padding(20.px)
// custom property (or not supported out of a box)
property("font-family", "Arial, Helvetica, sans-serif")
}
}) { /* content goes here */ }
Style(AppStylesheet)
Container {
Text("Content")
}
}
}