First Widgets
Getting Started
Start by importing the singleton Astal.Application instance.
import { App } from "astal/gtk3"
App.start({
main() {
// you will instantiate Widgets here
// and setup anything else if you need
}
})
After your bundle step run gjs -m app.js
, and that's it! Now you have an Astal instance running written in TypeScript.
Root of every shell component: Window
Astal apps are composed of widgets. A widget is a piece of UI that has its own logic and style. A widget can be as small as a button or an entire bar. The top level widget is always a Window which will hold all widgets.
function Bar(monitor = 0) {
return <window className="Bar" monitor={monitor}>
<box>Content of the widget</box>
</window>
}
import Bar from "./widget/Bar"
App.start({
main() {
Bar(0)
Bar(1) // instantiate for each monitor
},
})
Creating and nesting widgets
Widgets are JavaScript functions which return Gtk widgets, either by using JSX or using a widget constructor.
function MyButton(): JSX.Element {
return <button onClicked="echo hello">
<label label="Click me!" />
</button>
}
import { Widget } from "astal/gtk3"
function MyButton(): Widget.Button {
return new Widget.Button(
{ onClicked: "echo hello" },
new Widget.Label({ label: "Click me!" }),
)
}
INFO
The only difference between the two is the return type. Using markup the return type is always Gtk.Widget
(globally available as JSX.Element
), while using constructors the return type is the actual type of the widget. It is rare to need the actual return type, so most if not all of the time, you can use markup.
Now that you have declared MyButton
, you can nest it into another component.
function MyBar() {
return <window>
<box>
Click The button
<MyButton />
</box>
</window>
}
Notice that widgets you defined start with a capital letter <MyButton />
. Lowercase tags are builtin widgets, while capital letter is for custom widgets.
Displaying Data
JSX lets you put markup into JavaScript. Curly braces let you “escape back” into JavaScript so that you can embed some variable from your code and display it.
function MyWidget() {
const label = "hello"
return <button>{label}</button>
}
You can also pass JavaScript to markup attributes
function MyWidget() {
const label = "hello"
return <button label={label} />
}
Conditional Rendering
You can use the same techniques as you use when writing regular JavaScript code. For example, you can use an if statement to conditionally include JSX:
function MyWidget() {
let content
if (condition) {
content = <True />
} else {
content = <False />
}
return <box>{content}</box>
}
You can also inline a conditional ?
(ternary) expression.
function MyWidget() {
return <box>{condition ? <True /> : <False />}</box>
}
When you don’t need the else
branch, you can also use a shorter logical && syntax:
function MyWidget() {
return <box>{condition && <True />}</box>
}
INFO
As you can guess from the above snippet, falsy values are not rendered.
Rendering lists
You can use for
loops or array map()
function.
function MyWidget() {
const labels = [
"label1"
"label2"
"label3"
]
return <box>
{labels.map(label => (
<label label={label} />
))}
</box>
}
Widget signal handlers
You can respond to events by declaring event handler functions inside your widget:
function MyButton() {
function onClicked(self: Widget.Button, ...args) {
console.log(self, "was clicked")
}
return <button onClicked={onClicked} />
}
The handler can also be a string, which will get executed in a subprocess asynchronously.
function MyButton() {
return <button onClicked="echo hello" />
}
INFO
Attributes prefixed with on
will connect to a signal
of the widget. Their types are not generated, but written by hand, which means not all of them are typed. Refer to the Gtk and Astal docs to have a full list of them.
How properties are passed
Using JSX, a custom widget will always have a single object as its parameter.
type Props = {
myprop: string
child?: JSX.Element // when only one child is passed
children?: Array<JSX.Element> // when multiple children are passed
}
function MyWidget({ myprop, child, children }: Props) {
//
}
// child prop of MyWidget is the box
return <MyWidget myprop="hello">
<box />
</MyWidget>
// children prop of MyWidget is [box, box, box]
return <MyWidget myprop="hello">
<box />
<box />
<box />
</MyWidget>
State management
The state of widgets are handled with Bindings. A Binding lets you connect the state of an object to a widget so it re-renders when that state changes.
Use the bind
function to create a Binding
object from a Variable
or a regular GObject
and one of its properties.
Here is an example of a Counter widget that uses a Variable
as its state:
import { Variable, bind } from "astal"
function Counter() {
const count = Variable(0)
function increment() {
count.set(count.get() + 1)
}
return <box>
<label label={bind(count).as(num => num.toString())} />
<button onClicked={increment}>
Click to increment
</button>
</box>
}
INFO
Bindings have an .as()
method which lets you transform the assigned value. In the case of a Label, its label property expects a string, so it needs to be turned to a string first.
TIP
Variables
have a shorthand for bind(variable).as(transform)
const v = Variable(0)
const transform = (v) => v.toString()
return <box>
{/* these two are equivalent */}
<label label={bind(v).as(transform)} />
<label label={v(transform)} />
</box>
Here is an example of a battery percent label that binds the percentage
property of the Battery object from the Battery Library:
import Battery from "gi://AstalBattery"
import { bind } from "astal"
function BatteryPercentage() {
const bat = Battery.get_default()
return <label label={bind(bat, "percentage").as((p) => p * 100 + " %")} />
}
Dynamic children
You can also use a Binding
for child
and children
properties.
const child = Variable(<box />)
return <box>{child}</box>
const num = Variable(3)
const range = (n) => [...Array(n).keys()]
return <box>
{num(n => range(n).map(i => (
<button>
{i.toString()}
<button/>
)))}
<box>
TIP
Binding children of widgets will implicitly call .destroy()
on widgets that would be left without a parent. You can opt out of this behavior by setting noImplicityDestroy
property on the container widget.
INFO
The above example destroys and recreates every widget in the list every time the value of the Variable
changes. There might be cases where you would want to handle child creation and deletion yourself, because you don't want to lose the inner state of widgets that does not need to be recreated. In this case you can create a custom reactive structure
How children are passed
Here is full list of how children and bound children can be passed to custom widgets.
import Binding from "astal/binding"
function Parent(props: {
child?: JSX.Element | Binding<JSX.Element> | Binding<Array<JSX.Element>>
children?: Array<JSX.Element> | Binding<Array<JSX.Element>>
})
// { child: JSX.Element }
<Parent>
<child />
</Parent>
// { children: Array<JSX.Element> }
<Parent>
<child />
<child />
</Parent>
// { child: Binding<JSX.Element> }
<Parent>
{variable(c => (
<child />
))}
</Parent>
// { child: Binding<Array<JSX.Element>> }
<Parent>
{variable(c => (
<child />
<child />
))}
</Parent>
// { children: Binding<Array<JSX.Element>> }
<Parent>
<child />
{variable(c => (
<child />
))}
</Parent>
// { children: Binding<Array<JSX.Element>> }
<Parent>
<child />
{variable(c => (
<child />
<child />
))}
</Parent>
TIP
If you have a widget where you pass widgets in various ways, you can wrap child
in children
in a Subscribable
and handle all cases as if they were bindings.
INFO
You can pass the followings as children:
- widgets
- deeply nested arrays of widgets
- bindings of widgets
- bindings of deeply nested arrays of widgets
falsy values are not rendered and anything not from this list will be coerced into a string and rendered as a label