Astal

Appearance

Theming ​

Since the widget toolkit is GTK3 theming is done with CSS.

GTK is not the web

While most features are implemented in GTK, you can't assume anything that works on the web will work with GTK. Refer to the GTK docs to see what is available.

So far every widget you made used your default GTK3 theme. To make them more custom, you can apply stylesheets to them.

From file at startup ​

You can pass a path to a file or css as a string in App.start

ts
const inlineCss = `
window {
    background-color: transparent;
}
`

App.start({
    css: "./style.css",
    css: `${SRC}/style.css'`,
    css: inlineCss,
})

INFO

The global SRC will point to the directory app.ts is in. AGS will set the current working directory to --config, so ./style.css also works.

Css Property on Widgets ​

ts
Widget.Label({
    css: "color: blue; padding: 1em;",
    label: "hello",
})

INFO

The css property of a widget will not cascade to its children.

Apply Stylesheets at Runtime ​

You can apply additional styles at runtime.

ts
App.apply_css("/path/to/file.css")
ts
App.apply_css(`
window {
    background-color: transparent;
}
`)
ts
App.reset_css() // reset if need

WARNING

App.apply_css will apply on top of other stylesheets applied before. You can reset stylesheets with App.resetCss

Inspector ​

If you are not sure about the widget hierarchy or any CSS selector, you can use the GTK inspector

sh
# to bring up the inspector run
ags --inspector

Using SCSS ​

Gtk's CSS only supports a subset of what the web offers. Most notably nested selectors are unsupported by Gtk, but this can be workaround by using preprocessors like SCSS.

sh
sudo pacman -Syu dart-sass
sh
npm install -g sass # not packaged on Fedora
sh
sudo apk add dart-sass
sh
npm install -g sass # not packaged on Ubuntu
sh
sudo zypper install dart-sass

Importing scss files will simply return transpiled css.

ts
import style from "./style.scss"

App.start({
    css: style,
    main() {},
})

TIP

If you for example want to set scss varibles from JS, You can inline import, compose, and transpile yourself.

ts
import style1 from "inline:./style1.scss"
import style2 from "inline:./style2.scss"

const tmpscss = "/tmp/style.scss"
const target = "/tmp/style.css"

writeFile(tmpscss, `
  $var1: red;
  $var1: blue;
  ${style1}
  ${style1}
`)

exec(`sass ${tmpscss} ${target}`)

App.start({
    css: target,
})

INFO

If you want other preprocessors support builtin open an Issue.