Doodle - A pure Kotlin, UI framework for the Web

I just released Doodle . A pure Kotlin UI framework for the Web. The difference compared to other frameworks is that it is not a nicer way to write HTML/CSS. Doodle apps actually don’t use browser concepts at all.


Doodle is written entirely in Kotlin and so are its apps. Doodle Applications do not use HTML, CSS styles or Javascript libraries. In fact, apps are not aware of the Browser (or Browser concepts) at all, and can be written entirely as common (cross-platform) code in multi-platform setups.


Creating expressive, intuitive apps is natural with Doodle. It makes complex rendering easy with powerful, vector-oriented rendering, provides fully customizable layouts and simplifies pointer and keyboard handling.

Simply define your View hierarchy, business logic and go.

Vector Oriented

It is easy to build beautifully detailed UIs with Doodle. All rendering in Doodle is vector-oriented; so ellipses, paths, lines, gradients, affine transforms etc. are as simple to use as images and rectangles.


Doodle gives you control over all aspects of the UI presentation, including pixel-level positioning, making it easier to precisely control rendering.


Doodle has several libraries and a collection of modules. This allows selective adoption of various features and helps with bundle size. Apps written with Doodle are also dependency-injected; and there are no global objects or state to make mocking challenging.

class HelloWorld(display: Display): Application {
    init {
        display.children += object: View() {
            init { size = display.size }

            override fun render(canvas: Canvas) {
                canvas.text("Hello, world!",
                    at = Origin, 
                    brush = ColorBrush(Black))

    override fun shutdown() {}

fun main() {
    application {
        HelloWorld(display = instance())
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Do I understand correctly that this is essentially like Flash, but with SVGs?

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It’s not quite like Flash since it ships pure JS when compiled. It uses SVG, but only for shapes that can’t easily be rendered with regular html elements.

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@joe_bloggs Are you creating any commercial / really used app using this framework?
Or this is just a nice toy? :slight_smile:

I don’t currently have a project that could use it. But I’d love to see what others might do with it, and hear feedback on how to continue improving it.

it is wonderful

Doodle 0.3.0 has been released. Join #doodle to ask questions or share use-cases.

  • Files now supported in drag-drop
  • New elliptical clip path support in Canvas
canvas.clip(ellipse) {
    // render into clipped region using Canvas receiver
  • Scheduler is now shutdown when app is
  • New API in Behavior to control content direction mirroring
  • New behavior delegate to centralize common operations
  • Initial work on DSL: new view {} and container {} functions
val panel = view {
    render = {
        // use Canvas receiver

val container = container {
    this += view {}
  • Improved ergonomics for adding/removing items to Display and Container
  • Changed Container from interface to concrete View, which replaces Box
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Doodle 0.4.2 released. Join #doodle to ask questions or share use-casses.

val ring   : Path = ring       (center, innerRadius, outerRadius)
val section: Path = ringSection(center, innerRadius, outerRadius, startAngle, endAngle)
object: ProgressIndicator() {
    init {
        size     = Size(200, 100)
        progress = 0.25
        behavior = PathProgressIndicatorBehavior(
            pathMetrics,          // injected
            path                = path("M10 80 C 40 10, 65 10, 95 80 S 150 150, 180 80")!!,
            foreground          = LinearGradientPaint(Black, Blue, Origin, Point(width, 0.0)),
            foregroundThickness = 5.0,
            background          = Lightgray.paint,
            backgroundThickness = 5.0

canvas.rect(rectangle = bounds.atOrigin.inset(10.0),
radius = 10.0,
stroke = Stroke(fill = LinearGradientPaint(Red, Green, Origin, Point(width, height)), thickness = 20.0))

See the full release notes for more details. (edited)