Laminar bindings for the SAP ui5 web components library

Laminar bindings for SAP ui5 web-components library

This repository contains Laminar bindings for SAP ui5 web-components.

Web components are a powerful technology to create near-native html elements. Laminar, for its part, is a Scala-js framework/library to manipulate the dom.


You can visit the live demo if you want to see these bindings in action.


In order to use these bindings within your Scala.js project, you need to add the following to your build.sbt:

// for Scala 3
libraryDependencies ++= List(
  "be.doeraene" %%% "web-components-ui5" % "<currently supported version>",
  "com.raquo" %%% "laminar" % "0.14.5"


// for Scala 2.13.10 (at least .10)
scalacOptions ++= List("-Ytasty-reader")
libraryDependencies ++= List(
  "be.doeraene" % "web-components-ui5_sjs1_3" % "<currently supported version>"
  "com.raquo" %%% "laminar" % "0.14.5"

where <currently supported version> must be replaced with the version of the library that you want to use (see the maven repo page to check existing versions). Major and minor numbers will correspond to the major and minor version of the npm UI5 library.

Using these bindings with an earlier version of UI5 will probably show stuff that did not exist at the time. Similarly, using these bindings with an older version will imply that you will not find certain bindings. Other than that, it is perfectly safe to mix mismatch versions.

Important: this is only the "Scala part" of the installation. We do not manage the dependencies to the npm library itself. See the "How to use" section below.

Note on the Laminar version

This library is built against a certain version of Laminar, but it is set as "provided". That means that you have to depend on Laminar yourself, but (for a large deal) you are not bound to the specific version used here.

What if I find a missing bindings?

First of all, don't panic. You can do the following things:

  1. Open an issue in this repository, referencing the missing component from the official docs
  2. In order to not be stuck in your project right away, you can implement the bindings you need yourself. See the section below to see how to do that
  3. If you feel like it, create a PR to this repository with your new implementation.

How to use

These bindings are barely "facades" types for the official UI5 library. They won't work if you don't handle that npm dependency on your own project. You will need the following imports in your package.json (or equivalent tool such as scala-js-bundler):

"@ui5/webcomponents": "1.9.1",
"@ui5/webcomponents-fiori": "1.9.1",
"@ui5/webcomponents-icons": "1.9.1"

(and thus npm install it). Then, you can use any of the components as defined in the be.doeraene.webcomponents.ui5 package.

For example, you can add an <ui5-input> in your Laminar code like this:

    _.required := true,
    _.valueState := ValueState.Information,
    _.placeholder := "Enter your name",
    onChange.mapToValue --> Observer(println)

This will be rendered as an input as documented here.

Remark for Scala 2.13 users

In order to achieve the highest ergonomics possible, the apply method of components uses a union type as argument. But this only would completely sacrifice the ability of Scala 2.13 users to use the library.

That is why all components also have an of method, only accepting mod functions (as opposed to accepting both mods and mod functions). This reduces the ergonomics a bit for Scala 2.13, but it allows us to move forward.

For you, concretely, instead of having, for example,

Input(_.required := true, onChange.mapToValue --> Observer(println))

you will have to write

Input.of(_.required := true, _ => onChange.mapToValue --> Observer(println))

Failing to do so will produce the following error message:

Unsupported Scala 3 union in parameter value mods; found in method apply in trait be.doeraene.webcomponents.WebComponent.

Running the Demo

The project contains a demo file for each component. These examples are located in the demo sub-project.

In order to run those, you need to have

  • npm with a recent enough version (>= 14 should do) (if you have nvm installed, you can do, e.g., nvm use 17)
  • sbt

Perform the following steps:

First time onl. Open a terminal. cd demo; npm install

  1. in one terminal, run sbt ~demo/fastLinkJS
  2. in another terminal, go to demo and run npm install then npm run dev
  3. when both steps are ready, go to http://localhost:3000/laminar-ui5-demo/ and the demo should be there, waiting for you.

If you're in vscode, try running the task, "runDemo" build task, it will do the above 3 steps for you.

How to use slots?

In web-components, certain components can have special dom children called "slots". In the dom, these "special" children are only singular in the fact that they have a property slot specifying which slot they fill in.

For example, the Dialog component as a footer slot. In raw html, this would look like

  <div slot="footer">I'm a footer</div>

Thanks to the slots object in the Dialog component, this is written in Scala as

  _.slots.footer := div("I'm a footer")

See the implementation of the Slot class to understand what it does.


As you may read from SAP's documentation, Icons need to be imported manually via something like:

import * as accidentalLeave from "@ui5/webcomponents-icons/dist/accidental-leave.js";

Or you can import all icons at once with

import * as allIcons from "@ui5/webcomponents-icons/dist/AllIcons.js";

With these bindings, you don't need to do any of that. Scala.js will detect automatically the imports that are required based on your usage of the IconName values. For example, if you have somewhere in your code

Icon( := IconName.`accidental-leave`

then the above import will be added in the compiled JS file.

Illustrated Messages

Illustrated Messages work the same way as icons (see above).

All possible choices are available in the IllustratedMessageType object. Illustrated messages within the tnt subdirectory are available in the tnt object thereof.

How to read the source code

Every component is implemented as an object with the following:

  • a RawElement (js-native) trait that defines methods that the underlying DOM element will have
  • a RawImport object only there to actually import the library
  • a few reactive html attributes specific to that component
  • a slots object that contains descriptions of the slots that the component can have. They allow syntax such as Input(_.slots.valueStateMessage := span("Hello")).
  • an events object containing specific events that the component can emit.
  • an apply method to build the component (following the example from the Laminar website, they take functions from the object to mods)
  • some components will have links to other tightly coupled components (for example, the TabContainer has a tab link to the Tab component). They allow syntax such as TabContainer( := ???).

Every object is named after the corresponding ui5 web-component, with the notable exception of List which is called UList to not interfere with the built-in Scala List type.

Config Keys package

The ui5 library contains a whole lot of "enums" that are used as properties of elements. In TypeScript, this would typically be represented as

type Stuff = "foo" | "bar" | "baz"

In Scala 3, this approach could work in theory, but not I'm not really fond of. Instead, I prefer to define those as sealed traits like this

sealed trait Stuff
object Stuff {
  case object Foo extends Stuff
  case object Bar extends Stuff
  case object Baz extends Stuff

In order to facilitate such usage with Laminar, these objects will typically extends EnumerationString, which helps by providing the codec required to represent this as a string.

Contributing: Implement bindings for a new component

If you found a missing component that you would like to see integrated in the repo, please find below small guidelines to help you with. There are quite a lot of steps but don't worry, in pratice you can do most of these by simply copy-pasting another existing component!

Before you start

Be sure to check the section about How to read the source code, above.

Also, verify that the component you are about to add is available in the current matching version defined in the build.sbt as

ThisBuild / version := "<current supported sap version>"

If not, please open an issue to upgrade to the new version. This does not prevent you to already do the following steps.

Create the scala file

In the be.doeraene.webcomponents.ui5 package, create a new object called the same way as the component, as visible in the docs page (for example, for the busy indicator, it will be BusyIndicator)

Make the docstring

Fill in the docstring for that object with the contents of the "Overview" section from the docs, and a @see referencing the official docs webpage

Write the boilerplate

In the object, add the following things:

  • make the object extends WebComponent
  • create a trait RawElement extending js.Object and annotated with @js.native
  • add an object RawImport extending js.Object and annotated with both @js.native and @JSImport, specifying the correct import (available in the official docs), setting JSImport.Default as second argument
  • call used(RawImport) the line after (this is done to be sure that scala-js actually import the JS dependency)
  • define an alias type Ref as dom.html.Element & RawElement
  • define the protected tag variable of type HtmlTag[Ref] specifying the ui5 tag name from the doc (for example, for the Button component, it's protected val tag: HtmlTag[Ref] = htmlTag("ui5-button")). ⚠️: when copy-pasting from an existing component, this is usually the one we forget! When that happens, you will observe a component doing basically nothing. It's a sign you put the wrong import.
  • create an empty object slots
  • create an empty object events
  • in the case where your component is linked to other components (for example a TableCell is always contained in TableRow, so the TableRow object will have a reference to the TableCell object)

Filling the reactive attributes

The official docs always have a "Properties/Attributes" section. All these properties should be converted into HtmlAttr. For example, the disabled attribute of Button is defined as

val disabled: HtmlAttr[Boolean] = htmlAttr("disabled", BooleanAsAttrPresenceCodec)

Note that while it's not mandatory that the name of the variable matches the name of the attribute, it's customary to use the same (camelCase) naming.

For "primitive" types (Boolean, String, Int), you can use the codecs provided by Laminar. For "enums", see below (essentially you will need to define an EnumerationString type as described in the next section).

For durations, expressed in millis, you can use the FiniteDurationCodec available for you in the package object.

You can decide to create more involved types a bit fancy and create custom codecs, but you need to decide whether it's worth it. Such example could be if you have a type representing numbers between 0 and 10 because that are the only values that are valid by ui5.

Some common attribute are "packaged" in traits that your component object can inherit from (e.g., HasIcon).

Note: in theory all these properties could (should?) also exist on the RawElement trait. However, it is not really idiomatic to Laminar to use these. If, for some reason, you still think some property should be there, it should be "readonly" (that is, defined as a def).

Reactive attributes for enums

A lot of attributes/properties of UI5 elements are enumerations. Usually, the official SAP docs itself gives a name to the "type" of the enum. For example, ValueState or BreadcrumbsSeparatorStyle.

Although you could define these properties as String, this would be poorly typed and lack semantics. For that reason, we create a sealed trait, with plenty of case objects to represent those.

They are all defined in the be.doeraene.webcomponents.ui5.configkeys package.

To implement a new enum, follow these steps:

  1. create a sealed trait named the same way as in the sap docs
  2. give this sealed trait a companion object, and fill it with one case object for each possible value
  3. make the companion object extend EnumerationString (available in the same package)
  4. Implement the valueOf and allValues abstract members
  5. use the AsStringCodec in your reactive values


Some UI5 components have custom events specific to them, usually with special type of emitted events.

All these events are represented as values of type EventProp. It takes a type parameter, which is the type of the values emitted by this event. This type has to be a subtype of dom.Event. Events from UI5 components are usually augmented with other properties. They are roughly documented, but most of the time you will have to trigger them manually and dom.console.log the emitted values to understand what they really are.

Some common patterns are:

  • values have a detail field of a certain type. The library has a helper HasDetail trait, and in that case the complete type will look like dom.Event & HasDetail[SomeOtherType]. An example taken from the Table component is val onSelectionChange = new EventProp[dom.Event & HasDetail[TableSelectionChangeDetail]]("selection-change").
  • events with a more precise target type (when you need the precise type instead of just HtmlElement). This type is EventWithPreciseTarget and already extends dom.Event. An example from the CheckBox component is val onChange: EventProp[EventWithPreciseTarget[Ref]] = new EventProp("change")
  • a combination of the above (combined with &)


In the slots object, define a value for each of the slot this component has, except for the (always present) default one.

All the slots for a component are documented in the Slots section in the docs.

For example, the footer slot of the Dialog is defined as

val footer: Slot = new Slot("footer")


Some SAP components have special methods to interact with. Among the most common, you will find the Dialog which has a show method. Some others like Popover will have showAt.

These methods must be defined as js.native method of the RawElement trait.

For methods that take as input or return some "not-so-scala-ish" types (such as js.Array), it is best to call them theMethodNameJS (annotating by JSName("theMethodName")) and to create an extension method called theMethodName taking/returning more Scala friendly types. For example, the ColourPicker RawElement is implemented as

trait RawElement extends js.Object {
  def colourJS: String = js.native

object RawElement {
  extension (rawElement: RawElement)
    /** The current colour as [[Colour]] instance. English UK spelling for consistency. */
    def colour: Colour = Colour.fromString(rawElement.colourJS)

Making the demos

The best way to make sure that your implementations work, and to also help future users at the same time, is to write a demo for the new component.

In the demo subproject, in the demo package, create an object MyComponentExample, extending Example with the SAP name of the component.

You will then need to fill the component def. You should make use of the DemoPanel and wrapping your example codes in //-- Begin: name of your demo panel and //-- End. Once your code will be merged on master, it will make the source code directly displayed beneath the examples.

You then need to add your example in the list in the EntryPoint in the demo package.

For the structure, you can take inspiration from the existing other examples. For the content of your demo, you can take inspiration from the official SAP docs.