Completion

Register a CompletionProvider. The editor triggers on Ctrl/⌘+Space (default maps) and on characters you mark as triggers.

controller.addCompletionProvider(object : CompletionProvider {
    override fun isTriggerCharacter(ch: String) = ch == "."

    override fun provideCompletions(context: CompletionContext, receiver: CompletionReceiver) {
        if (receiver.isCancelled) return
        receiver.accept(
            CompletionResult(
                items = listOf(
                    CompletionItem(
                        label = "println",
                        kind = CompletionItemKind.FUNCTION,
                        insertText = "println(\$0)",
                        insertTextFormat = CompletionInsertTextFormat.SNIPPET,
                    ),
                ),
            ),
        )
    }
})

How an item is applied

1. If textEdit is set, that range is replaced.
2. Otherwise insertText (or label) is inserted at the cursor.
3. SNIPPET format goes through insertSnippet.
4. additionalTextEdits are applied after the primary edit.

You can also push a list without a provider:

controller.showCompletionItems(items)
controller.applyCompletionItem(item)
controller.dismissCompletion()
controller.triggerCompletion()

Custom row UI

controller.setCompletionItemRenderer { item, selected, theme ->
    // Compose row for one item
}

Pass null to restore the default renderer.

See Completion API.