Decoration providers

A DecorationProvider computes decorations from the visible range and recent text changes. The session merges results onto the editor.

val provider = object : DecorationProvider {
    override fun capabilities() = setOf(DecorationType.SYNTAX_HIGHLIGHT)

    override fun provideDecorations(context: DecorationContext, receiver: DecorationReceiver) {
        if (receiver.isCancelled) return
        val spans = mapOf(
            context.visibleLineRange.startLine to listOf(
                StyleSpan(column = 0, length = 3, styleId = 1),
            ),
        )
        receiver.accept(
            DecorationResult(
                syntaxSpans = spans,
                syntaxSpansMode = DecorationApplyMode.REPLACE_RANGE,
            ),
        )
    }
}

controller.addDecorationProvider(provider)

Context

DecorationContext includes:

• visibleLineRange — lines currently on screen (plus overscan from settings)
• totalLineCount
• textChanges — last dispatched edits (may be empty on a refresh)
• languageConfiguration / editorMetadata if you set them

Apply modes

Mode	Meaning
MERGE	Combine with existing items of that type
REPLACE_ALL	Drop every item of that type, then apply
REPLACE_RANGE	Replace items that fall in the provided range / lines

Each field on DecorationResult has its own *Mode (default MERGE). Leave a field null to skip that type.

Refresh

controller.requestDecorationRefresh()
controller.removeDecorationProvider(provider)

Direct setter APIs (setLineSpans, setLineDiagnostics, …) still work. Providers are the scalable path when decorations depend on viewport or language services.

See Overlays for the payload types.