Inline Hints controller and API proposal

src/vs/editor/browser/services/codeEditorServiceImpl.ts

@@ -347,6 +347,8 @@ const _CSS_MAP: { [prop: string]: string; } = {
 
 	fontStyle: 'font-style:{0};',
 	fontWeight: 'font-weight:{0};',
+	fontSize: 'font-size:{0};',
+	fontFamily: 'font-family:{0};',
 	textDecoration: 'text-decoration:{0};',
 	cursor: 'cursor:{0};',
 	letterSpacing: 'letter-spacing:{0};',
@@ -357,6 +359,7 @@ const _CSS_MAP: { [prop: string]: string; } = {
 	contentText: 'content:\'{0}\';',
 	contentIconPath: 'content:{0};',
 	margin: 'margin:{0};',
+	padding: 'padding:{0};',
 	width: 'width:{0};',
 	height: 'height:{0};'
 };
@@ -529,7 +532,7 @@ class DecorationCSSRules {
 
 				cssTextArr.push(strings.format(_CSS_MAP.contentText, escaped));
 			}
-			this.collectCSSText(opts, ['fontStyle', 'fontWeight', 'textDecoration', 'color', 'opacity', 'backgroundColor', 'margin'], cssTextArr);
+			this.collectCSSText(opts, ['fontStyle', 'fontWeight', 'fontSize', 'fontFamily', 'textDecoration', 'color', 'opacity', 'backgroundColor', 'margin', 'padding'], cssTextArr);
 			if (this.collectCSSText(opts, ['width', 'height'], cssTextArr)) {
 				cssTextArr.push('display:inline-block;');
 			}

src/vs/editor/browser/widget/codeEditorWidget.ts

@@ -1835,6 +1835,7 @@ export class EditorModeContext extends Disposable {
 	private readonly _hasMultipleDocumentFormattingProvider: IContextKey<boolean>;
 	private readonly _hasMultipleDocumentSelectionFormattingProvider: IContextKey<boolean>;
 	private readonly _hasSignatureHelpProvider: IContextKey<boolean>;
+	private readonly _hasInlineHintsProvider: IContextKey<boolean>;
 	private readonly _isInWalkThrough: IContextKey<boolean>;
 
 	constructor(
@@ -1857,6 +1858,7 @@ export class EditorModeContext extends Disposable {
 		this._hasReferenceProvider = EditorContextKeys.hasReferenceProvider.bindTo(_contextKeyService);
 		this._hasRenameProvider = EditorContextKeys.hasRenameProvider.bindTo(_contextKeyService);
 		this._hasSignatureHelpProvider = EditorContextKeys.hasSignatureHelpProvider.bindTo(_contextKeyService);
+		this._hasInlineHintsProvider = EditorContextKeys.hasInlineHintsProvider.bindTo(_contextKeyService);
 		this._hasDocumentFormattingProvider = EditorContextKeys.hasDocumentFormattingProvider.bindTo(_contextKeyService);
 		this._hasDocumentSelectionFormattingProvider = EditorContextKeys.hasDocumentSelectionFormattingProvider.bindTo(_contextKeyService);
 		this._hasMultipleDocumentFormattingProvider = EditorContextKeys.hasMultipleDocumentFormattingProvider.bindTo(_contextKeyService);
@@ -1885,6 +1887,7 @@ export class EditorModeContext extends Disposable {
 		this._register(modes.DocumentFormattingEditProviderRegistry.onDidChange(update));
 		this._register(modes.DocumentRangeFormattingEditProviderRegistry.onDidChange(update));
 		this._register(modes.SignatureHelpProviderRegistry.onDidChange(update));
+		this._register(modes.InlineHintsProviderRegistry.onDidChange(update));
 
 		update();
 	}
@@ -1936,6 +1939,7 @@ export class EditorModeContext extends Disposable {
 			this._hasReferenceProvider.set(modes.ReferenceProviderRegistry.has(model));
 			this._hasRenameProvider.set(modes.RenameProviderRegistry.has(model));
 			this._hasSignatureHelpProvider.set(modes.SignatureHelpProviderRegistry.has(model));
+			this._hasInlineHintsProvider.set(modes.InlineHintsProviderRegistry.has(model));
 			this._hasDocumentFormattingProvider.set(modes.DocumentFormattingEditProviderRegistry.has(model) || modes.DocumentRangeFormattingEditProviderRegistry.has(model));
 			this._hasDocumentSelectionFormattingProvider.set(modes.DocumentRangeFormattingEditProviderRegistry.has(model));
 			this._hasMultipleDocumentFormattingProvider.set(modes.DocumentFormattingEditProviderRegistry.all(model).length + modes.DocumentRangeFormattingEditProviderRegistry.all(model).length > 1);

src/vs/editor/common/config/editorOptions.ts

@@ -625,6 +625,10 @@ export interface IEditorOptions {
 	 * Controls strikethrough deprecated variables.
 	 */
 	showDeprecated?: boolean;
+	/**
+	 * Control the behavior and rendering of the inline hints.
+	 */
+	inlineHints?: IEditorInlineHintsOptions;
 }
 
 /**
@@ -2369,6 +2373,74 @@ class EditorLightbulb extends BaseEditorOption<EditorOption.lightbulb, EditorLig
 
 //#endregion
 
+//#region inlineHints
+
+/**
+ * Configuration options for editor inlineHints
+ */
+export interface IEditorInlineHintsOptions {
+	/**
+	 * Enable the inline hints.
+	 * Defaults to true.
+	 */
+	enabled?: boolean;
+
+	/**
+	 * Font size of inline hints.
+	 * Default to 90% of the editor font size.
+	 */
+	fontSize?: number;
+
+	/**
+	 * Font family of inline hints.
+	 * Defaults to editor font family.
+	 */
+	fontFamily?: string;
+}
+
+export type EditorInlineHintsOptions = Readonly<Required<IEditorInlineHintsOptions>>;
+
+class EditorInlineHints extends BaseEditorOption<EditorOption.inlineHints, EditorInlineHintsOptions> {
+
+	constructor() {
+		const defaults: EditorInlineHintsOptions = { enabled: true, fontSize: 0, fontFamily: EDITOR_FONT_DEFAULTS.fontFamily };
+		super(
+			EditorOption.inlineHints, 'inlineHints', defaults,
+			{
+				'editor.inlineHints.enabled': {
+					type: 'boolean',
+					default: defaults.enabled,
+					description: nls.localize('inlineHints.enable', "Enables the inline hints in the editor.")
+				},
+				'editor.inlineHints.fontSize': {
+					type: 'number',
+					default: defaults.fontSize,
+					description: nls.localize('inlineHints.fontSize', "Controls font size of inline hints in the editor. When set to `0`, the 90% of `#editor.fontSize#` is used.")
+				},
+				'editor.inlineHints.fontFamily': {
+					type: 'string',
+					default: defaults.fontFamily,
+					description: nls.localize('inlineHints.fontFamily', "Controls font family of inline hints in the editor.")
+				},
+			}
+		);
+	}
+
+	public validate(_input: any): EditorInlineHintsOptions {
+		if (!_input || typeof _input !== 'object') {
+			return this.defaultValue;
+		}
+		const input = _input as IEditorInlineHintsOptions;
+		return {
+			enabled: boolean(input.enabled, this.defaultValue.enabled),
+			fontSize: EditorIntOption.clampedInt(input.fontSize, this.defaultValue.fontSize, 0, 100),
+			fontFamily: EditorStringOption.string(input.fontFamily, this.defaultValue.fontFamily)
+		};
+	}
+}
+
+//#endregion
+
 //#region lineHeight
 
 class EditorLineHeight extends EditorIntOption<EditorOption.lineHeight> {
@@ -3759,7 +3831,7 @@ export const enum EditorOption {
 	wrappingIndent,
 	wrappingStrategy,
 	showDeprecated,
-
+	inlineHints,
 	// Leave these at the end (because they have dependencies!)
 	editorClassName,
 	pixelRatio,
@@ -4263,6 +4335,7 @@ export const EditorOptions = {
 		EditorOption.showDeprecated, 'showDeprecated', true,
 		{ description: nls.localize('showDeprecated', "Controls strikethrough deprecated variables.") }
 	)),
+	inlineHints: register(new EditorInlineHints()),
 	snippetSuggestions: register(new EditorStringEnumOption(
 		EditorOption.snippetSuggestions, 'snippetSuggestions',
 		'inline' as 'top' | 'bottom' | 'inline' | 'none',

src/vs/editor/common/editorCommon.ts

@@ -606,6 +606,7 @@ export interface IThemeDecorationRenderOptions {
 
 	fontStyle?: string;
 	fontWeight?: string;
+	fontSize?: string;
 	textDecoration?: string;
 	cursor?: string;
 	color?: string | ThemeColor;
@@ -632,11 +633,14 @@ export interface IContentDecorationRenderOptions {
 	borderColor?: string | ThemeColor;
 	fontStyle?: string;
 	fontWeight?: string;
+	fontSize?: string;
+	fontFamily?: string;
 	textDecoration?: string;
 	color?: string | ThemeColor;
 	backgroundColor?: string | ThemeColor;
 
 	margin?: string;
+	padding?: string;
 	width?: string;
 	height?: string;
 }

src/vs/editor/common/editorContextKeys.ts

@@ -61,6 +61,7 @@ export namespace EditorContextKeys {
 	export const hasReferenceProvider = new RawContextKey<boolean>('editorHasReferenceProvider', false);
 	export const hasRenameProvider = new RawContextKey<boolean>('editorHasRenameProvider', false);
 	export const hasSignatureHelpProvider = new RawContextKey<boolean>('editorHasSignatureHelpProvider', false);
+	export const hasInlineHintsProvider = new RawContextKey<boolean>('editorHasInlineHintsProvider', false);
 
 	// -- mode context keys: formatting
 	export const hasDocumentFormattingProvider = new RawContextKey<boolean>('editorHasDocumentFormattingProvider', false);

src/vs/editor/common/modes.ts

@@ -1659,6 +1659,19 @@ export interface CodeLensProvider {
 	resolveCodeLens?(model: model.ITextModel, codeLens: CodeLens, token: CancellationToken): ProviderResult<CodeLens>;
 }
 
+export interface InlineHint {
+	text: string;
+	range: IRange;
+	hoverMessage?: string;
+	whitespaceBefore?: boolean;
+	whitespaceAfter?: boolean;
+}
+
+export interface InlineHintsProvider {
+	onDidChangeInlineHints?: Event<void> | undefined;
+	provideInlineHints(model: model.ITextModel, range: Range, token: CancellationToken): ProviderResult<InlineHint[]>;
+}
+
 export interface SemanticTokensLegend {
 	readonly tokenTypes: string[];
 	readonly tokenModifiers: string[];
@@ -1764,6 +1777,11 @@ export const TypeDefinitionProviderRegistry = new LanguageFeatureRegistry<TypeDe
  */
 export const CodeLensProviderRegistry = new LanguageFeatureRegistry<CodeLensProvider>();
 
+/**
+ * @internal
+ */
+export const InlineHintsProviderRegistry = new LanguageFeatureRegistry<InlineHintsProvider>();
+
 /**
  * @internal
  */

src/vs/editor/common/standalone/standaloneEnums.ts

@@ -287,11 +287,12 @@ export enum EditorOption {
 	wrappingIndent = 117,
 	wrappingStrategy = 118,
 	showDeprecated = 119,
-	editorClassName = 120,
-	pixelRatio = 121,
-	tabFocusMode = 122,
-	layoutInfo = 123,
-	wrappingInfo = 124
+	inlineHints = 120,
+	editorClassName = 121,
+	pixelRatio = 122,
+	tabFocusMode = 123,
+	layoutInfo = 124,
+	wrappingInfo = 125
 }
 
 /**