Add 'trailing' option to render whitespace

src/vs/editor/browser/viewParts/lines/viewLine.ts

@@ -72,7 +72,7 @@ export class DomReadingContext {
 
 export class ViewLineOptions {
 	public readonly themeType: ThemeType;
-	public readonly renderWhitespace: 'none' | 'boundary' | 'selection' | 'all';
+	public readonly renderWhitespace: 'none' | 'boundary' | 'selection' | 'trailing' | 'all';
 	public readonly renderControlCharacters: boolean;
 	public readonly spaceWidth: number;
 	public readonly middotWidth: number;

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

@@ -529,7 +529,7 @@ export interface IEditorOptions {
 	 * Enable rendering of whitespace.
 	 * Defaults to none.
 	 */
-	renderWhitespace?: 'none' | 'boundary' | 'selection' | 'all';
+	renderWhitespace?: 'none' | 'boundary' | 'selection' | 'trailing' | 'all';
 	/**
 	 * Enable rendering of control characters.
 	 * Defaults to false.
@@ -4037,13 +4037,14 @@ export const EditorOptions = {
 	)),
 	renderWhitespace: register(new EditorStringEnumOption(
 		EditorOption.renderWhitespace, 'renderWhitespace',
-		'selection' as 'selection' | 'none' | 'boundary' | 'all',
-		['none', 'boundary', 'selection', 'all'] as const,
+		'selection' as 'selection' | 'none' | 'boundary' | 'trailing' | 'all',
+		['none', 'boundary', 'selection', 'trailing', 'all'] as const,
 		{
 			enumDescriptions: [
 				'',
 				nls.localize('renderWhitespace.boundary', "Render whitespace characters except for single spaces between words."),
 				nls.localize('renderWhitespace.selection', "Render whitespace characters only on selected text."),
+				nls.localize('renderWhitespace.trailing', "Render only trailing whitespace characters"),
 				''
 			],
 			description: nls.localize('renderWhitespace', "Controls how the editor should render whitespace characters.")

src/vs/editor/common/viewLayout/viewLineRenderer.ts

@@ -14,7 +14,8 @@ export const enum RenderWhitespace {
 	None = 0,
 	Boundary = 1,
 	Selection = 2,
-	All = 3
+	Trailing = 3,
+	All = 4
 }
 
 export const enum LinePartMetadata {
@@ -113,7 +114,7 @@ export class RenderLineInput {
 		middotWidth: number,
 		wsmiddotWidth: number,
 		stopRenderingLineAfter: number,
-		renderWhitespace: 'none' | 'boundary' | 'selection' | 'all',
+		renderWhitespace: 'none' | 'boundary' | 'selection' | 'trailing' | 'all',
 		renderControlCharacters: boolean,
 		fontLigatures: boolean,
 		selectionsOnLine: LineRange[] | null
@@ -138,6 +139,8 @@ export class RenderLineInput {
 					? RenderWhitespace.Boundary
 					: renderWhitespace === 'selection'
 						? RenderWhitespace.Selection
+						: renderWhitespace === 'trailing'
+							? RenderWhitespace.Trailing
 							: RenderWhitespace.None
 		);
 		this.renderControlCharacters = renderControlCharacters;
@@ -435,7 +438,11 @@ function resolveRenderLineInput(input: RenderLineInput): ResolvedRenderLineInput
 	}
 
 	let tokens = transformAndRemoveOverflowing(input.lineTokens, input.fauxIndentLength, len);
-	if (input.renderWhitespace === RenderWhitespace.All || input.renderWhitespace === RenderWhitespace.Boundary || (input.renderWhitespace === RenderWhitespace.Selection && !!input.selectionsOnLine)) {
+	if (input.renderWhitespace === RenderWhitespace.All ||
+		input.renderWhitespace === RenderWhitespace.Boundary ||
+		(input.renderWhitespace === RenderWhitespace.Selection && !!input.selectionsOnLine) ||
+		input.renderWhitespace === RenderWhitespace.Trailing) {
+
 		tokens = _applyRenderWhitespace(input, lineContent, len, tokens);
 	}
 	let containsForeignElements = ForeignElementType.None;
@@ -592,6 +599,7 @@ function _applyRenderWhitespace(input: RenderLineInput, lineContent: string, len
 	const useMonospaceOptimizations = input.useMonospaceOptimizations;
 	const selections = input.selectionsOnLine;
 	const onlyBoundary = (input.renderWhitespace === RenderWhitespace.Boundary);
+	const onlyTrailing = (input.renderWhitespace === RenderWhitespace.Trailing);
 	const generateLinePartForEachWhitespace = (input.renderSpaceWidth !== input.spaceWidth);
 
 	let result: LinePart[] = [], resultLen = 0;
@@ -600,10 +608,11 @@ function _applyRenderWhitespace(input: RenderLineInput, lineContent: string, len
 	let tokenEndIndex = tokens[tokenIndex].endIndex;
 	const tokensLength = tokens.length;
 
+	let lineIsEmptyOrWhitespace = false;
 	let firstNonWhitespaceIndex = strings.firstNonWhitespaceIndex(lineContent);
 	let lastNonWhitespaceIndex: number;
 	if (firstNonWhitespaceIndex === -1) {
-		// The entire line is whitespace
+		lineIsEmptyOrWhitespace = true;
 		firstNonWhitespaceIndex = len;
 		lastNonWhitespaceIndex = len;
 	} else {
@@ -651,6 +660,11 @@ function _applyRenderWhitespace(input: RenderLineInput, lineContent: string, len
 			isInWhitespace = !!currentSelection && currentSelection.startOffset <= charIndex && currentSelection.endOffset > charIndex;
 		}
 
+		// If rendering only trailing whitespace, check that the charIndex points to trailing whitespace.
+		if (isInWhitespace && onlyTrailing) {
+			isInWhitespace = lineIsEmptyOrWhitespace || charIndex > lastNonWhitespaceIndex;
+		}
+
 		if (wasInWhitespace) {
 			// was in whitespace token
 			if (!isInWhitespace || (!useMonospaceOptimizations && tmpIndent >= tabSize)) {

src/vs/editor/test/common/viewLayout/viewLineRenderer.test.ts

@@ -869,7 +869,7 @@ suite('viewLineRenderer.renderLine', () => {
 
 suite('viewLineRenderer.renderLine 2', () => {
 
-	function testCreateLineParts(fontIsMonospace: boolean, lineContent: string, tokens: ViewLineToken[], fauxIndentLength: number, renderWhitespace: 'none' | 'boundary' | 'selection' | 'all', selections: LineRange[] | null, expected: string): void {
+	function testCreateLineParts(fontIsMonospace: boolean, lineContent: string, tokens: ViewLineToken[], fauxIndentLength: number, renderWhitespace: 'none' | 'boundary' | 'selection' | 'trailing' | 'all', selections: LineRange[] | null, expected: string): void {
 		let actual = renderViewLine(new RenderLineInput(
 			fontIsMonospace,
 			true,
@@ -1355,6 +1355,95 @@ suite('viewLineRenderer.renderLine 2', () => {
 		);
 	});
 
+	test('createLineParts render whitespace for trailing with leading, inner, and without trailing whitespace', () => {
+		testCreateLineParts(
+			false,
+			' Hello world!',
+			[
+				createPart(4, 0),
+				createPart(6, 1),
+				createPart(14, 2)
+			],
+			0,
+			'trailing',
+			null,
+			[
+				'<span>',
+				'<span class="mtk0">\u00a0Hel</span>',
+				'<span class="mtk1">lo</span>',
+				'<span class="mtk2">\u00a0world!</span>',
+				'</span>',
+			].join('')
+		);
+	});
+
+	test('createLineParts render whitespace for trailing with leading, inner, and trailing whitespace', () => {
+		testCreateLineParts(
+			false,
+			' Hello world! \t',
+			[
+				createPart(4, 0),
+				createPart(6, 1),
+				createPart(15, 2)
+			],
+			0,
+			'trailing',
+			null,
+			[
+				'<span>',
+				'<span class="mtk0">\u00a0Hel</span>',
+				'<span class="mtk1">lo</span>',
+				'<span class="mtk2">\u00a0world!</span>',
+				'<span class="mtkz" style="width:30px">\u00b7\u2192\u00a0</span>',
+				'</span>',
+			].join('')
+		);
+	});
+
+	test('createLineParts render whitespace for trailing with 8 leading and 8 trailing whitespaces', () => {
+		testCreateLineParts(
+			false,
+			'        Hello world!        ',
+			[
+				createPart(8, 1),
+				createPart(10, 2),
+				createPart(28, 3)
+			],
+			0,
+			'trailing',
+			null,
+			[
+				'<span>',
+				'<span class="mtk1">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0</span>',
+				'<span class="mtk2">He</span>',
+				'<span class="mtk3">llo\u00a0world!</span>',
+				'<span class="mtkz" style="width:40px">\u00b7\u00b7\u00b7\u00b7</span>',
+				'<span class="mtkz" style="width:40px">\u00b7\u00b7\u00b7\u00b7</span>',
+				'</span>',
+			].join('')
+		);
+	});
+
+	test('createLineParts render whitespace for trailing with line containing only whitespaces', () => {
+		testCreateLineParts(
+			false,
+			' \t ',
+			[
+				createPart(2, 0),
+				createPart(3, 1),
+			],
+			0,
+			'trailing',
+			null,
+			[
+				'<span>',
+				'<span class="mtkz" style="width:40px">\u00b7\u2192\u00a0\u00a0</span>',
+				'<span class="mtkz" style="width:10px">\u00b7</span>',
+				'</span>',
+			].join('')
+		);
+	});
+
 	test('createLineParts can handle unsorted inline decorations', () => {
 		let actual = renderViewLine(new RenderLineInput(
 			false,

src/vs/monaco.d.ts

@@ -3068,7 +3068,7 @@ declare namespace monaco.editor {
 		 * Enable rendering of whitespace.
 		 * Defaults to none.
 		 */
-		renderWhitespace?: 'none' | 'boundary' | 'selection' | 'all';
+		renderWhitespace?: 'none' | 'boundary' | 'selection' | 'trailing' | 'all';
 		/**
 		 * Enable rendering of control characters.
 		 * Defaults to false.
@@ -4048,7 +4048,7 @@ declare namespace monaco.editor {
 		renderLineHighlight: IEditorOption<EditorOption.renderLineHighlight, 'all' | 'line' | 'none' | 'gutter'>;
 		renderLineHighlightOnlyWhenFocus: IEditorOption<EditorOption.renderLineHighlightOnlyWhenFocus, boolean>;
 		renderValidationDecorations: IEditorOption<EditorOption.renderValidationDecorations, 'on' | 'off' | 'editable'>;
-		renderWhitespace: IEditorOption<EditorOption.renderWhitespace, 'all' | 'none' | 'boundary' | 'selection'>;
+		renderWhitespace: IEditorOption<EditorOption.renderWhitespace, 'all' | 'none' | 'boundary' | 'selection' | 'trailing'>;
 		revealHorizontalRightPadding: IEditorOption<EditorOption.revealHorizontalRightPadding, number>;
 		roundedSelection: IEditorOption<EditorOption.roundedSelection, boolean>;
 		rulers: IEditorOption<EditorOption.rulers, {}>;