viewLineRenderer.ts

/*---------------------------------------------------------------------------------------------
 *  Copyright (c) Microsoft Corporation. All rights reserved.
 *  Licensed under the MIT License. See License.txt in the project root for license information.
 *--------------------------------------------------------------------------------------------*/

import * as nls from '../../../nls.js';
import { CharCode } from '../../../base/common/charCode.js';
import * as strings from '../../../base/common/strings.js';
import { IViewLineTokens } from '../tokens/lineTokens.js';
import { StringBuilder } from '../core/stringBuilder.js';
import { LineDecoration, LineDecorationsNormalizer } from './lineDecorations.js';
import { LinePart, LinePartMetadata } from './linePart.js';
import { OffsetRange } from '../core/ranges/offsetRange.js';
import { InlineDecorationType } from '../viewModel/inlineDecorations.js';
import { TextDirection } from '../model.js';

export const enum RenderWhitespace {
	None = 0,
	Boundary = 1,
	Selection = 2,
	Trailing = 3,
	All = 4
}

export class RenderLineInput {

	public readonly useMonospaceOptimizations: boolean;
	public readonly canUseHalfwidthRightwardsArrow: boolean;
	public readonly lineContent: string;
	public readonly continuesWithWrappedLine: boolean;
	public readonly isBasicASCII: boolean;
	public readonly containsRTL: boolean;
	public readonly fauxIndentLength: number;
	public readonly lineTokens: IViewLineTokens;
	public readonly lineDecorations: LineDecoration[];
	public readonly tabSize: number;
	public readonly startVisibleColumn: number;
	public readonly spaceWidth: number;
	public readonly renderSpaceWidth: number;
	public readonly renderSpaceCharCode: number;
	public readonly stopRenderingLineAfter: number;
	public readonly renderWhitespace: RenderWhitespace;
	public readonly renderControlCharacters: boolean;
	public readonly fontLigatures: boolean;
	public readonly textDirection: TextDirection | null;
	public readonly verticalScrollbarSize: number;

	/**
	 * Defined only when renderWhitespace is 'selection'. Selections are non-overlapping,
	 * and ordered by position within the line.
	 */
	public readonly selectionsOnLine: OffsetRange[] | null;
	/**
	 * When rendering an empty line, whether to render a new line instead
	 */
	public readonly renderNewLineWhenEmpty: boolean;

	public get isLTR(): boolean {
		return !this.containsRTL && this.textDirection !== TextDirection.RTL;
	}

	constructor(
		useMonospaceOptimizations: boolean,
		canUseHalfwidthRightwardsArrow: boolean,
		lineContent: string,
		continuesWithWrappedLine: boolean,
		isBasicASCII: boolean,
		containsRTL: boolean,
		fauxIndentLength: number,
		lineTokens: IViewLineTokens,
		lineDecorations: LineDecoration[],
		tabSize: number,
		startVisibleColumn: number,
		spaceWidth: number,
		middotWidth: number,
		wsmiddotWidth: number,
		stopRenderingLineAfter: number,
		renderWhitespace: 'none' | 'boundary' | 'selection' | 'trailing' | 'all',
		renderControlCharacters: boolean,
		fontLigatures: boolean,
		selectionsOnLine: OffsetRange[] | null,
		textDirection: TextDirection | null,
		verticalScrollbarSize: number,
		renderNewLineWhenEmpty: boolean = false,
	) {
		this.useMonospaceOptimizations = useMonospaceOptimizations;
		this.canUseHalfwidthRightwardsArrow = canUseHalfwidthRightwardsArrow;
		this.lineContent = lineContent;
		this.continuesWithWrappedLine = continuesWithWrappedLine;
		this.isBasicASCII = isBasicASCII;
		this.containsRTL = containsRTL;
		this.fauxIndentLength = fauxIndentLength;
		this.lineTokens = lineTokens;
		this.lineDecorations = lineDecorations.sort(LineDecoration.compare);
		this.tabSize = tabSize;
		this.startVisibleColumn = startVisibleColumn;
		this.spaceWidth = spaceWidth;
		this.stopRenderingLineAfter = stopRenderingLineAfter;
		this.renderWhitespace = (
			renderWhitespace === 'all'
				? RenderWhitespace.All
				: renderWhitespace === 'boundary'
					? RenderWhitespace.Boundary
					: renderWhitespace === 'selection'
						? RenderWhitespace.Selection
						: renderWhitespace === 'trailing'
							? RenderWhitespace.Trailing
							: RenderWhitespace.None
		);
		this.renderControlCharacters = renderControlCharacters;
		this.fontLigatures = fontLigatures;
		this.selectionsOnLine = selectionsOnLine && selectionsOnLine.sort((a, b) => a.start < b.start ? -1 : 1);
		this.renderNewLineWhenEmpty = renderNewLineWhenEmpty;
		this.textDirection = textDirection;
		this.verticalScrollbarSize = verticalScrollbarSize;

		const wsmiddotDiff = Math.abs(wsmiddotWidth - spaceWidth);
		const middotDiff = Math.abs(middotWidth - spaceWidth);
		if (wsmiddotDiff < middotDiff) {
			this.renderSpaceWidth = wsmiddotWidth;
			this.renderSpaceCharCode = 0x2E31; // U+2E31 - WORD SEPARATOR MIDDLE DOT
		} else {
			this.renderSpaceWidth = middotWidth;
			this.renderSpaceCharCode = 0xB7; // U+00B7 - MIDDLE DOT
		}
	}

	private sameSelection(otherSelections: OffsetRange[] | null): boolean {
		if (this.selectionsOnLine === null) {
			return otherSelections === null;
		}

		if (otherSelections === null) {
			return false;
		}

		if (otherSelections.length !== this.selectionsOnLine.length) {
			return false;
		}

		for (let i = 0; i < this.selectionsOnLine.length; i++) {
			if (!this.selectionsOnLine[i].equals(otherSelections[i])) {
				return false;
			}
		}

		return true;
	}

	public equals(other: RenderLineInput): boolean {
		return (
			this.useMonospaceOptimizations === other.useMonospaceOptimizations
			&& this.canUseHalfwidthRightwardsArrow === other.canUseHalfwidthRightwardsArrow
			&& this.lineContent === other.lineContent
			&& this.continuesWithWrappedLine === other.continuesWithWrappedLine
			&& this.isBasicASCII === other.isBasicASCII
			&& this.containsRTL === other.containsRTL
			&& this.fauxIndentLength === other.fauxIndentLength
			&& this.tabSize === other.tabSize
			&& this.startVisibleColumn === other.startVisibleColumn
			&& this.spaceWidth === other.spaceWidth
			&& this.renderSpaceWidth === other.renderSpaceWidth
			&& this.renderSpaceCharCode === other.renderSpaceCharCode
			&& this.stopRenderingLineAfter === other.stopRenderingLineAfter
			&& this.renderWhitespace === other.renderWhitespace
			&& this.renderControlCharacters === other.renderControlCharacters
			&& this.fontLigatures === other.fontLigatures
			&& LineDecoration.equalsArr(this.lineDecorations, other.lineDecorations)
			&& this.lineTokens.equals(other.lineTokens)
			&& this.sameSelection(other.selectionsOnLine)
			&& this.textDirection === other.textDirection
			&& this.verticalScrollbarSize === other.verticalScrollbarSize
			&& this.renderNewLineWhenEmpty === other.renderNewLineWhenEmpty
		);
	}
}

const enum CharacterMappingConstants {
	PART_INDEX_MASK = 0b11111111111111110000000000000000,
	CHAR_INDEX_MASK = 0b00000000000000001111111111111111,

	CHAR_INDEX_OFFSET = 0,
	PART_INDEX_OFFSET = 16
}

export class DomPosition {
	constructor(
		public readonly partIndex: number,
		public readonly charIndex: number
	) { }
}

/**
 * Provides a both direction mapping between a line's character and its rendered position.
 */
export class CharacterMapping {

	private static getPartIndex(partData: number): number {
		return (partData & CharacterMappingConstants.PART_INDEX_MASK) >>> CharacterMappingConstants.PART_INDEX_OFFSET;
	}

	private static getCharIndex(partData: number): number {
		return (partData & CharacterMappingConstants.CHAR_INDEX_MASK) >>> CharacterMappingConstants.CHAR_INDEX_OFFSET;
	}

	public readonly length: number;
	private readonly _data: Uint32Array;
	private readonly _horizontalOffset: Uint32Array;

	constructor(length: number, partCount: number) {
		this.length = length;
		this._data = new Uint32Array(this.length);
		this._horizontalOffset = new Uint32Array(this.length);
	}

	public setColumnInfo(column: number, partIndex: number, charIndex: number, horizontalOffset: number): void {
		const partData = (
			(partIndex << CharacterMappingConstants.PART_INDEX_OFFSET)
			| (charIndex << CharacterMappingConstants.CHAR_INDEX_OFFSET)
		) >>> 0;
		this._data[column - 1] = partData;
		this._horizontalOffset[column - 1] = horizontalOffset;
	}

	public getHorizontalOffset(column: number): number {
		if (this._horizontalOffset.length === 0) {
			// No characters on this line
			return 0;
		}
		return this._horizontalOffset[column - 1];
	}

	private charOffsetToPartData(charOffset: number): number {
		if (this.length === 0) {
			return 0;
		}
		if (charOffset < 0) {
			return this._data[0];
		}
		if (charOffset >= this.length) {
			return this._data[this.length - 1];
		}
		return this._data[charOffset];
	}

	public getDomPosition(column: number): DomPosition {
		const partData = this.charOffsetToPartData(column - 1);
		const partIndex = CharacterMapping.getPartIndex(partData);
		const charIndex = CharacterMapping.getCharIndex(partData);
		return new DomPosition(partIndex, charIndex);
	}

	public getColumn(domPosition: DomPosition, partLength: number): number {
		const charOffset = this.partDataToCharOffset(domPosition.partIndex, partLength, domPosition.charIndex);
		return charOffset + 1;
	}

	private partDataToCharOffset(partIndex: number, partLength: number, charIndex: number): number {
		if (this.length === 0) {
			return 0;
		}

		const searchEntry = (
			(partIndex << CharacterMappingConstants.PART_INDEX_OFFSET)
			| (charIndex << CharacterMappingConstants.CHAR_INDEX_OFFSET)
		) >>> 0;

		let min = 0;
		let max = this.length - 1;
		while (min + 1 < max) {
			const mid = ((min + max) >>> 1);
			const midEntry = this._data[mid];
			if (midEntry === searchEntry) {
				return mid;
			} else if (midEntry > searchEntry) {
				max = mid;
			} else {
				min = mid;
			}
		}

		if (min === max) {
			return min;
		}

		const minEntry = this._data[min];
		const maxEntry = this._data[max];

		if (minEntry === searchEntry) {
			return min;
		}
		if (maxEntry === searchEntry) {
			return max;
		}

		const minPartIndex = CharacterMapping.getPartIndex(minEntry);
		const minCharIndex = CharacterMapping.getCharIndex(minEntry);

		const maxPartIndex = CharacterMapping.getPartIndex(maxEntry);
		let maxCharIndex: number;

		if (minPartIndex !== maxPartIndex) {
			// sitting between parts
			maxCharIndex = partLength;
		} else {
			maxCharIndex = CharacterMapping.getCharIndex(maxEntry);
		}

		const minEntryDistance = charIndex - minCharIndex;
		const maxEntryDistance = maxCharIndex - charIndex;

		if (minEntryDistance <= maxEntryDistance) {
			return min;
		}
		return max;
	}

	public inflate() {
		const result: [number, number, number][] = [];
		for (let i = 0; i < this.length; i++) {
			const partData = this._data[i];
			const partIndex = CharacterMapping.getPartIndex(partData);
			const charIndex = CharacterMapping.getCharIndex(partData);
			const visibleColumn = this._horizontalOffset[i];
			result.push([partIndex, charIndex, visibleColumn]);
		}
		return result;
	}
}

export const enum ForeignElementType {
	None = 0,
	Before = 1,
	After = 2
}

export class RenderLineOutput {
	_renderLineOutputBrand: void = undefined;

	readonly characterMapping: CharacterMapping;
	readonly containsForeignElements: ForeignElementType;

	constructor(characterMapping: CharacterMapping, containsForeignElements: ForeignElementType) {
		this.characterMapping = characterMapping;
		this.containsForeignElements = containsForeignElements;
	}
}

export function renderViewLine(input: RenderLineInput, sb: StringBuilder): RenderLineOutput {
	if (input.lineContent.length === 0) {

		if (input.lineDecorations.length > 0) {
			// This line is empty, but it contains inline decorations
			sb.appendString(`<span>`);

			let beforeCount = 0;
			let afterCount = 0;
			let containsForeignElements = ForeignElementType.None;
			for (const lineDecoration of input.lineDecorations) {
				if (lineDecoration.type === InlineDecorationType.Before || lineDecoration.type === InlineDecorationType.After) {
					sb.appendString(`<span class="`);
					sb.appendString(lineDecoration.className);
					sb.appendString(`"></span>`);

					if (lineDecoration.type === InlineDecorationType.Before) {
						containsForeignElements |= ForeignElementType.Before;
						beforeCount++;
					}
					if (lineDecoration.type === InlineDecorationType.After) {
						containsForeignElements |= ForeignElementType.After;
						afterCount++;
					}
				}
			}

			sb.appendString(`</span>`);

			const characterMapping = new CharacterMapping(1, beforeCount + afterCount);
			characterMapping.setColumnInfo(1, beforeCount, 0, 0);

			return new RenderLineOutput(
				characterMapping,
				containsForeignElements
			);
		}

		// completely empty line
		if (input.renderNewLineWhenEmpty) {
			sb.appendString('<span><span>\n</span></span>');
		} else {
			sb.appendString('<span><span></span></span>');
		}
		return new RenderLineOutput(
			new CharacterMapping(0, 0),
			ForeignElementType.None
		);
	}

	return _renderLine(resolveRenderLineInput(input), sb);
}

export class RenderLineOutput2 {
	constructor(
		public readonly characterMapping: CharacterMapping,
		public readonly html: string,
		public readonly containsForeignElements: ForeignElementType
	) {
	}
}

export function renderViewLine2(input: RenderLineInput): RenderLineOutput2 {
	const sb = new StringBuilder(10000);
	const out = renderViewLine(input, sb);
	return new RenderLineOutput2(out.characterMapping, sb.build(), out.containsForeignElements);
}

class ResolvedRenderLineInput {
	constructor(
		public readonly fontIsMonospace: boolean,
		public readonly canUseHalfwidthRightwardsArrow: boolean,
		public readonly lineContent: string,
		public readonly len: number,
		public readonly isOverflowing: boolean,
		public readonly overflowingCharCount: number,
		public readonly parts: LinePart[],
		public readonly containsForeignElements: ForeignElementType,
		public readonly fauxIndentLength: number,
		public readonly tabSize: number,
		public readonly startVisibleColumn: number,
		public readonly spaceWidth: number,
		public readonly renderSpaceCharCode: number,
		public readonly renderWhitespace: RenderWhitespace,
		public readonly renderControlCharacters: boolean,
	) {
		//
	}
}

function resolveRenderLineInput(input: RenderLineInput): ResolvedRenderLineInput {
	const lineContent = input.lineContent;

	let isOverflowing: boolean;
	let overflowingCharCount: number;
	let len: number;

	if (input.stopRenderingLineAfter !== -1 && input.stopRenderingLineAfter < lineContent.length) {
		isOverflowing = true;
		overflowingCharCount = lineContent.length - input.stopRenderingLineAfter;
		len = input.stopRenderingLineAfter;
	} else {
		isOverflowing = false;
		overflowingCharCount = 0;
		len = lineContent.length;
	}

	let tokens = transformAndRemoveOverflowing(lineContent, input.containsRTL, input.lineTokens, input.fauxIndentLength, len);
	if (input.renderControlCharacters && !input.isBasicASCII) {
		// Calling `extractControlCharacters` before adding (possibly empty) line parts
		// for inline decorations. `extractControlCharacters` removes empty line parts.
		tokens = extractControlCharacters(lineContent, tokens);
	}
	if (input.renderWhitespace === RenderWhitespace.All ||
		input.renderWhitespace === RenderWhitespace.Boundary ||
		(input.renderWhitespace === RenderWhitespace.Selection && !!input.selectionsOnLine) ||
		(input.renderWhitespace === RenderWhitespace.Trailing && !input.continuesWithWrappedLine)
	) {
		tokens = _applyRenderWhitespace(input, lineContent, len, tokens);
	}
	let containsForeignElements = ForeignElementType.None;
	if (input.lineDecorations.length > 0) {
		for (let i = 0, len = input.lineDecorations.length; i < len; i++) {
			const lineDecoration = input.lineDecorations[i];
			if (lineDecoration.type === InlineDecorationType.RegularAffectingLetterSpacing) {
				// Pretend there are foreign elements... although not 100% accurate.
				containsForeignElements |= ForeignElementType.Before;
			} else if (lineDecoration.type === InlineDecorationType.Before) {
				containsForeignElements |= ForeignElementType.Before;
			} else if (lineDecoration.type === InlineDecorationType.After) {
				containsForeignElements |= ForeignElementType.After;
			}
		}
		tokens = _applyInlineDecorations(lineContent, len, tokens, input.lineDecorations);
	}
	if (!input.containsRTL) {
		// We can never split RTL text, as it ruins the rendering
		tokens = splitLargeTokens(lineContent, tokens, !input.isBasicASCII || input.fontLigatures);
	}

	return new ResolvedRenderLineInput(
		input.useMonospaceOptimizations,
		input.canUseHalfwidthRightwardsArrow,
		lineContent,
		len,
		isOverflowing,
		overflowingCharCount,
		tokens,
		containsForeignElements,
		input.fauxIndentLength,
		input.tabSize,
		input.startVisibleColumn,
		input.spaceWidth,
		input.renderSpaceCharCode,
		input.renderWhitespace,
		input.renderControlCharacters
	);
}

/**
 * In the rendering phase, characters are always looped until token.endIndex.
 * Ensure that all tokens end before `len` and the last one ends precisely at `len`.
 */
function transformAndRemoveOverflowing(lineContent: string, lineContainsRTL: boolean, tokens: IViewLineTokens, fauxIndentLength: number, len: number): LinePart[] {
	const result: LinePart[] = [];
	let resultLen = 0;

	// The faux indent part of the line should have no token type
	if (fauxIndentLength > 0) {
		result[resultLen++] = new LinePart(fauxIndentLength, '', 0, false);
	}
	let startOffset = fauxIndentLength;
	for (let tokenIndex = 0, tokensLen = tokens.getCount(); tokenIndex < tokensLen; tokenIndex++) {
		const endIndex = tokens.getEndOffset(tokenIndex);
		if (endIndex <= fauxIndentLength) {
			// The faux indent part of the line should have no token type
			continue;
		}
		const type = tokens.getClassName(tokenIndex);
		if (endIndex >= len) {
			const tokenContainsRTL = (lineContainsRTL ? strings.containsRTL(lineContent.substring(startOffset, len)) : false);
			result[resultLen++] = new LinePart(len, type, 0, tokenContainsRTL);
			break;
		}
		const tokenContainsRTL = (lineContainsRTL ? strings.containsRTL(lineContent.substring(startOffset, endIndex)) : false);
		result[resultLen++] = new LinePart(endIndex, type, 0, tokenContainsRTL);
		startOffset = endIndex;
	}

	return result;
}

/**
 * written as a const enum to get value inlining.
 */
const enum Constants {
	LongToken = 50
}

/**
 * See https://github.com/microsoft/vscode/issues/6885.
 * It appears that having very large spans causes very slow reading of character positions.
 * So here we try to avoid that.
 */
function splitLargeTokens(lineContent: string, tokens: LinePart[], onlyAtSpaces: boolean): LinePart[] {
	let lastTokenEndIndex = 0;
	const result: LinePart[] = [];
	let resultLen = 0;

	if (onlyAtSpaces) {
		// Split only at spaces => we need to walk each character
		for (let i = 0, len = tokens.length; i < len; i++) {
			const token = tokens[i];
			const tokenEndIndex = token.endIndex;
			if (lastTokenEndIndex + Constants.LongToken < tokenEndIndex) {
				const tokenType = token.type;
				const tokenMetadata = token.metadata;
				const tokenContainsRTL = token.containsRTL;

				let lastSpaceOffset = -1;
				let currTokenStart = lastTokenEndIndex;
				for (let j = lastTokenEndIndex; j < tokenEndIndex; j++) {
					if (lineContent.charCodeAt(j) === CharCode.Space) {
						lastSpaceOffset = j;
					}
					if (lastSpaceOffset !== -1 && j - currTokenStart >= Constants.LongToken) {
						// Split at `lastSpaceOffset` + 1
						result[resultLen++] = new LinePart(lastSpaceOffset + 1, tokenType, tokenMetadata, tokenContainsRTL);
						currTokenStart = lastSpaceOffset + 1;
						lastSpaceOffset = -1;
					}
				}
				if (currTokenStart !== tokenEndIndex) {
					result[resultLen++] = new LinePart(tokenEndIndex, tokenType, tokenMetadata, tokenContainsRTL);
				}
			} else {
				result[resultLen++] = token;
			}

			lastTokenEndIndex = tokenEndIndex;
		}
	} else {
		// Split anywhere => we don't need to walk each character
		for (let i = 0, len = tokens.length; i < len; i++) {
			const token = tokens[i];
			const tokenEndIndex = token.endIndex;
			const diff = (tokenEndIndex - lastTokenEndIndex);
			if (diff > Constants.LongToken) {
				const tokenType = token.type;
				const tokenMetadata = token.metadata;
				const tokenContainsRTL = token.containsRTL;
				const piecesCount = Math.ceil(diff / Constants.LongToken);
				for (let j = 1; j < piecesCount; j++) {
					const pieceEndIndex = lastTokenEndIndex + (j * Constants.LongToken);
					result[resultLen++] = new LinePart(pieceEndIndex, tokenType, tokenMetadata, tokenContainsRTL);
				}
				result[resultLen++] = new LinePart(tokenEndIndex, tokenType, tokenMetadata, tokenContainsRTL);
			} else {
				result[resultLen++] = token;
			}
			lastTokenEndIndex = tokenEndIndex;
		}
	}

	return result;
}

function isControlCharacter(charCode: number): boolean {
	if (charCode < 32) {
		return (charCode !== CharCode.Tab);
	}
	if (charCode === 127) {
		// DEL
		return true;
	}

	if (
		(charCode >= 0x202A && charCode <= 0x202E)
		|| (charCode >= 0x2066 && charCode <= 0x2069)
		|| (charCode >= 0x200E && charCode <= 0x200F)
		|| charCode === 0x061C
	) {
		// Unicode Directional Formatting Characters
		// LRE	U+202A	LEFT-TO-RIGHT EMBEDDING
		// RLE	U+202B	RIGHT-TO-LEFT EMBEDDING
		// PDF	U+202C	POP DIRECTIONAL FORMATTING
		// LRO	U+202D	LEFT-TO-RIGHT OVERRIDE
		// RLO	U+202E	RIGHT-TO-LEFT OVERRIDE
		// LRI	U+2066	LEFT-TO-RIGHT ISOLATE
		// RLI	U+2067	RIGHT-TO-LEFT ISOLATE
		// FSI	U+2068	FIRST STRONG ISOLATE
		// PDI	U+2069	POP DIRECTIONAL ISOLATE
		// LRM	U+200E	LEFT-TO-RIGHT MARK
		// RLM	U+200F	RIGHT-TO-LEFT MARK
		// ALM	U+061C	ARABIC LETTER MARK
		return true;
	}

	return false;
}

function extractControlCharacters(lineContent: string, tokens: LinePart[]): LinePart[] {
	const result: LinePart[] = [];
	let lastLinePart: LinePart = new LinePart(0, '', 0, false);
	let charOffset = 0;
	for (const token of tokens) {
		const tokenEndIndex = token.endIndex;
		for (; charOffset < tokenEndIndex; charOffset++) {
			const charCode = lineContent.charCodeAt(charOffset);
			if (isControlCharacter(charCode)) {
				if (charOffset > lastLinePart.endIndex) {
					// emit previous part if it has text
					lastLinePart = new LinePart(charOffset, token.type, token.metadata, token.containsRTL);
					result.push(lastLinePart);
				}
				lastLinePart = new LinePart(charOffset + 1, 'mtkcontrol', token.metadata, false);
				result.push(lastLinePart);
			}
		}
		if (charOffset > lastLinePart.endIndex) {
			// emit previous part if it has text
			lastLinePart = new LinePart(tokenEndIndex, token.type, token.metadata, token.containsRTL);
			result.push(lastLinePart);
		}
	}
	return result;
}

/**
 * Whitespace is rendered by "replacing" tokens with a special-purpose `mtkw` type that is later recognized in the rendering phase.
 * Moreover, a token is created for every visual indent because on some fonts the glyphs used for rendering whitespace (&rarr; or &middot;) do not have the same width as &nbsp;.
 * The rendering phase will generate `style="width:..."` for these tokens.
 */
function _applyRenderWhitespace(input: RenderLineInput, lineContent: string, len: number, tokens: LinePart[]): LinePart[] {

	const continuesWithWrappedLine = input.continuesWithWrappedLine;
	const fauxIndentLength = input.fauxIndentLength;
	const tabSize = input.tabSize;
	const startVisibleColumn = input.startVisibleColumn;
	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);

	const result: LinePart[] = [];
	let resultLen = 0;
	let tokenIndex = 0;
	let tokenType = tokens[tokenIndex].type;
	let tokenContainsRTL = tokens[tokenIndex].containsRTL;
	let tokenEndIndex = tokens[tokenIndex].endIndex;
	const tokensLength = tokens.length;

	let lineIsEmptyOrWhitespace = false;
	let firstNonWhitespaceIndex = strings.firstNonWhitespaceIndex(lineContent);
	let lastNonWhitespaceIndex: number;
	if (firstNonWhitespaceIndex === -1) {
		lineIsEmptyOrWhitespace = true;
		firstNonWhitespaceIndex = len;
		lastNonWhitespaceIndex = len;
	} else {
		lastNonWhitespaceIndex = strings.lastNonWhitespaceIndex(lineContent);
	}

	let wasInWhitespace = false;
	let currentSelectionIndex = 0;
	let currentSelection = selections && selections[currentSelectionIndex];
	let tmpIndent = startVisibleColumn % tabSize;
	for (let charIndex = fauxIndentLength; charIndex < len; charIndex++) {
		const chCode = lineContent.charCodeAt(charIndex);

		if (currentSelection && currentSelection.endExclusive <= charIndex) {
			currentSelectionIndex++;
			currentSelection = selections && selections[currentSelectionIndex];
		}

		let isInWhitespace: boolean;
		if (charIndex < firstNonWhitespaceIndex || charIndex > lastNonWhitespaceIndex) {
			// in leading or trailing whitespace
			isInWhitespace = true;
		} else if (chCode === CharCode.Tab) {
			// a tab character is rendered both in all and boundary cases
			isInWhitespace = true;
		} else if (chCode === CharCode.Space) {
			// hit a space character
			if (onlyBoundary) {
				// rendering only boundary whitespace
				if (wasInWhitespace) {
					isInWhitespace = true;
				} else {
					const nextChCode = (charIndex + 1 < len ? lineContent.charCodeAt(charIndex + 1) : CharCode.Null);
					isInWhitespace = (nextChCode === CharCode.Space || nextChCode === CharCode.Tab);
				}
			} else {
				isInWhitespace = true;
			}
		} else {
			isInWhitespace = false;
		}

		// If rendering whitespace on selection, check that the charIndex falls within a selection
		if (isInWhitespace && selections) {
			isInWhitespace = !!currentSelection && currentSelection.start <= charIndex && charIndex < currentSelection.endExclusive;
		}

		// If rendering only trailing whitespace, check that the charIndex points to trailing whitespace.
		if (isInWhitespace && onlyTrailing) {
			isInWhitespace = lineIsEmptyOrWhitespace || charIndex > lastNonWhitespaceIndex;
		}

		if (isInWhitespace && tokenContainsRTL) {
			// If the token contains RTL text, breaking it up into multiple line parts
			// to render whitespace might affect the browser's bidi layout.
			//
			// We render whitespace in such tokens only if the whitespace
			// is the leading or the trailing whitespace of the line,
			// which doesn't affect the browser's bidi layout.
			if (charIndex >= firstNonWhitespaceIndex && charIndex <= lastNonWhitespaceIndex) {
				isInWhitespace = false;
			}
		}

		if (wasInWhitespace) {
			// was in whitespace token
			if (!isInWhitespace || (!useMonospaceOptimizations && tmpIndent >= tabSize)) {
				// leaving whitespace token or entering a new indent
				if (generateLinePartForEachWhitespace) {
					const lastEndIndex = (resultLen > 0 ? result[resultLen - 1].endIndex : fauxIndentLength);
					for (let i = lastEndIndex + 1; i <= charIndex; i++) {
						result[resultLen++] = new LinePart(i, 'mtkw', LinePartMetadata.IS_WHITESPACE, false);
					}
				} else {
					result[resultLen++] = new LinePart(charIndex, 'mtkw', LinePartMetadata.IS_WHITESPACE, false);
				}
				tmpIndent = tmpIndent % tabSize;
			}
		} else {
			// was in regular token
			if (charIndex === tokenEndIndex || (isInWhitespace && charIndex > fauxIndentLength)) {
				result[resultLen++] = new LinePart(charIndex, tokenType, 0, tokenContainsRTL);
				tmpIndent = tmpIndent % tabSize;
			}
		}

		if (chCode === CharCode.Tab) {
			tmpIndent = tabSize;
		} else if (strings.isFullWidthCharacter(chCode)) {
			tmpIndent += 2;
		} else {
			tmpIndent++;
		}

		wasInWhitespace = isInWhitespace;

		while (charIndex === tokenEndIndex) {
			tokenIndex++;
			if (tokenIndex < tokensLength) {
				tokenType = tokens[tokenIndex].type;
				tokenContainsRTL = tokens[tokenIndex].containsRTL;
				tokenEndIndex = tokens[tokenIndex].endIndex;
			} else {
				break;
			}
		}
	}

	let generateWhitespace = false;
	if (wasInWhitespace) {
		// was in whitespace token
		if (continuesWithWrappedLine && onlyBoundary) {
			const lastCharCode = (len > 0 ? lineContent.charCodeAt(len - 1) : CharCode.Null);
			const prevCharCode = (len > 1 ? lineContent.charCodeAt(len - 2) : CharCode.Null);
			const isSingleTrailingSpace = (lastCharCode === CharCode.Space && (prevCharCode !== CharCode.Space && prevCharCode !== CharCode.Tab));
			if (!isSingleTrailingSpace) {
				generateWhitespace = true;
			}
		} else {
			generateWhitespace = true;
		}
	}

	if (generateWhitespace) {
		if (generateLinePartForEachWhitespace) {
			const lastEndIndex = (resultLen > 0 ? result[resultLen - 1].endIndex : fauxIndentLength);
			for (let i = lastEndIndex + 1; i <= len; i++) {
				result[resultLen++] = new LinePart(i, 'mtkw', LinePartMetadata.IS_WHITESPACE, false);
			}
		} else {
			result[resultLen++] = new LinePart(len, 'mtkw', LinePartMetadata.IS_WHITESPACE, false);
		}
	} else {
		result[resultLen++] = new LinePart(len, tokenType, 0, tokenContainsRTL);
	}

	return result;
}

/**
 * Inline decorations are "merged" on top of tokens.
 * Special care must be taken when multiple inline decorations are at play and they overlap.
 */
function _applyInlineDecorations(lineContent: string, len: number, tokens: LinePart[], _lineDecorations: LineDecoration[]): LinePart[] {
	_lineDecorations.sort(LineDecoration.compare);
	const lineDecorations = LineDecorationsNormalizer.normalize(lineContent, _lineDecorations);
	const lineDecorationsLen = lineDecorations.length;

	let lineDecorationIndex = 0;
	const result: LinePart[] = [];
	let resultLen = 0;
	let lastResultEndIndex = 0;
	for (let tokenIndex = 0, len = tokens.length; tokenIndex < len; tokenIndex++) {
		const token = tokens[tokenIndex];
		const tokenEndIndex = token.endIndex;
		const tokenType = token.type;
		const tokenMetadata = token.metadata;
		const tokenContainsRTL = token.containsRTL;

		while (lineDecorationIndex < lineDecorationsLen && lineDecorations[lineDecorationIndex].startOffset < tokenEndIndex) {
			const lineDecoration = lineDecorations[lineDecorationIndex];

			if (lineDecoration.startOffset > lastResultEndIndex) {
				lastResultEndIndex = lineDecoration.startOffset;
				result[resultLen++] = new LinePart(lastResultEndIndex, tokenType, tokenMetadata, tokenContainsRTL);
			}

			if (lineDecoration.endOffset + 1 <= tokenEndIndex) {
				// This line decoration ends before this token ends
				lastResultEndIndex = lineDecoration.endOffset + 1;
				result[resultLen++] = new LinePart(lastResultEndIndex, tokenType + ' ' + lineDecoration.className, tokenMetadata | lineDecoration.metadata, tokenContainsRTL);
				lineDecorationIndex++;
			} else {
				// This line decoration continues on to the next token
				lastResultEndIndex = tokenEndIndex;
				result[resultLen++] = new LinePart(lastResultEndIndex, tokenType + ' ' + lineDecoration.className, tokenMetadata | lineDecoration.metadata, tokenContainsRTL);
				break;
			}
		}

		if (tokenEndIndex > lastResultEndIndex) {
			lastResultEndIndex = tokenEndIndex;
			result[resultLen++] = new LinePart(lastResultEndIndex, tokenType, tokenMetadata, tokenContainsRTL);
		}
	}

	const lastTokenEndIndex = tokens[tokens.length - 1].endIndex;
	if (lineDecorationIndex < lineDecorationsLen && lineDecorations[lineDecorationIndex].startOffset === lastTokenEndIndex) {
		while (lineDecorationIndex < lineDecorationsLen && lineDecorations[lineDecorationIndex].startOffset === lastTokenEndIndex) {
			const lineDecoration = lineDecorations[lineDecorationIndex];
			result[resultLen++] = new LinePart(lastResultEndIndex, lineDecoration.className, lineDecoration.metadata, false);
			lineDecorationIndex++;
		}
	}

	return result;
}

/**
 * This function is on purpose not split up into multiple functions to allow runtime type inference (i.e. performance reasons).
 * Notice how all the needed data is fully resolved and passed in (i.e. no other calls).
 */
function _renderLine(input: ResolvedRenderLineInput, sb: StringBuilder): RenderLineOutput {
	const fontIsMonospace = input.fontIsMonospace;
	const canUseHalfwidthRightwardsArrow = input.canUseHalfwidthRightwardsArrow;
	const containsForeignElements = input.containsForeignElements;
	const lineContent = input.lineContent;
	const len = input.len;
	const isOverflowing = input.isOverflowing;
	const overflowingCharCount = input.overflowingCharCount;
	const parts = input.parts;
	const fauxIndentLength = input.fauxIndentLength;
	const tabSize = input.tabSize;
	const startVisibleColumn = input.startVisibleColumn;
	const spaceWidth = input.spaceWidth;
	const renderSpaceCharCode = input.renderSpaceCharCode;
	const renderWhitespace = input.renderWhitespace;
	const renderControlCharacters = input.renderControlCharacters;

	const characterMapping = new CharacterMapping(len + 1, parts.length);
	let lastCharacterMappingDefined = false;

	let charIndex = 0;
	let visibleColumn = startVisibleColumn;
	let charOffsetInPart = 0; // the character offset in the current part
	let charHorizontalOffset = 0; // the character horizontal position in terms of chars relative to line start

	let partDisplacement = 0;

	sb.appendString('<span>');

	for (let partIndex = 0, tokensLen = parts.length; partIndex < tokensLen; partIndex++) {

		const part = parts[partIndex];
		const partEndIndex = part.endIndex;
		const partType = part.type;
		const partContainsRTL = part.containsRTL;
		const partRendersWhitespace = (renderWhitespace !== RenderWhitespace.None && part.isWhitespace());
		const partRendersWhitespaceWithWidth = partRendersWhitespace && !fontIsMonospace && (partType === 'mtkw'/*only whitespace*/ || !containsForeignElements);
		const partIsEmptyAndHasPseudoAfter = (charIndex === partEndIndex && part.isPseudoAfter());
		charOffsetInPart = 0;

		sb.appendString('<span ');
		if (partContainsRTL) {
			sb.appendString('style="unicode-bidi:isolate" ');
		}
		sb.appendString('class="');
		sb.appendString(partRendersWhitespaceWithWidth ? 'mtkz' : partType);
		sb.appendASCIICharCode(CharCode.DoubleQuote);

		if (partRendersWhitespace) {

			let partWidth = 0;
			{
				let _charIndex = charIndex;
				let _visibleColumn = visibleColumn;

				for (; _charIndex < partEndIndex; _charIndex++) {
					const charCode = lineContent.charCodeAt(_charIndex);
					const charWidth = (charCode === CharCode.Tab ? (tabSize - (_visibleColumn % tabSize)) : 1) | 0;
					partWidth += charWidth;
					if (_charIndex >= fauxIndentLength) {
						_visibleColumn += charWidth;
					}
				}
			}

			if (partRendersWhitespaceWithWidth) {
				sb.appendString(' style="width:');
				sb.appendString(String(spaceWidth * partWidth));
				sb.appendString('px"');
			}
			sb.appendASCIICharCode(CharCode.GreaterThan);

			for (; charIndex < partEndIndex; charIndex++) {
				characterMapping.setColumnInfo(charIndex + 1, partIndex - partDisplacement, charOffsetInPart, charHorizontalOffset);
				partDisplacement = 0;
				const charCode = lineContent.charCodeAt(charIndex);

				let producedCharacters: number;
				let charWidth: number;

				if (charCode === CharCode.Tab) {
					producedCharacters = (tabSize - (visibleColumn % tabSize)) | 0;
					charWidth = producedCharacters;

					if (!canUseHalfwidthRightwardsArrow || charWidth > 1) {
						sb.appendCharCode(0x2192); // RIGHTWARDS ARROW
					} else {
						sb.appendCharCode(0xFFEB); // HALFWIDTH RIGHTWARDS ARROW
					}
					for (let space = 2; space <= charWidth; space++) {
						sb.appendCharCode(0xA0); // &nbsp;
					}

				} else { // must be CharCode.Space
					producedCharacters = 2;
					charWidth = 1;

					sb.appendCharCode(renderSpaceCharCode); // &middot; or word separator middle dot
					sb.appendCharCode(0x200C); // ZERO WIDTH NON-JOINER
				}

				charOffsetInPart += producedCharacters;
				charHorizontalOffset += charWidth;
				if (charIndex >= fauxIndentLength) {
					visibleColumn += charWidth;
				}
			}

		} else {

			sb.appendASCIICharCode(CharCode.GreaterThan);

			for (; charIndex < partEndIndex; charIndex++) {
				characterMapping.setColumnInfo(charIndex + 1, partIndex - partDisplacement, charOffsetInPart, charHorizontalOffset);
				partDisplacement = 0;
				const charCode = lineContent.charCodeAt(charIndex);

				let producedCharacters = 1;
				let charWidth = 1;

				switch (charCode) {
					case CharCode.Tab:
						producedCharacters = (tabSize - (visibleColumn % tabSize));
						charWidth = producedCharacters;
						for (let space = 1; space <= producedCharacters; space++) {
							sb.appendCharCode(0xA0); // &nbsp;
						}
						break;

					case CharCode.Space:
						sb.appendCharCode(0xA0); // &nbsp;
						break;

					case CharCode.LessThan:
						sb.appendString('&lt;');
						break;

					case CharCode.GreaterThan:
						sb.appendString('&gt;');
						break;

					case CharCode.Ampersand:
						sb.appendString('&amp;');
						break;

					case CharCode.Null:
						if (renderControlCharacters) {
							// See https://unicode-table.com/en/blocks/control-pictures/
							sb.appendCharCode(9216);
						} else {
							sb.appendString('&#00;');
						}
						break;

					case CharCode.UTF8_BOM:
					case CharCode.LINE_SEPARATOR:
					case CharCode.PARAGRAPH_SEPARATOR:
					case CharCode.NEXT_LINE:
						sb.appendCharCode(0xFFFD);
						break;

					default:
						if (strings.isFullWidthCharacter(charCode)) {
							charWidth++;
						}
						// See https://unicode-table.com/en/blocks/control-pictures/
						if (renderControlCharacters && charCode < 32) {
							sb.appendCharCode(9216 + charCode);
						} else if (renderControlCharacters && charCode === 127) {
							// DEL
							sb.appendCharCode(9249);
						} else if (renderControlCharacters && isControlCharacter(charCode)) {
							sb.appendString('[U+');
							sb.appendString(to4CharHex(charCode));
							sb.appendString(']');
							producedCharacters = 8;
							charWidth = producedCharacters;
						} else {
							sb.appendCharCode(charCode);
						}
				}

				charOffsetInPart += producedCharacters;
				charHorizontalOffset += charWidth;
				if (charIndex >= fauxIndentLength) {
					visibleColumn += charWidth;
				}
			}
		}

		if (partIsEmptyAndHasPseudoAfter) {
			partDisplacement++;
		} else {
			partDisplacement = 0;
		}

		if (charIndex >= len && !lastCharacterMappingDefined && part.isPseudoAfter()) {
			lastCharacterMappingDefined = true;
			characterMapping.setColumnInfo(charIndex + 1, partIndex, charOffsetInPart, charHorizontalOffset);
		}

		sb.appendString('</span>');

	}

	if (!lastCharacterMappingDefined) {
		// When getting client rects for the last character, we will position the
		// text range at the end of the span, insteaf of at the beginning of next span
		characterMapping.setColumnInfo(len + 1, parts.length - 1, charOffsetInPart, charHorizontalOffset);
	}

	if (isOverflowing) {
		sb.appendString('<span class="mtkoverflow">');
		sb.appendString(nls.localize('showMore', "Show more ({0})", renderOverflowingCharCount(overflowingCharCount)));
		sb.appendString('</span>');
	}

	sb.appendString('</span>');

	return new RenderLineOutput(characterMapping, containsForeignElements);
}

function to4CharHex(n: number): string {
	return n.toString(16).toUpperCase().padStart(4, '0');
}

function renderOverflowingCharCount(n: number): string {
	if (n < 1024) {
		return nls.localize('overflow.chars', "{0} chars", n);
	}
	if (n < 1024 * 1024) {
		return `${(n / 1024).toFixed(1)} KB`;
	}
	return `${(n / 1024 / 1024).toFixed(1)} MB`;
}