120 lines
3.6 KiB
JavaScript
120 lines
3.6 KiB
JavaScript
import stripAnsi from 'strip-ansi';
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import {eastAsianWidth} from 'get-east-asian-width';
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/**
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Logic:
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- Segment graphemes to match how terminals render clusters.
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- Width rules:
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1. Skip non-printing clusters (Default_Ignorable, Control, pure Mark, lone Surrogates). Tabs are ignored by design.
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2. RGI emoji clusters (\p{RGI_Emoji}) are double-width.
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3. Minimally-qualified/unqualified emoji clusters (ZWJ sequences with 2+ Extended_Pictographic, or keycap sequences) are double-width.
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4. Otherwise use East Asian Width of the cluster's first visible code point, and add widths for trailing Halfwidth/Fullwidth Forms within the same cluster (e.g., dakuten/handakuten/prolonged sound mark).
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*/
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const segmenter = new Intl.Segmenter();
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// Whole-cluster zero-width
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const zeroWidthClusterRegex = /^(?:\p{Default_Ignorable_Code_Point}|\p{Control}|\p{Format}|\p{Mark}|\p{Surrogate})+$/v;
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// Pick the base scalar if the cluster starts with Prepend/Format/Marks
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const leadingNonPrintingRegex = /^[\p{Default_Ignorable_Code_Point}\p{Control}\p{Format}\p{Mark}\p{Surrogate}]+/v;
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// RGI emoji sequences
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const rgiEmojiRegex = /^\p{RGI_Emoji}$/v;
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// Detect minimally-qualified/unqualified emoji sequences (missing VS16 but still render as double-width)
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const unqualifiedKeycapRegex = /^[\d#*]\u20E3$/;
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const extendedPictographicRegex = /\p{Extended_Pictographic}/gu;
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function isDoubleWidthNonRgiEmojiSequence(segment) {
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// Real emoji clusters are < 30 chars; guard against pathological input
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if (segment.length > 50) {
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return false;
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}
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if (unqualifiedKeycapRegex.test(segment)) {
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return true;
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}
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// ZWJ sequences with 2+ Extended_Pictographic
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if (segment.includes('\u200D')) {
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const pictographics = segment.match(extendedPictographicRegex);
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return pictographics !== null && pictographics.length >= 2;
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}
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return false;
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}
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function baseVisible(segment) {
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return segment.replace(leadingNonPrintingRegex, '');
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}
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function isZeroWidthCluster(segment) {
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return zeroWidthClusterRegex.test(segment);
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}
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function trailingHalfwidthWidth(segment, eastAsianWidthOptions) {
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let extra = 0;
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if (segment.length > 1) {
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for (const char of segment.slice(1)) {
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if (char >= '\uFF00' && char <= '\uFFEF') {
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extra += eastAsianWidth(char.codePointAt(0), eastAsianWidthOptions);
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}
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}
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}
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return extra;
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}
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export default function stringWidth(input, options = {}) {
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if (typeof input !== 'string' || input.length === 0) {
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return 0;
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}
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const {
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ambiguousIsNarrow = true,
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countAnsiEscapeCodes = false,
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} = options;
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let string = input;
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// Avoid calling stripAnsi when there are no ANSI escape sequences (ESC = 0x1B, CSI = 0x9B)
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if (!countAnsiEscapeCodes && (string.includes('\u001B') || string.includes('\u009B'))) {
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string = stripAnsi(string);
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}
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if (string.length === 0) {
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return 0;
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}
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// Fast path: printable ASCII (0x20–0x7E) needs no segmenter, regex, or EAW lookup — width equals length.
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if (/^[\u0020-\u007E]*$/.test(string)) {
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return string.length;
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}
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let width = 0;
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const eastAsianWidthOptions = {ambiguousAsWide: !ambiguousIsNarrow};
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for (const {segment} of segmenter.segment(string)) {
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// Zero-width / non-printing clusters
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if (isZeroWidthCluster(segment)) {
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continue;
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}
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// Emoji width logic
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if (rgiEmojiRegex.test(segment) || isDoubleWidthNonRgiEmojiSequence(segment)) {
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width += 2;
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continue;
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}
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// Everything else: EAW of the cluster’s first visible scalar
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const codePoint = baseVisible(segment).codePointAt(0);
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width += eastAsianWidth(codePoint, eastAsianWidthOptions);
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// Add width for trailing Halfwidth and Fullwidth Forms (e.g., ﾞ, ﾟ, ｰ)
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width += trailingHalfwidthWidth(segment, eastAsianWidthOptions);
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}
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return width;
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}
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