215 lines
8.2 KiB
JavaScript
215 lines
8.2 KiB
JavaScript
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import { lst } from "./misc.js"
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// BIDI HELPERS
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export function iterateBidiSections(order, from, to, f) {
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if (!order) return f(from, to, "ltr", 0)
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let found = false
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for (let i = 0; i < order.length; ++i) {
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let part = order[i]
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if (part.from < to && part.to > from || from == to && part.to == from) {
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f(Math.max(part.from, from), Math.min(part.to, to), part.level == 1 ? "rtl" : "ltr", i)
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found = true
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}
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}
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if (!found) f(from, to, "ltr")
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}
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export let bidiOther = null
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export function getBidiPartAt(order, ch, sticky) {
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let found
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bidiOther = null
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for (let i = 0; i < order.length; ++i) {
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let cur = order[i]
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if (cur.from < ch && cur.to > ch) return i
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if (cur.to == ch) {
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if (cur.from != cur.to && sticky == "before") found = i
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else bidiOther = i
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}
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if (cur.from == ch) {
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if (cur.from != cur.to && sticky != "before") found = i
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else bidiOther = i
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}
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}
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return found != null ? found : bidiOther
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}
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// Bidirectional ordering algorithm
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// See http://unicode.org/reports/tr9/tr9-13.html for the algorithm
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// that this (partially) implements.
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// One-char codes used for character types:
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// L (L): Left-to-Right
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// R (R): Right-to-Left
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// r (AL): Right-to-Left Arabic
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// 1 (EN): European Number
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// + (ES): European Number Separator
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// % (ET): European Number Terminator
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// n (AN): Arabic Number
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// , (CS): Common Number Separator
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// m (NSM): Non-Spacing Mark
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// b (BN): Boundary Neutral
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// s (B): Paragraph Separator
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// t (S): Segment Separator
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// w (WS): Whitespace
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// N (ON): Other Neutrals
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// Returns null if characters are ordered as they appear
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// (left-to-right), or an array of sections ({from, to, level}
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// objects) in the order in which they occur visually.
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let bidiOrdering = (function() {
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// Character types for codepoints 0 to 0xff
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let lowTypes = "bbbbbbbbbtstwsbbbbbbbbbbbbbbssstwNN%%%NNNNNN,N,N1111111111NNNNNNNLLLLLLLLLLLLLLLLLLLLLLLLLLNNNNNNLLLLLLLLLLLLLLLLLLLLLLLLLLNNNNbbbbbbsbbbbbbbbbbbbbbbbbbbbbbbbbb,N%%%%NNNNLNNNNN%%11NLNNN1LNNNNNLLLLLLLLLLLLLLLLLLLLLLLNLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLN"
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// Character types for codepoints 0x600 to 0x6f9
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let arabicTypes = "nnnnnnNNr%%r,rNNmmmmmmmmmmmrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrmmmmmmmmmmmmmmmmmmmmmnnnnnnnnnn%nnrrrmrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrmmmmmmmnNmmmmmmrrmmNmmmmrr1111111111"
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function charType(code) {
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if (code <= 0xf7) return lowTypes.charAt(code)
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else if (0x590 <= code && code <= 0x5f4) return "R"
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else if (0x600 <= code && code <= 0x6f9) return arabicTypes.charAt(code - 0x600)
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else if (0x6ee <= code && code <= 0x8ac) return "r"
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else if (0x2000 <= code && code <= 0x200b) return "w"
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else if (code == 0x200c) return "b"
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else return "L"
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}
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let bidiRE = /[\u0590-\u05f4\u0600-\u06ff\u0700-\u08ac]/
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let isNeutral = /[stwN]/, isStrong = /[LRr]/, countsAsLeft = /[Lb1n]/, countsAsNum = /[1n]/
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function BidiSpan(level, from, to) {
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this.level = level
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this.from = from; this.to = to
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}
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return function(str, direction) {
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let outerType = direction == "ltr" ? "L" : "R"
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if (str.length == 0 || direction == "ltr" && !bidiRE.test(str)) return false
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let len = str.length, types = []
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for (let i = 0; i < len; ++i)
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types.push(charType(str.charCodeAt(i)))
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// W1. Examine each non-spacing mark (NSM) in the level run, and
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// change the type of the NSM to the type of the previous
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// character. If the NSM is at the start of the level run, it will
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// get the type of sor.
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for (let i = 0, prev = outerType; i < len; ++i) {
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let type = types[i]
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if (type == "m") types[i] = prev
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else prev = type
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}
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// W2. Search backwards from each instance of a European number
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// until the first strong type (R, L, AL, or sor) is found. If an
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// AL is found, change the type of the European number to Arabic
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// number.
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// W3. Change all ALs to R.
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for (let i = 0, cur = outerType; i < len; ++i) {
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let type = types[i]
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if (type == "1" && cur == "r") types[i] = "n"
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else if (isStrong.test(type)) { cur = type; if (type == "r") types[i] = "R" }
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}
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// W4. A single European separator between two European numbers
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// changes to a European number. A single common separator between
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// two numbers of the same type changes to that type.
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for (let i = 1, prev = types[0]; i < len - 1; ++i) {
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let type = types[i]
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if (type == "+" && prev == "1" && types[i+1] == "1") types[i] = "1"
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else if (type == "," && prev == types[i+1] &&
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(prev == "1" || prev == "n")) types[i] = prev
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prev = type
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}
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// W5. A sequence of European terminators adjacent to European
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// numbers changes to all European numbers.
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// W6. Otherwise, separators and terminators change to Other
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// Neutral.
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for (let i = 0; i < len; ++i) {
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let type = types[i]
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if (type == ",") types[i] = "N"
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else if (type == "%") {
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let end
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for (end = i + 1; end < len && types[end] == "%"; ++end) {}
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let replace = (i && types[i-1] == "!") || (end < len && types[end] == "1") ? "1" : "N"
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for (let j = i; j < end; ++j) types[j] = replace
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i = end - 1
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}
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}
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// W7. Search backwards from each instance of a European number
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// until the first strong type (R, L, or sor) is found. If an L is
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// found, then change the type of the European number to L.
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for (let i = 0, cur = outerType; i < len; ++i) {
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let type = types[i]
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if (cur == "L" && type == "1") types[i] = "L"
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else if (isStrong.test(type)) cur = type
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}
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// N1. A sequence of neutrals takes the direction of the
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// surrounding strong text if the text on both sides has the same
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// direction. European and Arabic numbers act as if they were R in
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// terms of their influence on neutrals. Start-of-level-run (sor)
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// and end-of-level-run (eor) are used at level run boundaries.
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// N2. Any remaining neutrals take the embedding direction.
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for (let i = 0; i < len; ++i) {
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if (isNeutral.test(types[i])) {
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let end
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for (end = i + 1; end < len && isNeutral.test(types[end]); ++end) {}
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let before = (i ? types[i-1] : outerType) == "L"
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let after = (end < len ? types[end] : outerType) == "L"
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let replace = before == after ? (before ? "L" : "R") : outerType
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for (let j = i; j < end; ++j) types[j] = replace
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i = end - 1
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}
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}
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// Here we depart from the documented algorithm, in order to avoid
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// building up an actual levels array. Since there are only three
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// levels (0, 1, 2) in an implementation that doesn't take
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// explicit embedding into account, we can build up the order on
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// the fly, without following the level-based algorithm.
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let order = [], m
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for (let i = 0; i < len;) {
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if (countsAsLeft.test(types[i])) {
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let start = i
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for (++i; i < len && countsAsLeft.test(types[i]); ++i) {}
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order.push(new BidiSpan(0, start, i))
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} else {
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let pos = i, at = order.length
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for (++i; i < len && types[i] != "L"; ++i) {}
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for (let j = pos; j < i;) {
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if (countsAsNum.test(types[j])) {
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if (pos < j) order.splice(at, 0, new BidiSpan(1, pos, j))
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let nstart = j
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for (++j; j < i && countsAsNum.test(types[j]); ++j) {}
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order.splice(at, 0, new BidiSpan(2, nstart, j))
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pos = j
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} else ++j
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}
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if (pos < i) order.splice(at, 0, new BidiSpan(1, pos, i))
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}
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}
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if (direction == "ltr") {
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if (order[0].level == 1 && (m = str.match(/^\s+/))) {
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order[0].from = m[0].length
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order.unshift(new BidiSpan(0, 0, m[0].length))
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}
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if (lst(order).level == 1 && (m = str.match(/\s+$/))) {
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lst(order).to -= m[0].length
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order.push(new BidiSpan(0, len - m[0].length, len))
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}
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}
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return direction == "rtl" ? order.reverse() : order
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}
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})()
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// Get the bidi ordering for the given line (and cache it). Returns
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// false for lines that are fully left-to-right, and an array of
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// BidiSpan objects otherwise.
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export function getOrder(line, direction) {
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let order = line.order
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if (order == null) order = line.order = bidiOrdering(line.text, direction)
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return order
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}
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