553 lines
19 KiB
JavaScript
553 lines
19 KiB
JavaScript
/*
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* Copyright (C) 2020-2021 Yomichan Authors
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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/**
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* A class used to scan text in a document.
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*/
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class DOMTextScanner {
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/**
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* Creates a new instance of a DOMTextScanner.
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* @param node The DOM Node to start at.
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* @param offset The character offset in to start at when node is a text node.
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* Use 0 for non-text nodes.
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*/
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constructor(node, offset, forcePreserveWhitespace=false, generateLayoutContent=true) {
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const ruby = DOMTextScanner.getParentRubyElement(node);
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const resetOffset = (ruby !== null);
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if (resetOffset) { node = ruby; }
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this._node = node;
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this._offset = offset;
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this._content = '';
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this._remainder = 0;
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this._resetOffset = resetOffset;
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this._newlines = 0;
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this._lineHasWhitespace = false;
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this._lineHasContent = false;
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this._forcePreserveWhitespace = forcePreserveWhitespace;
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this._generateLayoutContent = generateLayoutContent;
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}
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/**
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* Gets the current node being scanned.
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* @returns A DOM Node.
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*/
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get node() {
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return this._node;
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}
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/**
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* Gets the current offset corresponding to the node being scanned.
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* This value is only applicable for text nodes.
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* @returns An integer.
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*/
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get offset() {
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return this._offset;
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}
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/**
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* Gets the remaining number of characters that weren't scanned in the last seek() call.
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* This value is usually 0 unless the end of the document was reached.
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* @returns An integer.
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*/
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get remainder() {
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return this._remainder;
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}
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/**
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* Gets the accumulated content string resulting from calls to seek().
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* @returns A string.
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*/
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get content() {
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return this._content;
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}
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/**
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* Seeks a given length in the document and accumulates the text content.
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* @param length A positive or negative integer corresponding to how many characters
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* should be added to content. Content is only added to the accumulation string,
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* never removed, so mixing seek calls with differently signed length values
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* may give unexpected results.
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* @returns this
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*/
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seek(length) {
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const forward = (length >= 0);
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this._remainder = (forward ? length : -length);
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if (length === 0) { return this; }
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const TEXT_NODE = Node.TEXT_NODE;
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const ELEMENT_NODE = Node.ELEMENT_NODE;
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const generateLayoutContent = this._generateLayoutContent;
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let node = this._node;
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let lastNode = node;
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let resetOffset = this._resetOffset;
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let newlines = 0;
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while (node !== null) {
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let enterable = false;
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const nodeType = node.nodeType;
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if (nodeType === TEXT_NODE) {
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lastNode = node;
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if (!(
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forward ?
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this._seekTextNodeForward(node, resetOffset) :
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this._seekTextNodeBackward(node, resetOffset)
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)) {
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// Length reached
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break;
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}
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} else if (nodeType === ELEMENT_NODE) {
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lastNode = node;
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this._offset = 0;
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[enterable, newlines] = DOMTextScanner.getElementSeekInfo(node);
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if (newlines > this._newlines && generateLayoutContent) {
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this._newlines = newlines;
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}
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}
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const exitedNodes = [];
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node = DOMTextScanner.getNextNode(node, forward, enterable, exitedNodes);
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for (const exitedNode of exitedNodes) {
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if (exitedNode.nodeType !== ELEMENT_NODE) { continue; }
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newlines = DOMTextScanner.getElementSeekInfo(exitedNode)[1];
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if (newlines > this._newlines && generateLayoutContent) {
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this._newlines = newlines;
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}
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}
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resetOffset = true;
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}
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this._node = lastNode;
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this._resetOffset = resetOffset;
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return this;
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}
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// Private
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/**
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* Seeks forward in a text node.
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* @param textNode The text node to use.
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* @param resetOffset Whether or not the text offset should be reset.
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* @returns true if scanning should continue, or false if the scan length has been reached.
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*/
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_seekTextNodeForward(textNode, resetOffset) {
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const nodeValue = textNode.nodeValue;
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const nodeValueLength = nodeValue.length;
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const [preserveNewlines, preserveWhitespace] = (
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this._forcePreserveWhitespace ?
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[true, true] :
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DOMTextScanner.getWhitespaceSettings(textNode)
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);
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let lineHasWhitespace = this._lineHasWhitespace;
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let lineHasContent = this._lineHasContent;
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let content = this._content;
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let offset = resetOffset ? 0 : this._offset;
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let remainder = this._remainder;
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let newlines = this._newlines;
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while (offset < nodeValueLength) {
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const char = nodeValue[offset];
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const charAttributes = DOMTextScanner.getCharacterAttributes(char, preserveNewlines, preserveWhitespace);
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++offset;
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if (charAttributes === 0) {
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// Character should be ignored
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continue;
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} else if (charAttributes === 1) {
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// Character is collapsible whitespace
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lineHasWhitespace = true;
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} else {
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// Character should be added to the content
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if (newlines > 0) {
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if (content.length > 0) {
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const useNewlineCount = Math.min(remainder, newlines);
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content += '\n'.repeat(useNewlineCount);
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remainder -= useNewlineCount;
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newlines -= useNewlineCount;
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} else {
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newlines = 0;
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}
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lineHasContent = false;
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lineHasWhitespace = false;
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if (remainder <= 0) {
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--offset; // Revert character offset
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break;
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}
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}
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lineHasContent = (charAttributes === 2); // 3 = character is a newline
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if (lineHasWhitespace) {
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if (lineHasContent) {
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content += ' ';
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lineHasWhitespace = false;
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if (--remainder <= 0) {
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--offset; // Revert character offset
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break;
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}
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} else {
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lineHasWhitespace = false;
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}
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}
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content += char;
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if (--remainder <= 0) { break; }
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}
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}
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this._lineHasWhitespace = lineHasWhitespace;
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this._lineHasContent = lineHasContent;
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this._content = content;
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this._offset = offset;
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this._remainder = remainder;
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this._newlines = newlines;
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return (remainder > 0);
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}
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/**
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* Seeks backward in a text node.
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* This function is nearly the same as _seekTextNodeForward, with the following differences:
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* - Iteration condition is reversed to check if offset is greater than 0.
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* - offset is reset to nodeValueLength instead of 0.
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* - offset is decremented instead of incremented.
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* - offset is decremented before getting the character.
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* - offset is reverted by incrementing instead of decrementing.
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* - content string is prepended instead of appended.
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* @param textNode The text node to use.
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* @param resetOffset Whether or not the text offset should be reset.
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* @returns true if scanning should continue, or false if the scan length has been reached.
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*/
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_seekTextNodeBackward(textNode, resetOffset) {
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const nodeValue = textNode.nodeValue;
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const nodeValueLength = nodeValue.length;
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const [preserveNewlines, preserveWhitespace] = (
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this._forcePreserveWhitespace ?
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[true, true] :
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DOMTextScanner.getWhitespaceSettings(textNode)
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);
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let lineHasWhitespace = this._lineHasWhitespace;
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let lineHasContent = this._lineHasContent;
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let content = this._content;
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let offset = resetOffset ? nodeValueLength : this._offset;
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let remainder = this._remainder;
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let newlines = this._newlines;
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while (offset > 0) {
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--offset;
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const char = nodeValue[offset];
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const charAttributes = DOMTextScanner.getCharacterAttributes(char, preserveNewlines, preserveWhitespace);
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if (charAttributes === 0) {
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// Character should be ignored
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continue;
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} else if (charAttributes === 1) {
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// Character is collapsible whitespace
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lineHasWhitespace = true;
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} else {
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// Character should be added to the content
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if (newlines > 0) {
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if (content.length > 0) {
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const useNewlineCount = Math.min(remainder, newlines);
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content = '\n'.repeat(useNewlineCount) + content;
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remainder -= useNewlineCount;
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newlines -= useNewlineCount;
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} else {
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newlines = 0;
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}
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lineHasContent = false;
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lineHasWhitespace = false;
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if (remainder <= 0) {
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++offset; // Revert character offset
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break;
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}
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}
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lineHasContent = (charAttributes === 2); // 3 = character is a newline
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if (lineHasWhitespace) {
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if (lineHasContent) {
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content = ' ' + content;
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lineHasWhitespace = false;
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if (--remainder <= 0) {
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++offset; // Revert character offset
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break;
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}
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} else {
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lineHasWhitespace = false;
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}
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}
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content = char + content;
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if (--remainder <= 0) { break; }
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}
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}
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this._lineHasWhitespace = lineHasWhitespace;
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this._lineHasContent = lineHasContent;
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this._content = content;
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this._offset = offset;
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this._remainder = remainder;
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this._newlines = newlines;
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return (remainder > 0);
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}
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// Static helpers
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/**
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* Gets the next node in the document for a specified scanning direction.
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* @param node The current DOM Node.
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* @param forward Whether to scan forward in the document or backward.
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* @param visitChildren Whether the children of the current node should be visited.
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* @param exitedNodes An array which stores nodes which were exited.
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* @returns The next node in the document, or null if there is no next node.
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*/
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static getNextNode(node, forward, visitChildren, exitedNodes) {
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let next = visitChildren ? (forward ? node.firstChild : node.lastChild) : null;
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if (next === null) {
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while (true) {
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exitedNodes.push(node);
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next = (forward ? node.nextSibling : node.previousSibling);
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if (next !== null) { break; }
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next = node.parentNode;
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if (next === null) { break; }
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node = next;
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}
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}
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return next;
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}
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/**
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* Gets the parent element of a given Node.
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* @param node The node to check.
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* @returns The parent element if one exists, otherwise null.
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*/
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static getParentElement(node) {
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while (node !== null && node.nodeType !== Node.ELEMENT_NODE) {
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node = node.parentNode;
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}
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return node;
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}
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/**
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* Gets the parent <ruby> element of a given node, if one exists. For efficiency purposes,
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* this only checks the immediate parent elements and does not check all ancestors, so
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* there are cases where the node may be in a ruby element but it is not returned.
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* @param node The node to check.
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* @returns A <ruby> node if the input node is contained in one, otherwise null.
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*/
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static getParentRubyElement(node) {
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node = DOMTextScanner.getParentElement(node);
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if (node !== null && node.nodeName.toUpperCase() === 'RT') {
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node = node.parentNode;
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if (node !== null && node.nodeName.toUpperCase() === 'RUBY') {
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return node;
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}
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}
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return null;
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}
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/**
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* @returns [enterable: boolean, newlines: integer]
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* The enterable value indicates whether the content of this node should be entered.
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* The newlines value corresponds to the number of newline characters that should be added.
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* 1 newline corresponds to a simple new line in the layout.
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* 2 newlines corresponds to a significant visual distinction since the previous content.
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*/
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static getElementSeekInfo(element) {
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let enterable = true;
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switch (element.nodeName.toUpperCase()) {
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case 'HEAD':
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case 'RT':
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case 'SCRIPT':
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case 'STYLE':
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return [false, 0];
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case 'BR':
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return [false, 1];
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case 'TEXTAREA':
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case 'INPUT':
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case 'BUTTON':
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enterable = false;
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break;
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}
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const style = window.getComputedStyle(element);
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const display = style.display;
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const visible = (display !== 'none' && DOMTextScanner.isStyleVisible(style));
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let newlines = 0;
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if (!visible) {
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enterable = false;
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} else {
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switch (style.position) {
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case 'absolute':
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case 'fixed':
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case 'sticky':
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newlines = 2;
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break;
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}
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if (newlines === 0 && DOMTextScanner.doesCSSDisplayChangeLayout(display)) {
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newlines = 1;
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}
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}
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return [enterable, newlines];
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}
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/**
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* Gets information about how whitespace characters are treated.
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* @param textNode The Text node to check.
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* @returns [preserveNewlines: boolean, preserveWhitespace: boolean]
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* The value of preserveNewlines indicates whether or not newline characters are treated as line breaks.
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* The value of preserveWhitespace indicates whether or not sequences of whitespace characters are collapsed.
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*/
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static getWhitespaceSettings(textNode) {
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const element = DOMTextScanner.getParentElement(textNode);
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if (element !== null) {
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const style = window.getComputedStyle(element);
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switch (style.whiteSpace) {
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case 'pre':
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case 'pre-wrap':
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case 'break-spaces':
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return [true, true];
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case 'pre-line':
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return [true, false];
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}
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}
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return [false, false];
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}
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/**
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* Gets attributes for the specified character.
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* @param character A string containing a single character.
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* @returns An integer representing the attributes of the character.
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* 0: Character should be ignored.
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* 1: Character is collapsible whitespace.
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* 2: Character should be added to the content.
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* 3: Character should be added to the content and is a newline.
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*/
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static getCharacterAttributes(character, preserveNewlines, preserveWhitespace) {
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switch (character.charCodeAt(0)) {
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case 0x09: // Tab ('\t')
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case 0x0c: // Form feed ('\f')
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case 0x0d: // Carriage return ('\r')
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case 0x20: // Space (' ')
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return preserveWhitespace ? 2 : 1;
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case 0x0a: // Line feed ('\n')
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return preserveNewlines ? 3 : 1;
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case 0x200b: // Zero-width space
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case 0x200c: // Zero-width non-joiner
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return 0;
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default: // Other
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return 2;
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}
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}
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/**
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* Checks whether a given style is visible or not.
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* This function does not check style.display === 'none'.
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* @param style An object implementing the CSSStyleDeclaration interface.
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* @returns true if the style should result in an element being visible, otherwise false.
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*/
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static isStyleVisible(style) {
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return !(
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style.visibility === 'hidden' ||
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parseFloat(style.opacity) <= 0 ||
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parseFloat(style.fontSize) <= 0 ||
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(
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!DOMTextScanner.isStyleSelectable(style) &&
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(
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DOMTextScanner.isCSSColorTransparent(style.color) ||
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DOMTextScanner.isCSSColorTransparent(style.webkitTextFillColor)
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)
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)
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);
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}
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/**
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* Checks whether a given style is selectable or not.
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* @param style An object implementing the CSSStyleDeclaration interface.
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* @returns true if the style is selectable, otherwise false.
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*/
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static isStyleSelectable(style) {
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return !(
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style.userSelect === 'none' ||
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style.webkitUserSelect === 'none' ||
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style.MozUserSelect === 'none' ||
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style.msUserSelect === 'none'
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);
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}
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/**
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* Checks whether a CSS color is transparent or not.
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* @param cssColor A CSS color string, expected to be encoded in rgb(a) form.
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* @returns true if the color is transparent, otherwise false.
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*/
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static isCSSColorTransparent(cssColor) {
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return (
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typeof cssColor === 'string' &&
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cssColor.startsWith('rgba(') &&
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/,\s*0.?0*\)$/.test(cssColor)
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);
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}
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/**
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* Checks whether a CSS display value will cause a layout change for text.
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* @param cssDisplay A CSS string corresponding to the value of the display property.
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* @returns true if the layout is changed by this value, otherwise false.
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*/
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static doesCSSDisplayChangeLayout(cssDisplay) {
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let pos = cssDisplay.indexOf(' ');
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if (pos >= 0) {
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// Truncate to <display-outside> part
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cssDisplay = cssDisplay.substring(0, pos);
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}
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pos = cssDisplay.indexOf('-');
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if (pos >= 0) {
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// Truncate to first part of kebab-case value
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cssDisplay = cssDisplay.substring(0, pos);
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}
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switch (cssDisplay) {
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case 'block':
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case 'flex':
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case 'grid':
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case 'list': // list-item
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case 'table': // table, table-*
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return true;
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case 'ruby': // rubt-*
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return (pos >= 0);
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default:
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return false;
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}
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}
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|
}
|