feat(assets): bundle runtime assets and vendor dependencies

vendor/yomitan/js/dom/text-source-generator.js

@@ -0,0 +1,690 @@
+/*
+ * Copyright (C) 2024-2025  Yomitan Authors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+import {computeZoomScale, isPointInAnyRect} from './document-util.js';
+import {DOMTextScanner} from './dom-text-scanner.js';
+import {TextSourceElement} from './text-source-element.js';
+import {TextSourceRange} from './text-source-range.js';
+
+export class TextSourceGenerator {
+    constructor() {
+        /** @type {RegExp} @readonly */
+        this._transparentColorPattern = /rgba\s*\([^)]*,\s*0(?:\.0+)?\s*\)/;
+        /** @type {import('text-source-generator').GetRangeFromPointHandler[]} @readonly */
+        this._getRangeFromPointHandlers = [];
+    }
+
+    /**
+     * @param {number} x
+     * @param {number} y
+     * @param {import('document-util').GetRangeFromPointOptions} options
+     * @returns {?import('text-source').TextSource}
+     */
+    getRangeFromPoint(x, y, options) {
+        for (const handler of this._getRangeFromPointHandlers) {
+            const result = handler(x, y, options);
+            if (result !== null) { return result; }
+        }
+        return this._getRangeFromPointInternal(x, y, options);
+    }
+
+    /**
+     * Registers a custom handler for scanning for text or elements at the input position.
+     * @param {import('text-source-generator').GetRangeFromPointHandler} handler The handler callback which will be invoked when calling `getRangeFromPoint`.
+     */
+    registerGetRangeFromPointHandler(handler) {
+        this._getRangeFromPointHandlers.push(handler);
+    }
+
+    /**
+     * Extract a sentence from a document.
+     * @param {import('text-source').TextSource} source The text source object, either `TextSourceRange` or `TextSourceElement`.
+     * @param {boolean} layoutAwareScan Whether or not layout-aware scan mode should be used.
+     * @param {number} extent The length of the sentence to extract.
+     * @param {boolean} terminateAtNewlines Whether or not a sentence should be terminated at newline characters.
+     * @param {import('text-scanner').SentenceTerminatorMap} terminatorMap A mapping of characters that terminate a sentence.
+     * @param {import('text-scanner').SentenceForwardQuoteMap} forwardQuoteMap A mapping of quote characters that delimit a sentence.
+     * @param {import('text-scanner').SentenceBackwardQuoteMap} backwardQuoteMap A mapping of quote characters that delimit a sentence, which is the inverse of forwardQuoteMap.
+     * @returns {{text: string, offset: number}} The sentence and the offset to the original source.
+     */
+    extractSentence(source, layoutAwareScan, extent, terminateAtNewlines, terminatorMap, forwardQuoteMap, backwardQuoteMap) {
+        // Scan text
+        source = source.clone();
+        const startLength = source.setStartOffset(extent, layoutAwareScan);
+        const endLength = source.setEndOffset(extent * 2 - startLength, true, layoutAwareScan);
+        const text = [...source.text()];
+        const textLength = text.length;
+        const textEndAnchor = textLength - endLength;
+
+        /** Relative start position of the sentence (inclusive). */
+        let cursorStart = startLength;
+        /** Relative end position of the sentence (exclusive). */
+        let cursorEnd = textEndAnchor;
+
+        // Move backward
+        let quoteStack = [];
+        for (; cursorStart > 0; --cursorStart) {
+            // Check if the previous character should be included.
+            let c = text[cursorStart - 1];
+            if (c === '\n' && terminateAtNewlines) { break; }
+
+            if (quoteStack.length === 0) {
+                let terminatorInfo = terminatorMap.get(c);
+                if (typeof terminatorInfo !== 'undefined') {
+                    // Include the previous character while it is a terminator character and is included at start.
+                    while (terminatorInfo[0] && cursorStart > 0) {
+                        --cursorStart;
+                        if (cursorStart === 0) { break; }
+                        c = text[cursorStart - 1];
+                        terminatorInfo = terminatorMap.get(c);
+                        if (typeof terminatorInfo === 'undefined') { break; }
+                    }
+                    break;
+                }
+            }
+
+            let quoteInfo = forwardQuoteMap.get(c);
+            if (typeof quoteInfo !== 'undefined') {
+                if (quoteStack.length === 0) {
+                    // Include the previous character while it is a quote character and is included at start.
+                    while (quoteInfo[1] && cursorStart > 0) {
+                        --cursorStart;
+                        if (cursorStart === 0) { break; }
+                        c = text[cursorStart - 1];
+                        quoteInfo = forwardQuoteMap.get(c);
+                        if (typeof quoteInfo === 'undefined') { break; }
+                    }
+                    break;
+                } else if (quoteStack[0] === c) {
+                    quoteStack.pop();
+                    continue;
+                }
+            }
+
+            quoteInfo = backwardQuoteMap.get(c);
+            if (typeof quoteInfo !== 'undefined') {
+                quoteStack.unshift(quoteInfo[0]);
+            }
+        }
+
+        // Move forward
+        quoteStack = [];
+        for (; cursorEnd < textLength; ++cursorEnd) {
+            // Check if the following character should be included.
+            let c = text[cursorEnd];
+            if (c === '\n' && terminateAtNewlines) { break; }
+
+            if (quoteStack.length === 0) {
+                let terminatorInfo = terminatorMap.get(c);
+                if (typeof terminatorInfo !== 'undefined') {
+                    // Include the following character while it is a terminator character and is included at end.
+                    while (terminatorInfo[1] && cursorEnd < textLength) {
+                        ++cursorEnd;
+                        if (cursorEnd === textLength) { break; }
+                        c = text[cursorEnd];
+                        terminatorInfo = terminatorMap.get(c);
+                        if (typeof terminatorInfo === 'undefined') { break; }
+                    }
+                    break;
+                }
+            }
+
+            let quoteInfo = backwardQuoteMap.get(c);
+            if (typeof quoteInfo !== 'undefined') {
+                if (quoteStack.length === 0) {
+                    // Include the following character while it is a quote character and is included at end.
+                    while (quoteInfo[1] && cursorEnd < textLength) {
+                        ++cursorEnd;
+                        if (cursorEnd === textLength) { break; }
+                        c = text[cursorEnd];
+                        quoteInfo = forwardQuoteMap.get(c);
+                        if (typeof quoteInfo === 'undefined') { break; }
+                    }
+                    break;
+                } else if (quoteStack[0] === c) {
+                    quoteStack.pop();
+                    continue;
+                }
+            }
+
+            quoteInfo = forwardQuoteMap.get(c);
+            if (typeof quoteInfo !== 'undefined') {
+                quoteStack.unshift(quoteInfo[0]);
+            }
+        }
+
+        // Trim whitespace
+        for (; cursorStart < startLength && this._isWhitespace(text[cursorStart]); ++cursorStart) { /* NOP */ }
+        for (; cursorEnd > textEndAnchor && this._isWhitespace(text[cursorEnd - 1]); --cursorEnd) { /* NOP */ }
+
+        // Result
+        return {
+            text: text.slice(cursorStart, cursorEnd).join(''),
+            offset: startLength - cursorStart,
+        };
+    }
+
+    /**
+     * Scans the document for text or elements with text information at the given coordinate.
+     * Coordinates are provided in [client space](https://developer.mozilla.org/en-US/docs/Web/CSS/CSSOM_View/Coordinate_systems).
+     * @param {number} x The x coordinate to search at.
+     * @param {number} y The y coordinate to search at.
+     * @param {import('document-util').GetRangeFromPointOptions} options Options to configure how element detection is performed.
+     * @returns {?import('text-source').TextSource} A range for the hovered text or element, or `null` if no applicable content was found.
+     */
+    _getRangeFromPointInternal(x, y, options) {
+        const {deepContentScan, normalizeCssZoom, language} = options;
+
+        const elements = this._getElementsFromPoint(x, y, deepContentScan);
+        /** @type {?HTMLDivElement} */
+        let imposter = null;
+        /** @type {?HTMLDivElement} */
+        let imposterContainer = null;
+        /** @type {?Element} */
+        let imposterSourceElement = null;
+        if (elements.length > 0) {
+            const element = elements[0];
+            switch (element.nodeName.toUpperCase()) {
+                case 'IMG':
+                case 'BUTTON':
+                case 'SELECT':
+                    return TextSourceElement.create(element);
+                case 'INPUT':
+                    if (
+                        /** @type {HTMLInputElement} */ (element).type === 'text' ||
+                        /** @type {HTMLInputElement} */ (element).type === 'search'
+                    ) {
+                        imposterSourceElement = element;
+                        [imposter, imposterContainer] = this._createImposter(/** @type {HTMLInputElement} */ (element), false);
+                    }
+                    break;
+                case 'TEXTAREA':
+                    imposterSourceElement = element;
+                    [imposter, imposterContainer] = this._createImposter(/** @type {HTMLTextAreaElement} */ (element), true);
+                    break;
+            }
+        }
+
+        const range = this._caretRangeFromPointExt(x, y, deepContentScan ? elements : [], normalizeCssZoom, language);
+        if (range !== null) {
+            if (imposter !== null) {
+                this._setImposterStyle(/** @type {HTMLDivElement} */ (imposterContainer).style, 'z-index', '-2147483646');
+                this._setImposterStyle(imposter.style, 'pointer-events', 'none');
+                return TextSourceRange.createFromImposter(range, /** @type {HTMLDivElement} */ (imposterContainer), /** @type {HTMLElement} */ (imposterSourceElement));
+            }
+            return TextSourceRange.create(range);
+        } else {
+            if (imposterContainer !== null) {
+                const {parentNode} = imposterContainer;
+                if (parentNode !== null) {
+                    parentNode.removeChild(imposterContainer);
+                }
+            }
+            return null;
+        }
+    }
+
+    /**
+     * @param {CSSStyleDeclaration} style
+     * @param {string} propertyName
+     * @param {string} value
+     */
+    _setImposterStyle(style, propertyName, value) {
+        style.setProperty(propertyName, value, 'important');
+    }
+
+    /**
+     * @param {HTMLInputElement|HTMLTextAreaElement} element
+     * @param {boolean} isTextarea
+     * @returns {[imposter: ?HTMLDivElement, container: ?HTMLDivElement]}
+     */
+    _createImposter(element, isTextarea) {
+        const body = document.body;
+        if (body === null) { return [null, null]; }
+
+        const elementStyle = window.getComputedStyle(element);
+        const elementRect = element.getBoundingClientRect();
+        const documentRect = document.documentElement.getBoundingClientRect();
+        let left = elementRect.left - documentRect.left;
+        let top = elementRect.top - documentRect.top;
+
+        // Container
+        const container = document.createElement('div');
+        const containerStyle = container.style;
+        this._setImposterStyle(containerStyle, 'all', 'initial');
+        this._setImposterStyle(containerStyle, 'position', 'absolute');
+        this._setImposterStyle(containerStyle, 'left', '0');
+        this._setImposterStyle(containerStyle, 'top', '0');
+        this._setImposterStyle(containerStyle, 'width', `${documentRect.width}px`);
+        this._setImposterStyle(containerStyle, 'height', `${documentRect.height}px`);
+        this._setImposterStyle(containerStyle, 'overflow', 'hidden');
+        this._setImposterStyle(containerStyle, 'opacity', '0');
+        this._setImposterStyle(containerStyle, 'pointer-events', 'none');
+        this._setImposterStyle(containerStyle, 'z-index', '2147483646');
+
+        // Imposter
+        const imposter = document.createElement('div');
+        const imposterStyle = imposter.style;
+
+        let value = element.value;
+        if (value.endsWith('\n')) { value += '\n'; }
+        imposter.textContent = value;
+
+        for (let i = 0, ii = elementStyle.length; i < ii; ++i) {
+            const property = elementStyle[i];
+            this._setImposterStyle(imposterStyle, property, elementStyle.getPropertyValue(property));
+        }
+        this._setImposterStyle(imposterStyle, 'position', 'absolute');
+        this._setImposterStyle(imposterStyle, 'top', `${top}px`);
+        this._setImposterStyle(imposterStyle, 'left', `${left}px`);
+        this._setImposterStyle(imposterStyle, 'margin', '0');
+        this._setImposterStyle(imposterStyle, 'pointer-events', 'auto');
+
+        if (isTextarea) {
+            if (elementStyle.overflow === 'visible') {
+                this._setImposterStyle(imposterStyle, 'overflow', 'auto');
+            }
+        } else {
+            this._setImposterStyle(imposterStyle, 'overflow', 'hidden');
+            this._setImposterStyle(imposterStyle, 'white-space', 'nowrap');
+            this._setImposterStyle(imposterStyle, 'line-height', elementStyle.height);
+        }
+
+        container.appendChild(imposter);
+        body.appendChild(container);
+
+        // Adjust size
+        const imposterRect = imposter.getBoundingClientRect();
+        if (imposterRect.width !== elementRect.width || imposterRect.height !== elementRect.height) {
+            const width = Number.parseFloat(elementStyle.width) + (elementRect.width - imposterRect.width);
+            const height = Number.parseFloat(elementStyle.height) + (elementRect.height - imposterRect.height);
+            this._setImposterStyle(imposterStyle, 'width', `${width}px`);
+            this._setImposterStyle(imposterStyle, 'height', `${height}px`);
+        }
+        if (imposterRect.left !== elementRect.left || imposterRect.top !== elementRect.top) {
+            left += (elementRect.left - imposterRect.left);
+            top += (elementRect.top - imposterRect.top);
+            this._setImposterStyle(imposterStyle, 'left', `${left}px`);
+            this._setImposterStyle(imposterStyle, 'top', `${top}px`);
+        }
+
+        imposter.scrollTop = element.scrollTop;
+        imposter.scrollLeft = element.scrollLeft;
+
+        return [imposter, container];
+    }
+
+    /**
+     * @param {number} x
+     * @param {number} y
+     * @param {boolean} all
+     * @returns {Element[]}
+     */
+    _getElementsFromPoint(x, y, all) {
+        if (all) {
+            // document.elementsFromPoint can return duplicates which must be removed.
+            const elements = document.elementsFromPoint(x, y);
+            return elements.filter((e, i) => elements.indexOf(e) === i);
+        }
+
+        const e = document.elementFromPoint(x, y);
+        return e !== null ? [e] : [];
+    }
+
+    /**
+     * @param {number} x
+     * @param {number} y
+     * @param {Range} range
+     * @param {boolean} normalizeCssZoom
+     * @param {?string} language
+     * @returns {boolean}
+     */
+    _isPointInRange(x, y, range, normalizeCssZoom, language) {
+        // Require a text node to start
+        const {startContainer} = range;
+        if (startContainer.nodeType !== Node.TEXT_NODE) {
+            return false;
+        }
+
+        // Convert CSS zoom coordinates
+        if (normalizeCssZoom) {
+            const scale = computeZoomScale(startContainer);
+            x /= scale;
+            y /= scale;
+        }
+
+        // Scan forward
+        const nodePre = range.endContainer;
+        const offsetPre = range.endOffset;
+        try {
+            const {node, offset, content} = new DOMTextScanner(nodePre, offsetPre, true, false).seek(1);
+            range.setEnd(node, offset);
+
+            if (!this._isWhitespace(content) && isPointInAnyRect(x, y, range.getClientRects(), language)) {
+                return true;
+            }
+        } finally {
+            range.setEnd(nodePre, offsetPre);
+        }
+
+        // Scan backward
+        const {node, offset, content} = new DOMTextScanner(startContainer, range.startOffset, true, false).seek(-1);
+        range.setStart(node, offset);
+
+        if (!this._isWhitespace(content) && isPointInAnyRect(x, y, range.getClientRects(), language)) {
+            // This purposefully leaves the starting offset as modified and sets the range length to 0.
+            range.setEnd(node, offset);
+            return true;
+        }
+
+        // No match
+        return false;
+    }
+
+    /**
+     * @param {number} x
+     * @param {number} y
+     * @returns {?Range}
+     */
+    _caretRangeFromPoint(x, y) {
+        if (typeof document.caretPositionFromPoint === 'function') {
+            // Firefox
+            // 128+ Chrome, Edge
+            const caretPositionFromPointResult = this._caretPositionFromPoint(x, y);
+            // Older Chromium based browsers (such as Kiwi) pretend to support `caretPositionFromPoint` but it doesn't work
+            // Allow falling through if `caretPositionFromPointResult` is null to let `caretRangeFromPoint` be used in these cases
+            if (caretPositionFromPointResult) {
+                return caretPositionFromPointResult;
+            }
+        }
+
+        if (typeof document.caretRangeFromPoint === 'function') {
+            // Fallback Chrome, Edge
+            return document.caretRangeFromPoint(x, y);
+        }
+
+        // No support
+        return null;
+    }
+
+    /**
+     * @param {Element | ShadowRoot} inputElement
+     * @returns {ShadowRoot[]}
+     */
+    _findShadowRoots(inputElement) {
+        const allElements = [inputElement, ...inputElement.querySelectorAll('*')];
+        /** @type {Element[]} */
+        const shadowRootContainingElements = [];
+        for (const element of allElements) {
+            if (!(element instanceof ShadowRoot) && !!element.shadowRoot) {
+                shadowRootContainingElements.push(element);
+            }
+        }
+        /** @type {ShadowRoot[]} */
+        const shadowRoots = [];
+        for (const element of shadowRootContainingElements) {
+            if (element.shadowRoot) {
+                shadowRoots.push(element.shadowRoot);
+                const nestedShadowRoots = this._findShadowRoots(element.shadowRoot);
+                if (nestedShadowRoots) {
+                    shadowRoots.push(...nestedShadowRoots);
+                }
+            }
+        }
+        return shadowRoots;
+    }
+
+    /**
+     * @param {number} x
+     * @param {number} y
+     * @returns {?Range}
+     */
+    _caretPositionFromPoint(x, y) {
+        const documentCaretPositionFromPoint = document.caretPositionFromPoint(x, y);
+        const documentCaretPositionOffsetNode = documentCaretPositionFromPoint?.offsetNode;
+
+        // nodeName `#text` indicates we have already drilled down as far as required to scan the text
+        const shadowRootSearchRequired = documentCaretPositionOffsetNode instanceof Element && documentCaretPositionOffsetNode.nodeName !== '#text';
+        const shadowRoots = shadowRootSearchRequired ? this._findShadowRoots(documentCaretPositionOffsetNode) : [];
+
+        const position = shadowRoots.length > 0 ? document.caretPositionFromPoint(x, y, {shadowRoots: shadowRoots}) : documentCaretPositionFromPoint;
+        if (position === null) {
+            return null;
+        }
+        const node = position.offsetNode;
+        if (node === null) {
+            return null;
+        }
+
+        let offset = 0;
+        const {nodeType} = node;
+        switch (nodeType) {
+            case Node.TEXT_NODE:
+                offset = position.offset;
+                break;
+            case Node.ELEMENT_NODE:
+                // Elements with user-select: all will return the element
+                // instead of a text point inside the element.
+                if (this._isElementUserSelectAll(/** @type {Element} */ (node))) {
+                    return this._caretPositionFromPointNormalizeStyles(x, y, /** @type {Element} */ (node));
+                }
+                break;
+        }
+
+        try {
+            const range = document.createRange();
+            range.setStart(node, offset);
+            range.setEnd(node, offset);
+            return range;
+        } catch (e) {
+            // Firefox throws new DOMException("The operation is insecure.")
+            // when trying to select a node from within a ShadowRoot.
+            return null;
+        }
+    }
+
+    /**
+     * @param {number} x
+     * @param {number} y
+     * @param {Element} nextElement
+     * @returns {?Range}
+     */
+    _caretPositionFromPointNormalizeStyles(x, y, nextElement) {
+        /** @type {Map<Element, ?string>} */
+        const previousStyles = new Map();
+        try {
+            while (true) {
+                if (nextElement instanceof HTMLElement) {
+                    this._recordPreviousStyle(previousStyles, nextElement);
+                    nextElement.style.setProperty('user-select', 'text', 'important');
+                }
+
+                const position = /** @type {(x: number, y: number) => ?{offsetNode: Node, offset: number}} */ (document.caretPositionFromPoint)(x, y);
+                if (position === null) {
+                    return null;
+                }
+                const node = position.offsetNode;
+                if (node === null) {
+                    return null;
+                }
+
+                let offset = 0;
+                const {nodeType} = node;
+                switch (nodeType) {
+                    case Node.TEXT_NODE:
+                        offset = position.offset;
+                        break;
+                    case Node.ELEMENT_NODE:
+                        // Elements with user-select: all will return the element
+                        // instead of a text point inside the element.
+                        if (this._isElementUserSelectAll(/** @type {Element} */ (node))) {
+                            if (previousStyles.has(/** @type {Element} */ (node))) {
+                                // Recursive
+                                return null;
+                            }
+                            nextElement = /** @type {Element} */ (node);
+                            continue;
+                        }
+                        break;
+                }
+
+                try {
+                    const range = document.createRange();
+                    range.setStart(node, offset);
+                    range.setEnd(node, offset);
+                    return range;
+                } catch (e) {
+                    // Firefox throws new DOMException("The operation is insecure.")
+                    // when trying to select a node from within a ShadowRoot.
+                    return null;
+                }
+            }
+        } finally {
+            this._revertStyles(previousStyles);
+        }
+    }
+
+    /**
+     * @param {number} x
+     * @param {number} y
+     * @param {Element[]} elements
+     * @param {boolean} normalizeCssZoom
+     * @param {?string} language
+     * @returns {?Range}
+     */
+    _caretRangeFromPointExt(x, y, elements, normalizeCssZoom, language) {
+        /** @type {?Map<Element, ?string>} */
+        let previousStyles = null;
+        try {
+            let i = 0;
+            let startContainerPre = null;
+            while (true) {
+                const range = this._caretRangeFromPoint(x, y);
+                if (range === null) {
+                    return null;
+                }
+
+                const startContainer = range.startContainer;
+                if (startContainerPre !== startContainer) {
+                    if (this._isPointInRange(x, y, range, normalizeCssZoom, language)) {
+                        return range;
+                    }
+                    startContainerPre = startContainer;
+                }
+
+                if (previousStyles === null) { previousStyles = new Map(); }
+                i = this._disableTransparentElement(elements, i, previousStyles);
+                if (i < 0) {
+                    return null;
+                }
+            }
+        } finally {
+            if (previousStyles !== null && previousStyles.size > 0) {
+                this._revertStyles(previousStyles);
+            }
+        }
+    }
+
+    /**
+     * @param {Element[]} elements
+     * @param {number} i
+     * @param {Map<Element, ?string>} previousStyles
+     * @returns {number}
+     */
+    _disableTransparentElement(elements, i, previousStyles) {
+        while (true) {
+            if (i >= elements.length) {
+                return -1;
+            }
+
+            const element = elements[i++];
+            if (this._isElementTransparent(element)) {
+                if (element instanceof HTMLElement) {
+                    this._recordPreviousStyle(previousStyles, element);
+                    element.style.setProperty('pointer-events', 'none', 'important');
+                }
+                return i;
+            }
+        }
+    }
+
+    /**
+     * @param {Map<Element, ?string>} previousStyles
+     * @param {Element} element
+     */
+    _recordPreviousStyle(previousStyles, element) {
+        if (previousStyles.has(element)) { return; }
+        const style = element.hasAttribute('style') ? element.getAttribute('style') : null;
+        previousStyles.set(element, style);
+    }
+
+    /**
+     * @param {Map<Element, ?string>} previousStyles
+     */
+    _revertStyles(previousStyles) {
+        for (const [element, style] of previousStyles.entries()) {
+            if (style === null) {
+                element.removeAttribute('style');
+            } else {
+                element.setAttribute('style', style);
+            }
+        }
+    }
+
+    /**
+     * @param {Element} element
+     * @returns {boolean}
+     */
+    _isElementTransparent(element) {
+        if (
+            element === document.body ||
+            element === document.documentElement
+        ) {
+            return false;
+        }
+        const style = window.getComputedStyle(element);
+        return (
+            Number.parseFloat(style.opacity) <= 0 ||
+            style.visibility === 'hidden' ||
+            (style.backgroundImage === 'none' && this._isColorTransparent(style.backgroundColor))
+        );
+    }
+
+    /**
+     * @param {string} cssColor
+     * @returns {boolean}
+     */
+    _isColorTransparent(cssColor) {
+        return this._transparentColorPattern.test(cssColor);
+    }
+
+    /**
+     * @param {Element} element
+     * @returns {boolean}
+     */
+    _isElementUserSelectAll(element) {
+        return getComputedStyle(element).userSelect === 'all';
+    }
+
+    /**
+     * @param {string} string
+     * @returns {boolean}
+     */
+    _isWhitespace(string) {
+        return string.trim().length === 0;
+    }
+}