pdfjs-dist/lib/web/text_highlighter.js

/**
 * @licstart The following is the entire license notice for the
 * JavaScript code in this page
 *
 * Copyright 2022 Mozilla Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * @licend The above is the entire license notice for the
 * JavaScript code in this page
 */
"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.TextHighlighter = void 0;

class TextHighlighter {
  constructor({
    findController,
    eventBus,
    pageIndex
  }) {
    this.findController = findController;
    this.matches = [];
    this.eventBus = eventBus;
    this.pageIdx = pageIndex;
    this._onUpdateTextLayerMatches = null;
    this.textDivs = null;
    this.textContentItemsStr = null;
    this.enabled = false;
  }

  setTextMapping(divs, texts) {
    this.textDivs = divs;
    this.textContentItemsStr = texts;
  }

  enable() {
    if (!this.textDivs || !this.textContentItemsStr) {
      throw new Error("Text divs and strings have not been set.");
    }

    if (this.enabled) {
      throw new Error("TextHighlighter is already enabled.");
    }

    this.enabled = true;

    if (!this._onUpdateTextLayerMatches) {
      this._onUpdateTextLayerMatches = evt => {
        if (evt.pageIndex === this.pageIdx || evt.pageIndex === -1) {
          this._updateMatches();
        }
      };

      this.eventBus._on("updatetextlayermatches", this._onUpdateTextLayerMatches);
    }

    this._updateMatches();
  }

  disable() {
    if (!this.enabled) {
      return;
    }

    this.enabled = false;

    if (this._onUpdateTextLayerMatches) {
      this.eventBus._off("updatetextlayermatches", this._onUpdateTextLayerMatches);

      this._onUpdateTextLayerMatches = null;
    }
  }

  _convertMatches(matches, matchesLength) {
    if (!matches) {
      return [];
    }

    const {
      textContentItemsStr
    } = this;
    let i = 0,
        iIndex = 0;
    const end = textContentItemsStr.length - 1;
    const result = [];

    for (let m = 0, mm = matches.length; m < mm; m++) {
      let matchIdx = matches[m];

      while (i !== end && matchIdx >= iIndex + textContentItemsStr[i].length) {
        iIndex += textContentItemsStr[i].length;
        i++;
      }

      if (i === textContentItemsStr.length) {
        console.error("Could not find a matching mapping");
      }

      const match = {
        begin: {
          divIdx: i,
          offset: matchIdx - iIndex
        }
      };
      matchIdx += matchesLength[m];

      while (i !== end && matchIdx > iIndex + textContentItemsStr[i].length) {
        iIndex += textContentItemsStr[i].length;
        i++;
      }

      match.end = {
        divIdx: i,
        offset: matchIdx - iIndex
      };
      result.push(match);
    }

    return result;
  }

  _renderMatches(matches) {
    if (matches.length === 0) {
      return;
    }

    const {
      findController,
      pageIdx
    } = this;
    const {
      textContentItemsStr,
      textDivs
    } = this;
    const isSelectedPage = pageIdx === findController.selected.pageIdx;
    const selectedMatchIdx = findController.selected.matchIdx;
    const highlightAll = findController.state.highlightAll;
    let prevEnd = null;
    const infinity = {
      divIdx: -1,
      offset: undefined
    };

    function beginText(begin, className) {
      const divIdx = begin.divIdx;
      textDivs[divIdx].textContent = "";
      return appendTextToDiv(divIdx, 0, begin.offset, className);
    }

    function appendTextToDiv(divIdx, fromOffset, toOffset, className) {
      let div = textDivs[divIdx];

      if (div.nodeType === Node.TEXT_NODE) {
        const span = document.createElement("span");
        div.before(span);
        span.append(div);
        textDivs[divIdx] = span;
        div = span;
      }

      const content = textContentItemsStr[divIdx].substring(fromOffset, toOffset);
      const node = document.createTextNode(content);

      if (className) {
        const span = document.createElement("span");
        span.className = `${className} appended`;
        span.append(node);
        div.append(span);
        return className.includes("selected") ? span.offsetLeft : 0;
      }

      div.append(node);
      return 0;
    }

    let i0 = selectedMatchIdx,
        i1 = i0 + 1;

    if (highlightAll) {
      i0 = 0;
      i1 = matches.length;
    } else if (!isSelectedPage) {
      return;
    }

    for (let i = i0; i < i1; i++) {
      const match = matches[i];
      const begin = match.begin;
      const end = match.end;
      const isSelected = isSelectedPage && i === selectedMatchIdx;
      const highlightSuffix = isSelected ? " selected" : "";
      let selectedLeft = 0;

      if (!prevEnd || begin.divIdx !== prevEnd.divIdx) {
        if (prevEnd !== null) {
          appendTextToDiv(prevEnd.divIdx, prevEnd.offset, infinity.offset);
        }

        beginText(begin);
      } else {
        appendTextToDiv(prevEnd.divIdx, prevEnd.offset, begin.offset);
      }

      if (begin.divIdx === end.divIdx) {
        selectedLeft = appendTextToDiv(begin.divIdx, begin.offset, end.offset, "highlight" + highlightSuffix);
      } else {
        selectedLeft = appendTextToDiv(begin.divIdx, begin.offset, infinity.offset, "highlight begin" + highlightSuffix);

        for (let n0 = begin.divIdx + 1, n1 = end.divIdx; n0 < n1; n0++) {
          textDivs[n0].className = "highlight middle" + highlightSuffix;
        }

        beginText(end, "highlight end" + highlightSuffix);
      }

      prevEnd = end;

      if (isSelected) {
        findController.scrollMatchIntoView({
          element: textDivs[begin.divIdx],
          selectedLeft,
          pageIndex: pageIdx,
          matchIndex: selectedMatchIdx
        });
      }
    }

    if (prevEnd) {
      appendTextToDiv(prevEnd.divIdx, prevEnd.offset, infinity.offset);
    }
  }

  _updateMatches() {
    if (!this.enabled) {
      return;
    }

    const {
      findController,
      matches,
      pageIdx
    } = this;
    const {
      textContentItemsStr,
      textDivs
    } = this;
    let clearedUntilDivIdx = -1;

    for (let i = 0, ii = matches.length; i < ii; i++) {
      const match = matches[i];
      const begin = Math.max(clearedUntilDivIdx, match.begin.divIdx);

      for (let n = begin, end = match.end.divIdx; n <= end; n++) {
        const div = textDivs[n];
        div.textContent = textContentItemsStr[n];
        div.className = "";
      }

      clearedUntilDivIdx = match.end.divIdx + 1;
    }

    if (!findController?.highlightMatches) {
      return;
    }

    const pageMatches = findController.pageMatches[pageIdx] || null;
    const pageMatchesLength = findController.pageMatchesLength[pageIdx] || null;
    this.matches = this._convertMatches(pageMatches, pageMatchesLength);

    this._renderMatches(this.matches);
  }

}

exports.TextHighlighter = TextHighlighter;