pdfjs-dist/lib/display/text_layer.js

/**
 * @licstart The following is the entire license notice for the
 * Javascript code in this page
 *
 * Copyright 2021 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.renderTextLayer = renderTextLayer;

var _util = require("../shared/util.js");

const MAX_TEXT_DIVS_TO_RENDER = 100000;
const DEFAULT_FONT_SIZE = 30;
const DEFAULT_FONT_ASCENT = 0.8;
const ascentCache = new Map();
const AllWhitespaceRegexp = /^\s+$/g;

function getAscent(fontFamily, ctx) {
  const cachedAscent = ascentCache.get(fontFamily);

  if (cachedAscent) {
    return cachedAscent;
  }

  ctx.save();
  ctx.font = `${DEFAULT_FONT_SIZE}px ${fontFamily}`;
  const metrics = ctx.measureText("");
  let ascent = metrics.fontBoundingBoxAscent;
  let descent = Math.abs(metrics.fontBoundingBoxDescent);

  if (ascent) {
    ctx.restore();
    const ratio = ascent / (ascent + descent);
    ascentCache.set(fontFamily, ratio);
    return ratio;
  }

  ctx.strokeStyle = "red";
  ctx.clearRect(0, 0, DEFAULT_FONT_SIZE, DEFAULT_FONT_SIZE);
  ctx.strokeText("g", 0, 0);
  let pixels = ctx.getImageData(0, 0, DEFAULT_FONT_SIZE, DEFAULT_FONT_SIZE).data;
  descent = 0;

  for (let i = pixels.length - 1 - 3; i >= 0; i -= 4) {
    if (pixels[i] > 0) {
      descent = Math.ceil(i / 4 / DEFAULT_FONT_SIZE);
      break;
    }
  }

  ctx.clearRect(0, 0, DEFAULT_FONT_SIZE, DEFAULT_FONT_SIZE);
  ctx.strokeText("A", 0, DEFAULT_FONT_SIZE);
  pixels = ctx.getImageData(0, 0, DEFAULT_FONT_SIZE, DEFAULT_FONT_SIZE).data;
  ascent = 0;

  for (let i = 0, ii = pixels.length; i < ii; i += 4) {
    if (pixels[i] > 0) {
      ascent = DEFAULT_FONT_SIZE - Math.floor(i / 4 / DEFAULT_FONT_SIZE);
      break;
    }
  }

  ctx.restore();

  if (ascent) {
    const ratio = ascent / (ascent + descent);
    ascentCache.set(fontFamily, ratio);
    return ratio;
  }

  ascentCache.set(fontFamily, DEFAULT_FONT_ASCENT);
  return DEFAULT_FONT_ASCENT;
}

function appendText(task, geom, styles, ctx) {
  const textDiv = document.createElement("span");
  const textDivProperties = task._enhanceTextSelection ? {
    angle: 0,
    canvasWidth: 0,
    hasText: geom.str !== "",
    hasEOL: geom.hasEOL,
    originalTransform: null,
    paddingBottom: 0,
    paddingLeft: 0,
    paddingRight: 0,
    paddingTop: 0,
    scale: 1
  } : {
    angle: 0,
    canvasWidth: 0,
    hasText: geom.str !== "",
    hasEOL: geom.hasEOL
  };

  task._textDivs.push(textDiv);

  const tx = _util.Util.transform(task._viewport.transform, geom.transform);

  let angle = Math.atan2(tx[1], tx[0]);
  const style = styles[geom.fontName];

  if (style.vertical) {
    angle += Math.PI / 2;
  }

  const fontHeight = Math.hypot(tx[2], tx[3]);
  const fontAscent = fontHeight * getAscent(style.fontFamily, ctx);
  let left, top;

  if (angle === 0) {
    left = tx[4];
    top = tx[5] - fontAscent;
  } else {
    left = tx[4] + fontAscent * Math.sin(angle);
    top = tx[5] - fontAscent * Math.cos(angle);
  }

  textDiv.style.left = `${left}px`;
  textDiv.style.top = `${top}px`;
  textDiv.style.fontSize = `${fontHeight}px`;
  textDiv.style.fontFamily = style.fontFamily;
  textDiv.setAttribute("role", "presentation");
  textDiv.textContent = geom.str;
  textDiv.dir = geom.dir;

  if (task._fontInspectorEnabled) {
    textDiv.dataset.fontName = geom.fontName;
  }

  if (angle !== 0) {
    textDivProperties.angle = angle * (180 / Math.PI);
  }

  let shouldScaleText = false;

  if (geom.str.length > 1 || task._enhanceTextSelection && AllWhitespaceRegexp.test(geom.str)) {
    shouldScaleText = true;
  } else if (geom.str !== " " && geom.transform[0] !== geom.transform[3]) {
    const absScaleX = Math.abs(geom.transform[0]),
          absScaleY = Math.abs(geom.transform[3]);

    if (absScaleX !== absScaleY && Math.max(absScaleX, absScaleY) / Math.min(absScaleX, absScaleY) > 1.5) {
      shouldScaleText = true;
    }
  }

  if (shouldScaleText) {
    if (style.vertical) {
      textDivProperties.canvasWidth = geom.height * task._viewport.scale;
    } else {
      textDivProperties.canvasWidth = geom.width * task._viewport.scale;
    }
  }

  task._textDivProperties.set(textDiv, textDivProperties);

  if (task._textContentStream) {
    task._layoutText(textDiv);
  }

  if (task._enhanceTextSelection && textDivProperties.hasText) {
    let angleCos = 1,
        angleSin = 0;

    if (angle !== 0) {
      angleCos = Math.cos(angle);
      angleSin = Math.sin(angle);
    }

    const divWidth = (style.vertical ? geom.height : geom.width) * task._viewport.scale;
    const divHeight = fontHeight;
    let m, b;

    if (angle !== 0) {
      m = [angleCos, angleSin, -angleSin, angleCos, left, top];
      b = _util.Util.getAxialAlignedBoundingBox([0, 0, divWidth, divHeight], m);
    } else {
      b = [left, top, left + divWidth, top + divHeight];
    }

    task._bounds.push({
      left: b[0],
      top: b[1],
      right: b[2],
      bottom: b[3],
      div: textDiv,
      size: [divWidth, divHeight],
      m
    });
  }
}

function render(task) {
  if (task._canceled) {
    return;
  }

  const textDivs = task._textDivs;
  const capability = task._capability;
  const textDivsLength = textDivs.length;

  if (textDivsLength > MAX_TEXT_DIVS_TO_RENDER) {
    task._renderingDone = true;
    capability.resolve();
    return;
  }

  if (!task._textContentStream) {
    for (let i = 0; i < textDivsLength; i++) {
      task._layoutText(textDivs[i]);
    }
  }

  task._renderingDone = true;
  capability.resolve();
}

function findPositiveMin(ts, offset, count) {
  let result = 0;

  for (let i = 0; i < count; i++) {
    const t = ts[offset++];

    if (t > 0) {
      result = result ? Math.min(t, result) : t;
    }
  }

  return result;
}

function expand(task) {
  const bounds = task._bounds;
  const viewport = task._viewport;
  const expanded = expandBounds(viewport.width, viewport.height, bounds);

  for (let i = 0; i < expanded.length; i++) {
    const div = bounds[i].div;

    const divProperties = task._textDivProperties.get(div);

    if (divProperties.angle === 0) {
      divProperties.paddingLeft = bounds[i].left - expanded[i].left;
      divProperties.paddingTop = bounds[i].top - expanded[i].top;
      divProperties.paddingRight = expanded[i].right - bounds[i].right;
      divProperties.paddingBottom = expanded[i].bottom - bounds[i].bottom;

      task._textDivProperties.set(div, divProperties);

      continue;
    }

    const e = expanded[i],
          b = bounds[i];
    const m = b.m,
          c = m[0],
          s = m[1];
    const points = [[0, 0], [0, b.size[1]], [b.size[0], 0], b.size];
    const ts = new Float64Array(64);

    for (let j = 0, jj = points.length; j < jj; j++) {
      const t = _util.Util.applyTransform(points[j], m);

      ts[j + 0] = c && (e.left - t[0]) / c;
      ts[j + 4] = s && (e.top - t[1]) / s;
      ts[j + 8] = c && (e.right - t[0]) / c;
      ts[j + 12] = s && (e.bottom - t[1]) / s;
      ts[j + 16] = s && (e.left - t[0]) / -s;
      ts[j + 20] = c && (e.top - t[1]) / c;
      ts[j + 24] = s && (e.right - t[0]) / -s;
      ts[j + 28] = c && (e.bottom - t[1]) / c;
      ts[j + 32] = c && (e.left - t[0]) / -c;
      ts[j + 36] = s && (e.top - t[1]) / -s;
      ts[j + 40] = c && (e.right - t[0]) / -c;
      ts[j + 44] = s && (e.bottom - t[1]) / -s;
      ts[j + 48] = s && (e.left - t[0]) / s;
      ts[j + 52] = c && (e.top - t[1]) / -c;
      ts[j + 56] = s && (e.right - t[0]) / s;
      ts[j + 60] = c && (e.bottom - t[1]) / -c;
    }

    const boxScale = 1 + Math.min(Math.abs(c), Math.abs(s));
    divProperties.paddingLeft = findPositiveMin(ts, 32, 16) / boxScale;
    divProperties.paddingTop = findPositiveMin(ts, 48, 16) / boxScale;
    divProperties.paddingRight = findPositiveMin(ts, 0, 16) / boxScale;
    divProperties.paddingBottom = findPositiveMin(ts, 16, 16) / boxScale;

    task._textDivProperties.set(div, divProperties);
  }
}

function expandBounds(width, height, boxes) {
  const bounds = boxes.map(function (box, i) {
    return {
      x1: box.left,
      y1: box.top,
      x2: box.right,
      y2: box.bottom,
      index: i,
      x1New: undefined,
      x2New: undefined
    };
  });
  expandBoundsLTR(width, bounds);
  const expanded = new Array(boxes.length);

  for (const b of bounds) {
    const i = b.index;
    expanded[i] = {
      left: b.x1New,
      top: 0,
      right: b.x2New,
      bottom: 0
    };
  }

  boxes.map(function (box, i) {
    const e = expanded[i],
          b = bounds[i];
    b.x1 = box.top;
    b.y1 = width - e.right;
    b.x2 = box.bottom;
    b.y2 = width - e.left;
    b.index = i;
    b.x1New = undefined;
    b.x2New = undefined;
  });
  expandBoundsLTR(height, bounds);

  for (const b of bounds) {
    const i = b.index;
    expanded[i].top = b.x1New;
    expanded[i].bottom = b.x2New;
  }

  return expanded;
}

function expandBoundsLTR(width, bounds) {
  bounds.sort(function (a, b) {
    return a.x1 - b.x1 || a.index - b.index;
  });
  const fakeBoundary = {
    x1: -Infinity,
    y1: -Infinity,
    x2: 0,
    y2: Infinity,
    index: -1,
    x1New: 0,
    x2New: 0
  };
  const horizon = [{
    start: -Infinity,
    end: Infinity,
    boundary: fakeBoundary
  }];

  for (const boundary of bounds) {
    let i = 0;

    while (i < horizon.length && horizon[i].end <= boundary.y1) {
      i++;
    }

    let j = horizon.length - 1;

    while (j >= 0 && horizon[j].start >= boundary.y2) {
      j--;
    }

    let horizonPart, affectedBoundary;
    let q,
        k,
        maxXNew = -Infinity;

    for (q = i; q <= j; q++) {
      horizonPart = horizon[q];
      affectedBoundary = horizonPart.boundary;
      let xNew;

      if (affectedBoundary.x2 > boundary.x1) {
        xNew = affectedBoundary.index > boundary.index ? affectedBoundary.x1New : boundary.x1;
      } else if (affectedBoundary.x2New === undefined) {
        xNew = (affectedBoundary.x2 + boundary.x1) / 2;
      } else {
        xNew = affectedBoundary.x2New;
      }

      if (xNew > maxXNew) {
        maxXNew = xNew;
      }
    }

    boundary.x1New = maxXNew;

    for (q = i; q <= j; q++) {
      horizonPart = horizon[q];
      affectedBoundary = horizonPart.boundary;

      if (affectedBoundary.x2New === undefined) {
        if (affectedBoundary.x2 > boundary.x1) {
          if (affectedBoundary.index > boundary.index) {
            affectedBoundary.x2New = affectedBoundary.x2;
          }
        } else {
          affectedBoundary.x2New = maxXNew;
        }
      } else if (affectedBoundary.x2New > maxXNew) {
        affectedBoundary.x2New = Math.max(maxXNew, affectedBoundary.x2);
      }
    }

    const changedHorizon = [];
    let lastBoundary = null;

    for (q = i; q <= j; q++) {
      horizonPart = horizon[q];
      affectedBoundary = horizonPart.boundary;
      const useBoundary = affectedBoundary.x2 > boundary.x2 ? affectedBoundary : boundary;

      if (lastBoundary === useBoundary) {
        changedHorizon[changedHorizon.length - 1].end = horizonPart.end;
      } else {
        changedHorizon.push({
          start: horizonPart.start,
          end: horizonPart.end,
          boundary: useBoundary
        });
        lastBoundary = useBoundary;
      }
    }

    if (horizon[i].start < boundary.y1) {
      changedHorizon[0].start = boundary.y1;
      changedHorizon.unshift({
        start: horizon[i].start,
        end: boundary.y1,
        boundary: horizon[i].boundary
      });
    }

    if (boundary.y2 < horizon[j].end) {
      changedHorizon[changedHorizon.length - 1].end = boundary.y2;
      changedHorizon.push({
        start: boundary.y2,
        end: horizon[j].end,
        boundary: horizon[j].boundary
      });
    }

    for (q = i; q <= j; q++) {
      horizonPart = horizon[q];
      affectedBoundary = horizonPart.boundary;

      if (affectedBoundary.x2New !== undefined) {
        continue;
      }

      let used = false;

      for (k = i - 1; !used && k >= 0 && horizon[k].start >= affectedBoundary.y1; k--) {
        used = horizon[k].boundary === affectedBoundary;
      }

      for (k = j + 1; !used && k < horizon.length && horizon[k].end <= affectedBoundary.y2; k++) {
        used = horizon[k].boundary === affectedBoundary;
      }

      for (k = 0; !used && k < changedHorizon.length; k++) {
        used = changedHorizon[k].boundary === affectedBoundary;
      }

      if (!used) {
        affectedBoundary.x2New = maxXNew;
      }
    }

    Array.prototype.splice.apply(horizon, [i, j - i + 1].concat(changedHorizon));
  }

  for (const horizonPart of horizon) {
    const affectedBoundary = horizonPart.boundary;

    if (affectedBoundary.x2New === undefined) {
      affectedBoundary.x2New = Math.max(width, affectedBoundary.x2);
    }
  }
}

class TextLayerRenderTask {
  constructor({
    textContent,
    textContentStream,
    container,
    viewport,
    textDivs,
    textContentItemsStr,
    enhanceTextSelection
  }) {
    this._textContent = textContent;
    this._textContentStream = textContentStream;
    this._container = container;
    this._document = container.ownerDocument;
    this._viewport = viewport;
    this._textDivs = textDivs || [];
    this._textContentItemsStr = textContentItemsStr || [];
    this._enhanceTextSelection = !!enhanceTextSelection;
    this._fontInspectorEnabled = !!globalThis.FontInspector?.enabled;
    this._reader = null;
    this._layoutTextLastFontSize = null;
    this._layoutTextLastFontFamily = null;
    this._layoutTextCtx = null;
    this._textDivProperties = new WeakMap();
    this._renderingDone = false;
    this._canceled = false;
    this._capability = (0, _util.createPromiseCapability)();
    this._renderTimer = null;
    this._bounds = [];

    this._capability.promise.finally(() => {
      if (!this._enhanceTextSelection) {
        this._textDivProperties = null;
      }

      if (this._layoutTextCtx) {
        this._layoutTextCtx.canvas.width = 0;
        this._layoutTextCtx.canvas.height = 0;
        this._layoutTextCtx = null;
      }
    }).catch(() => {});
  }

  get promise() {
    return this._capability.promise;
  }

  cancel() {
    this._canceled = true;

    if (this._reader) {
      this._reader.cancel(new _util.AbortException("TextLayer task cancelled.")).catch(() => {});

      this._reader = null;
    }

    if (this._renderTimer !== null) {
      clearTimeout(this._renderTimer);
      this._renderTimer = null;
    }

    this._capability.reject(new Error("TextLayer task cancelled."));
  }

  _processItems(items, styleCache) {
    for (let i = 0, len = items.length; i < len; i++) {
      if (items[i].str === undefined) {
        if (items[i].type === "beginMarkedContentProps" || items[i].type === "beginMarkedContent") {
          const parent = this._container;
          this._container = document.createElement("span");

          this._container.classList.add("markedContent");

          if (items[i].id !== null) {
            this._container.setAttribute("id", `${items[i].id}`);
          }

          parent.appendChild(this._container);
        } else if (items[i].type === "endMarkedContent") {
          this._container = this._container.parentNode;
        }

        continue;
      }

      this._textContentItemsStr.push(items[i].str);

      appendText(this, items[i], styleCache, this._layoutTextCtx);
    }
  }

  _layoutText(textDiv) {
    const textDivProperties = this._textDivProperties.get(textDiv);

    let transform = "";

    if (textDivProperties.canvasWidth !== 0 && textDivProperties.hasText) {
      const {
        fontSize,
        fontFamily
      } = textDiv.style;

      if (fontSize !== this._layoutTextLastFontSize || fontFamily !== this._layoutTextLastFontFamily) {
        this._layoutTextCtx.font = `${fontSize} ${fontFamily}`;
        this._layoutTextLastFontSize = fontSize;
        this._layoutTextLastFontFamily = fontFamily;
      }

      const {
        width
      } = this._layoutTextCtx.measureText(textDiv.textContent);

      if (width > 0) {
        const scale = textDivProperties.canvasWidth / width;

        if (this._enhanceTextSelection) {
          textDivProperties.scale = scale;
        }

        transform = `scaleX(${scale})`;
      }
    }

    if (textDivProperties.angle !== 0) {
      transform = `rotate(${textDivProperties.angle}deg) ${transform}`;
    }

    if (transform.length > 0) {
      if (this._enhanceTextSelection) {
        textDivProperties.originalTransform = transform;
      }

      textDiv.style.transform = transform;
    }

    if (textDivProperties.hasText) {
      this._container.appendChild(textDiv);
    }

    if (textDivProperties.hasEOL) {
      const br = document.createElement("br");
      br.setAttribute("role", "presentation");

      this._container.appendChild(br);
    }
  }

  _render(timeout = 0) {
    const capability = (0, _util.createPromiseCapability)();
    let styleCache = Object.create(null);

    const canvas = this._document.createElement("canvas");

    canvas.height = canvas.width = DEFAULT_FONT_SIZE;
    canvas.mozOpaque = true;
    this._layoutTextCtx = canvas.getContext("2d", {
      alpha: false
    });

    if (this._textContent) {
      const textItems = this._textContent.items;
      const textStyles = this._textContent.styles;

      this._processItems(textItems, textStyles);

      capability.resolve();
    } else if (this._textContentStream) {
      const pump = () => {
        this._reader.read().then(({
          value,
          done
        }) => {
          if (done) {
            capability.resolve();
            return;
          }

          Object.assign(styleCache, value.styles);

          this._processItems(value.items, styleCache);

          pump();
        }, capability.reject);
      };

      this._reader = this._textContentStream.getReader();
      pump();
    } else {
      throw new Error('Neither "textContent" nor "textContentStream" parameters specified.');
    }

    capability.promise.then(() => {
      styleCache = null;

      if (!timeout) {
        render(this);
      } else {
        this._renderTimer = setTimeout(() => {
          render(this);
          this._renderTimer = null;
        }, timeout);
      }
    }, this._capability.reject);
  }

  expandTextDivs(expandDivs = false) {
    if (!this._enhanceTextSelection || !this._renderingDone) {
      return;
    }

    if (this._bounds !== null) {
      expand(this);
      this._bounds = null;
    }

    const transformBuf = [],
          paddingBuf = [];

    for (let i = 0, ii = this._textDivs.length; i < ii; i++) {
      const div = this._textDivs[i];

      const divProps = this._textDivProperties.get(div);

      if (!divProps.hasText) {
        continue;
      }

      if (expandDivs) {
        transformBuf.length = 0;
        paddingBuf.length = 0;

        if (divProps.originalTransform) {
          transformBuf.push(divProps.originalTransform);
        }

        if (divProps.paddingTop > 0) {
          paddingBuf.push(`${divProps.paddingTop}px`);
          transformBuf.push(`translateY(${-divProps.paddingTop}px)`);
        } else {
          paddingBuf.push(0);
        }

        if (divProps.paddingRight > 0) {
          paddingBuf.push(`${divProps.paddingRight / divProps.scale}px`);
        } else {
          paddingBuf.push(0);
        }

        if (divProps.paddingBottom > 0) {
          paddingBuf.push(`${divProps.paddingBottom}px`);
        } else {
          paddingBuf.push(0);
        }

        if (divProps.paddingLeft > 0) {
          paddingBuf.push(`${divProps.paddingLeft / divProps.scale}px`);
          transformBuf.push(`translateX(${-divProps.paddingLeft / divProps.scale}px)`);
        } else {
          paddingBuf.push(0);
        }

        div.style.padding = paddingBuf.join(" ");

        if (transformBuf.length) {
          div.style.transform = transformBuf.join(" ");
        }
      } else {
        div.style.padding = null;
        div.style.transform = divProps.originalTransform;
      }
    }
  }

}

function renderTextLayer(renderParameters) {
  const task = new TextLayerRenderTask({
    textContent: renderParameters.textContent,
    textContentStream: renderParameters.textContentStream,
    container: renderParameters.container,
    viewport: renderParameters.viewport,
    textDivs: renderParameters.textDivs,
    textContentItemsStr: renderParameters.textContentItemsStr,
    enhanceTextSelection: renderParameters.enhanceTextSelection
  });

  task._render(renderParameters.timeout);

  return task;
}