pdfjs-dist/lib/display/text_layer.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.TextLayerRenderTask = void 0;
exports.renderTextLayer = renderTextLayer;
exports.updateTextLayer = updateTextLayer;
var _util = require("../shared/util.js");
var _display_utils = require("./display_utils.js");
const MAX_TEXT_DIVS_TO_RENDER = 100000;
const DEFAULT_FONT_SIZE = 30;
const DEFAULT_FONT_ASCENT = 0.8;
const ascentCache = new Map();
function getCtx(size, isOffscreenCanvasSupported) {
  let ctx;
  if (isOffscreenCanvasSupported && _util.FeatureTest.isOffscreenCanvasSupported) {
    ctx = new OffscreenCanvas(size, size).getContext("2d", {
      alpha: false
    });
  } else {
    const canvas = document.createElement("canvas");
    canvas.width = canvas.height = size;
    ctx = canvas.getContext("2d", {
      alpha: false
    });
  }
  return ctx;
}
function getAscent(fontFamily, isOffscreenCanvasSupported) {
  const cachedAscent = ascentCache.get(fontFamily);
  if (cachedAscent) {
    return cachedAscent;
  }
  const ctx = getCtx(DEFAULT_FONT_SIZE, isOffscreenCanvasSupported);
  ctx.font = `${DEFAULT_FONT_SIZE}px ${fontFamily}`;
  const metrics = ctx.measureText("");
  let ascent = metrics.fontBoundingBoxAscent;
  let descent = Math.abs(metrics.fontBoundingBoxDescent);
  if (ascent) {
    const ratio = ascent / (ascent + descent);
    ascentCache.set(fontFamily, ratio);
    ctx.canvas.width = ctx.canvas.height = 0;
    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.canvas.width = ctx.canvas.height = 0;
  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) {
  const textDiv = document.createElement("span");
  const textDivProperties = {
    angle: 0,
    canvasWidth: 0,
    hasText: geom.str !== "",
    hasEOL: geom.hasEOL,
    fontSize: 0
  };
  task._textDivs.push(textDiv);
  const tx = _util.Util.transform(task._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, task._isOffscreenCanvasSupported);
  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);
  }
  const scaleFactorStr = "calc(var(--scale-factor)*";
  const divStyle = textDiv.style;
  if (task._container === task._rootContainer) {
    divStyle.left = `${(100 * left / task._pageWidth).toFixed(2)}%`;
    divStyle.top = `${(100 * top / task._pageHeight).toFixed(2)}%`;
  } else {
    divStyle.left = `${scaleFactorStr}${left.toFixed(2)}px)`;
    divStyle.top = `${scaleFactorStr}${top.toFixed(2)}px)`;
  }
  divStyle.fontSize = `${scaleFactorStr}${fontHeight.toFixed(2)}px)`;
  divStyle.fontFamily = style.fontFamily;
  textDivProperties.fontSize = fontHeight;
  textDiv.setAttribute("role", "presentation");
  textDiv.textContent = geom.str;
  textDiv.dir = geom.dir;
  if (task._fontInspectorEnabled) {
    textDiv.dataset.fontName = geom.fontName;
  }
  if (angle !== 0) {
    textDivProperties.angle = angle * (180 / Math.PI);
  }
  let shouldScaleText = false;
  if (geom.str.length > 1) {
    shouldScaleText = true;
  } else if (geom.str !== " " && geom.transform[0] !== geom.transform[3]) {
    const absScaleX = Math.abs(geom.transform[0]),
      absScaleY = Math.abs(geom.transform[3]);
    if (absScaleX !== absScaleY && Math.max(absScaleX, absScaleY) / Math.min(absScaleX, absScaleY) > 1.5) {
      shouldScaleText = true;
    }
  }
  if (shouldScaleText) {
    textDivProperties.canvasWidth = style.vertical ? geom.height : geom.width;
  }
  task._textDivProperties.set(textDiv, textDivProperties);
  if (task._isReadableStream) {
    task._layoutText(textDiv);
  }
}
function layout(params) {
  const {
    div,
    scale,
    properties,
    ctx,
    prevFontSize,
    prevFontFamily
  } = params;
  const {
    style
  } = div;
  let transform = "";
  if (properties.canvasWidth !== 0 && properties.hasText) {
    const {
      fontFamily
    } = style;
    const {
      canvasWidth,
      fontSize
    } = properties;
    if (prevFontSize !== fontSize || prevFontFamily !== fontFamily) {
      ctx.font = `${fontSize * scale}px ${fontFamily}`;
      params.prevFontSize = fontSize;
      params.prevFontFamily = fontFamily;
    }
    const {
      width
    } = ctx.measureText(div.textContent);
    if (width > 0) {
      transform = `scaleX(${canvasWidth * scale / width})`;
    }
  }
  if (properties.angle !== 0) {
    transform = `rotate(${properties.angle}deg) ${transform}`;
  }
  if (transform.length > 0) {
    style.transform = transform;
  }
}
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) {
    capability.resolve();
    return;
  }
  if (!task._isReadableStream) {
    for (const textDiv of textDivs) {
      task._layoutText(textDiv);
    }
  }
  capability.resolve();
}
class TextLayerRenderTask {
  constructor({
    textContentSource,
    container,
    viewport,
    textDivs,
    textDivProperties,
    textContentItemsStr,
    isOffscreenCanvasSupported
  }) {
    this._textContentSource = textContentSource;
    this._isReadableStream = textContentSource instanceof ReadableStream;
    this._container = this._rootContainer = container;
    this._textDivs = textDivs || [];
    this._textContentItemsStr = textContentItemsStr || [];
    this._fontInspectorEnabled = !!globalThis.FontInspector?.enabled;
    this._reader = null;
    this._textDivProperties = textDivProperties || new WeakMap();
    this._canceled = false;
    this._capability = (0, _util.createPromiseCapability)();
    this._layoutTextParams = {
      prevFontSize: null,
      prevFontFamily: null,
      div: null,
      scale: viewport.scale * (globalThis.devicePixelRatio || 1),
      properties: null,
      ctx: getCtx(0, isOffscreenCanvasSupported)
    };
    const {
      pageWidth,
      pageHeight,
      pageX,
      pageY
    } = viewport.rawDims;
    this._transform = [1, 0, 0, -1, -pageX, pageY + pageHeight];
    this._pageWidth = pageWidth;
    this._pageHeight = pageHeight;
    (0, _display_utils.setLayerDimensions)(container, viewport);
    this._capability.promise.finally(() => {
      this._layoutTextParams = 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;
    }
    this._capability.reject(new _util.AbortException("TextLayer task cancelled."));
  }
  _processItems(items, styleCache) {
    for (const item of items) {
      if (item.str === undefined) {
        if (item.type === "beginMarkedContentProps" || item.type === "beginMarkedContent") {
          const parent = this._container;
          this._container = document.createElement("span");
          this._container.classList.add("markedContent");
          if (item.id !== null) {
            this._container.setAttribute("id", `${item.id}`);
          }
          parent.append(this._container);
        } else if (item.type === "endMarkedContent") {
          this._container = this._container.parentNode;
        }
        continue;
      }
      this._textContentItemsStr.push(item.str);
      appendText(this, item, styleCache);
    }
  }
  _layoutText(textDiv) {
    const textDivProperties = this._layoutTextParams.properties = this._textDivProperties.get(textDiv);
    this._layoutTextParams.div = textDiv;
    layout(this._layoutTextParams);
    if (textDivProperties.hasText) {
      this._container.append(textDiv);
    }
    if (textDivProperties.hasEOL) {
      const br = document.createElement("br");
      br.setAttribute("role", "presentation");
      this._container.append(br);
    }
  }
  _render() {
    const capability = (0, _util.createPromiseCapability)();
    let styleCache = Object.create(null);
    if (this._isReadableStream) {
      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._textContentSource.getReader();
      pump();
    } else if (this._textContentSource) {
      const {
        items,
        styles
      } = this._textContentSource;
      this._processItems(items, styles);
      capability.resolve();
    } else {
      throw new Error('No "textContentSource" parameter specified.');
    }
    capability.promise.then(() => {
      styleCache = null;
      render(this);
    }, this._capability.reject);
  }
}
exports.TextLayerRenderTask = TextLayerRenderTask;
function renderTextLayer(params) {
  if (!params.textContentSource && (params.textContent || params.textContentStream)) {
    (0, _display_utils.deprecated)("The TextLayerRender `textContent`/`textContentStream` parameters " + "will be removed in the future, please use `textContentSource` instead.");
    params.textContentSource = params.textContent || params.textContentStream;
  }
  const task = new TextLayerRenderTask(params);
  task._render();
  return task;
}
function updateTextLayer({
  container,
  viewport,
  textDivs,
  textDivProperties,
  isOffscreenCanvasSupported,
  mustRotate = true,
  mustRescale = true
}) {
  if (mustRotate) {
    (0, _display_utils.setLayerDimensions)(container, {
      rotation: viewport.rotation
    });
  }
  if (mustRescale) {
    const ctx = getCtx(0, isOffscreenCanvasSupported);
    const scale = viewport.scale * (globalThis.devicePixelRatio || 1);
    const params = {
      prevFontSize: null,
      prevFontFamily: null,
      div: null,
      scale,
      properties: null,
      ctx
    };
    for (const div of textDivs) {
      params.properties = textDivProperties.get(div);
      params.div = div;
      layout(params);
    }
  }
}