Source: pdf_thumbnail_view.js

/* Copyright 2012 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.
 */

import {
  createPromiseCapability,
  RenderingCancelledException,
} from 'pdfjs-dist'
import { getOutputScale, NullL10n } from './ui_utils.js'
import { RenderingStates } from './pdf_rendering_queue.js'

const MAX_NUM_SCALING_STEPS = 3
const THUMBNAIL_CANVAS_BORDER_WIDTH = 1 // px
const THUMBNAIL_WIDTH = 98 // px

/**
 * @typedef {Object} PDFThumbnailViewOptions
 * @property {HTMLDivElement} container - The viewer element.
 * @property {number} id - The thumbnail's unique ID (normally its number).
 * @property {PageViewport} defaultViewport - The page viewport.
 * @property {Promise<OptionalContentConfig>} [optionalContentConfigPromise] -
 *   A promise that is resolved with an {@link OptionalContentConfig} instance.
 *   The default value is `null`.
 * @property {IPDFLinkService} linkService - The navigation/linking service.
 * @property {PDFRenderingQueue} renderingQueue - The rendering queue object.
 * @property {function} checkSetImageDisabled
 * @property {boolean} [disableCanvasToImageConversion] - Don't convert the
 *   canvas thumbnails to images. This prevents `toDataURL` calls, but
 *   increases the overall memory usage. The default value is `false`.
 * @property {IL10n} l10n - Localization service.
 */

const TempImageFactory = (function TempImageFactoryClosure() {
  let tempCanvasCache = null

  return {
    getCanvas(width, height) {
      let tempCanvas = tempCanvasCache
      if (!tempCanvas) {
        tempCanvas = document.createElement('canvas')
        tempCanvasCache = tempCanvas
      }
      tempCanvas.width = width
      tempCanvas.height = height

      // Since this is a temporary canvas, we need to fill it with a white
      // background ourselves. `_getPageDrawContext` uses CSS rules for this.
      if (
        typeof PDFJSDev === 'undefined' ||
        PDFJSDev.test('MOZCENTRAL || GENERIC')
      ) {
        tempCanvas.mozOpaque = true
      }

      const ctx = tempCanvas.getContext('2d', { alpha: false })
      ctx.save()
      ctx.fillStyle = 'rgb(255, 255, 255)'
      ctx.fillRect(0, 0, width, height)
      ctx.restore()
      return tempCanvas
    },

    destroyCanvas() {
      const tempCanvas = tempCanvasCache
      if (tempCanvas) {
        // Zeroing the width and height causes Firefox to release graphics
        // resources immediately, which can greatly reduce memory consumption.
        tempCanvas.width = 0
        tempCanvas.height = 0
      }
      tempCanvasCache = null
    },
  }
})()

/**
 * @implements {IRenderableView}
 */
class PDFThumbnailView {
  /**
   * @param {PDFThumbnailViewOptions} options
   */
  constructor({
    container,
    id,
    defaultViewport,
    optionalContentConfigPromise,
    linkService,
    renderingQueue,
    checkSetImageDisabled,
    disableCanvasToImageConversion = false,
    l10n = NullL10n,
  }) {
    this.id = id
    this.renderingId = 'thumbnail' + id
    this.pageLabel = null

    this.pdfPage = null
    this.rotation = 0
    this.viewport = defaultViewport
    this.pdfPageRotate = defaultViewport.rotation
    this._optionalContentConfigPromise = optionalContentConfigPromise || null

    this.linkService = linkService
    this.renderingQueue = renderingQueue

    this.renderTask = null
    this.renderingState = RenderingStates.INITIAL
    this.resume = null
    this._checkSetImageDisabled =
      checkSetImageDisabled ||
      function () {
        return false
      }
    this.disableCanvasToImageConversion = disableCanvasToImageConversion

    this.pageWidth = this.viewport.width
    this.pageHeight = this.viewport.height
    this.pageRatio = this.pageWidth / this.pageHeight

    this.canvasWidth = THUMBNAIL_WIDTH
    this.canvasHeight = (this.canvasWidth / this.pageRatio) | 0
    this.scale = this.canvasWidth / this.pageWidth

    this.l10n = l10n

    const anchor = document.createElement('a')
    anchor.href = linkService.getAnchorUrl('#page=' + id)
    this._thumbPageTitle.then((msg) => {
      anchor.title = msg
    })
    anchor.onclick = function () {
      linkService.page = id
      return false
    }
    this.anchor = anchor

    const div = document.createElement('div')
    div.className = 'thumbnail'
    div.setAttribute('data-page-number', this.id)
    this.div = div

    const ring = document.createElement('div')
    ring.className = 'thumbnailSelectionRing'
    const borderAdjustment = 2 * THUMBNAIL_CANVAS_BORDER_WIDTH
    ring.style.width = this.canvasWidth + borderAdjustment + 'px'
    ring.style.height = this.canvasHeight + borderAdjustment + 'px'
    this.ring = ring

    div.appendChild(ring)
    anchor.appendChild(div)
    container.appendChild(anchor)
  }

  rotate(rotation, actual_page) {
    if (this.id === actual_page) {
      this.rotation = (this.rotation + rotation) % 360
      this.viewport = this.viewport.clone({
        scale: 1,
        rotation: this.rotation,
      })
      this.reset()
    }
  }

  delete(actual_page) {
    if (this.id === actual_page) {
      this.div.hidden = true
      this.update()
    }
  }

  setPdfPage(pdfPage) {
    this.pdfPage = pdfPage
    this.pdfPageRotate = pdfPage.rotate
    const totalRotation = (this.rotation + this.pdfPageRotate) % 360
    this.viewport = pdfPage.getViewport({ scale: 1, rotation: totalRotation })
    this.reset()
  }

  reset() {
    this.cancelRendering()
    this.renderingState = RenderingStates.INITIAL

    this.pageWidth = this.viewport.width
    this.pageHeight = this.viewport.height
    this.pageRatio = this.pageWidth / this.pageHeight

    this.canvasHeight = (this.canvasWidth / this.pageRatio) | 0
    this.scale = this.canvasWidth / this.pageWidth

    this.div.removeAttribute('data-loaded')
    const ring = this.ring
    const childNodes = ring.childNodes
    for (let i = childNodes.length - 1; i >= 0; i--) {
      ring.removeChild(childNodes[i])
    }
    const borderAdjustment = 2 * THUMBNAIL_CANVAS_BORDER_WIDTH
    ring.style.width = this.canvasWidth + borderAdjustment + 'px'
    ring.style.height = this.canvasHeight + borderAdjustment + 'px'

    if (this.canvas) {
      // Zeroing the width and height causes Firefox to release graphics
      // resources immediately, which can greatly reduce memory consumption.
      this.canvas.width = 0
      this.canvas.height = 0
      delete this.canvas
    }
    if (this.image) {
      this.image.removeAttribute('src')
      delete this.image
    }
  }

  update(rotation) {
    if (typeof rotation !== 'undefined') {
      this.rotation = rotation
    }
    const totalRotation = (this.rotation + this.pdfPageRotate) % 360
    this.viewport = this.viewport.clone({
      scale: 1,
      rotation: totalRotation,
    })
    this.reset()
  }

  /**
   * PLEASE NOTE: Most likely you want to use the `this.reset()` method,
   *              rather than calling this one directly.
   */
  cancelRendering() {
    if (this.renderTask) {
      this.renderTask.cancel()
      this.renderTask = null
    }
    this.resume = null
  }

  /**
   * @private
   */
  _getPageDrawContext(noCtxScale = false) {
    const canvas = document.createElement('canvas')
    // Keep the no-thumbnail outline visible, i.e. `data-loaded === false`,
    // until rendering/image conversion is complete, to avoid display issues.
    this.canvas = canvas

    if (
      typeof PDFJSDev === 'undefined' ||
      PDFJSDev.test('MOZCENTRAL || GENERIC')
    ) {
      canvas.mozOpaque = true
    }
    const ctx = canvas.getContext('2d', { alpha: false })
    const outputScale = getOutputScale(ctx)

    canvas.width = (this.canvasWidth * outputScale.sx) | 0
    canvas.height = (this.canvasHeight * outputScale.sy) | 0
    canvas.style.width = this.canvasWidth + 'px'
    canvas.style.height = this.canvasHeight + 'px'

    if (!noCtxScale && outputScale.scaled) {
      ctx.scale(outputScale.sx, outputScale.sy)
    }
    return ctx
  }

  /**
   * @private
   */
  _convertCanvasToImage() {
    if (!this.canvas) {
      return
    }
    if (this.renderingState !== RenderingStates.FINISHED) {
      return
    }
    const className = 'thumbnailImage'

    if (this.disableCanvasToImageConversion) {
      this.canvas.className = className
      this._thumbPageCanvas.then((msg) => {
        this.canvas.setAttribute('aria-label', msg)
      })

      this.div.setAttribute('data-loaded', true)
      this.ring.appendChild(this.canvas)
      return
    }
    const image = document.createElement('img')
    image.className = className
    this._thumbPageCanvas.then((msg) => {
      image.setAttribute('aria-label', msg)
    })

    image.style.width = this.canvasWidth + 'px'
    image.style.height = this.canvasHeight + 'px'

    image.src = this.canvas.toDataURL()
    this.image = image

    this.div.setAttribute('data-loaded', true)
    this.ring.appendChild(image)

    // Zeroing the width and height causes Firefox to release graphics
    // resources immediately, which can greatly reduce memory consumption.
    this.canvas.width = 0
    this.canvas.height = 0
    delete this.canvas
  }

  draw() {
    if (this.renderingState !== RenderingStates.INITIAL) {
      console.error('Must be in new state before drawing')
      return Promise.resolve(undefined)
    }
    const { pdfPage } = this

    if (!pdfPage) {
      this.renderingState = RenderingStates.FINISHED
      return Promise.reject(new Error('pdfPage is not loaded'))
    }

    this.renderingState = RenderingStates.RUNNING

    const renderCapability = createPromiseCapability()
    const finishRenderTask = (error) => {
      // The renderTask may have been replaced by a new one, so only remove
      // the reference to the renderTask if it matches the one that is
      // triggering this callback.
      if (renderTask === this.renderTask) {
        this.renderTask = null
      }

      if (error instanceof RenderingCancelledException) {
        renderCapability.resolve(undefined)
        return
      }

      this.renderingState = RenderingStates.FINISHED
      this._convertCanvasToImage()

      if (!error) {
        renderCapability.resolve(undefined)
      } else {
        renderCapability.reject(error)
      }
    }

    const ctx = this._getPageDrawContext()
    const drawViewport = this.viewport.clone({ scale: this.scale })
    const renderContinueCallback = (cont) => {
      if (!this.renderingQueue.isHighestPriority(this)) {
        this.renderingState = RenderingStates.PAUSED
        this.resume = () => {
          this.renderingState = RenderingStates.RUNNING
          cont()
        }
        return
      }
      cont()
    }

    const renderContext = {
      canvasContext: ctx,
      viewport: drawViewport,
      optionalContentConfigPromise: this._optionalContentConfigPromise,
    }
    const renderTask = (this.renderTask = pdfPage.render(renderContext))
    renderTask.onContinue = renderContinueCallback

    renderTask.promise.then(
      function () {
        finishRenderTask(null)
      },
      function (error) {
        finishRenderTask(error)
      }
    )
    return renderCapability.promise
  }

  setImage(pageView) {
    if (this._checkSetImageDisabled()) {
      return
    }
    if (this.renderingState !== RenderingStates.INITIAL) {
      return
    }
    const img = pageView.canvas
    if (!img) {
      return
    }
    if (!this.pdfPage) {
      this.setPdfPage(pageView.pdfPage)
    }

    this.renderingState = RenderingStates.FINISHED

    const ctx = this._getPageDrawContext(true)
    const canvas = ctx.canvas
    if (img.width <= 2 * canvas.width) {
      ctx.drawImage(
        img,
        0,
        0,
        img.width,
        img.height,
        0,
        0,
        canvas.width,
        canvas.height
      )
      this._convertCanvasToImage()
      return
    }

    // drawImage does an awful job of rescaling the image, doing it gradually.
    let reducedWidth = canvas.width << MAX_NUM_SCALING_STEPS
    let reducedHeight = canvas.height << MAX_NUM_SCALING_STEPS
    const reducedImage = TempImageFactory.getCanvas(reducedWidth, reducedHeight)
    const reducedImageCtx = reducedImage.getContext('2d')

    while (reducedWidth > img.width || reducedHeight > img.height) {
      reducedWidth >>= 1
      reducedHeight >>= 1
    }
    reducedImageCtx.drawImage(
      img,
      0,
      0,
      img.width,
      img.height,
      0,
      0,
      reducedWidth,
      reducedHeight
    )
    while (reducedWidth > 2 * canvas.width) {
      reducedImageCtx.drawImage(
        reducedImage,
        0,
        0,
        reducedWidth,
        reducedHeight,
        0,
        0,
        reducedWidth >> 1,
        reducedHeight >> 1
      )
      reducedWidth >>= 1
      reducedHeight >>= 1
    }
    ctx.drawImage(
      reducedImage,
      0,
      0,
      reducedWidth,
      reducedHeight,
      0,
      0,
      canvas.width,
      canvas.height
    )
    this._convertCanvasToImage()
  }

  get _thumbPageTitle() {
    return this.l10n.get(
      'thumb_page_title',
      { page: this.pageLabel ?? this.id },
      'Page {{page}}'
    )
  }

  get _thumbPageCanvas() {
    return this.l10n.get(
      'thumb_page_canvas',
      { page: this.pageLabel ?? this.id },
      'Thumbnail of Page {{page}}'
    )
  }

  /**
   * @param {string|null} label
   */
  setPageLabel(label) {
    this.pageLabel = typeof label === 'string' ? label : null

    this._thumbPageTitle.then((msg) => {
      this.anchor.title = msg
    })

    if (this.renderingState !== RenderingStates.FINISHED) {
      return
    }

    this._thumbPageCanvas.then((msg) => {
      if (this.image) {
        this.image.setAttribute('aria-label', msg)
      } else if (this.disableCanvasToImageConversion && this.canvas) {
        this.canvas.setAttribute('aria-label', msg)
      }
    })
  }

  static cleanup() {
    TempImageFactory.destroyCanvas()
  }
}

export { PDFThumbnailView }