PDF.js profile slow pages

viewer_snippet.js

/*
 * Copy this gist into a snippet of the Sources panel of the DevTool and run it to profile slow pages
 * Alternatively the PDFView.PROFILE_THRESHOLD can be set in `ms`
 */

// threshold in ms to keep/discard CPU profile
PDFView.PROFILE_THRESHOLD = 500;

PDFView.renderHighestPriority = function pdfViewRenderHighestPriority_patched(currentlyVisiblePages) {
    if (PDFView.idleTimeout) {
      clearTimeout(PDFView.idleTimeout);
      PDFView.idleTimeout = null;
    }

    // Pages have a higher priority than thumbnails, so check them first.
    var visiblePages = currentlyVisiblePages || this.getVisiblePages();
    var pageView = this.getHighestPriority(visiblePages, this.pages,
                                           this.pageViewScroll.down);
    
    // start of page rendering log
    var now = Date.now();
    if (this.wasPageView) {
      var time = now - this._when;
      if (time < PDFView.PROFILE_THRESHOLD) {
        // discard the previous profile and start a short lived one called 'v_v'
        console.profile('v_v');
      }
      console.profileEnd();
      console.info(time + 'ms for the page #' + this.wasPageView.id +
        ' ' + this.url);
      this.wasPageView = null;
    }
    if (pageView) {
      this._when = now;
      this.wasPageView = pageView;
      now = new Date();
      console.profile(this.url +
        ' #' + pageView.id +
        ' ' + "SunMonTueWedThuFriSat".substr(now.getDay()*3, 3) +
        ' ' + now.toLocaleTimeString());
    }
    // end of page rendering log


    if (pageView) {
      this.renderView(pageView, 'page');
      return;
    }
    // No pages needed rendering so check thumbnails.
    if (this.sidebarOpen) {
      var visibleThumbs = this.getVisibleThumbs();
      var thumbView = this.getHighestPriority(visibleThumbs,
                                              this.thumbnails,
                                              this.thumbnailViewScroll.down);
      if (thumbView) {
        this.renderView(thumbView, 'thumbnail');
        return;
      }
    }

    PDFView.idleTimeout = setTimeout(function () {
      PDFView.cleanup();
    }, CLEANUP_TIMEOUT);
  }