Initial commit

folkugat_web/assets/static/js/pdf_viewer.js

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+const pdfjsLib = await import('./pdf/pdf.mjs');
+const pdfjsWorker = await import('./pdf/pdf.worker.mjs');
+
+// The workerSrc property shall be specified.
+pdfjsLib.GlobalWorkerOptions.workerSrc = pdfjsWorker;
+
+
+export function displayPdf(options) {
+  var pdfDoc = null,
+      pageNum = 1,
+      pageRendering = false,
+      pageNumPending = null,
+      ctx = options.canvas.getContext('2d');
+
+  /**
+   * Get page info from document, resize canvas accordingly, and render page.
+   * @param num Page number.
+   */
+  function renderPage(num) {
+    pageRendering = true;
+    // Using promise to fetch the page
+    pdfDoc.getPage(num).then(function(page) {
+      var canvasWidth = options.canvas.getBoundingClientRect().width,
+          pageWidth = page.getViewport({scale: 1.0}).width,
+          scale = canvasWidth/pageWidth,
+          viewport = page.getViewport({scale: scale});
+      options.canvas.height = viewport.height;
+      options.canvas.width = viewport.width;
+
+      // Render PDF page into canvas context
+      var renderContext = {
+        canvasContext: ctx,
+        viewport: viewport
+      };
+      var renderTask = page.render(renderContext);
+
+      // Wait for rendering to finish
+      renderTask.promise.then(function() {
+        pageRendering = false;
+        if (pageNumPending !== null) {
+          // New page rendering is pending
+          renderPage(pageNumPending);
+          pageNumPending = null;
+        }
+      });
+    });
+
+    // Update page counters
+    options.pageNum.textContent = num;
+  }
+
+  /**
+   * If another page rendering in progress, waits until the rendering is
+   * finised. Otherwise, executes rendering immediately.
+   */
+  function queueRenderPage(num) {
+    if (pageRendering) {
+      pageNumPending = num;
+    } else {
+      renderPage(num);
+    }
+  }
+
+  /**
+   * Re-render page (e.g. on resize)
+   */
+  function reRender() {
+      queueRenderPage(pageNum);
+  }
+  document.defaultView.addEventListener('resize', reRender)
+
+  /**
+   * Displays previous page.
+   */
+  function onPrevPage() {
+    if (pageNum <= 1) {
+      return;
+    }
+    pageNum--;
+    queueRenderPage(pageNum);
+  }
+  options.prevPage.addEventListener('click', onPrevPage);
+
+  /**
+   * Displays next page.
+   */
+  function onNextPage() {
+    if (pageNum >= pdfDoc.numPages) {
+      return;
+    }
+    pageNum++;
+    queueRenderPage(pageNum);
+  }
+  options.nextPage.addEventListener('click', onNextPage);
+
+  /**
+   * Asynchronously downloads PDF.
+   */
+  pdfjsLib.getDocument(options.url).promise.then(function(pdfDoc_) {
+    pdfDoc = pdfDoc_;
+    options.pageCount.textContent = pdfDoc.numPages;
+
+    // Initial/first page rendering
+    renderPage(pageNum);
+  });
+}