Update: Disable pdf.js streaming (#483)

Streaming performance in Chrome is still bad compared to just using range request, so disable until more progress on performance is made.

src/lib/viewers/doc/DocBaseViewer.js

@@ -51,6 +51,7 @@ const SCROLL_EVENT_THROTTLE_INTERVAL = 200;
 const SCROLL_END_TIMEOUT = this.isMobile ? 500 : 250;
 const RANGE_REQUEST_CHUNK_SIZE_US = 1048576; // 1MB
 const RANGE_REQUEST_CHUNK_SIZE_NON_US = 524288; // 512KB
+const MINIMUM_RANGE_REQUEST_FILE_SIZE_NON_US = 26214400; // 25MB
 const MOBILE_MAX_CANVAS_SIZE = 2949120; // ~3MP 1920x1536
 
 const LOADING_ICON_MAP = {
@@ -605,7 +606,7 @@ class DocBaseViewer extends BaseViewer {
     setupPdfjs() {
         // Set PDFJS worker & character maps
         const { file, location } = this.options;
-        const { watermark_info: watermarkInfo } = file;
+        const { size, watermark_info: watermarkInfo } = file;
         const assetUrlCreator = createAssetUrlCreator(location);
         PDFJS.workerSrc = assetUrlCreator(`third-party/doc/${DOC_STATIC_ASSETS_VERSION}/pdf.worker.min.js`);
         PDFJS.imageResourcesPath = assetUrlCreator(`third-party/doc/${DOC_STATIC_ASSETS_VERSION}/images/`);
@@ -615,13 +616,22 @@ class DocBaseViewer extends BaseViewer {
         // Open links in new tab
         PDFJS.externalLinkTarget = PDFJS.LinkTarget.BLANK;
 
+        // Disable streaming via fetch until performance is improved
+        PDFJS.disableStream = true;
+
         // Disable font faces on IOS 10.3.X
         // @NOTE(JustinHoldstock) 2017-04-11: Check to remove this after next IOS release after 10.3.1
         PDFJS.disableFontFace = PDFJS.disableFontFace || Browser.hasFontIssue();
 
-        // Disable range requests for watermarked files since they are streamed, otherwise override range request
-        // disabling by pdf.js's compatibility checking since all the browsers we support allow range requests
-        PDFJS.disableRange = watermarkInfo && watermarkInfo.is_watermarked;
+        // Disable range requests for files smaller than MINIMUM_RANGE_REQUEST_FILE_SIZE (25MB) for
+        // previews outside of the US since the additional latency overhead per range request can be
+        // more than the additional time for a continuous request. This also overrides any range request
+        // disabling that may be set by pdf.js's compatibility checking since the browsers we support
+        // should all be able to properly handle range requests.
+        PDFJS.disableRange = location.locale !== 'en-US' && size < MINIMUM_RANGE_REQUEST_FILE_SIZE_NON_US;
+
+        // Disable range requests for watermarked files since they are streamed
+        PDFJS.disableRange = PDFJS.disableRange || (watermarkInfo && watermarkInfo.is_watermarked);
 
         // Disable text layer if user doesn't have download permissions
         PDFJS.disableTextLayer =

src/lib/viewers/doc/__tests__/DocBaseViewer-test.js

@@ -953,7 +953,29 @@ describe('src/lib/viewers/doc/DocBaseViewer', () => {
             expect(PDFJS.disableFontFace).to.be.true;
         });
 
-        it('should not disable range requests normally', () => {
+        it('should not disable streaming', () => {
+            docBase.setupPdfjs();
+            expect(PDFJS.disableStream).to.be.true;
+        });
+
+        it('should not disable range requests if the locale is en-US', () => {
+            docBase.setupPdfjs();
+            expect(PDFJS.disableRange).to.be.false;
+        });
+
+        it('should disable range requests if locale is not en-US, the file is smaller than 25MB and is not an Excel file', () => {
+            docBase.options.file.size = 26000000;
+            docBase.options.extension = 'pdf';
+            docBase.options.location.locale = 'ja-JP';
+            docBase.setupPdfjs();
+            expect(PDFJS.disableRange).to.be.true;
+        });
+
+        it('should enable range requests if locale is not en-US, the file is greater than 25MB and is not watermarked', () => {
+            docBase.options.location.locale = 'ja-JP';
+            docBase.options.file.size = 26500000;
+            docBase.options.extension = 'pdf';
+            docBase.options.file.watermark_info.is_watermarked = false;
             docBase.setupPdfjs();
             expect(PDFJS.disableRange).to.be.false;
         });