Changed cast namespace check to include both window.cast and cast. Fa…

…llback to isTypeSupported() if 'cast' is available, but canDisplayType() isn't.

lib/polyfill/media_capabilities.js

@@ -105,30 +105,20 @@ shaka.polyfill.MediaCapabilities = class {
         return res;
       }
       // Use 'MediaSource.isTypeSupported' to check if the stream is supported.
+      // Cast platforms will additionally check canDisplayType(), which
+      // accepts extended MIME type parameters.
+      // See: https://github.com/shaka-project/shaka-player/issues/4726
       if (videoConfig) {
         const contentType = videoConfig.contentType;
         let isSupported = MediaSource.isTypeSupported(contentType);
         if (shaka.util.Platform.isChromecast()) {
-          // Cast platforms will additionally check canDisplayType(), which
-          // accepts extended MIME type parameters.
-          // There will be at most 2 calls:
-          // - The first call determines the stability of
-          // the API by validating a contentType input limited only to MIME type
-          // and codecs is identical to MediaSource.isTypeSupported().
-          // - If the same result is observed, a second call will be executed
-          // containing resolution, frame rate, and transfer function support.
-          // See: https://github.com/shaka-project/shaka-player/issues/4726
-          if (isSupported ===
-              shaka.polyfill.MediaCapabilities.canCastDisplayType_({
-                contentType})) {
-            isSupported = shaka.polyfill.MediaCapabilities.canCastDisplayType_({
-              contentType,
-              width: videoConfig.width,
-              height: videoConfig.height,
-              frameRate: videoConfig.framerate,
-              transferFunction: videoConfig.transferFunction,
-            });
-          }
+          isSupported = shaka.polyfill.MediaCapabilities.canCastDisplayType_({
+            contentType,
+            width: videoConfig.width,
+            height: videoConfig.height,
+            frameRate: videoConfig.framerate,
+            transferFunction: videoConfig.transferFunction,
+          });
         }
         if (!isSupported) {
           return res;
@@ -269,14 +259,19 @@ shaka.polyfill.MediaCapabilities = class {
     frameRate = undefined,
     transferFunction = undefined,
   }) {
-    if (!(window.cast && cast.__platform__ &&
-          cast.__platform__.canDisplayType)) {
+    if (!window.cast || !cast) {
       shaka.log.error('Expected cast namespace to be available!');
       throw new shaka.util.Error(
           shaka.util.Error.Severity.CRITICAL,
           shaka.util.Error.Category.CAST,
           shaka.util.Error.Code.CAST_UNEXPECTED_PLATFORM);
     }
+    if (!(cast.__platform__ && cast.__platform__.canDisplayType)) {
+      shaka.log.warning('Expected canDisplayType() API to be available!');
+      // We don't have access to the required API, so fallback to
+      // MediaSource.isTypeSupported().
+      return MediaSource.isTypeSupported(contentType);
+    }
     let displayType = contentType;
     if (width && height) {
       displayType += `; width=${width}; height=${height}`;

test/polyfill/media_capabilities_unit.js

@@ -6,12 +6,12 @@
 
 describe('MediaCapabilities', () => {
   const Util = shaka.test.Util;
+  const originalCast = window['cast'];
   const originalVendor = navigator.vendor;
   const originalUserAgent = navigator.userAgent;
   const originalRequestMediaKeySystemAccess =
     navigator.requestMediaKeySystemAccess;
   const originalMediaCapabilities = navigator.mediaCapabilities;
-  const originalCast = window['cast'];
 
   /** @type {MediaDecodingConfiguration} */
   let mockDecodingConfig;
@@ -182,9 +182,8 @@ describe('MediaCapabilities', () => {
           .toHaveBeenCalledTimes(1);
     });
 
-    it('fails when the cast namespace is not available', async () => {
-      // Mock Shaka throwing an error from identifying an unexpected, non-Cast
-      // platform when performing Cast logic.
+    it('throws when the cast namespace is not available', async () => {
+      // We don't set window['cast'] here to signal error.
       const isChromecastSpy =
           spyOn(shaka['util']['Platform'],
               'isChromecast').and.returnValue(true);
@@ -202,11 +201,34 @@ describe('MediaCapabilities', () => {
 
       // 1 (during install()) + 1 (for video config check).
       expect(isChromecastSpy).toHaveBeenCalledTimes(2);
-      // Called for decodingConfig.audio. This is never reached because of the
-      // error throw.
-      expect(isTypeSupportedSpy).not.toHaveBeenCalled();
+      // Called for decodingConfig.video. decodingConfig.audio is never reached
+      // due to the error thrown.
+      expect(isTypeSupportedSpy).toHaveBeenCalledTimes(1);
     });
 
+    it('falls back to isTypeSupported() when canDisplayType() missing',
+        async () => {
+          // Only set window['cast'], not cast.__platform__ or
+          // cast.__platform__.canDisplayType().
+          window['cast'] = {};
+          const isChromecastSpy =
+              spyOn(shaka['util']['Platform'],
+                  'isChromecast').and.returnValue(true);
+          const isTypeSupportedSpy =
+              spyOn(window['MediaSource'], 'isTypeSupported')
+                  .and.returnValue(true);
+
+          shaka.polyfill.MediaCapabilities.install();
+          await navigator.mediaCapabilities.decodingInfo(mockDecodingConfig);
+
+          expect(mockCanDisplayType).not.toHaveBeenCalled();
+          // 1 (during install()) + 1 (for video config check).
+          expect(isChromecastSpy).toHaveBeenCalledTimes(2);
+          // 1 (mockDecodingConfig.video) + 1 (canCastDisplayType() fallback)
+          // + 1 (mockDecodingConfig.audio).
+          expect(isTypeSupportedSpy).toHaveBeenCalledTimes(3);
+        });
+
     it('should use cast.__platform__.canDisplayType for "supported" field ' +
         'when platform is Cast', async () => {
       // We're using quotes to access window.cast because the compiler
@@ -241,10 +263,9 @@ describe('MediaCapabilities', () => {
 
       // 1 (during install()) + 1 (for video config check).
       expect(isChromecastSpy).toHaveBeenCalledTimes(2);
-      // Called once for mockDecodingConfig.audio. Resolution, frame rate, and
-      // EOTF aren't applicable for audio, so isTypeSupported() is sufficient.
-      expect(isTypeSupportedSpy).toHaveBeenCalledTimes(1);
-      // Called once for mockDecodingConfig.video.
+      // 1 (mockDecodingConfig.video) + 1 (mockDecodingConfig.audio).
+      expect(isTypeSupportedSpy).toHaveBeenCalledTimes(2);
+      // Called once in canCastDisplayType.
       expect(mockCanDisplayType).toHaveBeenCalledTimes(1);
     });
   });