fix quicktime video thumbnailing

src/ContentMessages.ts

@@ -292,7 +292,14 @@ function loadVideoElement(videoFile): Promise<HTMLVideoElement> {
                 reject(e);
             };
 
-            video.src = ev.target.result as string;
+            let dataUrl = ev.target.result as string;
+            // Chrome chokes on quicktime but likes mp4, and `file.type` is
+            // read only, so do this horrible hack to unbreak quicktime
+            if (dataUrl.startsWith("data:video/quicktime;")) {
+                dataUrl = dataUrl.replace("data:video/quicktime;", "data:video/mp4;");
+            }
+
+            video.src = dataUrl;
             video.load();
             video.play();
         };
@@ -588,6 +595,12 @@ export default class ContentMessages {
         // if we have a mime type for the file, add it to the message metadata
         if (file.type) {
             content.info.mimetype = file.type;
+
+            // clobber quicktime muxed files to be considered MP4 so browsers
+            // are willing to play them
+            if (content.info.mimetype == "video/quicktime") {
+                content.info.mimetype = "video/mp4";
+            }
         }
 
         const prom = new Promise<void>((resolve) => {