Make poster frame load blocker independent from media element's one

servo · bors-servo · Jan 15, 2019 · Nov 29, 2018 · Dec 26, 2018 · Jan 7, 2019
commit fde7d4589f9fe79a2727109e865674dde5250a4f
diff --git a/components/script/dom/htmlvideoelement.rs b/components/script/dom/htmlvideoelement.rs
@@ -2,6 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
+use crate::document_loader::{LoadBlocker, LoadType};
 use crate::dom::attr::Attr;
 use crate::dom::bindings::cell::DomRefCell;
 use crate::dom::bindings::codegen::Bindings::HTMLVideoElementBinding;
@@ -51,6 +52,9 @@ pub struct HTMLVideoElement {
     generation_id: Cell<u32>,
     /// Poster frame fetch request canceller.
     poster_frame_canceller: DomRefCell<FetchCanceller>,
+    /// Load event blocker. Will block the load event while the poster frame
+    /// is being fetched.
+    load_blocker: DomRefCell<Option<LoadBlocker>>,
 }
 
 impl HTMLVideoElement {
@@ -65,6 +69,7 @@ impl HTMLVideoElement {
             video_height: Cell::new(DEFAULT_HEIGHT),
             generation_id: Cell::new(0),
             poster_frame_canceller: DomRefCell::new(Default::default()),
+            load_blocker: Default::default(),
         }
     }
 
@@ -99,6 +104,10 @@ impl HTMLVideoElement {
         self.video_height.set(height);
     }
 
+    pub fn allow_load_event(&self) {
+        LoadBlocker::terminate(&mut *self.load_blocker.borrow_mut());
+    }
+
     /// https://html.spec.whatwg.org/multipage/#poster-frame
     fn fetch_poster_frame(&self, poster_url: &str) {
         // Step 1.
@@ -164,7 +173,16 @@ impl HTMLVideoElement {
         };
 
         // Step 5.
-        self.htmlmediaelement.delay_load_event(true);
+        // This delay must be independent from the ones created by HTMLMediaElement during
+        // its media load algorithm, otherwise a code like
+        // <video poster="poster.png"></video>
+        // (which triggers no media load algorithm unless a explicit call to .load() is done)
+        // will block the document's load event forever.
+        let mut blocker = self.load_blocker.borrow_mut();
+        *blocker = Some(LoadBlocker::new(
+            &document_from_node(self),
+            LoadType::Image(poster_url.clone()),
+        ));
 
         let window = window_from_node(self);
         let context = Arc::new(Mutex::new(PosterFrameFetchContext::new(
@@ -308,6 +326,7 @@ impl FetchResponseListener for PosterFrameFetchContext {
     }
 
     fn process_response_eof(&mut self, response: Result<ResourceFetchTiming, NetworkError>) {
+        self.elem.root().allow_load_event();
         self.image_cache
             .notify_pending_response(self.id, FetchResponseMsg::ProcessResponseEOF(response));
     }

diff --git a/tests/wpt/mozilla/meta/MANIFEST.json b/tests/wpt/mozilla/meta/MANIFEST.json

    "testharness"
   ], 
   "mozilla/video_poster_frame.html": [
-   "8b321ef5d82e0de6e16625ecd41190abc00bacb6",
+   "8e85bcd62303b70153f8d451a843cb2bdd96484d",
    "reftest"
   ], 
   "mozilla/video_poster_frame_ref.html": [
diff --git a/tests/wpt/mozilla/tests/mozilla/video_poster_frame.html b/tests/wpt/mozilla/tests/mozilla/video_poster_frame.html
@@ -6,15 +6,10 @@
     <link rel="match" href="video_poster_frame_ref.html">
   </head>
   <body>
-    <video src="" poster="poster.png"></video>
+    <video poster="poster.png"></video>
     <script>
       let video = document.querySelector("video");
       video.addEventListener("postershown", function() {
-        // Apart from removing the `reftest-wait` class we need to get
-        // the `load` event to signal that it's ok to take the reftest
-        // screenshot. Video loading delays the document `load` event,
-        // so we garantee that we get this event by setting an invalid
-        // src attribute to the video tag.
         document.documentElement.classList.remove("reftest-wait");
       });
     </script>