LibWeb: Implement the HTMLMediaElement show-poster flag

Note that this doesn't do much yet, as the HTMLVideoElement does not
handle its poster attribute as of this commit.

Userland/Libraries/LibWeb/HTML/HTMLMediaElement.cpp

@@ -385,7 +385,8 @@ WebIDL::ExceptionOr<void> HTMLMediaElement::select_resource()
     // 1. Set the element's networkState attribute to the NETWORK_NO_SOURCE value.
     m_network_state = NetworkState::NoSource;
 
-    // FIXME: 2. Set the element's show poster flag to true.
+    // 2. Set the element's show poster flag to true.
+    set_show_poster(true);
 
     // 3. Set the media element's delaying-the-load-event flag to true (this delays the load event).
     m_delaying_the_load_event.emplace(document());
@@ -877,7 +878,8 @@ WebIDL::ExceptionOr<void> HTMLMediaElement::handle_media_source_failure(Span<JS:
     // 3. Set the element's networkState attribute to the NETWORK_NO_SOURCE value.
     m_network_state = NetworkState::NoSource;
 
-    // FIXME: 4. Set the element's show poster flag to true.
+    // 4. Set the element's show poster flag to true.
+    set_show_poster(true);
 
     // 5. Fire an event named error at the media element.
     dispatch_event(TRY(DOM::Event::create(realm(), HTML::EventNames::error)));
@@ -994,7 +996,11 @@ void HTMLMediaElement::set_ready_state(ReadyState ready_state)
             // Set the paused attribute to false.
             set_paused(false);
 
-            // FIXME: If the element's show poster flag is true, set it to false and run the time marches on steps.
+            // If the element's show poster flag is true, set it to false and run the time marches on steps.
+            if (m_show_poster) {
+                set_show_poster(false);
+                time_marches_on();
+            }
 
             // Queue a media element task given the element to fire an event named play at the element.
             queue_a_media_element_task([this]() {
@@ -1034,7 +1040,11 @@ WebIDL::ExceptionOr<void> HTMLMediaElement::play_element()
         // 1. Change the value of paused to false.
         set_paused(false);
 
-        // FIXME: 2. If the show poster flag is true, set the element's show poster flag to false and run the time marches on steps.
+        // 2. If the show poster flag is true, set the element's show poster flag to false and run the time marches on steps.
+        if (m_show_poster) {
+            set_show_poster(false);
+            time_marches_on();
+        }
 
         // 3. Queue a media element task given the media element to fire an event named play at the element.
         queue_a_media_element_task([this]() {
@@ -1110,7 +1120,8 @@ WebIDL::ExceptionOr<void> HTMLMediaElement::pause_element()
 // https://html.spec.whatwg.org/multipage/media.html#dom-media-seek
 void HTMLMediaElement::seek_element(double playback_position, MediaSeekMode seek_mode)
 {
-    // FIXME: 1. Set the media element's show poster flag to false.
+    // 1. Set the media element's show poster flag to false.
+    set_show_poster(false);
 
     // 2. If the media element's readyState is HAVE_NOTHING, return.
     if (m_ready_state == ReadyState::HaveNothing)
@@ -1200,6 +1211,17 @@ void HTMLMediaElement::notify_about_playing()
     on_playing();
 }
 
+void HTMLMediaElement::set_show_poster(bool show_poster)
+{
+    if (m_show_poster == show_poster)
+        return;
+
+    m_show_poster = show_poster;
+
+    if (auto* layout_node = this->layout_node())
+        layout_node->set_needs_display();
+}
+
 void HTMLMediaElement::set_paused(bool paused)
 {
     if (m_paused == paused)

Userland/Libraries/LibWeb/HTML/HTMLMediaElement.h

@@ -68,6 +68,7 @@ public:
     void set_current_playback_position(double);
 
     double duration() const;
+    bool show_poster() const { return m_show_poster; }
     bool paused() const { return m_paused; }
     bool ended() const;
     bool potentially_playing() const;
@@ -113,6 +114,7 @@ private:
     WebIDL::ExceptionOr<void> pause_element();
     void seek_element(double playback_position, MediaSeekMode = MediaSeekMode::Accurate);
     void notify_about_playing();
+    void set_show_poster(bool);
     void set_paused(bool);
     void set_duration(double);
 
@@ -171,6 +173,9 @@ private:
     // https://html.spec.whatwg.org/multipage/media.html#default-playback-start-position
     double m_default_playback_start_position { 0 };
 
+    // https://html.spec.whatwg.org/multipage/media.html#show-poster-flag
+    bool m_show_poster { true };
+
     // https://html.spec.whatwg.org/multipage/media.html#dom-media-duration
     double m_duration { NAN };