[Media] Avoid play() call during seek flow before the finishSeek()

https://bugs.webkit.org/show_bug.cgi?id=283172

Reviewed by Xabier Rodriguez-Calvar.

During the video playback states should ideally flow as play -> pause ->
seek_start -> seek_done -> play, but randomly it is observed that the
play event is being sent before finishing the seek (seek_done) i.e, play
-> pause -> seek_start -> play -> seek_done. Ideally play call might be
triggered continuously by the webapp when we are playing a video, so in
our scenario between seek_start and seek_done we should avoid the play
call.

This commit adds a new condition to skip the playPlayer() call during
updatePlayState() when the seek is ongoing. This would avoid the play
event to happen.

There's also some special cases to not skip playPlayer() on first play,
because initial seeks aren't fully supported on WebKitGTK/WPE and that
play call might be required for them to work:

- First time playing
- Looping
- Resuming playback
- Seek after playback ended (either as part of a loop or a manual seek)

See: #1423
Co-authored with: gowthami <gchikkadasarahallilo.ext@libertyglobal.com>

* Source/WebCore/html/HTMLMediaElement.cpp:
(WebCore::HTMLMediaElement::seekWithTolerance): Set seek after playback ended flag when the current position is equal to duration.
(WebCore::HTMLMediaElement::finishSeek): Reset the seek after playback ended flag.
(WebCore::HTMLMediaElement::playInternal): Set seek after playback ended flag when needed.
(WebCore::HTMLMediaElement::updatePlayState): Add the new conditions and exceptions to disallow playback when seeking.
(WebCore::HTMLMediaElement::mayResumePlayback): Set the isResumingPlayback condition and reset it after the call to play().
* Source/WebCore/html/HTMLMediaElement.h: Added m_isResumingPlayback and m_seekAfterPlaybackEnded flags.

Canonical link: https://commits.webkit.org/287274@main

Author: eocanha

Source/WebCore/html/HTMLMediaElement.cpp

@@ -3212,6 +3212,10 @@ void HTMLMediaElement::seekWithTolerance(const MediaTime& inTime, const MediaTim
     refreshCachedTime();
     MediaTime now = currentMediaTime();
 
+    // Needed to detect a special case in updatePlayState().
+    if (now >= durationMediaTime())
+        m_seekAfterPlaybackEnded = true;
+
     // 3 - If the element's seeking IDL attribute is true, then another instance of this algorithm is
     // already running. Abort that other instance of the algorithm without waiting for the step that
     // it is running to complete.
@@ -3383,6 +3387,8 @@ void HTMLMediaElement::finishSeek()
 #endif
     if (wasPlayingBeforeSeeking)
         playInternal();
+
+    m_seekAfterPlaybackEnded = false;
 }
 
 HTMLMediaElement::ReadyState HTMLMediaElement::readyState() const
@@ -3804,8 +3810,10 @@ void HTMLMediaElement::playInternal()
     if (!m_player || m_networkState == NETWORK_EMPTY)
         selectMediaResource();
 
-    if (endedPlayback())
+    if (endedPlayback()) {
+        m_seekAfterPlaybackEnded = true;
         seekInternal(MediaTime::zeroTime());
+    }
 
     if (m_mediaController)
         m_mediaController->bringElementUpToSpeed(*this);
@@ -5768,7 +5776,17 @@ void HTMLMediaElement::updatePlayState()
     if (shouldBePlaying) {
         invalidateCachedTime();
 
-        if (playerPaused) {
+        // Play is always allowed, except when seeking (to avoid unpausing the video by mistake until the
+        // target time is reached). However, there are some exceptional situations when we allow playback
+        // during seek. This is because GStreamer-based implementation have a design limitation that doesn't
+        // allow initial seeks (seeking before going to playing state), and these exceptions make things
+        // work for those platforms.
+        bool isLooping = loop() && m_lastSeekTime == MediaTime::zeroTime();
+        bool playExceptionsWhenSeeking = m_seeking && (m_firstTimePlaying
+            || isLooping || m_isResumingPlayback || m_seekAfterPlaybackEnded);
+        bool allowPlay = !m_seeking || playExceptionsWhenSeeking;
+
+        if (playerPaused && allowPlay) {
             mediaSession().clientWillBeginPlayback();
 
             // Set rate, muted and volume before calling play in case they were set before the media engine was set up.
@@ -8113,8 +8131,11 @@ void HTMLMediaElement::resumeAutoplaying()
 void HTMLMediaElement::mayResumePlayback(bool shouldResume)
 {
     ALWAYS_LOG(LOGIDENTIFIER, "paused = ", paused());
-    if (paused() && shouldResume)
+    if (paused() && shouldResume) {
+        m_isResumingPlayback = true;
         play();
+        m_isResumingPlayback = false;
+    }
 }
 
 String HTMLMediaElement::mediaSessionTitle() const

Source/WebCore/html/HTMLMediaElement.h

@@ -1162,6 +1162,8 @@ class HTMLMediaElement
     bool m_shouldAudioPlaybackRequireUserGesture : 1;
     bool m_shouldVideoPlaybackRequireUserGesture : 1;
     bool m_volumeLocked : 1;
+    bool m_isResumingPlayback : 1 { false };
+    bool m_seekAfterPlaybackEnded : 1 { false };
 
     AutoplayEventPlaybackState m_autoplayEventPlaybackState { AutoplayEventPlaybackState::None };