Add additional logic when performing the 'BACK' action on a DVD to av…

…oid getting stuck.

[b16ccb6] relaxed the definition of a menu to any time one or more buttons are defined.  This can make it difficult to exit playback with the 'BACK' action if a DVD is authored such that the title or root jump points do not contain buttons (but maybe show several minutes of trailers before getting to the menu).

Fixes #11649

mythtv/libs/libmythdvdnav/dvdnav/navigation.c

@@ -276,9 +276,11 @@ dvdnav_status_t dvdnav_stop(dvdnav_t *this) {
 
 dvdnav_status_t dvdnav_go_up(dvdnav_t *this) {
   /* A nice easy function... delegate to the VM */
+  int32_t retval;
+
   pthread_mutex_lock(&this->vm_lock);
-  vm_jump_up(this->vm);
+  retval = vm_jump_up(this->vm);
   pthread_mutex_unlock(&this->vm_lock);
 
-  return DVDNAV_STATUS_OK;
+  return retval ? DVDNAV_STATUS_OK : DVDNAV_STATUS_ERR;
 }

mythtv/libs/libmythtv/DVD/dvdringbuffer.cpp

@@ -1341,6 +1341,52 @@ bool DVDRingBuffer::GoToMenu(const QString str)
     return false;
 }
 
+/** \brief Attempts to back-up by trying to jump to the 'Go up' PGC,
+ *         the root menu or the title menu in turn.
+ * \return true if a jump was possible, false if not.
+ */
+bool DVDRingBuffer::GoBack(void)
+{
+    bool success = false;
+    QString target;
+
+    QMutexLocker locker(&m_seekLock);
+
+    if (dvdnav_is_domain_vts(m_dvdnav) && !m_inMenu)
+    {
+        if(dvdnav_go_up(m_dvdnav) == DVDNAV_STATUS_OK)
+        {
+            target = "GoUp";
+            success = true;
+        }
+        else
+        if(dvdnav_menu_call(m_dvdnav, DVD_MENU_Root) == DVDNAV_STATUS_OK)
+        {
+            target = "Root";
+            success = true;
+        }
+        else
+        if(dvdnav_menu_call(m_dvdnav, DVD_MENU_Title) == DVDNAV_STATUS_OK)
+        {
+            target = "Title";
+            success = true;
+        }
+        else
+        {
+            target = "Nothing available";
+        }
+    }
+    else
+    {
+        target = QString("No jump, %1 menu").arg(m_inMenu ? "in" : "not in");
+    }
+
+    LOG(VB_PLAYBACK, LOG_INFO,
+        LOC + QString("DVDRingBuf: GoBack - %1").arg(target));
+
+    return success;
+}
+
 void DVDRingBuffer::GoToNextProgram(void)
 {
     QMutexLocker locker(&m_seekLock);

mythtv/libs/libmythtv/DVD/dvdringbuffer.h

@@ -165,6 +165,7 @@ class MTV_PUBLIC DVDRingBuffer : public RingBuffer
     bool GoToMenu(const QString str);
     void GoToNextProgram(void);
     void GoToPreviousProgram(void);
+    bool GoBack(void);
 
     virtual void IgnoreWaitStates(bool ignore) { m_skipstillorwait = ignore; }
     void AudioStreamsChanged(bool change) { m_audioStreamsChanged = change; }

mythtv/libs/libmythtv/tv_play.cpp

@@ -4463,14 +4463,11 @@ bool TV::ActiveHandleAction(PlayerContext *ctx,
             else
             {
                 // If it's a DVD, and we're not trying to execute a
-                // jumppoint, and it's not in a menu, then first try
-                // jumping to the title or root menu.
+                // jumppoint, try to back up.
                 if (isDVD &&
                     !GetMythMainWindow()->IsExitingToMain() &&
                     has_action("BACK", actions) &&
-                    !ctx->buffer->DVD()->IsInMenu() &&
-                    (ctx->player->GoToMenu("title") ||
-                     ctx->player->GoToMenu("root")))
+                    ctx->buffer->DVD()->GoBack())
                 {
                     return handled;
                 }