cache: improved code pathways for cache

Viewers are now more aware of each other and can pause each others' cache tasks
when one of them plays, as well as wait for other viewers' cache tasks to
finish before starting their own.

app/widget/viewer/viewer.cpp

@@ -46,6 +46,8 @@ const int kMaxPreQueueSize = 16;
 
 CacheTask* ViewerWidget::cache_background_task_ = nullptr;
 
+int ViewerWidget::busy_viewers_ = 0;
+
 ViewerWidget::ViewerWidget(QWidget *parent) :
   TimeBasedWidget(false, true, parent),
   playback_speed_(0),
@@ -55,7 +57,9 @@ ViewerWidget::ViewerWidget(QWidget *parent) :
   override_color_manager_(nullptr),
   time_changed_from_timer_(false),
   playback_is_audio_only_(false),
-  prequeuing_(false)
+  prequeuing_(false),
+  busy_(false),
+  our_cache_background_task_(nullptr)
 {
   // Set up main layout
   QVBoxLayout* layout = new QVBoxLayout(this);
@@ -237,7 +241,7 @@ void ViewerWidget::DisconnectNodeInternal(ViewerOutput *n)
   waveform_view_->SetViewer(nullptr);
   waveform_view_->ConnectTimelinePoints(nullptr);
 
-  StopAllBackgroundCacheTasks();
+  StopAllBackgroundCacheTasks(true);
   cache_background_task_ = nullptr;
   cache_wait_timer_.stop();
 }
@@ -360,9 +364,16 @@ void ViewerWidget::SetGizmos(Node *node)
   display_widget_->SetGizmos(node);
 }
 
-void ViewerWidget::StopAllBackgroundCacheTasks()
+void ViewerWidget::StopAllBackgroundCacheTasks(bool wait)
 {
-  TaskManager::instance()->CancelTaskAndWait(cache_background_task_);
+  if (cache_background_task_) {
+    if (wait) {
+      TaskManager::instance()->CancelTaskAndWait(cache_background_task_);
+    } else {
+      cache_background_task_->Cancel();
+    }
+    cache_background_task_ = nullptr;
+  }
 }
 
 void ViewerWidget::SetBackgroundCacheTask(CacheTask *t)
@@ -481,7 +492,36 @@ void ViewerWidget::PlayInternal(int speed, bool in_to_out_only)
     FillPlaybackQueue();
   }
 
-  StopBackgroundCache();
+  if (!busy_) {
+    busy_ = true;
+    busy_viewers_++;
+  }
+
+  StopAllBackgroundCacheTasks(false);
+  cache_wait_timer_.stop();
+}
+
+void ViewerWidget::PauseInternal()
+{
+  if (IsPlaying()) {
+    AudioManager::instance()->StopOutput();
+    playback_speed_ = 0;
+    controls_->ShowPlayButton();
+
+    if (playback_is_audio_only_) {
+      disconnect(AudioManager::instance(), &AudioManager::OutputNotified, this, &ViewerWidget::PlaybackTimerUpdate);
+    } else {
+      disconnect(display_widget_, &ViewerDisplayWidget::frameSwapped, this, &ViewerWidget::PlaybackTimerUpdate);
+    }
+
+    foreach (ViewerWindow* window, windows_) {
+      window->Pause();
+    }
+
+    playback_queue_.clear();
+  }
+
+  prequeuing_ = false;
 }
 
 void ViewerWidget::PushScrubbedAudio()
@@ -657,15 +697,6 @@ AudioRenderingParams ViewerWidget::GenerateAudioParams() const
                               SampleFormat::kInternalFormat);
 }
 
-void ViewerWidget::StopBackgroundCache()
-{
-  cache_wait_timer_.stop();
-  if (cache_background_task_) {
-    cache_background_task_->Cancel();
-    cache_background_task_ = nullptr;
-  }
-}
-
 void ViewerWidget::UpdateStack()
 {
   if (GetConnectedNode()
@@ -807,8 +838,14 @@ void ViewerWidget::HashGenerated()
 
 void ViewerWidget::StartBackgroundCaching()
 {
-  if (Config::Current()["AutoCache"].toBool()) {
-    if (cache_background_task_) {
+  if (busy_) {
+    busy_viewers_--;
+    busy_ = false;
+  }
+
+  if (GetConnectedNode()->video_frame_cache()->HasInvalidatedRanges()
+      && Config::Current()["AutoCache"].toBool()) {
+    if (cache_background_task_ || busy_viewers_) {
 
       // Something else is caching right now, we don't want to do multiple at once so we'll check
       // again in our next interval
@@ -820,6 +857,8 @@ void ViewerWidget::StartBackgroundCaching()
                                              GenerateAudioParams(),
                                              false);
 
+      our_cache_background_task_ = cache_background_task_;
+
       TaskManager::instance()->AddTask(cache_background_task_);
     }
   }
@@ -834,6 +873,12 @@ void ViewerWidget::BackgroundCacheFinished(Task* t)
 
 void ViewerWidget::UpdateRendererParameters()
 {
+  if (cache_background_task_ == our_cache_background_task_) {
+    StopAllBackgroundCacheTasks(false);
+  }
+
+  StartBackgroundCaching();
+
   renderer_->SetVideoParams(GenerateVideoParams());
 
   renderer_->SetAudioParams(GenerateAudioParams());
@@ -979,25 +1024,8 @@ void ViewerWidget::Play()
 
 void ViewerWidget::Pause()
 {
-  if (IsPlaying()) {
-    AudioManager::instance()->StopOutput();
-    playback_speed_ = 0;
-    controls_->ShowPlayButton();
+  PauseInternal();
 
-    if (playback_is_audio_only_) {
-      disconnect(AudioManager::instance(), &AudioManager::OutputNotified, this, &ViewerWidget::PlaybackTimerUpdate);
-    } else {
-      disconnect(display_widget_, &ViewerDisplayWidget::frameSwapped, this, &ViewerWidget::PlaybackTimerUpdate);
-    }
-
-    foreach (ViewerWindow* window, windows_) {
-      window->Pause();
-    }
-
-    playback_queue_.clear();
-  }
-
-  prequeuing_ = false;
   StartBackgroundCaching();
 }
 
@@ -1006,7 +1034,7 @@ void ViewerWidget::ShuttleLeft()
   int current_speed = playback_speed_;
 
   if (current_speed != 0) {
-    Pause();
+    PauseInternal();
   }
 
   current_speed--;
@@ -1028,7 +1056,7 @@ void ViewerWidget::ShuttleRight()
   int current_speed = playback_speed_;
 
   if (current_speed != 0) {
-    Pause();
+    PauseInternal();
   }
 
   current_speed++;
@@ -1170,8 +1198,16 @@ void ViewerWidget::ViewerInvalidatedRange(const TimeRange &range)
   }
 
   // Restart the cache wait timer
-  StopBackgroundCache();
-  cache_wait_timer_.start();
+  cache_wait_timer_.stop();
+  StopAllBackgroundCacheTasks(false);
+
+  if (qApp->mouseButtons() & Qt::LeftButton) {
+    cache_wait_timer_.start();
+  } else {
+    StartBackgroundCaching();
+  }
+
+
 
   /*
   QList<rational> invalidated_frames = GetConnectedNode()->video_frame_cache()->GetFrameListFromTimeRange({range});