renderer: implemented function to wait for workers in the main thread

The workers run in separate threads meaning if any significant change is made
(e.g. parameters changing, or even closing the program), these workers may still
be mid-render. This is particularly problematic when closing since the nodes a
worker is rendering may be deleted mid-render. Render backends now have a
function that pauses the main thread (but starts a second event loop so the UI
isn't frozen) until the worker threads are all finished. This way, massive
changes can be made safely without race conditions.

app/render/backend/opengl/openglbackend.cpp

@@ -39,7 +39,10 @@ bool OpenGLBackend::InitInternal()
 
   // Create master texture (the one sent to the viewer)
   master_texture_ = std::make_shared<OpenGLTexture>();
-  master_texture_->Create(share_ctx, params().effective_width(), params().effective_height(), params().format());
+  master_texture_->Create(share_ctx,
+                          params().effective_width(),
+                          params().effective_height(),
+                          params().format());
 
   // Create copy buffer/pipeline
   copy_buffer_.Create(share_ctx);
@@ -156,11 +159,13 @@ void OpenGLBackend::EmitCachedFrameReady(const rational &time, const QVariant &v
 
 void OpenGLBackend::ParamsChangedEvent()
 {
-  // Assume if the texture is allocated, it needs to be changed. Otherwise the texture should be created through
-  // InitInternal() with the correct parameters
-  if (master_texture_) {
+  // If we're initiated, we need to recreate the texture. Otherwise this backend isn't active so it doesn't matter.
+  if (IsInitiated()) {
     master_texture_->Destroy();
-    master_texture_->Create(QOpenGLContext::currentContext(), params().effective_width(), params().effective_height(), params().format());
+    master_texture_->Create(QOpenGLContext::currentContext(),
+                            params().effective_width(),
+                            params().effective_height(),
+                            params().format());
   }
 }
 

app/render/backend/renderbackend.cpp

@@ -3,6 +3,9 @@
 #include <QDateTime>
 #include <QThread>
 
+#include "core.h"
+#include "window/mainwindow/mainwindow.h"
+
 RenderBackend::RenderBackend(QObject *parent) :
   QObject(parent),
   compiled_(false),
@@ -12,6 +15,8 @@ RenderBackend::RenderBackend(QObject *parent) :
   recompile_queued_(false),
   input_update_queued_(false)
 {
+  // FIXME: Don't create in CLI mode
+  cancel_dialog_ = new RenderCancelDialog(Core::instance()->main_window());
 }
 
 bool RenderBackend::Init()
@@ -30,6 +35,8 @@ bool RenderBackend::Init()
     thread->start(QThread::LowPriority);
   }
 
+  cancel_dialog_->SetWorkerCount(threads_.size());
+
   started_ = InitInternal();
 
   // Connects workers and moves them to their respective threads
@@ -50,6 +57,8 @@ void RenderBackend::Close()
 
   started_ = false;
 
+  CancelQueue();
+
   Decompile();
 
   CloseInternal();
@@ -81,6 +90,8 @@ const QString &RenderBackend::GetError() const
 void RenderBackend::SetViewerNode(ViewerOutput *viewer_node)
 {
   if (viewer_node_ != nullptr) {
+    CancelQueue();
+
     DisconnectViewer(viewer_node_);
 
     Decompile();
@@ -297,6 +308,7 @@ void RenderBackend::CacheNext()
       render_job_info_.insert(cache_frame, job_time);
 
       SetWorkerBusyState(worker, true);
+      cancel_dialog_->WorkerStarted();
 
       QMetaObject::invokeMethod(worker,
                                 "Render",
@@ -312,6 +324,20 @@ ViewerOutput *RenderBackend::viewer_node() const
   return copied_viewer_node_;
 }
 
+void RenderBackend::CancelQueue()
+{
+  cache_queue_.clear();
+
+  int busy = 0;
+  for (int i=0;i<processor_busy_state_.size();i++) {
+    if (processor_busy_state_.at(i))
+      busy++;
+  }
+  qDebug() << this << "has" << busy << "busy workers";
+
+  cancel_dialog_->RunIfWorkersAreBusy();
+}
+
 bool RenderBackend::ViewerIsConnected() const
 {
   return viewer_node_ != nullptr;
@@ -375,6 +401,9 @@ void RenderBackend::InitWorkers()
     // Connect to it
     ConnectWorkerToThis(processor);
 
+    // Connect cancel dialog to it
+    connect(processor, &RenderWorker::CompletedCache, cancel_dialog_, &RenderCancelDialog::WorkerDone, Qt::QueuedConnection);
+
     // Finally, we can move it to its own thread
     processor->moveToThread(thread);
 

app/render/backend/renderbackend.h

@@ -4,6 +4,7 @@
 #include <QLinkedList>
 
 #include "common/constructors.h"
+#include "dialog/rendercancel/rendercancel.h"
 #include "decodercache.h"
 #include "node/graph.h"
 #include "node/output/viewer/viewer.h"
@@ -15,8 +16,6 @@ class RenderBackend : public QObject
 public:
   RenderBackend(QObject* parent = nullptr);
 
-  DISABLE_COPY_MOVE(RenderBackend)
-
   bool Init();
 
   void Close();
@@ -29,6 +28,8 @@ public:
 
   ViewerOutput* viewer_node() const;
 
+  void CancelQueue();
+
 public slots:
   void InvalidateCache(const rational &start_range, const rational &end_range);
 
@@ -142,6 +143,8 @@ private:
 
   QVector<bool> processor_busy_state_;
 
+  RenderCancelDialog* cancel_dialog_;
+
 };
 
 #endif // RENDERBACKEND_H

app/render/backend/videorenderbackend.cpp

@@ -76,10 +76,7 @@ const VideoRenderingParams &VideoRenderBackend::params() const
 
 void VideoRenderBackend::SetParameters(const VideoRenderingParams& params)
 {
-  if (!AllProcessorsAreAvailable()) {
-    qCritical() << "Attempted to set parameters on a backend whose workers are still busy";
-    return;
-  }
+  CancelQueue();
 
   // Set new parameters
   params_ = params;