work towards rewriting the render infrastructure

Mostly foundational work and re-implementing older code in a smarter way
(i.e. context creation code should be slightly faster than it was before)

app/render/backend/opengl/openglworker.cpp

@@ -0,0 +1,113 @@
+#include "openglworker.h"
+
+#include "node/node.h"
+
+OpenGLWorker::OpenGLWorker(QOpenGLContext *share_ctx, QObject *parent) :
+  QObject(parent),
+  share_ctx_(share_ctx),
+  ctx_(nullptr),
+  functions_(nullptr)
+{
+  surface_.create();
+}
+
+OpenGLWorker::~OpenGLWorker()
+{
+  surface_.destroy();
+}
+
+bool OpenGLWorker::IsStarted()
+{
+  return ctx_ != nullptr;
+}
+
+void OpenGLWorker::SetParameters(const VideoRenderingParams &video_params)
+{
+  video_params_ = video_params;
+}
+
+void OpenGLWorker::Init()
+{
+  // Create context object
+  ctx_ = new QOpenGLContext();
+
+  // Set share context
+  ctx_->setShareContext(share_ctx_);
+
+  // Create OpenGL context (automatically destroys any existing if there is one)
+  if (!ctx_->create()) {
+    qWarning() << "Failed to create OpenGL context in thread" << thread();
+    Close();
+    return;
+  }
+
+  ctx_->moveToThread(this->thread());
+
+  qDebug() << "Processor initialized in thread" << thread() << "- context is in" << ctx_->thread();
+
+  // The rest of the initialization needs to occur in the other thread, so we signal for it to start
+  QMetaObject::invokeMethod(this, "FinishInit", Qt::QueuedConnection);
+}
+
+void OpenGLWorker::Close()
+{
+  buffer_.Destroy();
+
+  functions_ = nullptr;
+  delete ctx_;
+}
+
+void OpenGLWorker::Render(const NodeDependency &path)
+{
+  NodeOutput* output = path.node();
+  Node* node = output->parent();
+
+  QList<Node*> all_deps = node->GetDependencies();
+
+  // Lock all Nodes to prevent UI changes during this render
+  foreach (Node* dep, all_deps) {
+    dep->Lock();
+  }
+  node->Lock();
+
+  // FIXME: Write traversal code
+
+  // Start OpenGL flushing now while we do clean up work on the CPU
+  functions_->glFlush();
+
+  // Unlock all Nodes so changes can be made again
+  foreach (Node* dep, all_deps) {
+    dep->Unlock();
+  }
+  node->Unlock();
+
+  // Now we need the texture done so we call glFinish()
+  functions_->glFinish();
+}
+
+void OpenGLWorker::UpdateViewportFromParams()
+{
+  if (functions_ != nullptr && video_params_.is_valid()) {
+    functions_->glViewport(0, 0, video_params_.effective_width(), video_params_.effective_height());
+  }
+}
+
+void OpenGLWorker::FinishInit()
+{
+  // Make context current on that surface
+  if (!ctx_->makeCurrent(&surface_)) {
+    qWarning() << "Failed to makeCurrent() on offscreen surface in thread" << thread();
+    return;
+  }
+
+  // Store OpenGL functions instance
+  functions_ = ctx_->functions();
+
+  // Set up OpenGL parameters as necessary
+  functions_->glEnable(GL_BLEND);
+  UpdateViewportFromParams();
+
+  buffer_.Create(ctx_);
+
+  qDebug() << "Context in" << ctx_->thread() << "successfully finished";
+}