Add support for threaded renderer

Author: barche

CMakeLists.txt

@@ -2,7 +2,7 @@ cmake_minimum_required(VERSION 3.16.0)
 
 project(JlQML)
 
-set(JlQML_VERSION 0.8.0)
+set(JlQML_VERSION 0.9.0)
 message(STATUS "Project version: v${JlQML_VERSION}")
 
 set(CMAKE_MACOSX_RPATH 1)

application_manager.cpp

@@ -94,7 +94,6 @@ void ApplicationManager::exec()
   {
     app->exit(status);
   });
-  ForeignThreadManager::instance().clear(QThread::currentThread());
   const int status = app->exec();
   if (status != 0)
   {
@@ -112,7 +111,10 @@ void ApplicationManager::add_import_path(std::string path)
 
 ApplicationManager::ApplicationManager()
 {
-  qputenv("QSG_RENDER_LOOP", QProcessEnvironment::systemEnvironment().value("QSG_RENDER_LOOP").toLocal8Bit());
+  if(QProcessEnvironment::systemEnvironment().contains("QSG_RENDER_LOOP"))
+  {
+    qputenv("QSG_RENDER_LOOP", QProcessEnvironment::systemEnvironment().value("QSG_RENDER_LOOP").toLocal8Bit());
+  }
 
   qInstallMessageHandler(julia_message_output);
 
@@ -154,6 +156,7 @@ void ApplicationManager::set_engine(QQmlEngine* e)
   {
     e->addImportPath(QString::fromStdString(path));
   }
+  ForeignThreadManager::instance().clear(QThread::currentThread());
 }
 
 void ApplicationManager::process_events()

foreign_thread_manager.cpp

@@ -1,3 +1,5 @@
+#include <QQuickWindow>
+
 #include "jlcxx/jlcxx.hpp"
 
 #include "foreign_thread_manager.hpp"
@@ -34,6 +36,53 @@ void ForeignThreadManager::clear(QThread* main_thread)
   m_mutex.unlock();
 }
 
+void ForeignThreadManager::add_window(QQuickItem* item)
+{
+  QObject::connect(item, &QQuickItem::windowChanged, [item, m_main_gc_state = JL_GC_STATE_UNSAFE, m_render_gc_state = JL_GC_STATE_UNSAFE] (QQuickWindow* w) mutable
+  {
+    if (w == nullptr)
+    {
+      return;
+    }
+    item->connect(w, &QQuickWindow::sceneGraphInitialized, [] ()
+    {
+      // Adopt the render thread when it is first initialized
+      ForeignThreadManager::instance().add_thread(QThread::currentThread());
+    });
+    item->connect(w, &QQuickWindow::afterAnimating, [&m_main_gc_state] ()
+    {
+      // afterAnimating is the last signal sent before locking the main loop, so indicate
+      // that the main loop is in a safe state for the Julia GC to run
+      jl_ptls_t ptls = jl_current_task->ptls;
+      m_main_gc_state = jl_gc_safe_enter(ptls);
+      ptls->engine_nqueued++;
+    });
+    item->connect(w, &QQuickWindow::beforeRendering, w, [&m_main_gc_state] ()
+    {
+      // beforeRendering is the first signal sent after unlocking the main thread, so restore
+      // the Julia GC state here. Queued connection so this is executed on the main thread
+      jl_ptls_t ptls = jl_current_task->ptls;
+      jl_gc_safe_leave(ptls, m_main_gc_state);
+      ptls->engine_nqueued--;
+    }, Qt::QueuedConnection);
+    item->connect(w, &QQuickWindow::afterFrameEnd, w, [&m_render_gc_state] ()
+    {
+      // After the rendering is done, the render thread may block for event handling, so we mark it as in a GC safe state
+      // to prevent deadlock
+      jl_ptls_t ptls = jl_current_task->ptls;
+      m_render_gc_state = jl_gc_safe_enter(ptls);
+      ptls->engine_nqueued++;
+    }, Qt::DirectConnection);
+    item->connect(w, &QQuickWindow::beforeFrameBegin, w, [&m_render_gc_state] ()
+    {
+      // Reset GC state when the render thread might execute Julia code again
+      jl_ptls_t ptls = jl_current_task->ptls;
+      jl_gc_safe_leave(ptls, m_render_gc_state);
+      ptls->engine_nqueued--;
+    }, Qt::DirectConnection);
+  });
+}
+
 ForeignThreadManager::ForeignThreadManager()
 {
 }

foreign_thread_manager.hpp

@@ -1,5 +1,6 @@
 #include <QSet>
 #include <QMutex>
+#include <QQuickItem>
 #include <QThread>
 
 class ForeignThreadManager
@@ -9,6 +10,7 @@ class ForeignThreadManager
 
   void add_thread(QThread* t);
   void clear(QThread* main_thread);
+  void add_window(QQuickItem* item);
 
 private:
   ForeignThreadManager();

julia_canvas.cpp

@@ -11,18 +11,18 @@ namespace qmlwrap
 
 JuliaCanvas::JuliaCanvas(QQuickItem *parent) : QQuickPaintedItem(parent)
 {
+  ForeignThreadManager::instance().add_window(this);
 }
 
 void JuliaCanvas::paint(QPainter *painter)
 {
-  ForeignThreadManager::instance().add_thread(QThread::currentThread());
   // allocate buffer for julia callback to draw on
   int iwidth = width();
   int iheight = height();
   unsigned int *draw_buffer = new unsigned int[iwidth * iheight];
 
   // call julia painter
-  m_callback(jlcxx::make_julia_array(draw_buffer, iwidth*iheight), iwidth, iheight);
+  m_callback(draw_buffer, iwidth, iheight);
 
   // make QImage
   QImage *image = new QImage((uchar*)draw_buffer, width(), height(), QImage::Format_ARGB32);
@@ -37,7 +37,7 @@ void JuliaCanvas::paint(QPainter *painter)
 
 void JuliaCanvas::setPaintFunction(jlcxx::SafeCFunction f)
 {
-  m_callback = jlcxx::make_function_pointer<void(jlcxx::ArrayRef<uint>, int, int)>(f); 
+  m_callback = jlcxx::make_function_pointer<void(unsigned int*, int, int)>(f); 
 }
 
 } // namespace qmlwrap

julia_canvas.hpp

@@ -18,7 +18,7 @@ class JuliaCanvas : public QQuickPaintedItem
   Q_PROPERTY(jlcxx::SafeCFunction paintFunction READ paintFunction WRITE setPaintFunction)
 
 public:
-  typedef void (*callback_t)(jlcxx::ArrayRef<unsigned int>, int, int);
+  typedef void (*callback_t)(unsigned int*, int, int);
   JuliaCanvas(QQuickItem *parent = 0);
   void paint(QPainter *painter);
   void setPaintFunction(jlcxx::SafeCFunction f);

julia_painteditem.cpp

@@ -10,10 +10,6 @@ namespace qmlwrap
 
 JuliaPaintedItem::JuliaPaintedItem(QQuickItem *parent) : QQuickPaintedItem(parent)
 {
-  if(qgetenv("QSG_RENDER_LOOP") != "basic")
-  {
-    qFatal("QSG_RENDER_LOOP must be set to basic to use JuliaPaintedItem. Add the line\nENV[\"QSG_RENDER_LOOP\"] = \"basic\"\nat the top of your Julia program");
-  }
 }
 
 void JuliaPaintedItem::paint(QPainter* painter)

opengl_viewport.cpp

@@ -1,8 +1,10 @@
 #include <QOpenGLFramebufferObject>
 #include <QQuickWindow>
+#include <QQuickOpenGLUtils>
 #include <QSGNode>
 #include <QSGSimpleTextureNode>
 
+#include "foreign_thread_manager.hpp"
 #include "opengl_viewport.hpp"
 
 namespace qmlwrap
@@ -26,6 +28,7 @@ class OpenGLViewport::JuliaRenderer : public QQuickFramebufferObject::Renderer
     m_vp->render();
     m_vp->post_render();
     m_vp->window()->endExternalCommands();
+    QQuickOpenGLUtils::resetOpenGLState();
   }
 
   void synchronize(QQuickFramebufferObject *item)
@@ -59,12 +62,9 @@ OpenGLViewport::OpenGLViewport(QQuickItem *parent, RenderFunction* render_func)
   {
     qFatal("OpenGL rendering required for OpenGLViewport or MakieViewport. Add the line\nQML.setGraphicsApi(QML.OpenGL)\nbefore loading the QML program.");
   }
-  if(qgetenv("QSG_RENDER_LOOP") != "basic")
-  {
-    qFatal("QSG_RENDER_LOOP must be set to basic to use OpenGLViewport or MakieViewport. Add the line\nENV[\"QSG_RENDER_LOOP\"] = \"basic\"\nat the top of your Julia program");
-  }
   QObject::connect(this, &OpenGLViewport::renderFunctionChanged, this, &OpenGLViewport::update);
   setMirrorVertically(true);
+  ForeignThreadManager::instance().add_window(this);
 }
 
 void OpenGLViewport::render()

wrap_qml.cpp

@@ -738,7 +738,7 @@ JLCXX_MODULE define_julia_module(jlcxx::Module& qml_module)
   qml_module.method("init_qquickview", []() { return qmlwrap::ApplicationManager::instance().init_qquickview(); });
   qml_module.method("cleanup", []() { qmlwrap::ApplicationManager::instance().cleanup(); });
   qml_module.method("qmlcontext", []() { return qmlwrap::ApplicationManager::instance().root_context(); });
-  qml_module.method("exec", []() { qmlwrap::ApplicationManager::instance().exec(); });
+  qml_module.method("app_exec", []() { qmlwrap::ApplicationManager::instance().exec(); });
   qml_module.method("process_events", qmlwrap::ApplicationManager::process_events);
   qml_module.method("add_import_path", [](std::string path) { qmlwrap::ApplicationManager::instance().add_import_path(path); });