From 62c252e8ef8e7d10b121d65810008e6b75f68b39 Mon Sep 17 00:00:00 2001
From: Zach Pomerantz <zach@highfidelity.io>
Date: Mon, 18 Apr 2016 13:26:40 -0700
Subject: [PATCH] Set GL in QML immediately

---
 libraries/gl/src/gl/OffscreenQmlSurface.cpp | 38 +++++++++++++++------
 1 file changed, 28 insertions(+), 10 deletions(-)

diff --git a/libraries/gl/src/gl/OffscreenQmlSurface.cpp b/libraries/gl/src/gl/OffscreenQmlSurface.cpp
index 9dc475ab27..e90ef9e782 100644
--- a/libraries/gl/src/gl/OffscreenQmlSurface.cpp
+++ b/libraries/gl/src/gl/OffscreenQmlSurface.cpp
@@ -83,11 +83,18 @@ protected:
     };
 
     friend class OffscreenQmlSurface;
+
+    QJsonObject getGLContextData();
+
     Queue _queue;
     QMutex _mutex;
     QWaitCondition _waitCondition;
     std::atomic<bool> _rendering { false };
 
+    QJsonObject _glData;
+    QMutex _glMutex;
+    QWaitCondition _glWait;
+
 private:
     // Event-driven methods
     void init();
@@ -211,22 +218,31 @@ void OffscreenQmlRenderThread::setupFbo() {
     }
 }
 
+QJsonObject OffscreenQmlRenderThread::getGLContextData() {
+    _glMutex.lock();
+    if (_glData.isEmpty()) {
+        _glWait.wait(&_glMutex);
+    }
+    _glMutex.unlock();
+    return _glData;
+}
+
 void OffscreenQmlRenderThread::init() {
     qDebug() << "Initializing QML Renderer";
 
-    connect(_renderControl, &QQuickRenderControl::renderRequested, _surface, &OffscreenQmlSurface::requestRender);
-    connect(_renderControl, &QQuickRenderControl::sceneChanged, _surface, &OffscreenQmlSurface::requestUpdate);
-
     if (!_canvas.makeCurrent()) {
         qWarning("Failed to make context current on QML Renderer Thread");
         _quit = true;
         return;
     }
 
-    // Expose GL data to QML
-    auto glData = getGLContextData();
-    auto setGL = [=]{ _surface->getRootContext()->setContextProperty("GL", glData); };
-    _surface->executeOnUiThread(setGL);
+    _glMutex.lock();
+    _glData = ::getGLContextData();
+    _glMutex.unlock();
+    _glWait.wakeAll();
+
+    connect(_renderControl, &QQuickRenderControl::renderRequested, _surface, &OffscreenQmlSurface::requestRender);
+    connect(_renderControl, &QQuickRenderControl::sceneChanged, _surface, &OffscreenQmlSurface::requestUpdate);
 
     _renderControl->initialize(_canvas.getContext());
     setupFbo();
@@ -386,14 +402,16 @@ void OffscreenQmlSurface::create(QOpenGLContext* shareContext) {
         _qmlEngine->setIncubationController(_renderer->_quickWindow->incubationController());
     }
 
+    _qmlEngine->rootContext()->setContextProperty("GL", _renderer->getGLContextData());
+    _qmlEngine->rootContext()->setContextProperty("offscreenWindow", QVariant::fromValue(getWindow()));
+    _qmlComponent = new QQmlComponent(_qmlEngine);
+
     // When Quick says there is a need to render, we will not render immediately. Instead,
     // a timer with a small interval is used to get better performance.
-    _updateTimer.setInterval(MIN_TIMER_MS);
     QObject::connect(&_updateTimer, &QTimer::timeout, this, &OffscreenQmlSurface::updateQuick);
     QObject::connect(qApp, &QCoreApplication::aboutToQuit, this, &OffscreenQmlSurface::onAboutToQuit);
+    _updateTimer.setInterval(MIN_TIMER_MS);
     _updateTimer.start();
-    _qmlComponent = new QQmlComponent(_qmlEngine);
-    _qmlEngine->rootContext()->setContextProperty("offscreenWindow", QVariant::fromValue(getWindow()));
 }
 
 void OffscreenQmlSurface::resize(const QSize& newSize_) {