Render text informing of ongoing shutdown (#696)

include/openspace/rendering/renderengine.h

@@ -93,6 +93,7 @@ public:
     bool mouseActivationCallback(const glm::dvec2& mousePosition) const;
 
     void renderOverlays(const ShutdownInformation& shutdownInfo);
+    void renderEndscreen();
     void postDraw();
 
     // Performance measurements

src/engine/openspaceengine.cpp

@@ -760,6 +760,11 @@ void OpenSpaceEngine::loadSingleAsset(const std::string& assetPath) {
 void OpenSpaceEngine::deinitialize() {
     LTRACE("OpenSpaceEngine::deinitialize(begin)");
 
+    // We want to render an image informing the user that we are shutting down
+    _renderEngine->renderEndscreen();
+
+    _engine->_windowWrapper->swapBuffer();
+
     for (const std::function<void()>& func : _engine->_moduleCallbacks.deinitializeGL) {
         func();
     }
@@ -1235,6 +1240,7 @@ void OpenSpaceEngine::postSynchronizationPreDraw() {
     if (_shutdown.inShutdown) {
         if (_shutdown.timer <= 0.f) {
             _windowWrapper->terminate();
+            return;
         }
         _shutdown.timer -= static_cast<float>(_windowWrapper->averageDeltaTime());
     }

src/rendering/renderengine.cpp

@@ -639,6 +639,23 @@ void RenderEngine::renderOverlays(const ShutdownInformation& shutdownInfo) {
     }
 }
 
+void RenderEngine::renderEndscreen() {
+    glClearColor(0.f, 0.f, 0.f, 0.25f);
+    glClear(GL_COLOR_BUFFER_BIT);
+
+    using FR = ghoul::fontrendering::FontRenderer;
+    using BBox = FR::BoundingBoxInformation;
+    BBox size = FR::defaultRenderer().boundingBox(
+        *_fontDate,
+        "Shutting down"
+    );
+    glm::vec2 penPosition = glm::vec2(
+        fontResolution().x / 2 - size.boundingBox.x / 2,
+        fontResolution().y / 2- size.boundingBox.y / 2
+    );
+    RenderFont(*_fontDate, penPosition, "Shutting down");
+}
+
 void RenderEngine::renderShutdownInformation(float timer, float fullTime) {
     timer = std::max(timer, 0.f);