viewer: detect nouveau and warn

Nouveau has poor compatibility with Olive (and most other graphically intensive
applications). For user benefit, we throw a warning messagebox if we detect the
user is using Nouveau.

app/widget/viewer/viewerglwidget.cpp

@@ -28,6 +28,10 @@
 #include "render/backend/opengl/openglrenderfunctions.h"
 #include "render/backend/opengl/openglshader.h"
 
+#ifdef Q_OS_LINUX
+bool ViewerGLWidget::nouveau_check_done_ = false;
+#endif
+
 ViewerGLWidget::ViewerGLWidget(QWidget *parent) :
   QOpenGLWidget(parent),
   texture_(0),
@@ -132,6 +136,21 @@ void ViewerGLWidget::initializeGL()
   SetupColorProcessor();
 
   connect(context(), SIGNAL(aboutToBeDestroyed()), this, SLOT(ContextCleanup()), Qt::DirectConnection);
+
+#ifdef Q_OS_LINUX
+  if (!nouveau_check_done_) {
+    const char* vendor = reinterpret_cast<const char*>(context()->functions()->glGetString(GL_VENDOR));
+
+    if (!strcmp(vendor, "nouveau")) {
+      // Working with Qt widgets in this function segfaults, so we queue the messagebox for later
+      QMetaObject::invokeMethod(this,
+                                "ShowNouveauWarning",
+                                Qt::QueuedConnection);
+    }
+
+    nouveau_check_done_ = true;
+  }
+#endif
 }
 
 void ViewerGLWidget::paintGL()
@@ -185,6 +204,18 @@ void ViewerGLWidget::RefreshColorPipeline()
   update();
 }
 
+#ifdef Q_OS_LINUX
+void ViewerGLWidget::ShowNouveauWarning()
+{
+  QMessageBox::warning(this,
+                       tr("Driver Warning"),
+                       tr("Olive has detected your system is using the Nouveau graphics driver.\n\nThis driver is "
+                          "known to have stability and performance issues with Olive. It is highly recommended "
+                          "you install the proprietary NVIDIA driver before continuing to use Olive."),
+                       QMessageBox::Ok);
+}
+#endif
+
 void ViewerGLWidget::SetupColorProcessor()
 {
   if (!context()) {

app/widget/viewer/viewerglwidget.h

@@ -186,6 +186,10 @@ private:
    */
   QMatrix4x4 matrix_;
 
+#ifdef Q_OS_LINUX
+  static bool nouveau_check_done_;
+#endif
+
 private slots:
   /**
    * @brief Slot to connect just before the OpenGL context is destroyed to clean up resources
@@ -197,6 +201,13 @@ private slots:
    */
   void RefreshColorPipeline();
 
+#ifdef Q_OS_LINUX
+  /**
+   * @brief Shows warning messagebox if Nouveau is detected
+   */
+  void ShowNouveauWarning();
+#endif
+
 };
 
 #endif // VIEWERGLWIDGET_H