performance enhancements

memory enhancements
prevent starting sensors more than once
fix for wifi lag issues
map scaling for huge buildings

ui/map/3D/MapView3D.cpp

@@ -108,14 +108,26 @@ void MapView3D::initializeGL() {
 	glEnable(GL_DEPTH_TEST);
 	glEnable(GL_CULL_FACE);
 
-	// start background update timer
-	timer.start(Settings::MapView::msPerFrame.ms(), this);
-
 	// OpenGL is now initialized
 	isGLInitialized = true;
 
 }
 
+void MapView3D::setVisible(bool visible) {
+
+	// inform parent
+	QOpenGLWidget::setVisible(visible);
+
+	if (!visible) {
+		// stop background update timer
+		timer.stop();
+	} else {
+		// start background update timer
+		timer.start(Settings::MapView3D::msPerFrame.ms(), this);
+	}
+
+}
+
 void MapView3D::paintGL() {
 	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 	draw();