selection fix - select multiple objects with control

src/ui/view/GUI.java

@@ -1306,7 +1306,6 @@ public class GUI<E> implements CategoryListener {
 		canvas.addMouseListener(new MouseAdapter() {
 			@Override
 			public void mousePressed(MouseEvent e) {
-				selectedElements.clear();
 				holonEleNamesDisplayed = Languages.getLanguage()[25];
 				// If any empty space is clicked
 				if (temp == null || temp.getID() != model.getSelectedObjectID()) {

src/ui/view/MyCanvas.java

@@ -642,7 +642,13 @@ public class MyCanvas extends JPanel implements MouseListener, MouseMotionListen
 				controller.addTextToConsole(", ID:", Color.BLACK, 12, false, false, false);
 				controller.addTextToConsole("" + cps.getID(), Color.RED, 12, true, false, true);
 				dragging = true;
-				controller.setSelectedObjectID(tempCps.getID());
+				if (e.isControlDown() && tempCps != null) {
+					if (model.getSelectedCpsObjects().contains(tempCps)) {
+						controller.deleteSelectedObject(tempCps);
+					} else {
+						controller.addSelectedObject(tempCps);
+					}
+				}
 				// If drawing an Edge (CTRL down)
 				if (tempCps.getClass() == HolonObject.class) {
 					HolonObject tempObj = ((HolonObject) tempCps);