Fix calibrator attempting to draw when it's activated (outside of draw() function)

src/Calibrator.java

@@ -38,12 +38,27 @@ class Calibrator {
 
     void activate() {
         this.active = true;
-        this.drawnScreen = projector.get(0, 0, projector.width, projector.height);
+
+        // Tell the projector that we want to save the state of the screen
+        //  next time it draws
+        ProjectorCommand saveCommand = (ProjectorApplet p) -> {
+            this.drawnScreen = p.get(0, 0, p.width, p.height);
+            return true;
+        };
+        projector.commandQueue.add(saveCommand);
     }
 
     void deactivate() {
-        projector.clear();
-        projector.set(projector.width, 0, this.drawnScreen);
+        // Create a command which will restore the screen to what it
+        //  looked like before we started calibrating
+        ProjectorCommand restore_command = (ProjectorApplet p) -> {
+            p.clear();
+            p.set(0, 0, this.drawnScreen);
+            return true;
+        };
+
+        // Insert the restore command at the front of the queue
+        projector.commandQueue.add(0, restore_command);
         this.active = false;
     }