added coordinate system documentation (in progress)

git-svn-id: svn://anubis/anaglym/trunk@273 99a6e188-d820-4881-8870-2d33a10e2619

tests/managed_objects.lua

@@ -11,6 +11,8 @@ function init_event()
         ag.exit()
     end
     ag.setCursorVisible(true)
+    pt_x = -1
+    pt_y = -1
 end
 
 function init_obj(obj)
@@ -66,5 +68,14 @@ function mousebutton_down_event(button, x, y)
                 obj:setColor(0, 0, 1)
             end
         end
+    elseif (button == 3) then
+        pt_x = x
+        pt_y = y
+    end
+end
+
+function update_overlay_event(width, height)
+    if (pt_x >= 0 and pt_y >= 0) then
+        ag.drawCircle(0, 1, 0, pt_x, pt_y, 5)
     end
 end