How to convert world position to canvas click

I have some code to fire at the cursor and I have set up a canvas like this. Problem is when I click on the screen I need to know where the player is on the canvas as well. However when I run the code touchScreenUI.getCanvasPoint(%obj.getPosition()); it returns numbers like -511, 477 when the mouse coords are coming back as -22, -10. It seems like the function is broken. How do I convert from world position to screen coords so I can get a vector to the mouse point to fire at it?

new t2dSceneWindow(touchScreenUI) {
      canSaveDynamicFields = "0";
      isContainer = "0";
      Profile = "GuiDefaultProfile";
      HorizSizing = "right";
      VertSizing = "bottom";
      Position = "0 0";
      Extent = "800 600";
      MinExtent = "8 2";
      canSave = "1";
      Visible = "1";
      hovertime = "1000";
      lockMouse = "1";
      useWindowMouseEvents = "1";
      useObjectMouseEvents = "1";
   };