Drawing a straight line if you click and drag. Showing a temporary preview line as you drag around.
Click and drag to draw a rectangle.  A temporary preview rectangle is drawn as you drag.  (Yes, it's pretty much the same code as drawing a line.)
Click and drag to draw a circle.  A temporary preview circle is drawn as you drag.
Combining all four tools so the app can handle any of them (without needing to uncomment the source, lolz) and adding buttons for the user to select which one they want to use.  The websocket transactions also support multiple tools.  Woo!