| color | an instance of color |
| dimension | a pair of integers denoting pixel size on screen |
| font | an instance of font |
| gadget | a graphical element which responds to user input. Gadgets are tuples which (directly or indirectly) inherit from gadget. |
| label specifier | a string, f or a gadget. See Button gadgets |
| orientation specifier | one of horizontal or vertical |
| point | a pair of integers denoting a pixel location on screen |