The motivation for writing this was that I have trouble remembering option and command arguments and the order in which they must appear. For example, I regularly use the postscript terminal driver, but have trouble remembering all of its arguments. When executing one of those key-sequences, a small frame will appear near the center of the window. The buffer displayed in this frame will contain widgets for setting all possible arguments to the selected command. Green buttons are sensitive to the middle mouse button and pop-up selection menus.
Grey areas are text boxes for filling in numeric or string arguments.
On the first line of this buffer is a black button which, when pressed, will open up a frame displaying the info page for the selected command. There are widget types for every kind of argument that gnuplot uses. In addition to the list, numeric, and string widget, there are widgets for entering file names, tic labels, and data ranges. This widget set is a quirky and behaves slightly differently from typical X Windows widget sets. But once you get the hang of it, the GUI is pretty handy.