Once I've decided on a general interface, I'll identify the components of the window that will need to move together. This means finding "frames" within which to put my user interface widgets. I'll determine that when the user resizes the window, I want certain widgets to expand, others to move, and others to stay put. Further development of the design brings us to this:

I've got two frames (as outlined by the red boxes), which I'll label "left" and "right." The left frame will hold the buttons (the buttons will be toggle buttons). This frame will not move and will resize only vertically. The right frame will hold the workspace and will not move but will expand to fit.

Now let's write some code!