simple canvas drag-and-drop

wow, I'm rusty. I can't seem to figure out how to do a simple
canvas widget that will have a couple of rectangles that the user
can click on and resize. I looked at the example in the
"widget" script and couldn't decode how it worked.
 
Anyone got a barebones bit of code that draws a canvas,
puts a rectangle on it, and then allows the user to click on
various parts of the rectangle and move it and resize it?
 
Much appreciated.
 
Greg