Open Source Software: Timing Editor

I needed to draw a timing diagram for a mixed signal class I took.  I found 

• Timing Editor

The problem I was solving is shown below in the image.  It's rather tedious to figure out.  You have to remember that once a gate capacitance is charged up it ideally holds that charge until it is connected to again by either Vdd or Ground.

The gate turns out to be a falling edge triggered flip flop.  You can see it in the wikipedia:flip flop article that includes this diagram which was found after I did the timing diagram.