Sorry for the noise... My previous question was answered, and I've fixed what I was doing wrong; but only so far as to allow me to phrase a new question, as my original problem still exists. :/
I am trying to apply a driver to the Y Location of a mapping node in a material definition:
Note that I have previously keyframed this Y value successfully, but now I want to use a driver so that I can drive this from a complex animation that's on a different object. I have deleted all its keyframes.
The driver tracks the value of a shape key:
However, when I scrub through the timeline, the value of the driver (in the bottom field of the driver panel) doesn't update. Instead, it shows the key shape's value for the frame that was current when the project loaded. I can prove this by saving it with the playhead in various places.
If I apply the same shape key to a driver that affects, say, an object's X scale, it works fine, updating as I scrub.
In my simple mind, I'm directing a single floating point value to a single floating point value, so I don't know why it's not working. Maybe I'm wrong?
The scripted expression simply maps the key shape's range (0.0 to 0.8) onto the range for Y Location that I was using when I keyframed it (-14.0 to 0.0).
Is there something I'm missing?