Thanks for the pointer pic.
If you search the string "baseline shift" in the AE reference, you get nada.
This control shifts the baseline based on a pixel value.
It would be handy to be able to shift in a percentage value (50%),
in order to easily center the axis without having to eyeball it.
In the thread I linked to above, the final post says:
"So if you center-style the text, slde the baseline shift, and BAM, you are centered."
1. What if I have a multi-line field of text that I want justified left,
but I want the rotation axis to be centered on the complete field of text?
2. In the old thread above, you also suggest there may be a way to use
"an expression using sampleImage()... that detects the text bounding box".
That post was in October 2009... do you know if this has come to pass?
3. Also, is there a way to automatically center the axis
of a null object to a field of text?
That's odd. I just tried the same search as the one shown in your screenshot, and it worked for me. Would you mind trying again? I'm trying to determine if there's a problem with our search interface or back end.
Regarding your original question: There is no built-in way to detect the center of the contents of a text layer. Some folks have written hacks that analyze the contents with the sampleImage method. Here's one:
(I found that with this search.)