Per the beamer user guide, the syntax of the overlayarea environment is:
\begin{overlayarea}{area width}{area height}
environment contents
\end{overlayarea}
I can't figure out how to get the width and height in properly.
From the customize interface, I added overlayarea as follows:
'(org-beamer-environments-extra (quote (("CJK" "Z" "\\begin{CJK}%a%H"
"\\end{CJK}") ("onlyenv" "O" "\\begin{onlyenv}%a" "\\end{onlyenv}")
("overlayarea" "Y" "\\begin{overlayarea}%o%a" "\\end{overlayarea}"))))
And I can plug text into %o using the BEAMER_OPT property:
*** Overlays :B_overlayarea:
:PROPERTIES:
:BEAMER_env: overlayarea
:BEAMER_OPT: {0.9\textwidth}{0.7\textheight}
:END:
-->
\begin{overlayarea}[{0.9\textwidth}{0.7\textheight}]
Oh, hello, BEAMER_OPT automatically adds square brackets, how charming.
I guess I can hack up a filter to remove the brackets after overlayarea.
.. 45 minutes after I started writing this email...
I copied someone else's ignoreheading filter and modified it for this
purpose:
(defun hjh-overlayarea (contents backend info)
"Remove brackets from options for overlayarea."
(when (and (org-export-derived-backend-p backend 'latex 'html 'ascii)
(string-match "\\\\begin{overlayarea}\\[\\(.*\\)\\]"
(downcase contents)))
(replace-match "\\\\begin{overlayarea}\\1" nil nil contents)))
Replace-match's handling of backslashes threw me at first, but this appears
to work.
Still, I wonder if there shouldn't be, e.g., %O for
options-without-brackets. Because that was 45 minutes I spent NOT writing
my slides :-|
Also, side note, [1] seems not to document BEAMER_OPT for environments
within a frame. Reading this page, you would think you could only use it
for frames. I had to dig into the source code to find how to populate %o.
hjh
[1] http://orgmode.org/worg/exporters/beamer/ox-beamer.html