I feel that it may be useful to have a section in the cookbook (maybe as an appendix), explaining how the GMT modern mode works. For example:
- the structure of Postscript file (Head + body1 + body2 +…+ bodyn + trailer, i.e., the -K and -O option)
- the classic way to create a figure (via -K, -O and redirection)
- the paper size (~11mX11m) and the plot origin (a few inches from the bottom left corner)
- how GMT knows the option history (via gmt.history, but the file is invisible in modern mode)
- what’s a GMT session, and session PPID
- the concept of session, figure, subplot, and inset and the different levels of CPTs and gmt.conf
- et al.
Most users don’t need to know how GMT modern mode works, but it’s useful for people to understanding some of the GMT’s behaviors.
I know that some of the points above are already documented in the cookbook or module manpage, but they’re in separated places and may make users difficult to follow.