bug#20983: 11.88.6; Toggling all previews' visibility on/off at once

[gojjoe]

Dear All,

This a feature request and a report of a strange behaviour 
of Preview's "preview-at-point".

In Preview, it would be useful to have a function that 
toggles on/off the visibility of all previews in the buffer, 
independently of the position of point. The key word here is 
"toggle", rather than "regenerate".

The function preview-at-point only toggles one preview, and 
only if the point is positioned on the preview. So if one 
only needs to take a quick look at the LaTeX code of a 
couple of formulae above or below point, one must 1. move 
point to the preview, 2. call preview-at-point (or mouse-2)
, 3. take a look and memorize the code of interest, 4. call 
preview-at-point, 5. move point back.  Another option is to 
clear all previews (say in the section) and then regenerate 
them – but this can take much longer time.

I tried to use/reverse engineer both "preview-at-point" and 
"preview-toggle" to build a function that toggles all 
previews at once, but failed (I don't understand how the 
"overlay" argument works). If anyone can suggest a method to 
do this, I'd be very grateful. Otherwise I'll leave this as 
a feature request.

The bug: While investigating the above, I noticed that 
calling "preview-at-point" (C-c C-p C-p) generates an error 
when point is not on a preview and a region is not selected. 
Is this the desired behaviour?


Preview and AUCTeX are great, thank you so much to all of you!
Joe


Emacs  : GNU Emacs 24.5.1 (i686-pc-mingw32)
 of 2015-04-11 on LEG570
Package: 11.88.6

current state:
==============
(setq
 AUCTeX-date "2015-05-08"
 window-system 'w32
 LaTeX-version "2e"
...