RE: purpose and usage of secondary-selection ???

[ken <gebser@mousecar.com>]

> >/Sometimes while typing on my laptop I accidentally brush against the/
> >/touchpad and inadvertantly mess up something. Today, while not even/
> >/emacs, this happened, affecting what happened in an emacs frame which/
> >/previously didn't even have the focus./
> >//
> >/What I ended up in that emacs frame was that a random section of text/
> >/was set to background yellow. Investigating further, I found that text/
> >/with the yellow background was a secondary-selection. But I couldn't/
> >/find anything in the Help screens describing anything about it, except/
> >/its properties. So here are my questions:/
> >//
> >/What is/are the purpose(s) of a secondary-selection?/
> >//
> >/What can be done with a secondary-selection...? and how to do them?/
> >//
> >/How do I undo this secondary-selection... i.e., make the selection go/
> >/away without changing the file/buffer in any way?/
>
> 1. Emacs Wiki is your friend:
> https://www.emacswiki.org/emacs/SecondarySelection
>
> 2. Its characteristics tell you its advantages and disadvantages.
>
> a. It is separate from the region.  So you have two pieces of text you
>     can paste/yank.
>
> b. It is unrelated to point (the cursor position).  The region always has
>     point as one of its end positions (mark is the other end).
>
> 3. A good use case: Selective replacement of things (same thing or
>     different things) with the same text.  Select some text, then yank
>     the secondary selection.  Repeat - anywhere; any text to replace.
>
>     You cannot do this with the region text, because as soon as you
>     select the text to replace you've redefined the region, and so
>     also the text to yank.
>
> 4. For the secondary selection to really be useful, IMHO, you need to
>     bind yanking it to a keyboard key, not just to a mouse action.
>
> 5. Library `second-sel.el' can help make the secondary selection
>     more useful.
>     https://www.emacswiki.org/emacs/SecondarySelection#secondary-sel.el
>
> 6. See the Emacs manual, node `Secondary Selection' for more info.
>     
> http://www.gnu.org/software/emacs/manual/html_node/emacs/Secondary-Selection.html
>
> 7. To make the secondary selection empty ("get rid of it"): Click
>     `M-mouse-1' (don't drag).

Whoever thought of and whoever maintains the list archives, thanks. I 
found my post there, as well as two replies.  Above is one which is very 
helpful.  Thanks, Drew.

I'll be doing some reading on this and playing around with it.  I like 
the fact that a secondary-selection's region is highlighted and that the 
highlighting doesn't follow the point around, that a region can be 
marked and *stays marked* while I move around within the file/buffer 
looking for something else, e.g., the place I want to move the region 
to.  I hope to find other helpful uses for it.

tnx++

PS (to developers): It would be nice if the emacs menus had some mention 
of secondary-selection, maybe some of its very basic functionality.  Not 
a big fan of mousing around in text processors or editors, but sometimes 
a menu can give a clue when I don't have one. :)