bug#22873: Can we support multiple Cursors?

[Keith David Bershatsky]

The second draft of the proposed feature for multiple fake cursors is attached. 
 For the record, I'm not a programmer -- just a hobbyist -- and the draft patch 
is not meant to be a proposed official patch -- it is just a working proof 
concept.  The patch contains a few extra things that I use for debugging and 
also for drawing my solid vertical line that tracks the cursor position.  It 
has been tested to some extent on Emacs built for OSX 10.6.8 and Windows XP 
(SP-3).  Different colors for each fake cursor have already been implemented on 
Emacs for OSX, but I haven't yet looked into how to accomplish that objective 
on Emacs for Windows.  The draft concept patch is for the master branch as of 
March 8, 2016 bearing commit "e0400b72a24d67b53f71c8b97915cae599e36c37".  After 
applying the patch, the new feature can be tested as follows:

(defun mc-test (&optional list)
"Draw fake cursors at all POS defined in the `mc-list'."
(interactive)
  (setq mc-list '(
    (3 "hbar" [1.0 0.0 0.0])
    (4 "bar" [0.0 1.0 0.0])
    (5 "box" [0.0 0.0 1.0])
    (6 "hollow" [1.0 1.0 1.0])
    (7 ("hbar" 3) [1.0 0.0 1.0])
    (8 ("bar" 3) [0.0 1.0 1.0]))))

(global-set-key [f1] 'mc-test)

To remove the cursors or change the cursors, just modify the buffer-local 
variable `mc-list' -- e.g., `(setq mc-list nil)` removes them all.  The colors 
on OSX are the standard RGB color vector.

Thank you, Marcin, for the referral to the ideit feature.  I will certainly try 
that feature out in the next few days, but have been buried in life's daily 
activities and also in acquiring the necessary skills to implement the fake 
cursors feature.

It sure would be great if a real programmer (instead of just a hobbyist like 
myself) could take this feature to the next level.  If the Windows setup is 
anything similar to OSX, implementing colors should not be that difficult to 
achieve (at least I hope that is the case).

I would like this feature to be similar to the original cursor such that a 
variable like `cursor-in-non-selected-windows' can be used to make the fake 
cursors displayed in only the selected window or in all windows where those 
points are visible.  At the present time, I've set it up so that only the 
selected window receives the fake cursors (as that is my personal preference).

Thank you for taking an interest in this potential new feature,

Keith

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At Sat, 05 Mar 2016 07:59:52 +0100,
Marcin Borkowski wrote:
> 
> * * *
> 
> Out of curiosity: did you try iedit?  How does it compare wrt speed in
> such extreme cases?  (If it's applicable at all, that is - it's way
> simpler than multiple-cursors, of course.)

multiple_cursors.diff
Description: application/diff