bug#27530: patch to cut and copy secondary

[Tak Kunihiro <tkk@misasa.okayama-u.ac.jp>]

I re-send a patch to cut and copy the secondary.

I saw https://www.emacswiki.org/emacs/second-sel.el and found it is a
super super-set of this patch.  As my submission, I try to maintain
this patch small and fit into `simple.el' and `mouse.el'.

> defun mouse-secondary-exists-p ()
> 
> Name probably shouldn't end in `-p' if the return value is
> mainly not a Boolean.  Non-nil here means overlay limits.

I changed docstring to match the name of function.

    Return if the secondary selection exists in current buffer.
    When exists, this returns start and end of the secondary selection.

> defun mouse-set-mark-and-point-from-secondary ()
> 
> Cf. `secondary-to-primary'.

I changed the name to mouse-set-primary-from-secondary.

> defun mouse-set-secondary-from-region ()
> 
> Cf. `primary-to-secondary'.

I changed the name to mouse-set-secondary-from-primary.

> IMO, the first, and simplest, improvement to add to Emacs is
> a way to create and yank the secondary selection using only
> the keyboard, not the mouse.  My guess is that the reason
> more users do not use the secondary selection is that there
> are no keyboard keybindings for it.

I made following the two functions to be interactive to be called from
keyboard.

    mouse-set-primary-from-secondary
    mouse-set-secondary-from-primary

My local plan is to set secondary by hook something like below.

    (add-hook 'view-mode-hook 'mouse-set-secondary-from-primary)


# Change log

2017-07-02  Tak Kunihiro  <tkk@misasa.okayama-u.ac.jp>

        Cut and copy the secondary selection when the region does not exist.

        * doc/emacs/killing.texi (Secondary Selection): Document support of cut and copy the secondary selection.
        * lisp/simple.el (kill-secondary-flag): Use also the secondary selection not only the region to cut and copy.
        (kill-region): Set target to the secondary selection not only the primary selection if kill-secondary-flag is non-nil.
        (kill-ring-save): Set target to the secondary selection not only the primary selection if kill-secondary-flag is non-nil.
        * lisp/mouse.el (mouse-secondary-exists-p): Return if the secondary selection exists in current buffer.
        (mouse-set-primary-from-secondary): Set the region to text in the secondary selection.
        (mouse-set-secondary-from-primary): Set the secondary selection to text in the region.

# NEWS

** Use can cut and copy secondary when region does not exist.
To cut and copy secondary using C-w and M-w, set 'kill-secondary-flag' to t.

# Code 1/2

diff --git a/mouse.260.el b/mouse.el
old mode 100644
new mode 100755
index 9b6b169..55357da
--- a/mouse.260.el
+++ b/mouse.el
@@ -1545,6 +1545,51 @@ CLICK position, kill the secondary selection."
 	 (> (length str) 0)
 	 (gui-set-selection 'SECONDARY str))))

+(defun mouse-secondary-exists-p ()
+  "Return if the secondary selection exists in current buffer.
+When exists, this returns start and end of the secondary selection."
+  (let ((buf (overlay-buffer mouse-secondary-overlay))
+        (beg (overlay-start mouse-secondary-overlay))
+        (end (overlay-end mouse-secondary-overlay)))
+    (when (and buf beg end
+               (equal buf (current-buffer))
+               (/= beg end))
+      (list beg end))))
+
+(defun mouse-set-primary-from-secondary ()
+  "Set the region to text in the secondary selection.
+This works when the secondary selection exists and the region
+does not exist in current buffer.  The mouse-secondary-overlay
+will be deleted."
+  (interactive)
+  (let ((secondary-to-kill (and (not (region-active-p))
+                                (mouse-secondary-exists-p))))
+    ;; Delete overlay even on different buffer.
+    ;; Deletion should be later than obtaining location.
+    (delete-overlay mouse-secondary-overlay)
+    (when secondary-to-kill
+      (push-mark (car secondary-to-kill) t t)
+      (goto-char (cadr secondary-to-kill)))))
+
+(defun mouse-set-secondary-from-primary ()
+  "Set the secondary selection to text in the region.
+When region does not exists, set mouse-secondary-start to the point.
+When point is in the secondary selection, do nothing."
+  (interactive)
+  (cond
+   ((region-active-p) ; Create mouse-secondary-overlay from region.
+    (delete-overlay mouse-secondary-overlay)
+    (move-overlay mouse-secondary-overlay (region-beginning) (region-end)))
+   ((member 'secondary-selection ; Do nothing.
+            (mapcar (lambda (xxx) (overlay-get xxx 'face))
+                    (overlays-at (point)))))
+   (t (delete-overlay mouse-secondary-overlay) ; Create mouse-secondary-start from point.
+      (push-mark (point))
+      (setq mouse-secondary-start (make-marker))
+      (move-marker mouse-secondary-start (point)))))
+
 \f
 (defcustom mouse-buffer-menu-maxlen 20
   "Number of buffers in one pane (submenu) of the buffer menu.

# Code 2/2

diff --git a/simple.252.el b/simple.el
index 5f70ade..a80953a 100644
--- a/simple.252.el
+++ b/simple.el
@@ -4287,11 +4287,21 @@ move the yanking point; just return the Nth kill forward."
   :type 'boolean
   :group 'killing)

+(defcustom kill-secondary-flag nil
+  "Kill the secondary selection when it exists but the region does not exist."
+  :type 'boolean
+  :group 'mouse
+  :version "26.1")
+
 (defun kill-region (beg end &optional region)
   "Kill (\"cut\") text between point and mark.
 This deletes the text from the buffer and saves it in the kill ring.
 The command \\[yank] can retrieve it from there.
 \(If you want to save the region without killing it, use \\[kill-ring-save].)
+If `kill-secondary-flag' is non-nil, kill
+mouse-secondary-overlay instead of the region.

 If you want to append the killed region to the last killed text,
 use \\[append-next-kill] before \\[kill-region].
@@ -4317,7 +4327,12 @@ Supply two arguments, character positions BEG and END indicating the
  region instead."
   ;; Pass mark first, then point, because the order matters when
   ;; calling `kill-append'.
-  (interactive (list (mark) (point) 'region))
+  (interactive
+   (progn (when kill-secondary-flag
+            (mouse-set-primary-from-secondary)) ; no region but secondary
+          (list (mark) (point) 'region)))
   (unless (and beg end)
     (user-error "The mark is not set now, so there is no region"))
   (condition-case nil
@@ -4387,6 +4402,8 @@ This command's old key binding has been given to `kill-ring-save'."
 In Transient Mark mode, deactivate the mark.
 If `interprogram-cut-function' is non-nil, also save the text for a window
 system cut and paste.
+If `kill-secondary-flag' is non-nil, save
+mouse-secondary-overlay instead of the region.

 If you want to append the killed line to the last killed text,
 use \\[append-next-kill] before \\[kill-ring-save].
@@ -4404,8 +4421,13 @@ This command is similar to `copy-region-as-kill', except that it gives
 visual feedback indicating the extent of the region being copied."
   ;; Pass mark first, then point, because the order matters when
   ;; calling `kill-append'.
-  (interactive (list (mark) (point)
-		     (prefix-numeric-value current-prefix-arg)))
+  (interactive
+   (progn (when kill-secondary-flag
+            (mouse-set-primary-from-secondary)) ; no region but secondary
+          (list (mark) (point)
+                (prefix-numeric-value current-prefix-arg))))
   (copy-region-as-kill beg end region)
   ;; This use of called-interactively-p is correct because the code it
   ;; controls just gives the user visual feedback.


# Info

diff --git a/killing.252.texi b/killing.texi
index 47de053..f554adb 100755
--- a/killing.252.texi
+++ b/killing.texi
@@ -624,6 +624,10 @@ end of the yanked text (@code{mouse-yank-secondary}).
 Double or triple clicking of @kbd{M-mouse-1} operates on words and
 lines, much like @kbd{mouse-1}.

+If @code{kill-secondary-flag} is non-@code{nil}, a command @kbd{C-w}
+(@code{kill-region}), and a command @kbd{M-w} (@code{kill-ring-save})
+will target the secondary selection when region does not exist.
+
 If @code{mouse-yank-at-point} is non-@code{nil}, @kbd{M-mouse-2} yanks
 at point.  Then it does not matter precisely where you click, or even
 which of the frame's windows you click on.  @xref{Mouse Commands}.