bug#10022: 24.0.91; `isearch-mouse-2' relies on `x-get-selection' - NG for Windows etc.

[Drew Adams]

> Steps to reproduce it, please.

As I said in the OP:

 "No, I am not certain this is a bug - you decide.
  ...
  Consider this only an FYI."

In case it helps, digging into this more shows that setting the X selection
explicitly is necessary for the code to work also with older Emacs versions.
That is not necessary for Emacs 24.

FWIW, I use this, which gives users the option to not have to move the mouse to
the echo area to yank the selection.  Option `isearchp-mouse-2-flag' is t by
default.

(defun isearch-mouse-2 (click)
  "Handle `mouse-2' in Isearch mode.
If `isearchp-mouse-2-flag' is non-nil, yank the X selection.
If `isearchp-mouse-2-flag' is nil, yank it only if the `mouse-2' click
is in the echo area.  Otherwise, invoke whatever `mouse-2' is bound to
outside of Isearch."
  (interactive "e")
  (if (not isearchp-mouse-2-flag)
      (let ((win  (posn-window (event-start click)))
            (overriding-terminal-local-map  nil)
            (binding
             (key-binding (this-command-keys-vector) t)))
        (if (and (window-minibuffer-p win)
                 (not (minibuffer-window-active-p win))) ; In echo area
            (isearchp-set-sel-and-yank)
          (when (functionp binding) (call-interactively binding))))
    (when (/= (region-beginning) (region-end))
      (isearchp-set-sel-and-yank))))

(defun isearchp-set-sel-and-yank ()
  "Set X selection and yank it into echo area."
  (x-set-selection 'PRIMARY (buffer-substring-no-properties
                             (region-beginning) (region-end)))
  (deactivate-mark)
  (isearch-yank-x-selection))

If it were not for needing the code to work with older Emacs versions, all that
would be needed would be this:

(defun isearch-mouse-2 (click)
  "..."
  (interactive "e")
  (if (not isearchp-mouse-2-flag)
      (let ((win  (posn-window (event-start click)))
            (overriding-terminal-local-map  nil)
            (binding
             (key-binding (this-command-keys-vector) t)))
        (if (and (window-minibuffer-p win)
                 (not (minibuffer-window-active-p win))) ; In echo area
            (isearch-yank-x-selection)
          (when (functionp binding) (call-interactively binding))))
    (when (/= (region-beginning) (region-end))
      (let ((select-active-regions  t))
        (deactivate-mark)
        (isearch-yank-x-selection)))))

The binding of `select-active-region' is needed, however.  Without that (and
with a customized setting of nil), `get-x-selection' returns nil - the problem I
mentioned earlier.

HTH.