New gui-selection-value consolidating x-selection-value.

* lisp/select.el (gui-selection-value-alist): New method.
(gui-selection-value): New function.
(x-selection-value): Make it an obsolete alias.
* lisp/simple.el (interprogram-paste-function): Default to gui-selection-value.
* lisp/w32-common-fns.el (w32-get-selection-value): Simplify.
(x-selection-value): Remove alias.
(interprogram-paste-function): Don't set.
(gui-selection-value): Define for w32.
* lisp/term/x-win.el (gui-selection-value): Define for x.
(x--selection-value): Rename from x--selection-value.
(interprogram-paste-function): Don't set.
* lisp/term/pc-win.el (w16-get-selection-value): Simplify.
(msdos-initialize-window-system): Don't set interprogram-paste-function.
(gui-selection-value): Define for pc.
* lisp/term/ns-win.el (x-selection-value): Remove.
(gui-selection-value): Define for ns, instead.
* lisp/term/common-win.el (x-setup-function-keys): Don't set
interprogram-paste-function.
* lisp/obsolete/mouse-sel.el (mouse-sel-get-selection-function):
Use gui-selection-value.

1 files changed, 22 insertions, 0 deletions

diff --git a/lisp/select.el b/lisp/select.el
index d6be917f291..9e48cc0b432 100644
--- a/lisp/select.el
+++ b/lisp/select.el
@@ -98,6 +98,9 @@ SELECTION-SYMBOL is typically `PRIMARY', `SECONDARY', or `CLIPBOARD'.
 TARGET-TYPE is the type of data desired, typically `STRING'.")
 
 (defvar gui-last-selected-text nil
+  ;; We keep track of the last text selected here, so we can check the
+  ;; current selection against it, and avoid passing back our own text
+  ;; from gui-selection-value.
   "Last text passed to `gui-select-text'.")
 
 (defun gui-select-text (text)
@@ -116,6 +119,25 @@ On MS-Windows, make TEXT the current selection."
   (setq gui-last-selected-text text))
 (define-obsolete-function-alias 'x-select-text 'gui-select-text "25.1")
 
+(gui-method-declare gui-selection-value #'ignore
+  "Method to return the GUI's selection.
+Takes no argument, and returns a string.
+Should obey `gui-select-enable-clipboard'.")
+
+(defun gui-selection-value ()
+  (let ((text (gui-call gui-selection-value)))
+    (if (string= text "") (setq text nil))
+    (cond
+     ((not text) nil)
+     ((eq text gui-last-selected-text) nil)
+     ((string= text gui-last-selected-text)
+      ;; Record the newer string, so subsequent calls can use the `eq' test.
+      (setq gui-last-selected-text text)
+      nil)
+     (t
+      (setq gui-last-selected-text text)))))
+(define-obsolete-function-alias 'x-selection-value 'gui-selection-value "25.1")
+
 (defun gui-get-selection (&optional type data-type)
   "Return the value of an X Windows selection.
 The argument TYPE (default `PRIMARY') says which selection,