X-Git-Url: https://code.delx.au/gnu-emacs/blobdiff_plain/7ad8fe5e2876518a8f33b80050f98dab4ff78398..c5ad92de10abe251165a21977b388d3e799660ac:/lisp/button.el

diff --git a/lisp/button.el b/lisp/button.el
index 6a558af445..0676ba8695 100644
--- a/lisp/button.el
+++ b/lisp/button.el
@@ -1,10 +1,10 @@
 ;;; button.el --- clickable buttons
 ;;
-;; Copyright (C) 2001, 2002, 2003, 2004, 2005,
-;;   2006, 2007, 2008 Free Software Foundation, Inc.
+;; Copyright (C) 2001-2013 Free Software Foundation, Inc.
 ;;
 ;; Author: Miles Bader <miles@gnu.org>
 ;; Keywords: extensions
+;; Package: emacs
 ;;
 ;; This file is part of GNU Emacs.
 ;;
@@ -37,10 +37,12 @@
 ;; the button is represented by a marker or buffer-position pointing
 ;; somewhere in the button.  In the latter case, no markers into the
 ;; buffer are retained, which is important for speed if there are are
-;; extremely large numbers of buttons.
+;; extremely large numbers of buttons.  Note however that if there is
+;; an existing face text-property at the site of the button, the
+;; button face may not be visible.  Using overlays avoids this.
 ;;
 ;; Using `define-button-type' to define default properties for buttons
-;; is not necessary, but it is is encouraged, since doing so makes the
+;; is not necessary, but it is encouraged, since doing so makes the
 ;; resulting code clearer and more efficient.
 ;;
 
@@ -52,10 +54,7 @@
 ;; Use color for the MS-DOS port because it doesn't support underline.
 ;; FIXME if MS-DOS correctly answers the (supports) question, it need
 ;; no longer be a special case.
-(defface button '((((type pc) (class color))
-		   (:foreground "lightblue"))
-		  (((supports :underline t)) :underline t)
-		  (t (:foreground "lightblue")))
+(defface button '((t :inherit link))
   "Default face used for buttons."
   :group 'basic-faces)
 
@@ -84,7 +83,7 @@ Mode-specific keymaps may want to use this as their parent keymap.")
 (put 'default-button 'type 'button)
 ;; action may be either a function to call, or a marker to go to
 (put 'default-button 'action 'ignore)
-(put 'default-button 'help-echo "mouse-2, RET: Push this button")
+(put 'default-button 'help-echo (purecopy "mouse-2, RET: Push this button"))
 ;; Make overlay buttons go away if their underlying text is deleted.
 (put 'default-button 'evaporate t)
 ;; Prevent insertions adjacent to the text-property buttons from
@@ -289,9 +288,12 @@ button-type from which to inherit other properties; see
 `define-button-type'.
 
 This function is like `make-button', except that the button is actually
-part of the text instead of being a property of the buffer.  Creating
-large numbers of buttons can also be somewhat faster using
-`make-text-button'.
+part of the text instead of being a property of the buffer.  That is,
+this function uses text properties, the other uses overlays.
+Creating large numbers of buttons can also be somewhat faster
+using `make-text-button'.  Note, however, that if there is an existing
+face property at the site of the button, the button face may not be visible.
+You may want to use `make-button' in that case.
 
 BEG can also be a string, in which case it is made into a button.
 
@@ -347,7 +349,9 @@ Also see `make-text-button'."
 ;; Finding buttons in a buffer
 
 (defun button-at (pos)
-  "Return the button at position POS in the current buffer, or nil."
+  "Return the button at position POS in the current buffer, or nil.
+If the button at POS is a text property button, the return value
+is a marker pointing to POS."
   (let ((button (get-char-property pos 'button)))
     (if (or (overlayp button) (null button))
 	button
@@ -437,15 +441,22 @@ Returns the button found."
 	    (goto-char (button-start button)))
       ;; Move to Nth next button
       (let ((iterator (if (> n 0) #'next-button #'previous-button))
-	    (wrap-start (if (> n 0) (point-min) (point-max))))
+	    (wrap-start (if (> n 0) (point-min) (point-max)))
+	    opoint fail)
 	(setq n (abs n))
 	(setq button t)			; just to start the loop
-	(while (and (> n 0) button)
+	(while (and (null fail) (> n 0) button)
 	  (setq button (funcall iterator (point)))
 	  (when (and (not button) wrap)
 	    (setq button (funcall iterator wrap-start t)))
 	  (when button
 	    (goto-char (button-start button))
+	    ;; Avoid looping forever (e.g., if all the buttons have
+	    ;; the `skip' property).
+	    (cond ((null opoint)
+		   (setq opoint (point)))
+		  ((= opoint (point))
+		   (setq fail t)))
 	    (unless (button-get button 'skip)
 	      (setq n (1- n)))))))
     (if (null button)
@@ -469,5 +480,4 @@ Returns the button found."
 
 (provide 'button)
 
-;; arch-tag: 5f2c7627-413b-4097-b282-630f89d9c5e9
 ;;; button.el ends here