Fix follow-mouse clicks on undraggable mode/header lines.

* mouse.el (mouse-drag-line): Even if the line is not draggable,
keep reading until we get the up-event anyway, in order to process
the up-event for mouse-1-click-follows-link.

Fixes: debbugs:12971

2 files changed, 13 insertions, 7 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 431f45c369..04aa1dc021 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,9 @@
+2012-11-24  Chong Yidong  <[email protected]>
+
+	* mouse.el (mouse-drag-line): Even if the line is not draggable,
+	keep reading until we get the up-event anyway, in order to process
+	the up-event for mouse-1-click-follows-link (Bug#12971).
+
 2012-11-23  Stefan Monnier  <[email protected]>
 
 	* emacs-lisp/bytecomp.el (byte-compile-file): Setup default value for
diff --git a/lisp/mouse.el b/lisp/mouse.el
index 61d70404bd..60a3d39088 100644
--- a/lisp/mouse.el
+++ b/lisp/mouse.el
@@ -425,7 +425,7 @@ must be one of the symbols `header', `mode', or `vertical'."
 				   (frame-parameters frame)))
 			'right)))
 	 (draggable t)
-	 event position growth dragged)
+	 finished event position growth dragged)
     (cond
      ((eq line 'header)
       ;; Check whether header-line can be dragged at all.
@@ -457,7 +457,7 @@ must be one of the symbols `header', `mode', or `vertical'."
     ;; Start tracking.
     (track-mouse
       ;; Loop reading events and sampling the position of the mouse.
-      (while draggable
+      (while (not finished)
 	(setq event (read-event))
 	(setq position (mouse-position))
 	;; Do nothing if
@@ -472,7 +472,7 @@ must be one of the symbols `header', `mode', or `vertical'."
 	;;   - there is a keyboard event or some other unknown event.
 	(cond
 	 ((not (consp event))
-	  (setq draggable nil))
+	  (setq finished t))
 	 ((memq (car event) '(switch-frame select-window))
 	  nil)
 	 ((not (memq (car event) '(mouse-movement scroll-bar-movement)))
@@ -480,15 +480,15 @@ must be one of the symbols `header', `mode', or `vertical'."
 	    ;; Do not unread a drag-mouse-1 event to avoid selecting
 	    ;; some other window.  For vertical line dragging do not
 	    ;; unread mouse-1 events either (but only if we dragged at
-	    ;; least once to allow mouse-1 clicks get through.
+	    ;; least once to allow mouse-1 clicks get through).
 	    (unless (and dragged
 			 (if (eq line 'vertical)
 			     (memq (car event) '(drag-mouse-1 mouse-1))
 			   (eq (car event) 'drag-mouse-1)))
 	      (push event unread-command-events)))
-	  (setq draggable nil))
-	 ((or (not (eq (car position) frame))
-	      (null (car (cdr position))))
+	  (setq finished t))
+	 ((not (and (eq (car position) frame)
+		    (cadr position)))
 	  nil)
 	 ((eq line 'vertical)
 	  ;; Drag vertical divider.