Prevent artist-mode from creating runaway timers (Bug#6130).

* subr.el (posnp): Correct docstring of `posnp'.
(posn-col-row): Make it work with all mouse position objects.
* textmodes/artist.el (artist-mouse-draw-continously): Cancel
timers if an error occurs during continuous drawing.  (Bug#6130)

* commands.texi (Drag Events, Motion Events, Event Examples)
(Accessing Mouse): Describe actual range of values that mouse
position objects can have.

3 files changed, 77 insertions, 58 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 20efe68bff6..280f6022007 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,10 @@
+2015-01-21  Daniel Koning  <dk@danielkoning.com>  (tiny change)
+
+        * subr.el (posnp): Correct docstring of `posnp'.
+        (posn-col-row): Make it work with all mouse position objects.
+        * textmodes/artist.el (artist-mouse-draw-continously): Cancel
+        timers if an error occurs during continuous drawing.  (Bug#6130)
+
 2015-01-20  Eli Zaretskii  <eliz@gnu.org>
 
         * button.el (button-activate, push-button): Doc fix.  (Bug#19628)
diff --git a/lisp/subr.el b/lisp/subr.el
index d71de87b42c..a48038fa12b 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -1062,7 +1062,12 @@ The return value is a positive integer."
 ;;;; Extracting fields of the positions in an event.
 
 (defun posnp (obj)
-  "Return non-nil if OBJ appears to be a valid `posn' object."
+  "Return non-nil if OBJ appears to be a valid `posn' object specifying a window.
+If OBJ is a valid `posn' object, but specifies a frame rather
+than a window, return nil."
+  ;; FIXME: Correct the behavior of this function so that all valid
+  ;; `posn' objects are recognized, after updating other code that
+  ;; depends on its present behavior.
   (and (windowp (car-safe obj))
        (atom (car-safe (setq obj (cdr obj))))                ;AREA-OR-POS.
        (integerp (car-safe (car-safe (setq obj (cdr obj))))) ;XOFFSET.
@@ -1122,24 +1127,28 @@ For a scroll-bar event, the result column is 0, and the row
 corresponds to the vertical position of the click in the scroll bar.
 POSITION should be a list of the form returned by the `event-start'
 and `event-end' functions."
-  (let* ((pair   (posn-x-y position))
-         (window (posn-window position))
-         (area   (posn-area position)))
+  (let* ((pair            (posn-x-y position))
+         (frame-or-window (posn-window position))
+         (frame           (if (framep frame-or-window)
+                              frame-or-window
+                            (window-frame frame-or-window)))
+         (window          (when (windowp frame-or-window) frame-or-window))
+         (area            (posn-area position)))
     (cond
-     ((null window)
+     ((null frame-or-window)
       '(0 . 0))
      ((eq area 'vertical-scroll-bar)
       (cons 0 (scroll-bar-scale pair (1- (window-height window)))))
      ((eq area 'horizontal-scroll-bar)
       (cons (scroll-bar-scale pair (window-width window)) 0))
      (t
-      (let* ((frame (if (framep window) window (window-frame window)))
-             ;; FIXME: This should take line-spacing properties on
-             ;; newlines into account.
-             (spacing (when (display-graphic-p frame)
-                        (or (with-current-buffer (window-buffer window)
-                              line-spacing)
-                            (frame-parameter frame 'line-spacing)))))
+      ;; FIXME: This should take line-spacing properties on
+      ;; newlines into account.
+      (let* ((spacing (when (display-graphic-p frame)
+                        (or (with-current-buffer
+                                (window-buffer (frame-selected-window frame))
+                              line-spacing)
+                            (frame-parameter frame 'line-spacing)))))
         (cond ((floatp spacing)
                (setq spacing (truncate (* spacing
                                           (frame-char-height frame)))))
diff --git a/lisp/textmodes/artist.el b/lisp/textmodes/artist.el
index 8a2383c12ff..85d9410868a 100644
--- a/lisp/textmodes/artist.el
+++ b/lisp/textmodes/artist.el
@@ -4963,52 +4963,55 @@ The event, EV, is the mouse event."
     (artist-funcall init-fn x1 y1)
     (if (not artist-rubber-banding)
         (artist-no-rb-set-point1 x1 y1))
-    (track-mouse
-      (while (or (mouse-movement-p ev)
-                 (member 'down (event-modifiers ev)))
-        (setq ev-start-pos (artist-coord-win-to-buf
-                            (posn-col-row (event-start ev))))
-        (setq x1 (car ev-start-pos))
-        (setq y1 (cdr ev-start-pos))
-
-        ;; Cancel previous timer
-        (if timer
-            (cancel-timer timer))
-
-        (if (not (eq initial-win (posn-window (event-start ev))))
-            ;; If we moved outside the window, do nothing
-            nil
-
-          ;; Still in same window:
-          ;;
-          ;; Check if user presses or releases shift key
-          (if (artist-shift-has-changed shift-state ev)
-
-              ;; First check that the draw-how is the same as we
-              ;; already have. Otherwise, ignore the changed shift-state.
-              (if (not (eq draw-how
-                           (artist-go-get-draw-how-from-symbol
-                            (if (not shift-state) shifted unshifted))))
-                  (message "Cannot switch to shifted operation")
-
-                ;; progn is "implicit" since this is the else-part
-                (setq shift-state (not shift-state))
-                (setq op          (if shift-state shifted unshifted))
-                (setq draw-how    (artist-go-get-draw-how-from-symbol op))
-                (setq draw-fn     (artist-go-get-draw-fn-from-symbol op))))
-
-          ;; Draw the new shape
-          (setq shape (artist-funcall draw-fn x1 y1))
-          (artist-move-to-xy x1 y1)
-
-          ;; Start the timer to call `draw-fn' repeatedly every
-          ;; `interval' second
-          (if (and interval draw-fn)
-              (setq timer (run-at-time interval interval draw-fn x1 y1))))
-
-        ;; Read next event
-        (setq ev (read-event))))
-
+    (unwind-protect
+        (track-mouse
+          (while (or (mouse-movement-p ev)
+                     (member 'down (event-modifiers ev)))
+            (setq ev-start-pos (artist-coord-win-to-buf
+                                (posn-col-row (event-start ev))))
+            (setq x1 (car ev-start-pos))
+            (setq y1 (cdr ev-start-pos))
+
+            ;; Cancel previous timer
+            (if timer
+                (cancel-timer timer))
+
+            (if (not (eq initial-win (posn-window (event-start ev))))
+                ;; If we moved outside the window, do nothing
+                nil
+
+              ;; Still in same window:
+              ;;
+              ;; Check if user presses or releases shift key
+              (if (artist-shift-has-changed shift-state ev)
+
+                  ;; First check that the draw-how is the same as we
+                  ;; already have. Otherwise, ignore the changed shift-state.
+                  (if (not (eq draw-how
+                               (artist-go-get-draw-how-from-symbol
+                                (if (not shift-state) shifted unshifted))))
+                      (message "Cannot switch to shifted operation")
+
+                    ;; progn is "implicit" since this is the else-part
+                    (setq shift-state (not shift-state))
+                    (setq op          (if shift-state shifted unshifted))
+                    (setq draw-how    (artist-go-get-draw-how-from-symbol op))
+                    (setq draw-fn     (artist-go-get-draw-fn-from-symbol op))))
+
+              ;; Draw the new shape
+              (setq shape (artist-funcall draw-fn x1 y1))
+              (artist-move-to-xy x1 y1)
+
+              ;; Start the timer to call `draw-fn' repeatedly every
+              ;; `interval' second
+              (if (and interval draw-fn)
+                  (setq timer (run-at-time interval interval draw-fn x1 y1))))
+
+            ;; Read next event
+            (setq ev (read-event))))
+      ;; Cleanup: get rid of any active timer.
+      (if timer
+          (cancel-timer timer)))
     ;; Cancel any timers
     (if timer
         (cancel-timer timer))