Avoid code duplication between prev_frame and next_frame.

* frame.c (candidate_frame): New function.  Add comment.
(prev_frame, next_frame): Use it.  Adjust comment.

src/ChangeLog

+2012-12-06  Dmitry Antipov  <dmantipov@yandex.ru>
+
+	Avoid code duplication between prev_frame and next_frame.
+	* frame.c (candidate_frame): New function.  Add comment.
+	(prev_frame, next_frame): Use it.  Adjust comment.
+
 2012-12-06  Eli Zaretskii  <eliz@gnu.org>
 
 	* callproc.c (Fcall_process_region) [!HAVE_MKSTEMP]: If mktemp

src/frame.c

@@ -895,13 +895,58 @@ DEFUN ("frame-list", Fframe_list, Sframe_list,
   return frames;
 }
 
-/* Return the next frame in the frame list after FRAME.
-   If MINIBUF is nil, exclude minibuffer-only frames.
-   If MINIBUF is a window, include only its own frame
-   and any frame now using that window as the minibuffer.
-   If MINIBUF is `visible', include all visible frames.
-   If MINIBUF is 0, include all visible and iconified frames.
-   Otherwise, include all frames.  */
+/* Return CANDIDATE if it can be used as 'other-than-FRAME' frame on the
+   same tty (for tty frames) or among frames which uses FRAME's keyboard.
+   If MINIBUF is nil, do not consider minibuffer-only candidate.
+   If MINIBUF is `visible', do not consider an invisible candidate. 
+   If MINIBUF is a window, consider only its own frame and candidate now
+   using that window as the minibuffer.
+   If MINIBUF is 0, consider candidate if it is visible or iconified.
+   Otherwise consider any candidate and return nil if CANDIDATE is not
+   acceptable.  */
+
+static Lisp_Object
+candidate_frame (Lisp_Object candidate, Lisp_Object frame, Lisp_Object minibuf)
+{
+  struct frame *c = XFRAME (candidate), *f = XFRAME (frame);
+
+  if ((!FRAME_TERMCAP_P (c) && !FRAME_TERMCAP_P (f)
+       && FRAME_KBOARD (c) == FRAME_KBOARD (f))
+      || (FRAME_TERMCAP_P (c) && FRAME_TERMCAP_P (f)
+	  && FRAME_TTY (c) == FRAME_TTY (f)))
+    {
+      if (NILP (minibuf))
+	{
+	  if (!FRAME_MINIBUF_ONLY_P (c))
+	    return candidate;
+	}
+      else if (EQ (minibuf, Qvisible))
+	{
+	  FRAME_SAMPLE_VISIBILITY (c);
+	  if (FRAME_VISIBLE_P (c))
+	    return candidate;
+	}
+      else if (WINDOWP (minibuf))
+	{
+	  if (EQ (FRAME_MINIBUF_WINDOW (c), minibuf)
+	      || EQ (WINDOW_FRAME (XWINDOW (minibuf)), candidate)
+	      || EQ (WINDOW_FRAME (XWINDOW (minibuf)),
+		     FRAME_FOCUS_FRAME (c)))
+	    return candidate;
+	}
+      else if (XFASTINT (minibuf) == 0)
+	{
+	  FRAME_SAMPLE_VISIBILITY (c);
+	  if (FRAME_VISIBLE_P (c) || FRAME_ICONIFIED_P (c))
+	    return candidate;
+	}
+      else
+	return candidate;
+    }
+  return Qnil;
+}
+
+/* Return the next frame in the frame list after FRAME.  */
 
 static Lisp_Object
 next_frame (Lisp_Object frame, Lisp_Object minibuf)
@@ -910,72 +955,24 @@ next_frame (Lisp_Object frame, Lisp_Object minibuf)
   int passed = 0;
 
   /* There must always be at least one frame in Vframe_list.  */
-  if (! CONSP (Vframe_list))
-    emacs_abort ();
-
-  /* If this frame is dead, it won't be in Vframe_list, and we'll loop
-     forever.  Forestall that.  */
-  CHECK_LIVE_FRAME (frame);
+  eassert (CONSP (Vframe_list));
 
-  while (1)
+  while (passed < 2)
     FOR_EACH_FRAME (tail, f)
       {
-	if (passed
-	    && ((!FRAME_TERMCAP_P (XFRAME (f)) && !FRAME_TERMCAP_P (XFRAME (frame))
-                 && FRAME_KBOARD (XFRAME (f)) == FRAME_KBOARD (XFRAME (frame)))
-                || (FRAME_TERMCAP_P (XFRAME (f)) && FRAME_TERMCAP_P (XFRAME (frame))
-                    && FRAME_TTY (XFRAME (f)) == FRAME_TTY (XFRAME (frame)))))
+	if (passed)
 	  {
-	    /* Decide whether this frame is eligible to be returned.  */
-
-	    /* If we've looped all the way around without finding any
-	       eligible frames, return the original frame.  */
-	    if (EQ (f, frame))
-	      return f;
-
-	    /* Let minibuf decide if this frame is acceptable.  */
-	    if (NILP (minibuf))
-	      {
-		if (! FRAME_MINIBUF_ONLY_P (XFRAME (f)))
-		  return f;
-	      }
-	    else if (EQ (minibuf, Qvisible))
-	      {
-		FRAME_SAMPLE_VISIBILITY (XFRAME (f));
-		if (FRAME_VISIBLE_P (XFRAME (f)))
-		  return f;
-	      }
-	    else if (INTEGERP (minibuf) && XINT (minibuf) == 0)
-	      {
-		FRAME_SAMPLE_VISIBILITY (XFRAME (f));
-		if (FRAME_VISIBLE_P (XFRAME (f))
-		    || FRAME_ICONIFIED_P (XFRAME (f)))
-		  return f;
-	      }
-	    else if (WINDOWP (minibuf))
-	      {
-		if (EQ (FRAME_MINIBUF_WINDOW (XFRAME (f)), minibuf)
-		    || EQ (WINDOW_FRAME (XWINDOW (minibuf)), f)
-		    || EQ (WINDOW_FRAME (XWINDOW (minibuf)),
-			   FRAME_FOCUS_FRAME (XFRAME (f))))
-		  return f;
-	      }
-	    else
+	    f = candidate_frame (f, frame, minibuf);
+	    if (!NILP (f))
 	      return f;
 	  }
-
 	if (EQ (frame, f))
 	  passed++;
       }
+  return frame;
 }
 
-/* Return the previous frame in the frame list before FRAME.
-   If MINIBUF is nil, exclude minibuffer-only frames.
-   If MINIBUF is a window, include only its own frame
-   and any frame now using that window as the minibuffer.
-   If MINIBUF is `visible', include all visible frames.
-   If MINIBUF is 0, include all visible and iconified frames.
-   Otherwise, include all frames.  */
+/* Return the previous frame in the frame list before FRAME.  */
 
 static Lisp_Object
 prev_frame (Lisp_Object frame, Lisp_Object minibuf)
@@ -989,43 +986,9 @@ prev_frame (Lisp_Object frame, Lisp_Object minibuf)
     {
       if (EQ (frame, f) && !NILP (prev))
 	return prev;
-
-      if ((!FRAME_TERMCAP_P (XFRAME (f)) && !FRAME_TERMCAP_P (XFRAME (frame))
-           && FRAME_KBOARD (XFRAME (f)) == FRAME_KBOARD (XFRAME (frame)))
-          || (FRAME_TERMCAP_P (XFRAME (f)) && FRAME_TERMCAP_P (XFRAME (frame))
-              && FRAME_TTY (XFRAME (f)) == FRAME_TTY (XFRAME (frame))))
-	{
-	  /* Decide whether this frame is eligible to be returned,
-	     according to minibuf.  */
-	  if (NILP (minibuf))
-	    {
-	      if (! FRAME_MINIBUF_ONLY_P (XFRAME (f)))
-		prev = f;
-	    }
-	  else if (WINDOWP (minibuf))
-	    {
-	      if (EQ (FRAME_MINIBUF_WINDOW (XFRAME (f)), minibuf)
-		  || EQ (WINDOW_FRAME (XWINDOW (minibuf)), f)
-		  || EQ (WINDOW_FRAME (XWINDOW (minibuf)),
-			 FRAME_FOCUS_FRAME (XFRAME (f))))
-		prev = f;
-	    }
-	  else if (EQ (minibuf, Qvisible))
-	    {
-	      FRAME_SAMPLE_VISIBILITY (XFRAME (f));
-	      if (FRAME_VISIBLE_P (XFRAME (f)))
-		prev = f;
-	    }
-	  else if (XFASTINT (minibuf) == 0)
-	    {
-	      FRAME_SAMPLE_VISIBILITY (XFRAME (f));
-	      if (FRAME_VISIBLE_P (XFRAME (f))
-		  || FRAME_ICONIFIED_P (XFRAME (f)))
-		prev = f;
-	    }
-	  else
-	    prev = f;
-	}
+      f = candidate_frame (f, frame, minibuf);
+      if (!NILP (f))
+	prev = f;
     }
 
   /* We've scanned the entire list.  */
@@ -1056,7 +1019,6 @@ Otherwise, include all frames.  */)
 {
   if (NILP (frame))
     frame = selected_frame;
-
   CHECK_LIVE_FRAME (frame);
   return next_frame (frame, miniframe);
 }