Prevent sluggish bidi redisplay in small windows.

 src/xdisp.c (MAX_DISP_SCAN): Decrease to 250.  Prevents sluggish
 redisplay in small windows.

src/ChangeLog

+2011-09-10  Eli Zaretskii  <eliz@gnu.org>
+
+	* xdisp.c (MAX_DISP_SCAN): Decrease to 250.  Prevents sluggish
+	redisplay in small windows.
+
 2011-09-09  Eli Zaretskii  <eliz@gnu.org>
 
 	* frame.c (x_report_frame_params): Cast to avoid compiler warnings.

src/xdisp.c

@@ -3132,9 +3132,9 @@ next_overlay_change (EMACS_INT pos)
 }
 /* How many characters forward to search for a display property or
-   display string.  Enough for a screenful of 100 lines x 50
-   characters in a line.  */
-#define MAX_DISP_SCAN 5000
+   display string.  Searching too far forward makes the bidi display
+   sluggish, especially in small windows.  */
+#define MAX_DISP_SCAN 250
 /* Return the character position of a display string at or after
    position specified by POSITION.  If no display string exists at or