master f6501fded7 2/2: Don't try to guess a delta if a scroll valuator's state is unknown

[Po Lu]

branch: master
commit f6501fded744b729b72ed0bbc663e5a7953b04bb
Author: Po Lu <luangruo@yahoo.com>
Commit: Po Lu <luangruo@yahoo.com>

    Don't try to guess a delta if a scroll valuator's state is unknown
    
    * src/xterm.c (x_get_scroll_valuator_delta): Return DBL_MAX if
    the scroll valuator's value is unknown.
---
 src/xterm.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/xterm.c b/src/xterm.c
index c9120638a7..31e39280b3 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -502,9 +502,10 @@ x_init_master_valuators (struct x_display_info *dpyinfo)
 /* Return the delta of the scroll valuator VALUATOR_NUMBER under
    DEVICE_ID in the display DPYINFO with VALUE.  The valuator's
    valuator will be set to VALUE afterwards.  In case no scroll
-   valuator is found, or if device_id is not known to Emacs, DBL_MAX
-   is returned.  Otherwise, the valuator is returned in
-   VALUATOR_RETURN.  */
+   valuator is found, or if the valuator state is invalid (see the
+   comment under XI_Enter in handle_one_xevent), or if device_id is
+   not known to Emacs, DBL_MAX is returned.  Otherwise, the valuator
+   is returned in VALUATOR_RETURN.  */
 static double
 x_get_scroll_valuator_delta (struct x_display_info *dpyinfo, int device_id,
                             int valuator_number, double value,
@@ -531,7 +532,7 @@ x_get_scroll_valuator_delta (struct x_display_info 
*dpyinfo, int device_id,
                      *valuator_return = sv;
 
                      unblock_input ();
-                     return 0.0;
+                     return DBL_MAX;
                    }
                  else
                    {