master bb33446f2a: Better handle devices being enabled on XI2

[Po Lu]

branch: master
commit bb33446f2a4a2540fe3fcbc07d9fadacb024f963
Author: Po Lu <luangruo@yahoo.com>
Commit: Po Lu <luangruo@yahoo.com>

    Better handle devices being enabled on XI2
    
    * src/xterm.c (handle_one_xevent): Don't abort on DeviceChanged
    if the device couldn't be found, instead regenerating the device
    hierarchy to see if it was enabled.
---
 src/xterm.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/src/xterm.c b/src/xterm.c
index cff4b07c6e..9c24a074e3 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -581,6 +581,11 @@ x_free_xi_devices (struct x_display_info *dpyinfo)
 /* Setup valuator tracking for XI2 master devices on
    DPYINFO->display.  */
 
+/* This function's name is a misnomer: these days, it keeps a
+   client-side record of all devices, which includes basic information
+   about the device and also touchscreen tracking information, instead
+   of just scroll valuators.  */
+
 static void
 x_init_master_valuators (struct x_display_info *dpyinfo)
 {
@@ -11906,7 +11911,18 @@ handle_one_xevent (struct x_display_info *dpyinfo,
              device = xi_device_from_id (dpyinfo, device_changed->deviceid);
 
              if (!device)
-               emacs_abort ();
+               {
+                 /* An existing device might have been enabled.  */
+                 x_init_master_valuators (dpyinfo);
+
+                 /* Now try to find the device again, in case it was
+                    just enabled.  */
+                 device = xi_device_from_id (dpyinfo, 
device_changed->deviceid);
+               }
+
+             /* If it wasn't enabled, then stop handling this event.  */
+             if (!device)
+               goto XI_OTHER;
 
              /* Free data that we will regenerate from new
                 information.  */