master 5bedef8f87 1/2: Fix bug#57476

[Po Lu]

branch: master
commit 5bedef8f87d2103e21342a06c4c1c9d7efe06621
Author: Po Lu <luangruo@yahoo.com>
Commit: Po Lu <luangruo@yahoo.com>

    Fix bug#57476
    
    * src/xterm.c (handle_one_xevent): Don't reset valuators on certain
    crossing events, for the benefit of xfwm4.  (bug#57476)
---
 src/xterm.c | 31 ++++++++++++++++++++++++++++---
 1 file changed, 28 insertions(+), 3 deletions(-)

diff --git a/src/xterm.c b/src/xterm.c
index e0a8e13b24..3c05bc7807 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -20771,8 +20771,20 @@ handle_one_xevent (struct x_display_info *dpyinfo,
                any = x_any_window_to_frame (dpyinfo, enter->event);
 
 #ifdef HAVE_XINPUT2_1
-             xi_reset_scroll_valuators_for_device_id (dpyinfo, enter->deviceid,
-                                                      true);
+             /* xfwm4 selects for button events on the frame window,
+                resulting in passive grabs being generated along with
+                the delivery of emulated button events; this then
+                interferes with scrolling, since device valuators
+                will constantly be reset as the crossing events
+                related to those grabs arrive.  The only way to
+                remedy this is to never reset scroll valuators on a
+                grab-related crossing event.  (bug#57476) */
+             if (enter->mode != XINotifyUngrab
+                 && enter->mode != XINotifyGrab
+                 && enter->mode != XINotifyPassiveGrab
+                 && enter->mode != XINotifyPassiveUngrab)
+               xi_reset_scroll_valuators_for_device_id (dpyinfo, 
enter->deviceid,
+                                                        true);
 #endif
 
              {
@@ -20888,7 +20900,20 @@ handle_one_xevent (struct x_display_info *dpyinfo,
                 moves out of a frame (and not into one of its
                 children, which we know about).  */
 #ifdef HAVE_XINPUT2_1
-             if (leave->detail != XINotifyInferior && any)
+             if (leave->detail != XINotifyInferior && any
+                 /* xfwm4 selects for button events on the frame
+                    window, resulting in passive grabs being
+                    generated along with the delivery of emulated
+                    button events; this then interferes with
+                    scrolling, since device valuators will constantly
+                    be reset as the crossing events related to those
+                    grabs arrive.  The only way to remedy this is to
+                    never reset scroll valuators on a grab-related
+                    crossing event.  (bug#57476) */
+                 && leave->mode != XINotifyUngrab
+                 && leave->mode != XINotifyGrab
+                 && leave->mode != XINotifyPassiveUngrab
+                 && leave->mode != XINotifyPassiveGrab)
                xi_reset_scroll_valuators_for_device_id (dpyinfo,
                                                         leave->deviceid, 
false);
 #endif