Fix bug#57476

* src/xterm.c (handle_one_xevent): Don't reset valuators on certain
crossing events, for the benefit of xfwm4.  (bug#57476)

1 files changed, 28 insertions, 3 deletions

diff --git a/src/xterm.c b/src/xterm.c
index e0a8e13b24e..3c05bc7807d 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