Don't deliver touch or pinch events from master or slave devices

* src/xfns.c (setup_xi_event_mask): Select for gesture events on
only master devices if safe.
* src/xterm.c (handle_one_xevent): Deliver touchscreen events
only from direct slave devices, and gesture events only from
master pointers.

2 files changed, 58 insertions, 14 deletions

diff --git a/src/xfns.c b/src/xfns.c
index 5c9f58e3a96..fd4807fd5f5 100644
--- a/src/xfns.c
+++ b/src/xfns.c
@@ -4036,7 +4036,7 @@ setup_xi_event_mask (struct frame *f)
   selected->mask = ((unsigned char *) selected) + sizeof *selected;
   selected->mask_len = l;
   selected->deviceid = XIAllMasterDevices;
-#endif
+#endif /* !HAVE_XINPUT2_1 */
 
   mask.mask = m = alloca (l);
   memset (m, 0, l);
@@ -4056,7 +4056,19 @@ setup_xi_event_mask (struct frame *f)
   XISetMask (m, XI_FocusOut);
   XISetMask (m, XI_KeyPress);
   XISetMask (m, XI_KeyRelease);
-#endif
+#endif /* !USE_GTK */
+#if defined HAVE_XINPUT2_4
+  if (FRAME_DISPLAY_INFO (f)->xi2_version >= 4)
+    {
+      /* Select for gesture events.  Since this configuration doesn't
+         use GTK 3, Emacs is the only code that can change the XI
+         event mask, and can safely select for gesture events on
+         master pointers only.  */
+      XISetMask (m, XI_GesturePinchBegin);
+      XISetMask (m, XI_GesturePinchUpdate);
+      XISetMask (m, XI_GesturePinchEnd);
+    }
+#endif /* HAVE_XINPUT2_4 */
   XISelectEvents (FRAME_X_DISPLAY (f),
                   FRAME_X_WINDOW (f),
                   &mask, 1);
@@ -4065,7 +4077,7 @@ setup_xi_event_mask (struct frame *f)
      to get the event mask from the X server.  */
 #ifndef HAVE_XINPUT2_1
   memcpy (selected->mask, m, l);
-#endif
+#endif /* !HAVE_XINPUT2_1 */
 
   memset (m, 0, l);
 #endif /* !HAVE_GTK3 */
@@ -4080,35 +4092,45 @@ setup_xi_event_mask (struct frame *f)
                   FRAME_OUTER_WINDOW (f),
                   &mask, 1);
   memset (m, 0, l);
-#endif
+#endif /* USE_X_TOOLKIT */
 
 #ifdef HAVE_XINPUT2_2
   if (FRAME_DISPLAY_INFO (f)->xi2_version >= 2)
     {
+      /* Select for touch events from all devices.
+
+         Emacs will only process touch events originating
+         from slave devices, as master pointers may also
+         represent dependent touch devices.  */
       mask.deviceid = XIAllDevices;
 
       XISetMask (m, XI_TouchBegin);
       XISetMask (m, XI_TouchUpdate);
       XISetMask (m, XI_TouchEnd);
-#ifdef HAVE_XINPUT2_4
+
+#if defined HAVE_XINPUT2_4 && defined USE_GTK3
       if (FRAME_DISPLAY_INFO (f)->xi2_version >= 4)
         {
+          /* Now select for gesture events from all pointer devices.
+             Emacs will only handle gesture events from the master
+             pointer, but cannot afford to overwrite the event mask
+             set by GDK.  */
+
           XISetMask (m, XI_GesturePinchBegin);
           XISetMask (m, XI_GesturePinchUpdate);
           XISetMask (m, XI_GesturePinchEnd);
         }
-#endif
+#endif /* HAVE_XINPUT2_4 && USE_GTK3 */
 
-      XISelectEvents (FRAME_X_DISPLAY (f),
-                      FRAME_X_WINDOW (f),
+      XISelectEvents (FRAME_X_DISPLAY (f), FRAME_X_WINDOW (f),
                       &mask, 1);
     }
-#endif
+#endif /* HAVE_XINPUT2_2 */
 
 #ifndef HAVE_XINPUT2_1
   FRAME_X_OUTPUT (f)->xi_masks = selected;
   FRAME_X_OUTPUT (f)->num_xi_masks = 1;
-#endif
+#endif /* HAVE_XINPUT2_1 */
 
   unblock_input ();
 }
diff --git a/src/xterm.c b/src/xterm.c
index 9ecead03b08..5cc2dfdae1d 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -24259,7 +24259,13 @@ handle_one_xevent (struct x_display_info *dpyinfo,
               x_display_set_last_user_time (dpyinfo, xev->time,
                                             xev->send_event, true);
 
-              if (!device)
+              /* Don't process touch sequences from this device if
+                 it's a master pointer.  Touch sequences aren't
+                 canceled by the X server if a slave device is
+                 detached, and master pointers may also represent
+                 dependent touch devices.  */
+
+              if (!device || device->use == XIMasterPointer)
                 goto XI_OTHER;
 
               if (xi_find_touch_point (device, xev->detail))
@@ -24427,12 +24433,22 @@ handle_one_xevent (struct x_display_info *dpyinfo,
               x_display_set_last_user_time (dpyinfo, xev->time,
                                             xev->send_event, true);
 
+              /* Don't process touch sequences from this device if
+                 it's a master pointer.  Touch sequences aren't
+                 canceled by the X server if a slave device is
+                 detached, and master pointers may also represent
+                 dependent touch devices.  */
+
               if (!device)
                 goto XI_OTHER;
 
               touchpoint = xi_find_touch_point (device, xev->detail);
 
-              if (!touchpoint)
+              if (!touchpoint
+                  /* Don't send this event if nothing has changed
+                     either.  */
+                  || (touchpoint->x == (int) xev->event_x
+                      && touchpoint->y == (int) xev->event_y))
                 goto XI_OTHER;
 
               touchpoint->x = xev->event_x;
@@ -24475,7 +24491,13 @@ handle_one_xevent (struct x_display_info *dpyinfo,
               x_display_set_last_user_time (dpyinfo, xev->time,
                                             xev->send_event, true);
 
-              if (!device)
+              /* Don't process touch sequences from this device if
+                 it's a master pointer.  Touch sequences aren't
+                 canceled by the X server if a slave device is
+                 detached, and master pointers may also represent
+                 dependent touch devices.  */
+
+              if (!device || device->use == XIMasterPointer)
                 goto XI_OTHER;
 
               unlinked_p = xi_unlink_touch_point (xev->detail, device);
@@ -24543,7 +24565,7 @@ handle_one_xevent (struct x_display_info *dpyinfo,
               x_display_set_last_user_time (dpyinfo, pev->time,
                                             pev->send_event, true);
 
-              if (!device)
+              if (!device || device->use != XIMasterPointer)
                 goto XI_OTHER;
 
 #ifdef HAVE_XWIDGETS