From: Po Lu <luangruo@yahoo.com>
Date: Sat, 8 Jan 2022 10:24:53 +0000 (+0800)
Subject: Add an option to rely on passive touch grabs on X
X-Git-Tag: emacs-29.0.90~3199
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=86ed4b985871e20d55fe01c3d1e60de71cab91d9;p=emacs.git

Add an option to rely on passive touch grabs on X

This prevents crashes with three-finger touch gestures on
Xwayland running on GNOME Shell, and also when running some
programs that make use of an Emacs window's XID on the same X
server.

* src/xterm.c (handle_one_xevent): Respect
`x-input-grab-touch-events'.
(syms_of_xterm): New option `x-input-grab-touch-events.
---

diff --git a/src/xterm.c b/src/xterm.c
index 9b4bd4b8db2..6a05ad98949 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -11134,8 +11134,9 @@ handle_one_xevent (struct x_display_info *dpyinfo,
 		    {
 		      *finish = X_EVENT_DROP;
 		      x_catch_errors (dpyinfo->display);
-		      XIAllowTouchEvents (dpyinfo->display, xev->deviceid,
-					  xev->detail, xev->event, XIAcceptTouch);
+		      if (x_input_grab_touch_events)
+			XIAllowTouchEvents (dpyinfo->display, xev->deviceid,
+					    xev->detail, xev->event, XIAcceptTouch);
 		      if (!x_had_errors_p (dpyinfo->display))
 			{
 			  xi_link_touch_point (device, xev->detail, xev->event_x,
@@ -11154,8 +11155,9 @@ handle_one_xevent (struct x_display_info *dpyinfo,
 		  else
 		    {
 		      x_catch_errors (dpyinfo->display);
-		      XIAllowTouchEvents (dpyinfo->display, xev->deviceid,
-					  xev->detail, xev->event, XIRejectTouch);
+		      if (x_input_grab_touch_events)
+			XIAllowTouchEvents (dpyinfo->display, xev->deviceid,
+					    xev->detail, xev->event, XIRejectTouch);
 		      x_uncatch_errors ();
 		    }
 #endif
@@ -15946,4 +15948,12 @@ support. */);
 This provides better support for some modern input methods, and is
 only effective when Emacs is built with GTK.  */);
   x_gtk_use_native_input = false;
+
+  DEFVAR_BOOL ("x-input-grab-touch-events", x_input_grab_touch_events,
+	       doc: /* Non-nil means to actively grab touch events.
+This means touch sequences that started on an Emacs frame will
+reliably continue to receive updates even if the finger moves off the
+frame, but may cause crashes with some window managers and/or external
+programs.  */);
+  x_input_grab_touch_events = true;
 }