Add support for event processing via XInput 2

* configure.ac: Add an option to use XInput 2 if available.
* src/Makefile.in (XINPUT_LIBS, XINPUT_CFLAGS): New variables.
(EMACS_CFLAGS): Add Xinput CFLAGS.
(LIBES): Add XInput libs.
* src/xmenu.c (popup_activated_flag): Expose flag if
XInput 2 is available.
* src/xfns.c (x_window): Set XInput 2 event mask.
(setup_xi_event_mask): New function.
(syms_of_xfns): Provide XInput 2 feature.
* src/xterm.c (x_detect_focus_change): Handle XInput 2
GenericEvents.
(handle_one_xevent): Handle XInput 2 events.
(x_term_init): Ask the server for XInput 2 support and set
xkb_desc if available.
(x_delete_terminal): Free XKB kb desc if it exists, and free
XI2 devices if they exist.
(xi_grab_or_ungrab_device)
(xi_reset_scroll_valuators_for_device_id)
(x_free_xi_devices, x_init_master_valuators): New functions.
(x_get_scroll_valuator_delta): New function.
(init_xterm): Don't tell GTK to only use Core Input when built
with XInput 2 support.
* src/xterm.h (struct x_display_info): Add fields for XKB
and XI2 support.
* src/gtkutil.c (xg_event_is_for_menubar): Handle
XIDeviceEvents.
(xg_is_menu_window): New function.
(xg_event_is_for_scrollbar): Handle XIDeviceEvents.
* etc/NEWS: Document changes.

* lisp/mwheel.el (mouse-wheel-down-alternate-event)
(mouse-wheel-up-alternate-event)
(mouse-wheel-left-alternate-event)
(mouse-wheel-right-alternate-event): New user options.

(mouse-wheel-text-scale)
(mwheel-scroll): Test for alternate events.
(mouse-wheel--setup-bindings): Set up bindings for alternate
buttons.

1 files changed, 22 insertions, 0 deletions

diff --git a/configure.ac b/configure.ac
index c231c2ceae2..239bf72f716 100644
--- a/configure.ac
+++ b/configure.ac
@@ -487,6 +487,7 @@ OPTION_DEFAULT_ON([modules],[don't compile with dynamic modules support])
 OPTION_DEFAULT_ON([threads],[don't compile with elisp threading support])
 OPTION_DEFAULT_OFF([native-compilation],[compile with Emacs Lisp native compiler support])
 OPTION_DEFAULT_OFF([cygwin32-native-compilation],[use native compilation on 32-bit Cygwin])
+OPTION_DEFAULT_OFF([xinput2],[use version 2.0 the X Input Extension for input])
 
 AC_ARG_WITH([file-notification],[AS_HELP_STRING([--with-file-notification=LIB],
  [use a file notification library (LIB one of: yes, inotify, kqueue, gfile, w32, no)])],
@@ -4237,6 +4238,26 @@ fi
 AC_SUBST(XFIXES_CFLAGS)
 AC_SUBST(XFIXES_LIBS)
 
+## Use XInput 2.0 if available
+HAVE_XINPUT2=no
+if test "${HAVE_X11}" = "yes" && test "${with_xinput2}" != "no"; then
+   EMACS_CHECK_MODULES([XINPUT], [xi])
+   if test $HAVE_XINPUT = yes; then
+     # Now check for XInput2.h
+     AC_CHECK_HEADER(X11/extensions/XInput2.h,
+       [AC_CHECK_LIB(Xi, XIGrabButton, HAVE_XINPUT2=yes)])
+   fi
+   if test $HAVE_XINPUT2 = yes; then
+     AC_DEFINE(HAVE_XINPUT2, 1, [Define to 1 if the X Input Extension version 2.0 is present.])
+     if test "$USE_GTK_TOOLKIT" = "GTK2"; then
+       AC_MSG_WARN([You are building Emacs with GTK+ 2 and the X Input Extension version 2.
+This might lead to problems if your version of GTK+ is not built with support for XInput 2.])
+     fi
+   fi
+fi
+AC_SUBST(XINPUT_CFLAGS)
+AC_SUBST(XINPUT_LIBS)
+
 ### Use Xdbe (-lXdbe) if available
 HAVE_XDBE=no
 if test "${HAVE_X11}" = "yes"; then
@@ -6011,6 +6032,7 @@ AS_ECHO(["  Does Emacs use -lXaw3d?                                 ${HAVE_XAW3D
   Does Emacs support legacy unexec dumping?               ${with_unexec}
   Which dumping strategy does Emacs use?                  ${with_dumping}
   Does Emacs have native lisp compiler?                   ${HAVE_NATIVE_COMP}
+  Does Emacs use version 2 of the the X Input Extension?  ${HAVE_XINPUT2}
 "])
 
 if test -n "${EMACSDATA}"; then