Improve XInput2 version checking

* configure.ac: Check for various important structures from all
versions of libXi.

* src/xfns.c (setup_xi_event_mask):
* src/xwidget.c (x_draw_xwidget_glyph_string):
* src/xterm.c (x_init_master_valuators, handle_one_xevent)
(x_term_init): Replace XI version checks based on protocol
headers with new constants.

* src/xterm.h (HAVE_XINPUT2_1, HAVE_XINPUT2_2, HAVE_XINPUT2_3)
(HAVE_XINPUT2_4): New definitions.

5 files changed, 48 insertions, 26 deletions

diff --git a/configure.ac b/configure.ac
index 945e2ff8d4e..00711cccd5d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -4478,13 +4478,13 @@ if test "${HAVE_X11}" = "yes" && test "${with_xinput2}" != "no"; 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
-     # Detect both faulty installations of libXi where gesture event
-     # types are defined but gesture event structures are not, and
-     # also where gesture event structures are empty.
-     AC_CHECK_MEMBERS([XIGesturePinchEvent.delta_unaccel_y],
-       [AC_DEFINE(HAVE_USABLE_XI_GESTURE_PINCH_EVENT, 1,
-         [Define to 1 if XInput headers define gesture structures correctly.])],
-       [], [[#include <X11/extensions/XInput2.h>]])
+
+     # Now check for some members (which used in conjunction with
+     # protocol definitions) can be used to determine the version of
+     # XInput supported.
+     AC_CHECK_MEMBERS([XIScrollClassInfo.type, XITouchClassInfo.type,
+       XIBarrierReleasePointerInfo.deviceid, XIGestureClassInfo.type],
+       [], [], [#include <X11/extensions/XInput2.h>])
    fi
 fi
 AC_SUBST(XINPUT_CFLAGS)
diff --git a/src/xfns.c b/src/xfns.c
index b0e7af9d8fa..9afadd16e98 100644
--- a/src/xfns.c
+++ b/src/xfns.c
@@ -3565,13 +3565,13 @@ setup_xi_event_mask (struct frame *f)
   XISetMask (m, XI_PropertyEvent);
   XISetMask (m, XI_HierarchyChanged);
   XISetMask (m, XI_DeviceChanged);
-#ifdef XI_TouchBegin
+#ifdef HAVE_XINPUT2_2
   if (FRAME_DISPLAY_INFO (f)->xi2_version >= 2)
     {
       XISetMask (m, XI_TouchBegin);
       XISetMask (m, XI_TouchUpdate);
       XISetMask (m, XI_TouchEnd);
-#ifdef XI_GesturePinchBegin
+#ifdef HAVE_XINPUT2_4
       if (FRAME_DISPLAY_INFO (f)->xi2_version >= 4)
 	{
 	  XISetMask (m, XI_GesturePinchBegin);
diff --git a/src/xterm.c b/src/xterm.c
index dce0bf306ab..23721352f3c 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -629,7 +629,7 @@ x_init_master_valuators (struct x_display_info *dpyinfo)
 	    {
 	      switch (device->classes[c]->type)
 		{
-#ifdef XIScrollClass /* XInput 2.1 */
+#ifdef HAVE_XINPUT2_1
 		case XIScrollClass:
 		  {
 		    XIScrollClassInfo *info =
@@ -648,7 +648,7 @@ x_init_master_valuators (struct x_display_info *dpyinfo)
 		    break;
 		  }
 #endif
-#ifdef XITouchClass /* XInput 2.2 */
+#ifdef HAVE_XINPUT2_2
 		case XITouchClass:
 		  {
 		    XITouchClassInfo *info;
@@ -739,7 +739,7 @@ xi_device_from_id (struct x_display_info *dpyinfo, int deviceid)
   return NULL;
 }
 
-#ifdef XI_TouchBegin
+#ifdef HAVE_XINPUT2_2
 
 static void
 xi_link_touch_point (struct xi_device_t *device,
@@ -11046,7 +11046,7 @@ handle_one_xevent (struct x_display_info *dpyinfo,
 	      if (!device)
 		goto XI_OTHER;
 
-#ifdef XI_TouchBegin
+#ifdef HAVE_XINPUT2_2
 	      if (xev->flags & XIPointerEmulated)
 		goto XI_OTHER;
 #endif
@@ -11929,7 +11929,10 @@ handle_one_xevent (struct x_display_info *dpyinfo,
 	    {
 	      struct xi_device_t *device;
 	      struct xi_touch_point_t *tem, *last;
-	      int c, i;
+	      int c;
+#ifdef HAVE_XINPUT2_1
+	      int i;
+#endif
 
 	      device = xi_device_from_id (dpyinfo, device_changed->deviceid);
 
@@ -11959,7 +11962,7 @@ handle_one_xevent (struct x_display_info *dpyinfo,
 		{
 		  switch (device_changed->classes[c]->type)
 		    {
-#ifdef XIScrollClass
+#ifdef HAVE_XINPUT2_1
 		    case XIScrollClass:
 		      {
 			XIScrollClassInfo *info;
@@ -11979,7 +11982,7 @@ handle_one_xevent (struct x_display_info *dpyinfo,
 		      }
 #endif
 
-#ifdef XITouchClass
+#ifdef HAVE_XINPUT2_2
 		    case XITouchClass:
 		      {
 			XITouchClassInfo *info;
@@ -11993,7 +11996,7 @@ handle_one_xevent (struct x_display_info *dpyinfo,
 		    }
 		}
 
-#ifdef XIScrollClass
+#ifdef HAVE_XINPUT2_1
 	      for (c = 0; c < device_changed->num_classes; ++c)
 		{
 		  if (device_changed->classes[c]->type == XIValuatorClass)
@@ -12043,7 +12046,7 @@ handle_one_xevent (struct x_display_info *dpyinfo,
 	      goto XI_OTHER;
 	    }
 
-#ifdef XI_TouchBegin
+#ifdef HAVE_XINPUT2_2
 	  case XI_TouchBegin:
 	    {
 	      struct xi_device_t *device;
@@ -12205,13 +12208,13 @@ handle_one_xevent (struct x_display_info *dpyinfo,
 	    }
 
 #endif
-#ifdef XI_GesturePinchBegin
+
+#ifdef HAVE_XINPUT2_4
 	  case XI_GesturePinchBegin:
 	  case XI_GesturePinchUpdate:
 	    {
 	      x_display_set_last_user_time (dpyinfo, xi_event->time);
 
-#ifdef HAVE_USABLE_XI_GESTURE_PINCH_EVENT
 	      XIGesturePinchEvent *pev = (XIGesturePinchEvent *) xi_event;
 	      struct xi_device_t *device = xi_device_from_id (dpyinfo, pev->deviceid);
 
@@ -12243,7 +12246,7 @@ handle_one_xevent (struct x_display_info *dpyinfo,
 				       make_float (pev->scale),
 				       make_float (pev->delta_angle));
 		}
-#endif
+
 	      /* Once again GTK seems to crash when confronted by
 		 events it doesn't understand.  */
 	      *finish = X_EVENT_DROP;
@@ -16261,13 +16264,13 @@ x_term_init (Lisp_Object display_name, char *xrm_option, char *resource_name)
   dpyinfo->supports_xi2 = false;
   int rc;
   int major = 2;
-#ifdef XI_GesturePinchBegin /* XInput 2.4 */
+#ifdef HAVE_XINPUT2_4
   int minor = 4;
-#elif XI_BarrierHit /* XInput 2.3 */
+#elif defined HAVE_XINPUT2_3 /* XInput 2.3 */
   int minor = 3;
-#elif defined XI_TouchBegin /* XInput 2.2 */
+#elif defined HAVE_XINPUT2_2 /* XInput 2.2 */
   int minor = 2;
-#elif defined XIScrollClass /* XInput 2.1 */
+#elif defined HAVE_XINPUT2_1 /* XInput 2.1 */
   int minor = 1;
 #else /* Some old version of XI2 we're not interested in. */
   int minor = 0;
diff --git a/src/xterm.h b/src/xterm.h
index 14457b32cc2..e2256ce2dfb 100644
--- a/src/xterm.h
+++ b/src/xterm.h
@@ -42,6 +42,10 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 #include <X11/Xmu/Editres.h>
 #endif
 
+#ifdef HAVE_XINPUT2
+#include <X11/extensions/XInput2.h>
+#endif
+
 typedef Widget xt_or_gtk_widget;
 #endif
 
@@ -1465,6 +1469,21 @@ struct xi_device_t *xi_device_from_id (struct x_display_info *, int);
    (nr).width = (rwidth),				\
    (nr).height = (rheight))
 
+#ifdef HAVE_XINPUT2
+#if HAVE_XISCROLLCLASSINFO_TYPE && defined XIScrollClass
+#define HAVE_XINPUT2_1
+#endif
+#if HAVE_XITOUCHCLASSINFO_TYPE && defined XITouchClass
+#define HAVE_XINPUT2_2
+#endif
+#if HAVE_XIBARRIERRELEASEPOINTERINFO_DEVICEID && defined XIBarrierPointerReleased
+#define HAVE_XINPUT2_3
+#endif
+#if HAVE_XIGESTURECLASSINFO_TYPE && defined XIGestureClass
+#define HAVE_XINPUT2_4
+#endif
+#endif
+
 INLINE_HEADER_END
 
 #endif /* XTERM_H */
diff --git a/src/xwidget.c b/src/xwidget.c
index 9fbf6678ae8..e812b13f23b 100644
--- a/src/xwidget.c
+++ b/src/xwidget.c
@@ -2853,7 +2853,7 @@ x_draw_xwidget_glyph_string (struct glyph_string *s)
 	  XISetMask (m, XI_ButtonRelease);
 	  XISetMask (m, XI_Enter);
 	  XISetMask (m, XI_Leave);
-#ifdef XI_GesturePinchBegin
+#ifdef HAVE_XINPUT2_4
 	  if (FRAME_DISPLAY_INFO (s->f)->xi2_version >= 4)
 	    {
 	      XISetMask (m, XI_GesturePinchBegin);