master 62339e62d8 2/2: Add configure tests for faulty XI2 installations

[Po Lu]

branch: master
commit 62339e62d8480a9059e4f9f2e4bccdedcb60fc5e
Author: Po Lu <luangruo@yahoo.com>
Commit: Po Lu <luangruo@yahoo.com>

    Add configure tests for faulty XI2 installations
    
    * configure.ac: Detect cases where XI 2.4 headers are installed
    without the correct event structures.
    * src/xterm.c (handle_one_xevent): Don't use structures that
    might not exist unless configure found them.
---
 configure.ac | 7 +++++++
 src/xterm.c  | 2 ++
 2 files changed, 9 insertions(+)

diff --git a/configure.ac b/configure.ac
index 9fcc124758..5b94fc8e1b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -4489,6 +4489,13 @@ 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>]])
    fi
 fi
 AC_SUBST(XINPUT_CFLAGS)
diff --git a/src/xterm.c b/src/xterm.c
index 00cb04f005..8ba4f46c2c 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -11050,6 +11050,7 @@ handle_one_xevent (struct x_display_info *dpyinfo,
          case XI_GesturePinchBegin:
          case XI_GesturePinchUpdate:
            {
+#ifdef HAVE_USABLE_XI_GESTURE_PINCH_EVENT
              XIGesturePinchEvent *pev = (XIGesturePinchEvent *) xi_event;
              struct xi_device_t *device = xi_device_from_id (dpyinfo, 
pev->deviceid);
 
@@ -11070,6 +11071,7 @@ 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;