Tweak XInput2 event subscription

views/touchui/touch_factory.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "views/touchui/touch_factory.h"
 
 #include <X11/cursorfont.h>
 #include <X11/extensions/XInput.h>
 #include <X11/extensions/XInput2.h>
 #include <X11/extensions/XIproto.h>
@@ skipping 25 matching lines @@
   invisible_cursor_ = XCreatePixmapCursor(display, blank, blank,
                                           &black, &black, 0, 0);
   arrow_cursor_ = XCreateFontCursor(display, XC_arrow);
 
   SetCursorVisible(false, false);
 
   // Detect touch devices.
   // NOTE: The new API for retrieving the list of devices (XIQueryDevice) does
   // not provide enough information to detect a touch device. As a result, the
   // old version of query function (XListInputDevices) is used instead.
+  // If XInput2 is not supported, this will return null (with count of -1) so
+  // we assume there cannot be any touch devices.
   int count = 0;
   XDeviceInfo* devlist = XListInputDevices(display, &count);
   for (int i = 0; i < count; i++) {
     const char* devtype = XGetAtomName(display, devlist[i].type);
     if (devtype && !strcmp(devtype, XI_TOUCHSCREEN)) {
       touch_device_lookup_[devlist[i].id] = true;
       touch_device_list_.push_back(devlist[i].id);
     }
   }
-  XFreeDeviceList(devlist);
+  if (devlist)
+      XFreeDeviceList(devlist);
 }
 
 TouchFactory::~TouchFactory() {
   SetCursorVisible(true, false);
   Display* display = ui::GetXDisplay();
   XFreeCursor(display, invisible_cursor_);
   XFreeCursor(display, arrow_cursor_);
 }
 
 void TouchFactory::SetTouchDeviceList(
@@ skipping 70 matching lines @@
   Window window = DefaultRootWindow(display);
 
   if (is_cursor_visible_) {
     XDefineCursor(display, window, arrow_cursor_);
   } else {
     XDefineCursor(display, window, invisible_cursor_);
   }
 }
 
 }  // namespace views