Bug 1348: X11 XI Multitouch: Fixes of previous commit 92006e4baef57f1f3fb647dd307aed5989fd4c8d

Previous commit 92006e4baef57f1f3fb647dd307aed5989fd4c8d

(Note to Danny: I cannot test this now - please re-test and/or review)

X11Common::JavaWindow
- Owns XI extension's xiOpcode, selected xiTouchDeviceId and tracked XITouchPosition array

X11Window::CreateWindow
- Query XI extension only once @ window creation and earmark xiOpcode in JavaWindow instance

- Fix: Device selection code was "class->type != XITouchClass",
  but shouldn't it be 'XITouchClass == class->type' (as patched here)

- Fix: Free XIQueryDevice returned XIDeviceInfo array via XIFreeDeviceInfo

- Earmark deviceid in JavaWindow instance

X11Display
- Moved global static touch_coordinates to JavaWindow::xiTouchCoords instance

X11Display::DispatchMessage
- Changed event handling structure similar to https://keithp.com/blogs/Cursor_tracking/

- Fix: Free XGetEventData's optional memory allocation via XFreeEventData

- Reuse JavaWindow's queried xiOpcode

- Fix: Don't overrise windowPointer, instead validate and require a match. JavaWindow must match!

- Fix: Also validate chosen deviceid with JavaWindow's registered device

Newt Build:
- Added libXi in build recipe and doc

6 files changed, 137 insertions, 149 deletions

diff --git a/doc/HowToBuild.html b/doc/HowToBuild.html
index 5d63ae474..986559f9d 100644
--- a/doc/HowToBuild.html
+++ b/doc/HowToBuild.html
@@ -99,6 +99,7 @@
                                         <li>libxrandr-dev</li>
                                         <li>libxrender-dev</li>
                                         <li>libxcursor-dev</li>
+                                        <li>libxi-dev</li>
                                         <li>libudev-dev</li>
                                         <li>libstdc++6</li>
                                         <li>libstdc++6-4.7 or libstdc++-4.9-dev</li>
@@ -108,16 +109,16 @@
                                     <ul>
                                       <li><b>Debian</b> 7.00 Wheezy
                                       <pre>
-apt-get install openjdk-7-jre openjdk-7-jdk ant git-all p7zip-full gcc libgl1-mesa-dev libglu1-mesa-dev xorg-dev libice-dev libsm-dev libx11-dev libxext-dev libxxf86vm-dev libxinerama-dev libxrandr-dev libxrender-dev libxcursor-dev libudev-dev libc6-dev g++ libstdc++6 libstdc++6-4.7
+apt-get install openjdk-7-jre openjdk-7-jdk ant git-all p7zip-full gcc libgl1-mesa-dev libglu1-mesa-dev xorg-dev libice-dev libsm-dev libx11-dev libxext-dev libxxf86vm-dev libxinerama-dev libxrandr-dev libxrender-dev libxcursor-dev libxi-dev libudev-dev libc6-dev g++ libstdc++6 libstdc++6-4.7
                                       </pre></li>
 
                                       <li><b>Debian</b> 8.10 Jessie (also Ubuntu 15.04)
                                       <pre>
-apt-get install openjdk-7-jre openjdk-7-jdk ant git-all p7zip-full gcc libgl1-mesa-dev libglu1-mesa-dev xorg-dev libice-dev libsm-dev libx11-dev libxext-dev libxxf86vm-dev libxinerama-dev libxrandr-dev libxrender-dev libxcursor-dev libudev-dev libc6-dev g++ libstdc++6 libstdc++-4.9-dev
+apt-get install openjdk-7-jre openjdk-7-jdk ant git-all p7zip-full gcc libgl1-mesa-dev libglu1-mesa-dev xorg-dev libice-dev libsm-dev libx11-dev libxext-dev libxxf86vm-dev libxinerama-dev libxrandr-dev libxrender-dev libxcursor-dev libxi-dev libudev-dev libc6-dev g++ libstdc++6 libstdc++-4.9-dev
                                       </pre></li>
                                       <li><b>Debian</b> 9.00 Stretch
                                       <pre>
-apt-get install openjdk-8-jre openjdk-8-jdk ant git-all p7zip-full gcc libgl1-mesa-dev libglu1-mesa-dev xorg-dev libice-dev libsm-dev libx11-dev libxext-dev libxxf86vm-dev libxinerama-dev libxrandr-dev libxrender-dev libxcursor-dev libudev-dev libc6-dev g++ libstdc++6 libstdc++-6-dev
+apt-get install openjdk-8-jre openjdk-8-jdk ant git-all p7zip-full gcc libgl1-mesa-dev libglu1-mesa-dev xorg-dev libice-dev libsm-dev libx11-dev libxext-dev libxxf86vm-dev libxinerama-dev libxrandr-dev libxrender-dev libxcursor-dev libxi-dev libudev-dev libc6-dev g++ libstdc++6 libstdc++-6-dev
                                       </pre></li>
                                     </ul>
                                     Optional: Add <i>kernel</i> build utilities:
diff --git a/make/build-newt.xml b/make/build-newt.xml
index b19aa8fc4..733d5aebd 100644
--- a/make/build-newt.xml
+++ b/make/build-newt.xml
@@ -302,6 +302,7 @@
         <syslibset libs="X11"/>
         <syslibset libs="Xrandr"/>
         <syslibset libs="Xcursor"/>
+        <syslibset libs="Xi"/>
       </linker>
 
       <linker id="linker.cfg.freebsd.amd64.newt.x11" extends="linker.cfg.freebsd.amd64">
@@ -309,6 +310,7 @@
         <syslibset libs="X11"/>
         <syslibset libs="Xrandr"/>
         <syslibset libs="Xcursor"/>
+        <syslibset libs="Xi"/>
       </linker>
 
       <linker id="linker.cfg.linux.newt.bcm_egl" extends="linker.cfg.linux">
@@ -329,6 +331,7 @@
         <syslibset libs="X11"/>
         <syslibset libs="Xrandr"/>
         <syslibset libs="Xcursor"/>
+        <syslibset libs="Xi"/>
         <!--syslibset libs="xcb" /-->
         <!--syslibset libs="X11-xcb" /-->
       </linker>
@@ -337,6 +340,7 @@
         <syslibset libs="X11"/>
         <syslibset libs="Xrandr"/>
         <syslibset libs="Xcursor"/>
+        <syslibset libs="Xi"/>
         <!--syslibset libs="xcb" /-->
         <!--syslibset libs="X11-xcb" /-->
       </linker>
@@ -345,6 +349,7 @@
         <syslibset libs="X11"/>
         <syslibset libs="Xrandr"/>
         <syslibset libs="Xcursor"/>
+        <syslibset libs="Xi"/>
         <!--syslibset libs="xcb" /-->
         <!--syslibset libs="X11-xcb" /-->
       </linker>
@@ -353,12 +358,14 @@
         <syslibset dir="${env.TARGET_PLATFORM_ROOT}/usr/lib" libs="X11" />
         <syslibset dir="${env.TARGET_PLATFORM_ROOT}/usr/lib" libs="Xrandr" />
         <syslibset dir="${env.TARGET_PLATFORM_ROOT}/usr/lib" libs="Xcursor" />
+        <syslibset dir="${env.TARGET_PLATFORM_ROOT}/usr/lib" libs="Xi" />
       </linker>
 
       <linker id="linker.cfg.linux.aarch64.newt.x11" extends="linker.cfg.linux.aarch64">
         <syslibset dir="${env.TARGET_PLATFORM_ROOT}/usr/lib" libs="X11" />
         <syslibset dir="${env.TARGET_PLATFORM_ROOT}/usr/lib" libs="Xrandr" />
         <syslibset dir="${env.TARGET_PLATFORM_ROOT}/usr/lib" libs="Xcursor" />
+        <syslibset dir="${env.TARGET_PLATFORM_ROOT}/usr/lib" libs="Xi" />
       </linker>
 
       <linker id="linker.cfg.android.newt" extends="linker.cfg.android">
@@ -369,6 +376,7 @@
         <syslibset libs="X11"/>
         <syslibset libs="Xrandr"/>
         <syslibset libs="Xcursor"/>
+        <syslibset libs="Xi"/>
       </linker>
 
       <linker id="linker.cfg.solaris.sparcv9.newt.x11" extends="linker.cfg.solaris.sparcv9">
@@ -376,6 +384,7 @@
         <syslibset libs="X11"/>
         <syslibset libs="Xrandr"/>
         <syslibset libs="Xcursor"/>
+        <syslibset libs="Xi"/>
       </linker>
 
       <linker id="linker.cfg.solaris.amd64.newt.x11" extends="linker.cfg.solaris.amd64">
@@ -383,6 +392,7 @@
         <syslibset libs="X11"/>
         <syslibset libs="Xrandr"/>
         <syslibset libs="Xcursor"/>
+        <syslibset libs="Xi"/>
       </linker>
 
       <linker id="linker.cfg.win32.mingw.newt" extends="linker.cfg.win32.mingw">
diff --git a/make/scripts/tests.sh b/make/scripts/tests.sh
index 66dc7f300..ccd3a9871 100644
--- a/make/scripts/tests.sh
+++ b/make/scripts/tests.sh
@@ -150,7 +150,7 @@ function jrun() {
     #D_ARGS="-Dnativewindow.debug.JAWT"
     #D_ARGS="-Djogl.debug.GLContext.TraceSwitch"
     #D_ARGS="-Djogl.debug.GLContext -Djogl.debug.GLContext.TraceSwitch"
-    D_ARGS="-Djogl.debug.DebugGL -Djogl.debug.TraceGL -Djogl.debug.FixedFuncPipeline -Djogl.debug.GLSLState -Djogl.debug.GLSLCode"
+    #D_ARGS="-Djogl.debug.DebugGL -Djogl.debug.TraceGL -Djogl.debug.FixedFuncPipeline -Djogl.debug.GLSLState -Djogl.debug.GLSLCode"
     #D_ARGS="-Djogl.debug.FixedFuncPipeline -Djogl.debug.GLSLCode"
     #D_ARGS="-Djogl.debug.FixedFuncPipeline -Djogl.debug.GLSLState"
     #D_ARGS="-Djogl.debug.FixedFuncPipeline"
@@ -471,7 +471,7 @@ function testawtswt() {
 #testawt com.jogamp.opengl.test.junit.jogl.demos.es2.awt.TestGearsES2GLJPanelsAWT $*
 #testawt com.jogamp.opengl.test.junit.jogl.demos.es2.newt.TestGearsES2NewtCanvasAWT $*
 #testawt com.jogamp.opengl.test.junit.jogl.demos.es2.newt.TestLandscapeES2NewtCanvasAWT $*
-#testnoawt com.jogamp.opengl.test.junit.jogl.demos.es2.newt.TestGearsES2NEWT $*
+testnoawt com.jogamp.opengl.test.junit.jogl.demos.es2.newt.TestGearsES2NEWT $*
 #testnoawt com.jogamp.opengl.test.junit.jogl.demos.es2.newt.TestLandscapeES2NEWT $*
 #testawtswt com.jogamp.opengl.test.junit.jogl.demos.es2.newt.TestGearsES2NewtCanvasSWT $*
 #testnoawt com.jogamp.opengl.test.junit.jogl.demos.es2.newt.TestElektronenMultipliziererNEWT $*
@@ -854,7 +854,7 @@ function testawtswt() {
 #
 #testnoawt com.jogamp.opengl.test.junit.jogl.util.TestImmModeSinkES1NEWT $*
 #testnoawt com.jogamp.opengl.test.junit.jogl.util.TestImmModeSinkES2NEWT $*
-testnoawt com.jogamp.opengl.test.junit.jogl.util.TestES1FixedFunctionPipelineNEWT $*
+#testnoawt com.jogamp.opengl.test.junit.jogl.util.TestES1FixedFunctionPipelineNEWT $*
 
 #
 # Texture / TextureUtils
diff --git a/src/newt/native/X11Common.h b/src/newt/native/X11Common.h
index 78fa18cc8..99795b6e8 100644
--- a/src/newt/native/X11Common.h
+++ b/src/newt/native/X11Common.h
@@ -75,6 +75,14 @@ extern jmethodID visibleChangedID;
 extern jmethodID insetsVisibleChangedID;
 
 typedef struct {
+    int id;
+    int x;
+    int y;
+} XITouchPosition;
+
+#define XI_TOUCHCOORD_COUNT 10
+
+typedef struct {
     Window window;
     jobject jwindow;
     Atom * allAtoms;
@@ -86,6 +94,9 @@ typedef struct {
     Bool maxVert;
     /** flag whether window is mapped */
     Bool isMapped;
+    int xiOpcode;
+    int xiTouchDeviceId;
+    XITouchPosition xiTouchCoords[XI_TOUCHCOORD_COUNT];
 } JavaWindow;
 
 JavaWindow * getJavaWindowProperty(JNIEnv *env, Display *dpy, Window window, jlong javaObjectAtom, Bool showWarning);
diff --git a/src/newt/native/X11Display.c b/src/newt/native/X11Display.c
index effc488f9..1f3388fff 100644
--- a/src/newt/native/X11Display.c
+++ b/src/newt/native/X11Display.c
@@ -58,12 +58,6 @@ static jmethodID visibleChangedSendMouseEventID = NULL;
 static jmethodID sizePosMaxInsetsVisibleChangedID = NULL;
 static jmethodID sendTouchScreenEventID = NULL;
 
-struct touchPosition {
-    int touch_id;
-    int x;
-    int y;
-};
-
 /**
  * Keycode
  */
@@ -226,8 +220,6 @@ static jint X11InputState2NewtModifiers(unsigned int xstate, jshort javaVKey, jb
 }
 
 
-static struct touchPosition touch_coordinates[10];
-
 /**
  * Keycode
  */
@@ -275,8 +267,8 @@ JNIEXPORT jboolean JNICALL Java_jogamp_newt_driver_x11_DisplayDriver_initIDs0
     sendMouseEventID = (*env)->GetMethodID(env, X11NewtWindowClazz, "sendMouseEvent", "(SIIISF)V");
     sendMouseEventRequestFocusID = (*env)->GetMethodID(env, X11NewtWindowClazz, "sendMouseEventRequestFocus", "(SIIISF)V");
     visibleChangedSendMouseEventID = (*env)->GetMethodID(env, X11NewtWindowClazz, "visibleChangedSendMouseEvent", "(ZISIIISF)V");
-    sendKeyEventID = (*env)->GetMethodID(env, X11NewtWindowClazz, "sendKeyEvent", "(SISSCLjava/lang/String;)V");
     sendTouchScreenEventID = (*env)->GetMethodID(env, X11NewtWindowClazz, "sendTouchScreenEvent", "(SII[I[I[I[FF)V");
+    sendKeyEventID = (*env)->GetMethodID(env, X11NewtWindowClazz, "sendKeyEvent", "(SISSCLjava/lang/String;)V");
 
     if (displayCompletedID == NULL ||
         sendRRScreenChangeNotifyID == NULL ||
@@ -301,8 +293,6 @@ JNIEXPORT jboolean JNICALL Java_jogamp_newt_driver_x11_DisplayDriver_initIDs0
         return JNI_FALSE;
     }
 
-    memset(touch_coordinates, -1, sizeof(touch_coordinates));
-
     return JNI_TRUE;
 }
 
@@ -397,28 +387,24 @@ static int NewtWindows_updateVisibility(JNIEnv *env, Display *dpy, JavaWindow *j
     return visibleChange;
 }
 
-void sendTouchScreenEvent(JNIEnv *env, jobject window,
+static void sendTouchScreenEvent(JNIEnv *env, JavaWindow *jw,
         short eventType,  // MouseEvent.EVENT_MOUSE_PRESSED, MouseEvent.EVENT_MOUSE_RELEASED, MouseEvent.EVENT_MOUSE_MOVED
         int modifiers, // 0!
         int actionId) //  index of multiple-pointer arrays representing the pointer which triggered the event
 {
-    jint cnt = 0;
-    jint pointerNames[10];
-    jint x[10];
-    jint y[10];
-    jfloat pressure[] =  {1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f};
+    jint pointerNames[XI_TOUCHCOORD_COUNT];
+    jint x[XI_TOUCHCOORD_COUNT];
+    jint y[XI_TOUCHCOORD_COUNT];
+    jfloat pressure[] =  {1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f};
     jint actionIdx = -1;
-    int i = 0;
-
-    for(i = 0; i < 10; i++)
-    {
-        if(touch_coordinates[i].touch_id != -1)
-        {
-            x[cnt] = touch_coordinates[i].x;
-            y[cnt] = touch_coordinates[i].y;
-            pointerNames[cnt] = touch_coordinates[i].touch_id;
-            if (touch_coordinates[i].touch_id == actionId)
-            {
+    int i, cnt;
+
+    for(i = 0, cnt = 0; i < XI_TOUCHCOORD_COUNT; i++) {
+        if( -1 != jw->xiTouchCoords[i].id ) {
+            x[cnt] = jw->xiTouchCoords[i].x;
+            y[cnt] = jw->xiTouchCoords[i].y;
+            pointerNames[cnt] = jw->xiTouchCoords[i].id;
+            if (jw->xiTouchCoords[i].id == actionId) {
                 actionIdx = cnt;
             }
             cnt++;
@@ -449,10 +435,9 @@ void sendTouchScreenEvent(JNIEnv *env, jobject window,
     }
     (*env)->SetFloatArrayRegion(env, jPressure, 0, cnt, pressure);
 
-    (*env)->CallVoidMethod(env, window, sendTouchScreenEventID,
+    (*env)->CallVoidMethod(env, jw->jwindow, sendTouchScreenEventID,
             (jshort)eventType, (jint)modifiers, (jint)actionIdx,
             jNames, jX, jY, jPressure, (jfloat)1.0f);
-    
 }
 
 /*
@@ -521,36 +506,9 @@ JNIEXPORT void JNICALL Java_jogamp_newt_driver_x11_DisplayDriver_DispatchMessage
             continue;
         }
 
-        // DBG_PRINT( "X11: DispatchMessages dpy %p, win %p, Event %d\n", (void*)dpy, (void*)evt.xany.window, (int)evt.type);
-
         Window windowPointer = evt.xany.window;
+        // DBG_PRINT( "X11: DispatchMessages dpy %p, win %p, Event %d\n", (void*)dpy, (void*)windowPointer, (int)evt.type);
 
-        
-        int isXInputExtensionEvent = 0;        
-        XGenericEventCookie *cookie = &evt.xcookie; // hacks!
-        XIDeviceEvent *devev;
-
-
-        if (XGetEventData(dpy, cookie)) // extended event
-        {
-            int xi_opcode;
-            int ev;
-            int err;
-            XQueryExtension(dpy, "XInputExtension", &xi_opcode, &ev, &err);
-
-            // check if this belongs to XInput
-            if (cookie->type == GenericEvent
-                    && cookie->extension == xi_opcode) {
-                static int last = -1;
-
-                devev = cookie->data;
-                windowPointer = devev->event;
-                isXInputExtensionEvent = 1;
-
-            }
-        }
-        
-        
         jw = getJavaWindowProperty(env, dpy, windowPointer, javaObjectAtom,
         #ifdef VERBOSE_ON
                 True
@@ -564,59 +522,55 @@ JNIEXPORT void JNICALL Java_jogamp_newt_driver_x11_DisplayDriver_DispatchMessage
             continue;
         }
 
-        if (isXInputExtensionEvent) {
-            int i;
-
-            switch (devev->evtype) {
-                case XI_TouchBegin:
-    
-                    for (i = 0; i < 10; i++)
-                    {
-                        if (touch_coordinates[i].touch_id == -1)
-                        {
-                            touch_coordinates[i].touch_id = devev->detail % 32767;
-                            touch_coordinates[i].x = devev->event_x;
-                            touch_coordinates[i].y = devev->event_y;
-                            break;
+        XGenericEventCookie *cookie = &evt.xcookie; // hacks: https://keithp.com/blogs/Cursor_tracking/
+
+        if ( GenericEvent == cookie->type && jw->xiOpcode == cookie->extension && XGetEventData(dpy, cookie) ) {
+            // Valid registered XI Event w/ cookie data
+            // Here: https://www.x.org/wiki/Development/Documentation/Multitouch/
+            XIDeviceEvent *devev = cookie->data;
+            if( devev->event != windowPointer ) {
+                DBG_PRINT( "X11: DispatchMessages.XI dpy %p, win %p, Event %d: Event Window %p not matching\n", (void*)dpy, (void*)windowPointer, (int)evt.type, (void*)devev->event);
+            } else if( devev->deviceid != jw->xiTouchDeviceId) {
+                DBG_PRINT( "X11: DispatchMessages.XI dpy %p, win %p, Event %d: DeviceID not matching: Window %d, this %d\n", (void*)dpy, (void*)windowPointer, (int)evt.type, devev->deviceid, jw->xiTouchDeviceId);
+            } else {
+                int i;
+                switch (devev->evtype) {
+                    case XI_TouchBegin:
+                        for (i = 0; i < XI_TOUCHCOORD_COUNT; i++) {
+                            if (jw->xiTouchCoords[i].id == -1) {
+                                jw->xiTouchCoords[i].id = devev->detail % 32767;
+                                jw->xiTouchCoords[i].x = devev->event_x;
+                                jw->xiTouchCoords[i].y = devev->event_y;
+                                break;
+                            }
                         }
-                    }
-    
-                    sendTouchScreenEvent(env, jw->jwindow, EVENT_MOUSE_PRESSED,
-                            0, devev->detail % 32767);
-    
-                    break;
-                case XI_TouchUpdate:
-    
-                    for (i = 0; i < 10; i++)
-                    {
-                        if (touch_coordinates[i].touch_id == devev->detail  % 32767)
-                        {
-                            touch_coordinates[i].x = devev->event_x;
-                            touch_coordinates[i].y = devev->event_y;
+                        sendTouchScreenEvent(env, jw, EVENT_MOUSE_PRESSED, 0, devev->detail % 32767);
+                        break;
+
+                    case XI_TouchUpdate:
+                        for (i = 0; i < XI_TOUCHCOORD_COUNT; i++) {
+                            if (jw->xiTouchCoords[i].id == devev->detail  % 32767) {
+                                jw->xiTouchCoords[i].x = devev->event_x;
+                                jw->xiTouchCoords[i].y = devev->event_y;
+                            }
                         }
-                    }
-                    sendTouchScreenEvent(env, jw->jwindow, EVENT_MOUSE_MOVED, 0,
-                            devev->detail % 32767);
-    
-                    break;
-                case XI_TouchEnd:
-    
-                    sendTouchScreenEvent(env, jw->jwindow, EVENT_MOUSE_RELEASED,
-                            0, devev->detail % 32767);
-    
-                    for (i = 0; i < 10; i++)
-                    {
-                        if (touch_coordinates[i].touch_id == devev->detail % 32767)
-                        {
-                            touch_coordinates[i].touch_id = -1;
+                        sendTouchScreenEvent(env, jw, EVENT_MOUSE_MOVED, 0, devev->detail % 32767);
+                        break;
+
+                    case XI_TouchEnd:
+                        sendTouchScreenEvent(env, jw, EVENT_MOUSE_RELEASED, 0, devev->detail % 32767);
+                        for (i = 0; i < XI_TOUCHCOORD_COUNT; i++) {
+                            if (jw->xiTouchCoords[i].id == devev->detail % 32767) {
+                                jw->xiTouchCoords[i].id = -1;
+                            }
                         }
-                    }
-                    break;
-    
-                    continue;
+                        break;
+                }
             }
+            XFreeEventData(dpy, cookie);
+            continue; // next event, skip evt.type below
         }
-
+        
         switch(evt.type) {
             case KeyRelease:
                 if (XEventsQueued(dpy, QueuedAfterReading)) {
diff --git a/src/newt/native/X11Window.c b/src/newt/native/X11Window.c
index 7208b205a..8fb3ecbb9 100644
--- a/src/newt/native/X11Window.c
+++ b/src/newt/native/X11Window.c
@@ -953,47 +953,59 @@ JNIEXPORT jlongArray JNICALL Java_jogamp_newt_driver_x11_WindowDriver_CreateWind
         }
     }
     
+    // Register X11 Multitouch Events for new Window
+    // https://www.x.org/wiki/Development/Documentation/Multitouch/
     {
-      XIDeviceInfo *di;
-      XIDeviceInfo *dev;
-      XITouchClassInfo *class;
-      int devid = -1;
+        int xi_opcode, event, error;
+
+        javaWindow->xiTouchDeviceId = -1;
+
+        if( XQueryExtension(dpy, "XInputExtension", &xi_opcode, &event, &error) ) {
+            XIDeviceInfo *di;
+            int devid = -1;
+            int cnt = 0;
+
+            javaWindow->xiOpcode = xi_opcode;
+            di = XIQueryDevice(dpy, XIAllDevices, &cnt);
+
+            if( NULL != di && 0 < cnt ) {
+                XIDeviceInfo *dev;
+                int i, j;
       
-      int cnt;
-      int i, j;
-
-      di = XIQueryDevice(dpy, XIAllDevices, &cnt);
-      for (i = 0; i < cnt; i ++)
-      {
-        dev = &di[i];
-        for (j = 0; j < dev->num_classes; j ++)
-        {
-          class = (XITouchClassInfo*)(dev->classes[j]);
-          if (class->type != XITouchClass)
-          {
-            devid = dev->deviceid;
-            break;
-          }
-        }
-        if(devid != -1)
-        {
-          break;
-        }
-      }
+                // find the 1st XITouchClass device available
+                for (i = 0; i < cnt && -1 == devid; i ++) {
+                    dev = &di[i];
+                    for (j = 0; j < dev->num_classes; j ++) {
+                        XITouchClassInfo *class = (XITouchClassInfo*)(dev->classes[j]);
+                        if ( XITouchClass == class->type ) {
+                          devid = dev->deviceid;
+                          break;
+                        }
+                    }
+                }
+                XIFreeDeviceInfo(di);
+                di = NULL;
+                
+                if( -1 != devid ) {
+                    // register 1st XITouchClass device if available
+                    XIEventMask mask = {
+                      .deviceid = devid,
+                      .mask_len = XIMaskLen(XI_TouchEnd) // in bytes
+                    };
+                    
+                    mask.mask = (unsigned char*)calloc(mask.mask_len, sizeof(unsigned char));
+                    XISetMask(mask.mask, XI_TouchBegin);
+                    XISetMask(mask.mask, XI_TouchUpdate);
+                    XISetMask(mask.mask, XI_TouchEnd);
       
-      XIEventMask mask = {
-        .deviceid = devid, //XIAllDevices,
-        .mask_len = XIMaskLen(XI_TouchEnd)
-      };
+                    XISelectEvents(dpy, window, &mask, 1);
       
-      mask.mask = (unsigned char*)calloc(3, sizeof(char));
-      XISetMask(mask.mask, XI_TouchBegin);
-      XISetMask(mask.mask, XI_TouchUpdate);
-      XISetMask(mask.mask, XI_TouchEnd);
-
-      XISelectEvents(dpy, window, &mask, 1);
-
-      free(mask.mask);      
+                    free(mask.mask);      
+      
+                    javaWindow->xiTouchDeviceId = devid;
+                }
+            }
+        }
     }
     
     XFlush(dpy);