Don't set platform input context if it's not properly created.

Prevent xcb applications from failing to launch when IBus is not
initialized correctly.

Change-Id: I8425403e02d0eb5401f8d8bb0d012b53ab9400d9
Reviewed-on: http://codereview.qt.nokia.com/3044
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Matthew Cattell <matthew.cattell@nokia.com>

src/platformsupport/inputmethods/ibus/qibusplatforminputcontext.cpp

@@ -89,6 +89,11 @@ QIBusPlatformInputContext::~QIBusPlatformInputContext (void)
     delete d;
 }
 
+bool QIBusPlatformInputContext::isValid() const
+{
+    return d->valid;
+}
+
 void QIBusPlatformInputContext::mouseHandler (int x, QMouseEvent *event)
 {
     QPlatformInputContext::mouseHandler (x, event);

src/platformsupport/inputmethods/ibus/qibusplatforminputcontext.h

@@ -53,6 +53,8 @@ public:
     QIBusPlatformInputContext();
     ~QIBusPlatformInputContext();
 
+    bool isValid() const;
+
     void mouseHandler(int x, QMouseEvent *event);
     void reset(void);
     void update(void);

src/plugins/platforms/xcb/qxcbintegration.cpp

@@ -99,10 +99,14 @@ QXcbIntegration::QXcbIntegration(const QStringList &parameters)
     m_fontDatabase = new QGenericUnixFontDatabase();
     m_nativeInterface = new QXcbNativeInterface;
 
-#if defined(XCB_USE_IBUS)
-    m_inputContext = new QIBusPlatformInputContext;
-#else
     m_inputContext = 0;
+#if defined(XCB_USE_IBUS)
+    QIBusPlatformInputContext *context = new QIBusPlatformInputContext;
+    if (context->isValid()) {
+        m_inputContext = context;
+    } else {
+        delete context;
+    }
 #endif
 }
 

src/plugins/platforms/xcb/qxcbkeyboard.cpp

@@ -49,7 +49,6 @@
 #include <private/qguiapplication_p.h>
 #include <stdio.h>
 
-#define XCB_USE_IBUS
 #if defined(XCB_USE_IBUS)
 #include "QtPlatformSupport/qibusplatforminputcontext.h"
 #endif