Add support for querying "eglconfig" through the xcb native interface

We already support this for eglfs but for a desktop Qt configured with
-opengl es2 we need to expose it through xcb as well.

Change-Id: I36d0e255d8c86cc1cec56015f33470f61d7df466
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>

src/plugins/platforms/xcb/qxcbnativeinterface.cpp

@@ -79,6 +79,7 @@ static int resourceType(const QByteArray &key)
         QByteArrayLiteral("display"),  QByteArrayLiteral("egldisplay"),
         QByteArrayLiteral("connection"), QByteArrayLiteral("screen"),
         QByteArrayLiteral("eglcontext"),
+        QByteArrayLiteral("eglconfig"),
         QByteArrayLiteral("glxconfig"),
         QByteArrayLiteral("glxcontext"), QByteArrayLiteral("apptime"),
         QByteArrayLiteral("appusertime"), QByteArrayLiteral("hintstyle"),
@@ -241,6 +242,9 @@ void *QXcbNativeInterface::nativeResourceForContext(const QByteArray &resourceSt
     case EglContext:
         result = eglContextForContext(context);
         break;
+    case EglConfig:
+        result = eglConfigForContext(context);
+        break;
     case GLXConfig:
         result = glxConfigForContext(context);
         break;
@@ -462,6 +466,18 @@ void * QXcbNativeInterface::eglContextForContext(QOpenGLContext *context)
 #endif
 }
 
+void * QXcbNativeInterface::eglConfigForContext(QOpenGLContext *context)
+{
+    Q_ASSERT(context);
+#if defined(XCB_USE_EGL)
+    QEGLPlatformContext *eglPlatformContext = static_cast<QEGLPlatformContext *>(context->handle());
+    return eglPlatformContext->eglConfig();
+#else
+    Q_UNUSED(context);
+    return 0;
+#endif
+}
+
 void *QXcbNativeInterface::glxContextForContext(QOpenGLContext *context)
 {
     Q_ASSERT(context);

src/plugins/platforms/xcb/qxcbnativeinterface.h

@@ -63,6 +63,7 @@ public:
         Connection,
         Screen,
         EglContext,
+        EglConfig,
         GLXConfig,
         GLXContext,
         AppTime,
@@ -104,6 +105,7 @@ public:
     static void setAppTime(QScreen *screen, xcb_timestamp_t time);
     static void setAppUserTime(QScreen *screen, xcb_timestamp_t time);
     static void *eglContextForContext(QOpenGLContext *context);
+    static void *eglConfigForContext(QOpenGLContext *context);
     static void *glxContextForContext(QOpenGLContext *context);
     static void *glxConfigForContext(QOpenGLContext *context);