Resolve xcb_poll_for_queued_event at run-time.

By not making this a compile time decision we ensure forward
compatibility for older xcb versions if the xcb plugin is built against
a newer xcb.

Change-Id: I744777d53bf7b8deb6eff372494f4403d19d364c
Reviewed-by: Kai Koehne <kai.koehne@digia.com>

6 files changed, 50 insertions, 109 deletions

diff --git a/config.tests/qpa/xcb-poll-for-queued-event/xcb-poll-for-queued-event.cpp b/config.tests/qpa/xcb-poll-for-queued-event/xcb-poll-for-queued-event.cpp
deleted file mode 100644
index 3b244cc5e5..0000000000
--- a/config.tests/qpa/xcb-poll-for-queued-event/xcb-poll-for-queued-event.cpp
+++ /dev/null
@@ -1,64 +0,0 @@
-/****************************************************************************
-**
-** Copyright (C) 2012 Digia Plc and/or its subsidiary(-ies).
-** Contact: http://www.qt-project.org/legal
-**
-** This file is part of the config.tests of the Qt Toolkit.
-**
-** $QT_BEGIN_LICENSE:LGPL$
-** Commercial License Usage
-** Licensees holding valid commercial Qt licenses may use this file in
-** accordance with the commercial license agreement provided with the
-** Software or, alternatively, in accordance with the terms contained in
-** a written agreement between you and Digia.  For licensing terms and
-** conditions see http://qt.digia.com/licensing.  For further information
-** use the contact form at http://qt.digia.com/contact-us.
-**
-** GNU Lesser General Public License Usage
-** Alternatively, this file may be used under the terms of the GNU Lesser
-** General Public License version 2.1 as published by the Free Software
-** Foundation and appearing in the file LICENSE.LGPL included in the
-** packaging of this file.  Please review the following information to
-** ensure the GNU Lesser General Public License version 2.1 requirements
-** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
-**
-** In addition, as a special exception, Digia gives you certain additional
-** rights.  These rights are described in the Digia Qt LGPL Exception
-** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
-**
-** GNU General Public License Usage
-** Alternatively, this file may be used under the terms of the GNU
-** General Public License version 3.0 as published by the Free Software
-** Foundation and appearing in the file LICENSE.GPL included in the
-** packaging of this file.  Please review the following information to
-** ensure the GNU General Public License version 3.0 requirements will be
-** met: http://www.gnu.org/copyleft/gpl.html.
-**
-**
-** $QT_END_LICENSE$
-**
-****************************************************************************/
-
-#include <xcb/xcb.h>
-
-// FIXME This workaround can be removed for xcb-icccm > 3.8
-#define class class_name
-#include <xcb/xcb_icccm.h>
-#undef class
-
-#include <xcb/xfixes.h>
-#include <xcb/xcb_image.h>
-#include <xcb/xcb_keysyms.h>
-#include <xcb/sync.h>
-#include <xcb/shm.h>
-
-int main(int, char **)
-{
-    int primaryScreen = 0;
-
-    xcb_connection_t *connection = xcb_connect("", &primaryScreen);
-
-    xcb_generic_event_t *event = xcb_poll_for_queued_event(connection);
-
-    return 0;
-}
diff --git a/config.tests/qpa/xcb-poll-for-queued-event/xcb-poll-for-queued-event.pro b/config.tests/qpa/xcb-poll-for-queued-event/xcb-poll-for-queued-event.pro
deleted file mode 100644
index 6075c55c49..0000000000
--- a/config.tests/qpa/xcb-poll-for-queued-event/xcb-poll-for-queued-event.pro
+++ /dev/null
@@ -1,5 +0,0 @@
-SOURCES = xcb-poll-for-queued-event.cpp
-CONFIG -= qt
-
-LIBS += -lxcb -lxcb-image -lxcb-keysyms -lxcb-icccm -lxcb-sync -lxcb-xfixes
-
diff --git a/configure b/configure
index 4a4b48b1aa..97479f6432 100755
--- a/configure
+++ b/configure
@@ -803,7 +803,6 @@ CFG_XINPUT=runtime
 CFG_XKB=auto
 CFG_XCB=auto
 CFG_XCB_GLX=no
-CFG_XCB_LIMITED=yes
 CFG_EGLFS=auto
 CFG_DIRECTFB=auto
 CFG_LINUXFB=auto
@@ -4815,11 +4814,6 @@ if [ "$CFG_XCB" != "no" ]; then
             QT_CONFIG="$QT_CONFIG xcb-glx"
         fi
 
-        if compileTest qpa/xcb-poll-for-queued-event "xcb-poll-for-queued-event" $QMAKE_CFLAGS_XCB $QMAKE_LIBS_XCB; then
-            CFG_XCB_LIMITED=no
-            QT_CONFIG="$QT_CONFIG xcb-poll-for-queued-event"
-        fi
-
         if compileTest qpa/xcb-xlib "xcb-xlib" $QMAKE_CFLAGS_XCB $QMAKE_LIBS_XCB; then
             QT_CONFIG="$QT_CONFIG xcb-xlib"
         fi
@@ -6308,11 +6302,7 @@ if [ "$BUILD_ON_MAC" = "yes" ]; then
 fi
 echo "libICU support ......... $CFG_ICU"
 echo "PCRE support ........... $CFG_PCRE"
-if [ "$CFG_XCB_LIMITED" = "yes" ] && [ "$CFG_XCB" = "yes" ]; then
-    echo "Xcb support ............ limited (old version)"
-else
-    echo "Xcb support ............ $CFG_XCB"
-fi
+echo "Xcb support ............ $CFG_XCB"
 echo "Xrender support ........ $CFG_XRENDER"
 if [ "$XPLATFORM_MAEMO" = "yes" ] && [ "$CFG_XCB" = "yes" ]; then
     echo "XInput2 support ........ $CFG_XINPUT2"
diff --git a/src/plugins/platforms/xcb/qxcbconnection.cpp b/src/plugins/platforms/xcb/qxcbconnection.cpp
index e35954caf9..266491d5d9 100644
--- a/src/plugins/platforms/xcb/qxcbconnection.cpp
+++ b/src/plugins/platforms/xcb/qxcbconnection.cpp
@@ -58,6 +58,7 @@
 #include <QTimer>
 #include <QByteArray>
 
+#include <dlfcn.h>
 #include <stdio.h>
 #include <errno.h>
 #include <xcb/shm.h>
@@ -281,18 +282,16 @@ QXcbConnection::QXcbConnection(QXcbNativeInterface *nativeInterface, const char
         qFatal("QXcbConnection: Could not connect to display %s", m_displayName.constData());
 
     m_reader = new QXcbEventReader(this);
-#ifdef XCB_POLL_FOR_QUEUED_EVENT
     connect(m_reader, SIGNAL(eventPending()), this, SLOT(processXcbEvents()), Qt::QueuedConnection);
     connect(m_reader, SIGNAL(finished()), this, SLOT(processXcbEvents()));
-    m_reader->start();
-#else
-    QSocketNotifier *notifier = new QSocketNotifier(xcb_get_file_descriptor(xcb_connection()), QSocketNotifier::Read, this);
-    connect(notifier, SIGNAL(activated(int)), this, SLOT(processXcbEvents()));
+    if (!m_reader->startThread()) {
+        QSocketNotifier *notifier = new QSocketNotifier(xcb_get_file_descriptor(xcb_connection()), QSocketNotifier::Read, this);
+        connect(notifier, SIGNAL(activated(int)), this, SLOT(processXcbEvents()));
 
-    QAbstractEventDispatcher *dispatcher = QGuiApplicationPrivate::eventDispatcher;
-    connect(dispatcher, SIGNAL(aboutToBlock()), this, SLOT(processXcbEvents()));
-    connect(dispatcher, SIGNAL(awake()), this, SLOT(processXcbEvents()));
-#endif
+        QAbstractEventDispatcher *dispatcher = QGuiApplicationPrivate::eventDispatcher;
+        connect(dispatcher, SIGNAL(aboutToBlock()), this, SLOT(processXcbEvents()));
+        connect(dispatcher, SIGNAL(awake()), this, SLOT(processXcbEvents()));
+    }
 
     xcb_extension_t *extensions[] = {
         &xcb_shm_id, &xcb_xfixes_id, &xcb_randr_id, &xcb_shape_id, &xcb_sync_id,
@@ -364,10 +363,11 @@ QXcbConnection::~QXcbConnection()
     finalizeXInput2();
 #endif
 
-#ifdef XCB_POLL_FOR_QUEUED_EVENT
-    sendConnectionEvent(QXcbAtom::_QT_CLOSE_CONNECTION);
-    m_reader->wait();
-#endif
+    if (m_reader->isRunning()) {
+        sendConnectionEvent(QXcbAtom::_QT_CLOSE_CONNECTION);
+        m_reader->wait();
+    }
+
     delete m_reader;
 
 #ifdef XCB_USE_EGL
@@ -808,14 +808,37 @@ void QXcbConnection::addPeekFunc(PeekFunc f)
     m_peekFuncs.append(f);
 }
 
-#ifdef XCB_POLL_FOR_QUEUED_EVENT
+QXcbEventReader::QXcbEventReader(QXcbConnection *connection)
+    : m_connection(connection)
+    , m_xcb_poll_for_queued_event(0)
+{
+#ifdef RTLD_DEFAULT
+    m_xcb_poll_for_queued_event = (XcbPollForQueuedEventFunctionPointer)dlsym(RTLD_DEFAULT, "xcb_poll_for_queued_event");
+#endif
+
+#ifdef Q_XCB_DEBUG
+    if (m_xcb_poll_for_queued_event)
+        qDebug("Using threaded event reader with xcb_poll_for_queued_event");
+#endif
+}
+
+bool QXcbEventReader::startThread()
+{
+    if (m_xcb_poll_for_queued_event) {
+        QThread::start();
+        return true;
+    }
+
+    return false;
+}
+
 void QXcbEventReader::run()
 {
     xcb_generic_event_t *event;
     while (m_connection && (event = xcb_wait_for_event(m_connection->xcb_connection()))) {
         m_mutex.lock();
         addEvent(event);
-        while (m_connection && (event = xcb_poll_for_queued_event(m_connection->xcb_connection())))
+        while (m_connection && (event = m_xcb_poll_for_queued_event(m_connection->xcb_connection())))
             addEvent(event);
         m_mutex.unlock();
         emit eventPending();
@@ -824,7 +847,6 @@ void QXcbEventReader::run()
     for (int i = 0; i < m_events.size(); ++i)
         free(m_events.at(i));
 }
-#endif
 
 void QXcbEventReader::addEvent(xcb_generic_event_t *event)
 {
@@ -837,10 +859,10 @@ void QXcbEventReader::addEvent(xcb_generic_event_t *event)
 QXcbEventArray *QXcbEventReader::lock()
 {
     m_mutex.lock();
-#ifndef XCB_POLL_FOR_QUEUED_EVENT
-    while (xcb_generic_event_t *event = xcb_poll_for_event(m_connection->xcb_connection()))
-        m_events << event;
-#endif
+    if (!m_xcb_poll_for_queued_event) {
+        while (xcb_generic_event_t *event = xcb_poll_for_event(m_connection->xcb_connection()))
+            m_events << event;
+    }
     return &m_events;
 }
 
diff --git a/src/plugins/platforms/xcb/qxcbconnection.h b/src/plugins/platforms/xcb/qxcbconnection.h
index 8b2315c67e..f466928360 100644
--- a/src/plugins/platforms/xcb/qxcbconnection.h
+++ b/src/plugins/platforms/xcb/qxcbconnection.h
@@ -278,18 +278,15 @@ class QXcbEventReader : public QThread
 {
     Q_OBJECT
 public:
-    QXcbEventReader(QXcbConnection *connection)
-        : m_connection(connection)
-    {
-    }
+    QXcbEventReader(QXcbConnection *connection);
 
-#ifdef XCB_POLL_FOR_QUEUED_EVENT
     void run();
-#endif
 
     QXcbEventArray *lock();
     void unlock();
 
+    bool startThread();
+
 signals:
     void eventPending();
 
@@ -299,6 +296,9 @@ private:
     QMutex m_mutex;
     QXcbEventArray m_events;
     QXcbConnection *m_connection;
+
+    typedef xcb_generic_event_t * (*XcbPollForQueuedEventFunctionPointer)(xcb_connection_t *c);
+    XcbPollForQueuedEventFunctionPointer m_xcb_poll_for_queued_event;
 };
 
 class QAbstractEventDispatcher;
diff --git a/src/plugins/platforms/xcb/xcb.pro b/src/plugins/platforms/xcb/xcb.pro
index 34f7c74675..8a3e9e8e5e 100644
--- a/src/plugins/platforms/xcb/xcb.pro
+++ b/src/plugins/platforms/xcb/xcb.pro
@@ -40,9 +40,7 @@ HEADERS = \
         qxcbimage.h \
         qxlibconvenience.h
 
-contains(QT_CONFIG, xcb-poll-for-queued-event) {
-    DEFINES += XCB_POLL_FOR_QUEUED_EVENT
-}
+LIBS += -ldl
 
 # needed by GLX, Xcursor, XLookupString, ...
 contains(QT_CONFIG, xcb-xlib) {