xcb: call processXcbEvents() on every event loop iteration

It is necessary for QTBUG-69687. The original code processes the xcb
event queue only when new events have arrived, but if we want to do an
event filtering that buffers some events and processes them later based
on set/unset flags (e.g. QEventLoop::ExcludeUserInputEvents), we need
to call processXcbEvents() on every event loop iteration, not only when
new events have arrived from X server.

The required functionality is implemented by having custom event dispatchers,
instead of using the generic ones from QtGenericUnixDispatcher::
createUnixEventDispatcher() / eventdispatcher_support-private. This also
enables for further customizations, as might be necessary by QTBUG-70095.

Task-number: QTBUG-69687
Change-Id: I1f8b2400d26cccf17279d57bb4b678e40c615f33
Reviewed-by: Gatis Paeglis <gatis.paeglis@qt.io>

1 files changed, 117 insertions, 0 deletions

diff --git a/src/plugins/platforms/xcb/qxcbeventdispatcher.h b/src/plugins/platforms/xcb/qxcbeventdispatcher.h
new file mode 100644
index 0000000000..6aadd63a70
--- /dev/null
+++ b/src/plugins/platforms/xcb/qxcbeventdispatcher.h
@@ -0,0 +1,117 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtCore module 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 The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/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 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+#ifndef QXCBEVENTDISPATCHER_H
+#define QXCBEVENTDISPATCHER_H
+
+#include <QtCore/QObject>
+#include <QtCore/QEventLoop>
+
+#include <QtCore/private/qeventdispatcher_unix_p.h>
+#if QT_CONFIG(glib)
+#include <QtCore/private/qeventdispatcher_glib_p.h>
+#include <glib.h>
+#endif
+
+QT_BEGIN_NAMESPACE
+
+class QXcbConnection;
+
+class QXcbUnixEventDispatcher : public QEventDispatcherUNIX
+{
+    Q_OBJECT
+public:
+    explicit QXcbUnixEventDispatcher(QXcbConnection *connection, QObject *parent = nullptr);
+    ~QXcbUnixEventDispatcher();
+    bool processEvents(QEventLoop::ProcessEventsFlags flags) override;
+
+    // Maybe some user code depends on deprecated QUnixEventDispatcherQPA::
+    // hasPendingEvents() / flush() implementation, so keep it around until
+    // Qt 6. These methods are deprecated in QAbstractEventDispatcher.
+    bool hasPendingEvents() override; // ### Qt 6 remove
+    void flush() override;            // ### Qt 6 remove
+
+private:
+    QXcbConnection *m_connection;
+};
+
+#if QT_CONFIG(glib)
+
+struct XcbEventSource;
+class QXcbGlibEventDispatcherPrivate;
+
+class QXcbGlibEventDispatcher : public QEventDispatcherGlib
+{
+    Q_OBJECT
+    Q_DECLARE_PRIVATE(QXcbGlibEventDispatcher)
+
+public:
+    explicit QXcbGlibEventDispatcher(QXcbConnection *connection, QObject *parent = nullptr);
+    ~QXcbGlibEventDispatcher();
+
+    bool processEvents(QEventLoop::ProcessEventsFlags flags) override;
+    QEventLoop::ProcessEventsFlags flags() const { return m_flags; }
+
+private:
+    XcbEventSource *m_xcbEventSource;
+    GSourceFuncs m_xcbEventSourceFuncs;
+    QEventLoop::ProcessEventsFlags m_flags;
+};
+
+class QXcbGlibEventDispatcherPrivate : public QEventDispatcherGlibPrivate
+{
+    Q_DECLARE_PUBLIC(QXcbGlibEventDispatcher)
+
+public:
+    QXcbGlibEventDispatcherPrivate();
+};
+
+#endif // QT_CONFIG(glib)
+
+class QXcbEventDispatcher
+{
+public:
+    static QAbstractEventDispatcher *createEventDispatcher(QXcbConnection *connection);
+
+private:
+    QXcbConnection *m_connection;
+};
+
+QT_END_NAMESPACE
+
+#endif // QXCBEVENTDISPATCHER_H