Add QX11Info::peekEventQueue() APIv5.10.0-beta3v5.10.0-beta2v5.10.0-beta1v5.10.0-alpha1

[ChangeLog][QX11Info] Added new API to peek into the
XCB event queue - peekEventQueue(). This enables porting
certain Qt4-based applications to Qt5 (those using Xlib's
event handling functions to peek into the X11 event queue).

In Qt5 we set XCB to be the owner of the X11 event queue
with XSetEventQueueOwner(dpy, XCBOwnsEventQueue), which
means that only XCB event handling functions can be used
to read events from the X server. XCB does not have an
equivalent for Xlib's peeker API. For filtering out unwanted
native events Qt5 provides QAbstractNativeEventFilter::nativeEventFilter(),
but there isn't any API in Qt to just *peek* into the queue
while the GUI thread is busy processing a long task. The
peekEventQueue() function adds this capability via QX11Info.

Manual and auto test included.

Task-number: QTBUG-50358
Change-Id: Id31f797f7ff76d011ad7a55a9b6c13756aaaca60
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

1 files changed, 111 insertions, 0 deletions

diff --git a/tests/manual/peeker/main.cpp b/tests/manual/peeker/main.cpp
new file mode 100644
index 0000000..8c7b280
--- /dev/null
+++ b/tests/manual/peeker/main.cpp
@@ -0,0 +1,111 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 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.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QtGui>
+#include <QtX11Extras/QX11Info>
+
+class IntensivePainter : public QWindow
+{
+public:
+    IntensivePainter() : m_backingStore(new QBackingStore(this))
+    { setGeometry(100, 100, 900, 600); }
+
+protected:
+    bool interrupted() const { return m_stopPainting; }
+    void stopPainting() { m_stopPainting = true; }
+    void beginPaining() { m_stopPainting = false; }
+
+    void exposeEvent(QExposeEvent *)
+    {
+        bool useGreenColor = false;
+        QRect rect(0, 0, width(), height());
+        m_backingStore->resize(QSize(width(), height()));
+
+        qint32 peekerId = QX11Info::generatePeekerId();
+        if (peekerId == -1) {
+            qWarning() << "Internal error: QX11Info::generatePeekerId() returned -1";
+            exit(EXIT_FAILURE);
+        }
+
+        while (!interrupted()) { // Begin a long operation
+            m_backingStore->beginPaint(rect);
+            QPaintDevice *device = m_backingStore->paintDevice();
+            QPainter painter(device);
+            painter.fillRect(rect, useGreenColor ? Qt::green : Qt::red);
+            useGreenColor = !useGreenColor;
+            painter.drawText(rect, Qt::AlignCenter, QStringLiteral("Press any key to exit.\n"
+            "(make sure the window is in focus when testing)\n\n If key press does not "
+            "immediately exit the application,\n then that should be considered a bug/regression."
+            "\n\n A demo might appear frozen to some window managers\n and therefore "
+            "might get grayed out (e.g Unity), this is the expected behavior.\n On KWin, for "
+            "example, this demo does not get grayed out.\n Resizing the window on any system will "
+            "cause rendering artefacts, that is not a bug,\n but simply the way the test is "
+            "implemented."));
+            m_backingStore->endPaint();
+            m_backingStore->flush(rect);
+            QThread::msleep(500); // Reduce the speed of re-painting (blinking)
+
+            QX11Info::peekEventQueue([](xcb_generic_event_t *event, void *data) {
+                bool isKeyPress = (event->response_type & ~0x80) == XCB_KEY_PRESS;
+                if (isKeyPress) {
+                    IntensivePainter *painter = static_cast<IntensivePainter *>(data);
+                    painter->stopPainting();
+                }
+                return isKeyPress;
+            }, this, QX11Info::PeekOption::PeekFromCachedIndex, peekerId);
+        }
+
+        QX11Info::removePeekerId(peekerId);
+        exit(EXIT_SUCCESS);
+    }
+
+private:
+    QBackingStore *m_backingStore;
+    bool m_stopPainting = false;
+};
+
+int main(int argc, char** argv)
+{
+    QGuiApplication app(argc, argv);
+
+    IntensivePainter painterWindow;
+    painterWindow.show();
+
+    return app.exec();
+}