QPixmap: More safe failing if qApp is not a QGuiApplication

It can happen that QDataStream is fed a QVariant that contains a QPixmap
representation, that will make the application crash when trying to
restore it

This is specially important for cases in which applications expose dbus
interfaces with QVariantMaps

Change-Id: Ife4feaef30f30e7e27d88464bd6b2a247f743123
Reported-by: Fabian Vogt <fabian@ritter-vogt.de>
Reviewed-by: Fabian Vogt <fabian@ritter-vogt.de>
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/gui/image/qpixmap.cpp

@@ -1543,6 +1543,11 @@ QPixmap QPixmap::fromImage(const QImage &image, Qt::ImageConversionFlags flags)
     if (image.isNull())
         return QPixmap();
 
+    if (Q_UNLIKELY(!qobject_cast<QGuiApplication *>(QCoreApplication::instance()))) {
+        qWarning("QPixmap::fromImage: QPixmap cannot be created without a QGuiApplication");
+        return QPixmap();
+    }
+
     QScopedPointer<QPlatformPixmap> data(QGuiApplicationPrivate::platformIntegration()->createPlatformPixmap(QPlatformPixmap::PixmapType));
     data->fromImage(image, flags);
     return QPixmap(data.take());
@@ -1565,6 +1570,11 @@ QPixmap QPixmap::fromImageInPlace(QImage &image, Qt::ImageConversionFlags flags)
     if (image.isNull())
         return QPixmap();
 
+    if (Q_UNLIKELY(!qobject_cast<QGuiApplication *>(QCoreApplication::instance()))) {
+        qWarning("QPixmap::fromImageInPlace: QPixmap cannot be created without a QGuiApplication");
+        return QPixmap();
+    }
+
     QScopedPointer<QPlatformPixmap> data(QGuiApplicationPrivate::platformIntegration()->createPlatformPixmap(QPlatformPixmap::PixmapType));
     data->fromImageInPlace(image, flags);
     return QPixmap(data.take());
@@ -1584,6 +1594,11 @@ QPixmap QPixmap::fromImageInPlace(QImage &image, Qt::ImageConversionFlags flags)
 */
 QPixmap QPixmap::fromImageReader(QImageReader *imageReader, Qt::ImageConversionFlags flags)
 {
+    if (Q_UNLIKELY(!qobject_cast<QGuiApplication *>(QCoreApplication::instance()))) {
+        qWarning("QPixmap::fromImageReader: QPixmap cannot be created without a QGuiApplication");
+        return QPixmap();
+    }
+
     QScopedPointer<QPlatformPixmap> data(QGuiApplicationPrivate::platformIntegration()->createPlatformPixmap(QPlatformPixmap::PixmapType));
     data->fromImageReader(imageReader, flags);
     return QPixmap(data.take());

tests/auto/corelib/serialization/qdatastream_core_pixmap/qdatastream_core_pixmap.pro

@@ -0,0 +1,4 @@
+CONFIG += testcase
+TARGET = tst_qdatastream_core_pixmap
+QT += testlib
+SOURCES = tst_qdatastream_core_pixmap.cpp

tests/auto/corelib/serialization/qdatastream_core_pixmap/tst_qdatastream_core_pixmap.cpp

@@ -0,0 +1,68 @@
+/****************************************************************************
+**
+** Copyright (C) 2019 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:GPL-EXCEPT$
+** 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 General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** 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-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QtTest/QtTest>
+#include <QtGui/QBitmap>
+#include <QtGui/QPalette>
+#include <QtGui/QPixmap>
+#include <QtGui/QPicture>
+#include <QtGui/QTextLength>
+#include <QtGui/QPainter>
+#include <QtGui/QPen>
+
+class tst_QDataStream : public QObject
+{
+Q_OBJECT
+
+private slots:
+    void stream_with_pixmap();
+
+};
+
+void tst_QDataStream::stream_with_pixmap()
+{
+    // This is a QVariantMap with a 3x3 red QPixmap and two strings inside
+    const QByteArray ba = QByteArray::fromBase64("AAAAAwAAAAIAegAAAAoAAAAACgB0AGgAZQByAGUAAAACAHAAAABBAAAAAAGJUE5HDQoaCgAAAA1JSERSAAAAAwAAAAMIAgAAANlKIugAAAAJcEhZcwAADsQAAA7EAZUrDhsAAAAQSURBVAiZY/zPAAVMDJgsAB1bAQXZn5ieAAAAAElFTkSuQmCCAAAAAgBhAAAACgAAAAAKAGgAZQBsAGwAbw==");
+    QImage dummy; // Needed to make sure qtGui is loaded
+
+    QTest::ignoreMessage(QtWarningMsg, "QPixmap::fromImageInPlace: QPixmap cannot be created without a QGuiApplication");
+
+    QVariantMap map;
+    QDataStream d(ba);
+    d.setVersion(QDataStream::Qt_5_12);
+    d >> map;
+
+    QCOMPARE(map["a"].toString(), QString("hello"));
+    QCOMPARE(map["p"].value<QPixmap>(), QPixmap()); // the pixmap is null because this is not a QGuiApplication
+    QCOMPARE(map["z"].toString(), QString("there"));
+}
+
+QTEST_GUILESS_MAIN(tst_QDataStream)
+
+#include "tst_qdatastream_core_pixmap.moc"
+

tests/auto/corelib/serialization/serialization.pro

@@ -6,6 +6,7 @@ SUBDIRS = \
     qcborvalue \
     qcborvalue_json \
     qdatastream \
+    qdatastream_core_pixmap \
     qtextstream \
     qxmlstream