Buttons: defer the execution of the delegates

In practice, deferring the execution of the delegates (until
accessed) means that the default delegate item does not get created
at all, when a custom control replaces it at construction time.

    Button {
        background: Rectangle { ... }
    }

Before, such custom Button would never be faster than the original
one, because the default delegate was first created and then thrown
away at construction time. Originally, this was not considered a huge
problem, because the plan was to keep the default delegates so light-
weight that it wouldn't matter. However, then came the fancy styles
with shadows and effects and thus, heavier default delegates. There's
also a growing demand for more features, and the default delegates
are slowly getting heavier...

Now, after this patch, if you replace a heavy default delegate with
a light and simple custom delegate, the result is a much faster
control. For example, replacing Material style Button's background,
which has a shadow effect, with a plain Rectangle gives a ~10x boost,
because the default background with its heavy shadow effect is not
executed at all.

At the same time, deferring the execution of the default delegates
avoids troubles with asynchronous incubation, because we don't need
to destroy an object in the middle of the incubation process.

Task-number: QTBUG-50992
Change-Id: I2274bff99b9ff126d3748278d58d859222910c98
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

15 files changed, 939 insertions, 0 deletions

diff --git a/tests/auto/auto.pro b/tests/auto/auto.pro
index 0aeef414..17613796 100644
--- a/tests/auto/auto.pro
+++ b/tests/auto/auto.pro
@@ -4,6 +4,7 @@ SUBDIRS += \
     calendar \
     controls \
     cursor \
+    customization \
     focus \
     font \
     platform \
diff --git a/tests/auto/customization/customization.pro b/tests/auto/customization/customization.pro
new file mode 100644
index 00000000..472367a3
--- /dev/null
+++ b/tests/auto/customization/customization.pro
@@ -0,0 +1,11 @@
+CONFIG += testcase
+TARGET = tst_customization
+SOURCES += tst_customization.cpp
+
+macos:CONFIG -= app_bundle
+
+QT += core-private gui-private qml-private quick-private testlib quicktemplates2-private quickcontrols2
+
+include (../shared/util.pri)
+
+TESTDATA = data/*
diff --git a/tests/auto/customization/data/styles/empty/Button.qml b/tests/auto/customization/data/styles/empty/Button.qml
new file mode 100644
index 00000000..865c97f7
--- /dev/null
+++ b/tests/auto/customization/data/styles/empty/Button.qml
@@ -0,0 +1,57 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** 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.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+import QtQuick 2.9
+import QtQuick.Templates 2.2 as T
+
+T.Button {
+    id: control
+    objectName: "button-empty"
+}
diff --git a/tests/auto/customization/data/styles/empty/CheckBox.qml b/tests/auto/customization/data/styles/empty/CheckBox.qml
new file mode 100644
index 00000000..f01402bd
--- /dev/null
+++ b/tests/auto/customization/data/styles/empty/CheckBox.qml
@@ -0,0 +1,57 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** 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.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+import QtQuick 2.9
+import QtQuick.Templates 2.2 as T
+
+T.CheckBox {
+    id: control
+    objectName: "checkbox-empty"
+}
diff --git a/tests/auto/customization/data/styles/empty/RadioButton.qml b/tests/auto/customization/data/styles/empty/RadioButton.qml
new file mode 100644
index 00000000..9763227b
--- /dev/null
+++ b/tests/auto/customization/data/styles/empty/RadioButton.qml
@@ -0,0 +1,57 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** 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.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+import QtQuick 2.9
+import QtQuick.Templates 2.2 as T
+
+T.RadioButton {
+    id: control
+    objectName: "radiobutton-empty"
+}
diff --git a/tests/auto/customization/data/styles/incomplete/Button.qml b/tests/auto/customization/data/styles/incomplete/Button.qml
new file mode 100644
index 00000000..99a2a112
--- /dev/null
+++ b/tests/auto/customization/data/styles/incomplete/Button.qml
@@ -0,0 +1,61 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** 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.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+import QtQuick 2.9
+import QtQuick.Templates 2.2 as T
+
+T.Button {
+    id: control
+    objectName: "button-incomplete"
+
+    background: Item {
+        objectName: "button-background-incomplete"
+    }
+}
diff --git a/tests/auto/customization/data/styles/incomplete/CheckBox.qml b/tests/auto/customization/data/styles/incomplete/CheckBox.qml
new file mode 100644
index 00000000..50de13ac
--- /dev/null
+++ b/tests/auto/customization/data/styles/incomplete/CheckBox.qml
@@ -0,0 +1,61 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** 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.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+import QtQuick 2.9
+import QtQuick.Templates 2.2 as T
+
+T.CheckBox {
+    id: control
+    objectName: "checkbox-incomplete"
+
+    contentItem: Item {
+        objectName: "checkbox-contentItem-incomplete"
+    }
+}
diff --git a/tests/auto/customization/data/styles/incomplete/RadioButton.qml b/tests/auto/customization/data/styles/incomplete/RadioButton.qml
new file mode 100644
index 00000000..933f3f0e
--- /dev/null
+++ b/tests/auto/customization/data/styles/incomplete/RadioButton.qml
@@ -0,0 +1,61 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** 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.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+import QtQuick 2.9
+import QtQuick.Templates 2.2 as T
+
+T.CheckBox {
+    id: control
+    objectName: "radiobutton-incomplete"
+
+    indicator: Item {
+        objectName: "radiobutton-indicator-incomplete"
+    }
+}
diff --git a/tests/auto/customization/data/styles/override/Button.qml b/tests/auto/customization/data/styles/override/Button.qml
new file mode 100644
index 00000000..8ec8cb52
--- /dev/null
+++ b/tests/auto/customization/data/styles/override/Button.qml
@@ -0,0 +1,65 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** 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.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+import QtQuick 2.9
+import "../empty" as Empty
+
+Empty.Button {
+    id: control
+    objectName: "button-override"
+
+    contentItem: Rectangle {
+        objectName: "button-contentItem-override"
+    }
+
+    background: Rectangle {
+        objectName: "button-background-override"
+    }
+}
diff --git a/tests/auto/customization/data/styles/override/CheckBox.qml b/tests/auto/customization/data/styles/override/CheckBox.qml
new file mode 100644
index 00000000..5553ac5d
--- /dev/null
+++ b/tests/auto/customization/data/styles/override/CheckBox.qml
@@ -0,0 +1,63 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** 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.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+import QtQuick 2.9
+import "../incomplete" as Incomplete
+
+Incomplete.CheckBox {
+    id: control
+    objectName: "checkbox-override"
+
+    contentItem.visible: false
+
+    background: Rectangle {
+        objectName: "checkbox-background-override"
+    }
+}
diff --git a/tests/auto/customization/data/styles/override/RadioButton.qml b/tests/auto/customization/data/styles/override/RadioButton.qml
new file mode 100644
index 00000000..368ac892
--- /dev/null
+++ b/tests/auto/customization/data/styles/override/RadioButton.qml
@@ -0,0 +1,65 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** 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.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+import QtQuick 2.9
+import "../simple" as Simple
+
+Simple.RadioButton {
+    id: control
+    objectName: "radiobutton-override"
+
+    background: Rectangle {
+        objectName: "radiobutton-background-override"
+    }
+
+    indicator: Rectangle {
+        objectName: "radiobutton-indicator-override"
+    }
+}
diff --git a/tests/auto/customization/data/styles/simple/Button.qml b/tests/auto/customization/data/styles/simple/Button.qml
new file mode 100644
index 00000000..d06ae6c1
--- /dev/null
+++ b/tests/auto/customization/data/styles/simple/Button.qml
@@ -0,0 +1,72 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** 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.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+import QtQuick 2.9
+import QtQuick.Templates 2.2 as T
+
+T.Button {
+    id: control
+    objectName: "button-simple"
+
+    implicitWidth: Math.max(contentItem.implicitWidth, background.implicitWidth)
+    implicitHeight: Math.max(contentItem.implicitHeight, background.implicitHeight)
+
+    contentItem: Text {
+        objectName: "button-contentItem-simple"
+        text: control.text
+    }
+
+    background: Rectangle {
+        objectName: "button-background-simple"
+        implicitWidth: 20
+        implicitHeight: 20
+        color: control.pressed ? "red" : "green"
+    }
+}
diff --git a/tests/auto/customization/data/styles/simple/CheckBox.qml b/tests/auto/customization/data/styles/simple/CheckBox.qml
new file mode 100644
index 00000000..00d76614
--- /dev/null
+++ b/tests/auto/customization/data/styles/simple/CheckBox.qml
@@ -0,0 +1,70 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** 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.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+import QtQuick 2.9
+import QtQuick.Templates 2.2 as T
+
+T.CheckBox {
+    id: control
+    objectName: "checkbox-simple"
+
+    implicitWidth: contentItem.implicitWidth + indicator.implicitWidth
+    implicitHeight: Math.max(contentItem.implicitHeight, indicator.implicitHeight)
+
+    indicator: Text {
+        objectName: "checkbox-indicator-simple"
+        text: control.checked ? "V" : ""
+    }
+
+    contentItem: Text {
+        objectName: "checkbox-contentItem-simple"
+        text: control.text
+    }
+}
diff --git a/tests/auto/customization/data/styles/simple/RadioButton.qml b/tests/auto/customization/data/styles/simple/RadioButton.qml
new file mode 100644
index 00000000..8f07acc5
--- /dev/null
+++ b/tests/auto/customization/data/styles/simple/RadioButton.qml
@@ -0,0 +1,70 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** 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.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+import QtQuick 2.9
+import QtQuick.Templates 2.2 as T
+
+T.RadioButton {
+    id: control
+    objectName: "radiobutton-simple"
+
+    implicitWidth: contentItem.implicitWidth + indicator.implicitWidth
+    implicitHeight: Math.max(contentItem.implicitHeight, indicator.implicitHeight)
+
+    indicator: Text {
+        objectName: "radiobutton-indicator-simple"
+        text: control.checked ? "O" : ""
+    }
+
+    contentItem: Text {
+        objectName: "radiobutton-contentItem-simple"
+        text: control.text
+    }
+}
diff --git a/tests/auto/customization/tst_customization.cpp b/tests/auto/customization/tst_customization.cpp
new file mode 100644
index 00000000..3da13628
--- /dev/null
+++ b/tests/auto/customization/tst_customization.cpp
@@ -0,0 +1,168 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL3$
+** 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 http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://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.LGPLv3 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.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 later 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 2.0 requirements will be
+** met: http://www.gnu.org/licenses/gpl-2.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QtTest/qtest.h>
+#include <QtCore/private/qhooks_p.h>
+#include <QtCore/qregularexpression.h>
+#include <QtQml/qqmlengine.h>
+#include <QtQml/qqmlcomponent.h>
+#include <QtQuickControls2/qquickstyle.h>
+#include "../shared/visualtestutil.h"
+
+using namespace QQuickVisualTestUtil;
+
+class tst_customization : public QQmlDataTest
+{
+    Q_OBJECT
+
+private slots:
+    void init();
+    void cleanup();
+
+    void creation_data();
+    void creation();
+
+private:
+    void reset();
+    void addHooks();
+    void removeHooks();
+
+    QObject* createControl(const QString &type);
+
+    QQmlEngine *engine = nullptr;
+};
+
+Q_GLOBAL_STATIC(QStringList, qt_createdQObjects)
+Q_GLOBAL_STATIC(QStringList, qt_destroyedQObjects)
+
+extern "C" Q_DECL_EXPORT void qt_addQObject(QObject *object)
+{
+    // objectName is not set at construction time
+    QObject::connect(object, &QObject::objectNameChanged, [object](const QString &objectName) {
+        if (!objectName.isEmpty())
+            qt_createdQObjects()->append(objectName);
+    });
+}
+
+extern "C" Q_DECL_EXPORT void qt_removeQObject(QObject *object)
+{
+    QString objectName = object->objectName();
+    if (!objectName.isEmpty())
+        qt_destroyedQObjects()->append(objectName);
+}
+
+void tst_customization::init()
+{
+    engine = new QQmlEngine(this);
+
+    qtHookData[QHooks::AddQObject] = reinterpret_cast<quintptr>(&qt_addQObject);
+    qtHookData[QHooks::RemoveQObject] = reinterpret_cast<quintptr>(&qt_removeQObject);
+}
+
+void tst_customization::cleanup()
+{
+    qtHookData[QHooks::AddQObject] = 0;
+    qtHookData[QHooks::RemoveQObject] = 0;
+
+    delete engine;
+    engine = nullptr;
+
+    qmlClearTypeRegistrations();
+
+    reset();
+}
+
+void tst_customization::reset()
+{
+    qt_createdQObjects()->clear();
+    qt_destroyedQObjects()->clear();
+}
+
+QObject* tst_customization::createControl(const QString &name)
+{
+    QQmlComponent component(engine);
+    component.setData("import QtQuick.Controls 2.2; " + name.toUtf8() + " { }", QUrl());
+    return component.create();
+}
+
+void tst_customization::creation_data()
+{
+    QTest::addColumn<QString>("style");
+    QTest::addColumn<QString>("type");
+    QTest::addColumn<QStringList>("delegates");
+
+    // the "empty" style does not contain any delegates
+    QTest::newRow("empty:Button") << "empty" << "Button"<< (QStringList() << "button-empty");
+    QTest::newRow("empty:CheckBox") << "empty" << "CheckBox" << (QStringList() << "checkbox-empty");
+    QTest::newRow("empty:RadioButton") << "empty" << "RadioButton" << (QStringList() << "radiobutton-empty");
+
+    // the "incomplete" style is missing most delegates
+    QTest::newRow("incomplete:Button") << "incomplete" << "Button" << (QStringList() << "button-incomplete" << "button-background-incomplete");
+    QTest::newRow("incomplete:CheckBox") << "incomplete" << "CheckBox" << (QStringList() << "checkbox-incomplete" << "checkbox-contentItem-incomplete");
+    QTest::newRow("incomplete:RadioButton") << "incomplete" << "RadioButton" << (QStringList() << "radiobutton-incomplete" << "radiobutton-indicator-incomplete");
+
+    // the "simple" style simulates a proper style and contains most delegates
+    QTest::newRow("simple:Button") << "simple" << "Button" << (QStringList() << "button-simple" << "button-background-simple" << "button-contentItem-simple");
+    QTest::newRow("simple:CheckBox") << "simple" << "CheckBox" << (QStringList() << "checkbox-simple" << "checkbox-contentItem-simple" << "checkbox-indicator-simple");
+    QTest::newRow("simple:RadioButton") << "simple" << "RadioButton" << (QStringList() << "radiobutton-simple" << "radiobutton-contentItem-simple" << "radiobutton-indicator-simple");
+
+    // the "override" style overrides various delegates in the above styles
+    QTest::newRow("override:Button") << "override" << "Button" << (QStringList() << "button-override" << "button-background-override" << "button-contentItem-override" << "button-empty"); // overrides "empty"
+    QTest::newRow("override:CheckBox") << "override" << "CheckBox" << (QStringList() << "checkbox-override" << "checkbox-background-override" << "checkbox-contentItem-incomplete" << "checkbox-incomplete"); // overrides "incomplete"
+    QTest::newRow("override:RadioButton") << "override" << "RadioButton" << (QStringList() << "radiobutton-override"  << "radiobutton-background-override" << "radiobutton-contentItem-simple" << "radiobutton-indicator-override" << "radiobutton-simple"); // overrides "simple"
+}
+
+void tst_customization::creation()
+{
+    QFETCH(QString, style);
+    QFETCH(QString, type);
+    QFETCH(QStringList, delegates);
+
+    QQuickStyle::setStyle(testFile("styles/" + style));
+
+    QScopedPointer<QObject> control(createControl(type));
+    QVERIFY(control);
+
+    for (const QString &delegate : delegates)
+        QVERIFY2(qt_createdQObjects()->removeOne(delegate), qPrintable(delegate + " was not created as expected"));
+
+    QVERIFY2(qt_createdQObjects()->isEmpty(), qPrintable("unexpectedly created: " + qt_createdQObjects->join(", ")));
+    QVERIFY2(qt_destroyedQObjects()->isEmpty(), qPrintable("unexpectedly destroyed: " + qt_destroyedQObjects->join(", ") + " were unexpectedly destroyed"));
+}
+
+QTEST_MAIN(tst_customization)
+
+#include "tst_customization.moc"