Dialogs: allow preventing processing of standard buttons

Add an actionChosen() signal to DefaultDialogWrapper, allowing the
developer to stop further processing of the event by setting the
"accepted" field to false. This is especially useful when some
validation on the dialog contents need to take place before the dialog
can be accepted.

[ChangeLog][Dialogs] Add a signal to the Dialog class to allow the
client to intercept the button presses and optionally prevent further
processing of the event. This allows performing some validation on the
fields before dismissing the dialog.

Task-number: QTBUG-69095
Change-Id: I19bca0bd9fcbafc72d337a5870776a96634ba748
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

4 files changed, 304 insertions, 15 deletions

diff --git a/src/dialogs/DefaultDialogWrapper.qml b/src/dialogs/DefaultDialogWrapper.qml
index b446c316..3ca030c4 100644
--- a/src/dialogs/DefaultDialogWrapper.qml
+++ b/src/dialogs/DefaultDialogWrapper.qml
@@ -47,6 +47,9 @@ import "qml"
 AbstractDialog {
     id: root
     default property alias data: defaultContentItem.data
+
+    signal actionChosen(var action)
+
     onVisibilityChanged: if (visible && contentItem) contentItem.forceActiveFocus()
 
     Rectangle {
@@ -63,19 +66,7 @@ AbstractDialog {
             defaultContentItem.implicitWidth, buttonsRowImplicitWidth, Screen.pixelDensity * 50) + outerSpacing * 2)
         color: palette.window
         Keys.onPressed: {
-            event.accepted = true
-            switch (event.key) {
-                case Qt.Key_Escape:
-                case Qt.Key_Back:
-                    reject()
-                    break
-                case Qt.Key_Enter:
-                case Qt.Key_Return:
-                    accept()
-                    break
-                default:
-                    event.accepted = false
-            }
+            event.accepted = handleKey(event.key)
         }
 
         SystemPalette { id: palette }
@@ -109,7 +100,7 @@ AbstractDialog {
                 id: buttonsLeftRepeater
                 Button {
                     text: (buttonsLeftRepeater.model && buttonsLeftRepeater.model[index] ? buttonsLeftRepeater.model[index].text : index)
-                    onClicked: root.click(buttonsLeftRepeater.model[index].standardButton)
+                    onClicked: content.handleButton(buttonsLeftRepeater.model[index].standardButton)
                 }
             }
 
@@ -136,9 +127,54 @@ AbstractDialog {
                 // TODO maybe: insert gaps if the button requires it (destructive buttons only)
                 Button {
                     text: (buttonsRightRepeater.model && buttonsRightRepeater.model[index] ? buttonsRightRepeater.model[index].text : index)
-                    onClicked: root.click(buttonsRightRepeater.model[index].standardButton)
+                    onClicked: content.handleButton(buttonsRightRepeater.model[index].standardButton)
+                }
+            }
+        }
+
+        function handleButton(button) {
+            var action = {
+                "button": button,
+                "key": 0,
+                "accepted": true,
+            }
+            root.actionChosen(action)
+            if (action.accepted) {
+                click(button)
+            }
+        }
+
+        function handleKey(key) {
+            var button = 0
+            switch (key) {
+                case Qt.Key_Escape:
+                case Qt.Key_Back:
+                    button = StandardButton.Cancel
+                    break
+                case Qt.Key_Enter:
+                case Qt.Key_Return:
+                    button = StandardButton.Ok
+                    break
+                default:
+                    return false
+            }
+            var action = {
+                "button": button,
+                "key": key,
+                "accepted": true,
+            }
+            root.actionChosen(action)
+            if (action.accepted) {
+                switch (button) {
+                    case StandardButton.Cancel:
+                        reject()
+                        break
+                    case StandardButton.Ok:
+                        accept()
+                        break
                 }
             }
+            return true
         }
     }
     function setupButtons() {
diff --git a/src/dialogs/qquickdialog.cpp b/src/dialogs/qquickdialog.cpp
index 485eeb43..ef6a9a1f 100644
--- a/src/dialogs/qquickdialog.cpp
+++ b/src/dialogs/qquickdialog.cpp
@@ -154,6 +154,31 @@ QT_BEGIN_NAMESPACE
 */
 
 /*!
+    \qmlsignal Dialog::actionChosen(var action)
+
+    This signal is emitted when the user has pressed any button or a key
+    associated with some role (such as the Enter or Escape keys). The \a
+    action parameter carries information about the event:
+
+    \list
+    \li StandardButton button - The role of the button which was pressed. If a
+        key was pressed instead, this will be \c StandardButton.Ok if accepted
+        and \c StandardButton.Cancel if rejected.
+    \li Qt.Key key - The key which was pressed, or \c 0 if none
+    \li bool accepted - Set this to \c false to stop the event from triggering
+        its predefined action
+    \endlist
+
+    By handling this signal and setting the \c action.accepted field to \c
+    false, it's possible to implement some validation on the dialog contents
+    before accepting it, for example.
+
+    The corresponding handler is \c onActionChosen.
+
+    \since QtQuick.Controls 1.8
+*/
+
+/*!
     \qmlproperty bool Dialog::visible
 
     This property holds whether the dialog is visible. By default this is
diff --git a/tests/auto/dialogs/data/DialogButtonHandler.qml b/tests/auto/dialogs/data/DialogButtonHandler.qml
new file mode 100644
index 00000000..e19f88c8
--- /dev/null
+++ b/tests/auto/dialogs/data/DialogButtonHandler.qml
@@ -0,0 +1,88 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 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 2.3
+import QtQuick.Controls 1.2
+import QtQuick.Dialogs 1.2
+
+Dialog {
+    property bool handlerWasCalled: false
+    property var buttonCode
+    property var keyCode
+    property bool mustBlock: false
+    property string actionCalled: ""
+
+    visible: true
+    title: "Blue sky dialog"
+    standardButtons: buttonsFromTest
+
+    Item {
+        implicitWidth: 300
+        implicitHeight: 200
+    }
+
+    onActionChosen: {
+        handlerWasCalled = true
+        buttonCode = action.button
+        keyCode = action.key
+        if (mustBlock) {
+            action.accepted = false
+        }
+    }
+
+    onAccepted: actionCalled = "accepted"
+    onApply: actionCalled = "apply"
+    onDiscard: actionCalled = "discard"
+    onHelp: actionCalled = "help"
+    onNo: actionCalled = "no"
+    onRejected: actionCalled = "rejected"
+    onReset: actionCalled = "reset"
+    onYes: actionCalled = "yes"
+}
diff --git a/tests/auto/dialogs/tst_dialogs.cpp b/tests/auto/dialogs/tst_dialogs.cpp
index 1f802113..8303ff83 100644
--- a/tests/auto/dialogs/tst_dialogs.cpp
+++ b/tests/auto/dialogs/tst_dialogs.cpp
@@ -51,6 +51,10 @@ private slots:
     void dialogImplicitWidth_data();
     void dialogImplicitWidth();
     void dialogContentResize();
+    void dialogButtonHandler_data();
+    void dialogButtonHandler();
+    void dialogKeyHandler_data();
+    void dialogKeyHandler();
 
     // FileDialog
     void fileDialogDefaultModality();
@@ -113,6 +117,142 @@ void tst_dialogs::dialogContentResize()
     QVERIFY(userContent->height() > 200);
 }
 
+void tst_dialogs::dialogButtonHandler_data()
+{
+    QTest::addColumn<int>("standardButtons");
+    QTest::addColumn<bool>("mustBlock");
+    QTest::addColumn<QString>("expectedAction");
+
+    QTest::newRow("Cancel, ignored") <<
+        int(QQuickAbstractDialog::Cancel) <<
+        false <<
+        "rejected";
+    QTest::newRow("Cancel, blocked") <<
+        int(QQuickAbstractDialog::Cancel) <<
+        true <<
+        "";
+    QTest::newRow("OK, ignored") <<
+        int(QQuickAbstractDialog::Ok) <<
+        false <<
+        "accepted";
+    QTest::newRow("OK, blocked") <<
+        int(QQuickAbstractDialog::Ok) <<
+        true <<
+        "";
+}
+
+void tst_dialogs::dialogButtonHandler()
+{
+    QFETCH(int, standardButtons);
+    QFETCH(bool, mustBlock);
+    QFETCH(QString, expectedAction);
+
+    QQmlEngine engine;
+    engine.rootContext()->setContextProperty("buttonsFromTest", standardButtons);
+    QQmlComponent component(&engine);
+    component.loadUrl(testFileUrl("DialogButtonHandler.qml"));
+    QObject *root = component.create();
+    QScopedPointer<QObject> cleanup(root);
+    QVERIFY2(root, qPrintable(component.errorString()));
+
+    root->setProperty("visible", true);
+    root->setProperty("mustBlock", mustBlock);
+
+    QQuickWindow *window = root->findChild<QQuickWindow*>();
+    QTest::qWaitForWindowExposed(window);
+
+    /* Hack to find the created buttons: since they are created by a
+     * QQuickRepeater, they don't appear on the hierarchy tree; therefore, we
+     * first need to find the repeater, and then to get its child. */
+    const QList<QQuickItem*> children = root->findChildren<QQuickItem*>();
+    QQuickItem *buttonWidget = nullptr;
+    for (QQuickItem *child: children) {
+        if (qstrcmp(child->metaObject()->className(), "QQuickRepeater") == 0 &&
+            child->property("count").toInt() > 0) {
+            int index = 0;
+            QMetaObject::invokeMethod(child,
+                                      "itemAt",
+                                      Q_RETURN_ARG(QQuickItem *, buttonWidget),
+                                      Q_ARG(int, index));
+            break;
+        }
+    }
+    QVERIFY(buttonWidget);
+
+    const QPointF buttonCenterF(buttonWidget->width() / 2,
+                                buttonWidget->height() / 2);
+    const QPoint buttonCenter = buttonWidget->mapToScene(buttonCenterF).toPoint();
+
+    QTest::mouseClick(window, Qt::LeftButton, Qt::NoModifier, buttonCenter);
+    QTRY_VERIFY(root->property("handlerWasCalled").toBool());
+
+    QCOMPARE(root->property("buttonCode").toInt(), standardButtons);
+    QCOMPARE(root->property("keyCode").toInt(), 0);
+
+    QCOMPARE(root->property("actionCalled").toString(), expectedAction);
+}
+
+void tst_dialogs::dialogKeyHandler_data()
+{
+    QTest::addColumn<int>("key");
+    QTest::addColumn<bool>("mustBlock");
+    QTest::addColumn<int>("expectedButton");
+    QTest::addColumn<QString>("expectedAction");
+
+    QTest::newRow("Escape, ignored") <<
+        int(Qt::Key_Escape) <<
+        false <<
+        int(QQuickAbstractDialog::Cancel) <<
+        "rejected";
+    QTest::newRow("Cancel, blocked") <<
+        int(Qt::Key_Escape) <<
+        true <<
+        int(QQuickAbstractDialog::Cancel) <<
+        "";
+    QTest::newRow("Enter, ignored") <<
+        int(Qt::Key_Enter) <<
+        false <<
+        int(QQuickAbstractDialog::Ok) <<
+        "accepted";
+    QTest::newRow("Enter, blocked") <<
+        int(Qt::Key_Enter) <<
+        true <<
+        int(QQuickAbstractDialog::Ok) <<
+        "";
+}
+
+void tst_dialogs::dialogKeyHandler()
+{
+    QFETCH(int, key);
+    QFETCH(bool, mustBlock);
+    QFETCH(int, expectedButton);
+    QFETCH(QString, expectedAction);
+
+    QQmlEngine engine;
+    QQuickAbstractDialog::StandardButtons buttons =
+        QQuickAbstractDialog::Ok | QQuickAbstractDialog::Cancel;
+    engine.rootContext()->setContextProperty("buttonsFromTest", int(buttons));
+    QQmlComponent component(&engine);
+    component.loadUrl(testFileUrl("DialogButtonHandler.qml"));
+    QObject *root = component.create();
+    QScopedPointer<QObject> cleanup(root);
+    QVERIFY2(root, qPrintable(component.errorString()));
+
+    root->setProperty("visible", true);
+    root->setProperty("mustBlock", mustBlock);
+
+    QQuickWindow *window = root->findChild<QQuickWindow*>();
+    QTest::qWaitForWindowExposed(window);
+
+    QTest::keyClick(window, Qt::Key(key));
+    QTRY_VERIFY(root->property("handlerWasCalled").toBool());
+
+    QCOMPARE(root->property("buttonCode").toInt(), expectedButton);
+    QCOMPARE(root->property("keyCode").toInt(), key);
+
+    QCOMPARE(root->property("actionCalled").toString(), expectedAction);
+}
+
 void tst_dialogs::fileDialogDefaultModality()
 {
     QQuickView *window = new QQuickView;