Teach QErrorMessage to use native dialog helper if available

And implement for macOS. The default modality of the QErrorMessage
on macOS now depends on whether the dialog has a parent or not.

The QErrorMessage must be hidden and re-shown again after each message,
so that the native dialog has a chance to recreate itself.

Change-Id: I474ed35d6271118834fac8e97f6f540a6fb89b8c
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

src/gui/kernel/qplatformdialoghelper.cpp

@@ -776,6 +776,7 @@ public:
     QList<QMessageDialogOptions::CustomButton> customButtons;
     int nextCustomButtonId;
     QPixmap iconPixmap;
+    bool enableSupressionCheckBox = false;
 };
 
 QMessageDialogOptions::QMessageDialogOptions(QMessageDialogOptionsPrivate *dd)
@@ -906,6 +907,16 @@ const QMessageDialogOptions::CustomButton *QMessageDialogOptions::customButton(i
     return (i < 0 ? nullptr : &d->customButtons.at(i));
 }
 
+void QMessageDialogOptions::setSupressionCheckBoxEnabled(bool enabled)
+{
+    d->enableSupressionCheckBox = enabled;
+}
+
+bool QMessageDialogOptions::supressionCheckBoxEnabled() const
+{
+    return d->enableSupressionCheckBox;
+}
+
 QPlatformDialogHelper::ButtonRole QPlatformDialogHelper::buttonRole(QPlatformDialogHelper::StandardButton button)
 {
     switch (button) {

src/gui/kernel/qplatformdialoghelper.h

@@ -451,6 +451,9 @@ public:
     const QList<CustomButton> &customButtons();
     const CustomButton *customButton(int id);
 
+    void setSupressionCheckBoxEnabled(bool enabled);
+    bool supressionCheckBoxEnabled() const;
+
 private:
     QMessageDialogOptionsPrivate *d;
 };
@@ -464,6 +467,7 @@ public:
 
 Q_SIGNALS:
     void clicked(QPlatformDialogHelper::StandardButton button, QPlatformDialogHelper::ButtonRole role);
+    void supressionCheckBoxChanged(bool checked);
 
 private:
     QSharedPointer<QMessageDialogOptions> m_options;

src/plugins/platforms/android/qandroidplatformdialoghelpers.cpp

@@ -54,6 +54,9 @@ bool QAndroidPlatformMessageDialogHelper::show(Qt::WindowFlags windowFlags,
     if (!opt.data())
         return false;
 
+    if (opt->supressionCheckBoxEnabled())
+        return false; // Can't support
+
     m_javaMessageDialog.callMethod<void>("setIcon", "(I)V", opt->icon());
 
     QString str = htmlText(opt->windowTitle());

src/plugins/platforms/cocoa/qcocoamessagedialog.mm

@@ -180,6 +180,8 @@ bool QCocoaMessageDialog::show(Qt::WindowFlags windowFlags, Qt::WindowModality w
             StandardButton::Ok, ButtonRole::AcceptRole);
     }
 
+    m_alert.showsSuppressionButton = options()->supressionCheckBoxEnabled();
+
     qCDebug(lcQpaDialogs) << "Showing" << m_alert;
 
     if (windowModality == Qt::WindowModal) {
@@ -230,6 +232,15 @@ void QCocoaMessageDialog::processResponse(NSModalResponse response)
 {
     qCDebug(lcQpaDialogs) << "Processing response" << response << "for" << m_alert;
 
+    // We can't re-use the same dialog for the next show() anyways,
+    // since the options may have changed, so get rid of it now,
+    // before we emit anything that might recurse back to hide/show/etc.
+    auto alert = std::exchange(m_alert, nil);
+    [alert autorelease];
+
+    if (alert.showsSuppressionButton)
+        emit supressionCheckBoxChanged(alert.suppressionButton.state == NSControlStateValueOn);
+
      if (response >= NSAlertFirstButtonReturn) {
         // Safe range for user-defined modal responses
         if (response == kModalResponseDialogHidden) {
@@ -270,11 +281,6 @@ void QCocoaMessageDialog::processResponse(NSModalResponse response)
 
     if (m_eventLoop)
         m_eventLoop->exit(response);
-
-    // We can't re-use the same dialog for the next show() anyways,
-    // since the options may have changed, so get rid of it now.
-    [m_alert release];
-    m_alert = nil;
 }
 
 void QCocoaMessageDialog::hide()

src/plugins/platforms/ios/qiosmessagedialog.mm

@@ -92,6 +92,9 @@ bool QIOSMessageDialog::show(Qt::WindowFlags windowFlags, Qt::WindowModality win
             || windowModality == Qt::NonModal) // We can only do modal dialogs
         return false;
 
+    if (options()->supressionCheckBoxEnabled())
+        return false; // Can't support
+
     m_alertController = [[UIAlertController
         alertControllerWithTitle:options()->windowTitle().toNSString()
         message:messageTextPlain().toNSString()

src/widgets/dialogs/qerrormessage.cpp

@@ -52,8 +52,44 @@ public:
     bool isMessageToBeShown(const QString &message, const QString &type) const;
     bool nextPending();
     void retranslateStrings();
+
+private:
+    void initHelper(QPlatformDialogHelper *) override;
+    void helperPrepareShow(QPlatformDialogHelper *) override;
 };
 
+
+void QErrorMessagePrivate::initHelper(QPlatformDialogHelper *helper)
+{
+    Q_Q(QErrorMessage);
+    auto *messageDialogHelper = static_cast<QPlatformMessageDialogHelper *>(helper);
+    QObject::connect(messageDialogHelper, &QPlatformMessageDialogHelper::supressionCheckBoxChanged, q,
+        [this](bool supressionChecked) {
+            again->setChecked(!supressionChecked);
+        }
+    );
+    QObject::connect(messageDialogHelper, &QPlatformMessageDialogHelper::clicked, q,
+        [this](QPlatformDialogHelper::StandardButton, QPlatformDialogHelper::ButtonRole) {
+            Q_Q(QErrorMessage);
+            q->accept();
+        }
+    );
+}
+
+void QErrorMessagePrivate::helperPrepareShow(QPlatformDialogHelper *helper)
+{
+    Q_Q(QErrorMessage);
+    auto *messageDialogHelper = static_cast<QPlatformMessageDialogHelper *>(helper);
+    QSharedPointer<QMessageDialogOptions> options = QMessageDialogOptions::create();
+    options->setText(currentMessage);
+    options->setWindowTitle(q->windowTitle());
+    options->setText(QErrorMessage::tr("An error occurred"));
+    options->setInformativeText(currentMessage);
+    options->setIcon(QMessageDialogOptions::Critical);
+    options->setSupressionCheckBoxEnabled(true);
+    messageDialogHelper->setOptions(options);
+}
+
 namespace {
 class QErrorMessageTextView : public QTextEdit
 {
@@ -190,6 +226,10 @@ static void jump(QtMsgType t, const QMessageLogContext &context, const QString &
 /*!
     Constructs and installs an error handler window with the given \a
     parent.
+
+    The default \l{Qt::WindowModality} {window modality} of the dialog
+    depends on the platform. The window modality can be overridden via
+    setWindowModality() before calling showMessage().
 */
 
 QErrorMessage::QErrorMessage(QWidget * parent)
@@ -197,6 +237,10 @@ QErrorMessage::QErrorMessage(QWidget * parent)
 {
     Q_D(QErrorMessage);
 
+#if defined(Q_OS_MACOS)
+    setWindowModality(parent ? Qt::WindowModal : Qt::ApplicationModal);
+#endif
+
     d->icon = new QLabel(this);
     d->errors = new QErrorMessageTextView(this);
     d->again = new QCheckBox(this);
@@ -256,8 +300,12 @@ void QErrorMessage::done(int a)
     }
     d->currentMessage.clear();
     d->currentType.clear();
-    if (!d->nextPending()) {
-        QDialog::done(a);
+
+    QDialog::done(a);
+
+    if (d->nextPending()) {
+        show();
+    } else {
         if (this == qtMessageHandler && metFatal)
             exit(1);
     }
@@ -355,6 +403,23 @@ void QErrorMessage::showMessage(const QString &message, const QString &type)
         show();
 }
 
+void QErrorMessage::setVisible(bool visible)
+{
+    if (testAttribute(Qt::WA_WState_ExplicitShowHide) && testAttribute(Qt::WA_WState_Hidden) != visible)
+        return;
+
+    Q_D(QErrorMessage);
+    if (d->canBeNativeDialog())
+        d->setNativeDialogVisible(visible);
+
+    // Update WA_DontShowOnScreen based on whether the native dialog was shown,
+    // so that QDialog::setVisible(visible) below updates the QWidget state correctly,
+    // but skips showing the non-native version.
+    setAttribute(Qt::WA_DontShowOnScreen, d->nativeDialogInUse);
+
+    QDialog::setVisible(visible);
+}
+
 /*!
     \reimp
 */

src/widgets/dialogs/qerrormessage.h

@@ -28,6 +28,8 @@ public Q_SLOTS:
     void showMessage(const QString &message);
     void showMessage(const QString &message, const QString &type);
 
+    void setVisible(bool) override;
+
 protected:
     void done(int) override;
     void changeEvent(QEvent *e) override;