Plumb QMessageBox::setCheckBox() through QPlatformMessageDialogHelper

Without this plumbing we have no way of knowing if the QMessageBox
has a checkbox set, and can't decide to skip the native dialog,
leaving the user without the expected checkbox.

As the suppression checkbox on macOS can be customized, we can use
this plumbing to actually provide native dialog support for generic
check boxes.

This mechanism can also be used by QErrorMessage, which now matches
behavior between native and non-native dialogs in terms of the label
of the checkbox and its initial state. We might want to tweak this
in the future, since user's might expect the suppression label and
state to match the system default, but that's something we can
expose from the platform theme if so, and should apply equally
to the non-native dialog.

Fixes: QTBUG-111803
Change-Id: Ied9fc34383fe79fbd8437592ad1c1993b9396178
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
(cherry picked from commit a0313c85a9b8ab6ba0ec273f0c8638e2f7b8cc18)
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

src/gui/kernel/qplatformdialoghelper.cpp

@@ -776,7 +776,8 @@ public:
     QList<QMessageDialogOptions::CustomButton> customButtons;
     int nextCustomButtonId;
     QPixmap iconPixmap;
-    bool enableSupressionCheckBox = false;
+    QString checkBoxLabel;
+    Qt::CheckState checkBoxState = Qt::Unchecked;
 };
 
 QMessageDialogOptions::QMessageDialogOptions(QMessageDialogOptionsPrivate *dd)
@@ -907,14 +908,20 @@ const QMessageDialogOptions::CustomButton *QMessageDialogOptions::customButton(i
     return (i < 0 ? nullptr : &d->customButtons.at(i));
 }
 
-void QMessageDialogOptions::setSupressionCheckBoxEnabled(bool enabled)
+void QMessageDialogOptions::setCheckBox(const QString &label, Qt::CheckState state)
 {
-    d->enableSupressionCheckBox = enabled;
+    d->checkBoxLabel = label;
+    d->checkBoxState = state;
 }
 
-bool QMessageDialogOptions::supressionCheckBoxEnabled() const
+QString QMessageDialogOptions::checkBoxLabel() const
 {
-    return d->enableSupressionCheckBox;
+    return d->checkBoxLabel;
+}
+
+Qt::CheckState QMessageDialogOptions::checkBoxState() const
+{
+    return d->checkBoxState;
 }
 
 QPlatformDialogHelper::ButtonRole QPlatformDialogHelper::buttonRole(QPlatformDialogHelper::StandardButton button)

src/gui/kernel/qplatformdialoghelper.h

@@ -451,8 +451,9 @@ public:
     const QList<CustomButton> &customButtons();
     const CustomButton *customButton(int id);
 
-    void setSupressionCheckBoxEnabled(bool enabled);
-    bool supressionCheckBoxEnabled() const;
+    void setCheckBox(const QString &label, Qt::CheckState state);
+    QString checkBoxLabel() const;
+    Qt::CheckState checkBoxState() const;
 
 private:
     QMessageDialogOptionsPrivate *d;
@@ -467,7 +468,7 @@ public:
 
 Q_SIGNALS:
     void clicked(QPlatformDialogHelper::StandardButton button, QPlatformDialogHelper::ButtonRole role);
-    void supressionCheckBoxChanged(bool checked);
+    void checkBoxStateChanged(Qt::CheckState state);
 
 private:
     QSharedPointer<QMessageDialogOptions> m_options;

src/plugins/platforms/android/qandroidplatformdialoghelpers.cpp

@@ -54,7 +54,7 @@ bool QAndroidPlatformMessageDialogHelper::show(Qt::WindowFlags windowFlags,
     if (!opt.data())
         return false;
 
-    if (opt->supressionCheckBoxEnabled())
+    if (!opt->checkBoxLabel().isNull())
         return false; // Can't support
 
     m_javaMessageDialog.callMethod<void>("setIcon", "(I)V", opt->icon());

src/plugins/platforms/cocoa/qcocoamessagedialog.mm

@@ -46,6 +46,16 @@ static QString toPlainText(const QString &text)
     return textDocument.toPlainText();
 }
 
+static NSControlStateValue controlStateFor(Qt::CheckState state)
+{
+    switch (state) {
+    case Qt::Checked: return NSControlStateValueOn;
+    case Qt::Unchecked: return NSControlStateValueOff;
+    case Qt::PartiallyChecked: return NSControlStateValueMixed;
+    }
+    Q_UNREACHABLE();
+}
+
 /*
     Called from QDialogPrivate::setNativeDialogVisible() when the message box
     is ready to be shown.
@@ -185,7 +195,14 @@ bool QCocoaMessageDialog::show(Qt::WindowFlags windowFlags, Qt::WindowModality w
             StandardButton::Ok, ButtonRole::AcceptRole);
     }
 
-    m_alert.showsSuppressionButton = options()->supressionCheckBoxEnabled();
+    if (auto checkBoxLabel = options()->checkBoxLabel(); !checkBoxLabel.isNull()) {
+        checkBoxLabel = QPlatformTheme::removeMnemonics(checkBoxLabel);
+        m_alert.suppressionButton.title = checkBoxLabel.toNSString();
+        auto state = options()->checkBoxState();
+        m_alert.suppressionButton.allowsMixedState = state == Qt::PartiallyChecked;
+        m_alert.suppressionButton.state = controlStateFor(state);
+        m_alert.showsSuppressionButton = YES;
+    }
 
     qCDebug(lcQpaDialogs) << "Showing" << m_alert;
 
@@ -233,6 +250,16 @@ void QCocoaMessageDialog::exec()
 // Custom modal response code to record that the dialog was hidden by us
 static const NSInteger kModalResponseDialogHidden = NSAlertThirdButtonReturn + 1;
 
+static Qt::CheckState checkStateFor(NSControlStateValue state)
+{
+    switch (state) {
+    case NSControlStateValueOn: return Qt::Checked;
+    case NSControlStateValueOff: return Qt::Unchecked;
+    case NSControlStateValueMixed: return Qt::PartiallyChecked;
+    }
+    Q_UNREACHABLE();
+}
+
 void QCocoaMessageDialog::processResponse(NSModalResponse response)
 {
     qCDebug(lcQpaDialogs) << "Processing response" << response << "for" << m_alert;
@@ -244,7 +271,7 @@ void QCocoaMessageDialog::processResponse(NSModalResponse response)
     [alert autorelease];
 
     if (alert.showsSuppressionButton)
-        emit supressionCheckBoxChanged(alert.suppressionButton.state == NSControlStateValueOn);
+        emit checkBoxStateChanged(checkStateFor(alert.suppressionButton.state));
 
      if (response >= NSAlertFirstButtonReturn) {
         // Safe range for user-defined modal responses

src/plugins/platforms/ios/qiosmessagedialog.mm

@@ -92,7 +92,7 @@ bool QIOSMessageDialog::show(Qt::WindowFlags windowFlags, Qt::WindowModality win
             || windowModality == Qt::NonModal) // We can only do modal dialogs
         return false;
 
-    if (options()->supressionCheckBoxEnabled())
+    if (!options()->checkBoxLabel().isNull())
         return false; // Can't support
 
     m_alertController = [[UIAlertController

src/widgets/dialogs/qerrormessage.cpp

@@ -63,9 +63,9 @@ 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::checkBoxStateChanged, q,
+        [this](Qt::CheckState state) {
+            again->setCheckState(state);
         }
     );
     QObject::connect(messageDialogHelper, &QPlatformMessageDialogHelper::clicked, q,
@@ -86,7 +86,7 @@ void QErrorMessagePrivate::helperPrepareShow(QPlatformDialogHelper *helper)
     options->setText(QErrorMessage::tr("An error occurred"));
     options->setInformativeText(currentMessage);
     options->setIcon(QMessageDialogOptions::Critical);
-    options->setSupressionCheckBoxEnabled(true);
+    options->setCheckBox(again->text(), again->checkState());
     messageDialogHelper->setOptions(options);
 }
 

src/widgets/dialogs/qmessagebox.cpp

@@ -2682,6 +2682,15 @@ void QMessageBoxPrivate::initHelper(QPlatformDialogHelper *h)
     Q_Q(QMessageBox);
     QObject::connect(h, SIGNAL(clicked(QPlatformDialogHelper::StandardButton,QPlatformDialogHelper::ButtonRole)),
                      q, SLOT(_q_clicked(QPlatformDialogHelper::StandardButton,QPlatformDialogHelper::ButtonRole)));
+
+    auto *messageDialogHelper = static_cast<QPlatformMessageDialogHelper *>(h);
+    QObject::connect(messageDialogHelper, &QPlatformMessageDialogHelper::checkBoxStateChanged, q,
+        [this](Qt::CheckState state) {
+            if (checkbox)
+                checkbox->setCheckState(state);
+        }
+    );
+
     static_cast<QPlatformMessageDialogHelper *>(h)->setOptions(options);
 }
 
@@ -2720,6 +2729,8 @@ void QMessageBoxPrivate::helperPrepareShow(QPlatformDialogHelper *)
     options->setIcon(helperIcon(q->icon()));
     options->setIconPixmap(q->iconPixmap());
     options->setStandardButtons(helperStandardButtons(q));
+    if (checkbox)
+        options->setCheckBox(checkbox->text(), checkbox->checkState());
 }
 
 void QMessageBoxPrivate::helperDone(QDialog::DialogCode code, QPlatformDialogHelper *)