Return button index for deprecated QMessageBox APIs

The static QMessageBox APIs taking button texts instead of standard
buttons promises that the return value is 0, 1, or 2. After the change
in b30121041c07b1b8613eaf624c9aa55a51001aef the return value of exec
for custom buttons was changed (as the documentation says its an opaque
value), which unfortunately affected the deprecated functions.

To fix this, we use the index of the clicked button in the custom
button list, to restore the previous behavior of the deprecated
APIs.

Fixes: QTBUG-125858
Pick-to: 6.8 6.7
Change-Id: I96d39e42b64e2b55eab07e2f15df71b94cfe3e6d
Reviewed-by: Volker Hilsheimer <[email protected]>
Reviewed-by: Jan Arve Sæther <[email protected]>
(cherry picked from commit a428c6933565ee8368367534cf306ccc6957f5a5)
Reviewed-by: Qt Cherry-pick Bot <[email protected]>

2 files changed, 23 insertions, 2 deletions

diff --git a/src/widgets/dialogs/qmessagebox.cpp b/src/widgets/dialogs/qmessagebox.cpp
index bf56b17f55f..f24cd905ccf 100644
--- a/src/widgets/dialogs/qmessagebox.cpp
+++ b/src/widgets/dialogs/qmessagebox.cpp
@@ -2158,7 +2158,11 @@ int QMessageBoxPrivate::showOldMessageBox(QWidget *parent, QMessageBox::Icon ico
     messageBox.setDefaultButton(static_cast<QPushButton *>(buttonList.value(defaultButtonNumber)));
     messageBox.setEscapeButton(buttonList.value(escapeButtonNumber));
 
-    return messageBox.exec();
+    messageBox.exec();
+
+    // Ignore exec return value and use button index instead,
+    // as that's what the documentation promises.
+    return buttonList.indexOf(messageBox.clickedButton());
 }
 
 void QMessageBoxPrivate::retranslateStrings()
diff --git a/tests/auto/widgets/dialogs/qmessagebox/tst_qmessagebox.cpp b/tests/auto/widgets/dialogs/qmessagebox/tst_qmessagebox.cpp
index 94afff6e408..26a62451643 100644
--- a/tests/auto/widgets/dialogs/qmessagebox/tst_qmessagebox.cpp
+++ b/tests/auto/widgets/dialogs/qmessagebox/tst_qmessagebox.cpp
@@ -63,6 +63,7 @@ private slots:
     void hideNativeByDestruction();
 
     void explicitDoneAfterButtonClicked();
+    void legacyApiReturnValue();
 
     void cleanup();
 };
@@ -511,7 +512,7 @@ QT_WARNING_DISABLE_DEPRECATED
     // the button text versions
     closeHelper.start(Qt::Key_Enter);
     ret = QMessageBox::information(nullptr, "title", "text", "Yes", "No", QString(), 1);
-    COMPARE(ret, 3); // Custom button opaque result
+    COMPARE(ret, 1);
     QVERIFY(closeHelper.done());
 #endif // QT_DEPRECATED_SINCE(6, 2)
 #undef COMPARE
@@ -863,5 +864,21 @@ void tst_QMessageBox::explicitDoneAfterButtonClicked()
     QCOMPARE(rejectedSpy.size(), 3);
 }
 
+void tst_QMessageBox::legacyApiReturnValue()
+{
+    ExecCloseHelper closeHelper;
+    for (int i = 0; i < 3; ++i) {
+        closeHelper.start(Qt::Key_Enter);
+QT_WARNING_PUSH
+QT_WARNING_DISABLE_DEPRECATED
+        QCOMPARE(QMessageBox::warning(nullptr, "Title", "Text",
+            "Button 0", "Button 1", "Button 2", i), i);
+        closeHelper.start(Qt::Key_Escape);
+        QCOMPARE(QMessageBox::warning(nullptr, "Title", "Text",
+            "Button 0", "Button 1", "Button 2", 0, i), i);
+QT_WARNING_POP
+    }
+}
+
 QTEST_MAIN(tst_QMessageBox)
 #include "tst_qmessagebox.moc"