QMessageBox::about / aboutQt - use native modal dialog on iOS

The about / aboutQt statics in QMessageBox used a non-native, non-modal
dialog box on all operating systems. This creates a grid layout with
labels for heading, text and icon.

This has two unwanted side-effects on iOS:
- When the screen size is not sufficient to display all text, the text
is not rendered. On an iPhone SE for example, only the Qt icon is visible.
- When the screen height exceeds the minimum requirement, the informative
text is bottom-aligned.

=> Show about(Qt) message boxes in a modal, native dialog.
=> Update documentation.

This partly reverts aafed07dee5fd2d22518e49c4fa7798735e9e681.

[ChangeLog][iOS] QMessageBox::about(Qt) now shows native, modal dialog.

Fixes: QTBUG-115832
Pick-to: 6.6 6.5 6.2
Change-Id: I4cfbce416e7d2717058bef9a050a85d424b8a03d
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

1 files changed, 17 insertions, 6 deletions

diff --git a/src/widgets/dialogs/qmessagebox.cpp b/src/widgets/dialogs/qmessagebox.cpp
index 6f93837b8e..b81df2bb07 100644
--- a/src/widgets/dialogs/qmessagebox.cpp
+++ b/src/widgets/dialogs/qmessagebox.cpp
@@ -1910,9 +1910,10 @@ QMessageBox::StandardButton QMessageBox::critical(QWidget *parent, const QString
     \li As a last resort it uses the Information icon.
     \endlist
 
-    The about box has a single button labelled "OK". On \macos, the
-    about box is popped up as a modeless window; on other platforms,
-    it is currently application modal.
+    The about box has a single button labelled "OK".
+
+    On \macos, the about box is popped up as a modeless window; on
+    other platforms, it is currently application modal.
 
     \sa QWidget::windowIcon(), QApplication::activeWindow()
 */
@@ -1942,8 +1943,13 @@ void QMessageBox::about(QWidget *parent, const QString &title, const QString &te
     // should perhaps be a style hint
 #ifdef Q_OS_MAC
     oldMsgBox = msgBox;
-    msgBox->d_func()->buttonBox->setCenterButtons(true);
+    auto *d = msgBox->d_func();
+    d->buttonBox->setCenterButtons(true);
+#ifdef Q_OS_IOS
+    msgBox->setModal(true);
+#else
     msgBox->setModal(false);
+#endif
     msgBox->show();
 #else
     msgBox->exec();
@@ -1960,7 +1966,7 @@ void QMessageBox::about(QWidget *parent, const QString &title, const QString &te
 
     QApplication provides this functionality as a slot.
 
-    On \macos, the about box is popped up as a modeless window; on
+    On \macos, the aboutQt box is popped up as a modeless window; on
     other platforms, it is currently application modal.
 
     \sa QApplication::aboutQt()
@@ -2023,8 +2029,13 @@ void QMessageBox::aboutQt(QWidget *parent, const QString &title)
     // should perhaps be a style hint
 #ifdef Q_OS_MAC
     oldMsgBox = msgBox;
-    msgBox->d_func()->buttonBox->setCenterButtons(true);
+    auto *d = msgBox->d_func();
+    d->buttonBox->setCenterButtons(true);
+#ifdef Q_OS_IOS
+    msgBox->setModal(true);
+#else
     msgBox->setModal(false);
+#endif
     msgBox->show();
 #else
     msgBox->exec();