QDialogButtonBox: Manage hide and show of standard buttons

0b421fa58b9a73d657bf17834788fd1175c4767e ensured a correct focus chain,
when buttons in a QDialogButtonBox were hidden.

The implementation did not check, if a hidden button was added via
setStandardButtons(). In consequence, it was removed from the
standardButtonHash and never added again.
QDialogButtonBox::button() returned nullptr for a standard button,
once it had been hidden. That introduced a regression.

This follow-up patch makes sure, a standard button is not removed
from standardButtonHash, when hidden. By no longer removing it from
standardButtonHash, it makes showQDialogButtonBox::button() always
return the pointer to the standard button, even if it is hidden.

The function handleButtonDestroyed() used the argument
QDialogButtonBoxPrivate::RemoveRule::KeepConnections, in order to leave
signal/slot connections untouched. It expected the the destroyed button
to be removed from standardButtonHash. In order to retain that
functionality, the enum class RemoveRule is renamed to RemoveReason,
and one value was added. QDialogButtonBoxPrivate now handles all
necessary cases of removing a button:

ManualRemove (previously Disconnect):
- remove button from roles
- remove button from standardButtonHash
- disconnect all signals

LeaveEvent (previously KeepConnections):
- remove button from roles
- do not remove button form standardButtonHash
- do not disconnect signals

Destroyed (new):
- remove button from roles
- remove button from standardButtonHash
- do not disconnect signals (QObject will do that)

An autotest is added to tst_QDialogButtonBox.

Task-number: QTBUG-114377
Pick-to: 6.6 6.5
Change-Id: Ib28625d44fa89c3d06f181f64875c2e456cebbfa
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

1 files changed, 17 insertions, 0 deletions

diff --git a/tests/auto/widgets/widgets/qdialogbuttonbox/tst_qdialogbuttonbox.cpp b/tests/auto/widgets/widgets/qdialogbuttonbox/tst_qdialogbuttonbox.cpp
index b3f26e5dd8..3f5ffa687b 100644
--- a/tests/auto/widgets/widgets/qdialogbuttonbox/tst_qdialogbuttonbox.cpp
+++ b/tests/auto/widgets/widgets/qdialogbuttonbox/tst_qdialogbuttonbox.cpp
@@ -55,6 +55,7 @@ private slots:
 #ifdef QT_BUILD_INTERNAL
     void hideAndShowButton();
 #endif
+    void hideAndShowStandardButton();
     void buttonRole_data();
     void buttonRole();
     void setStandardButtons_data();
@@ -426,6 +427,22 @@ void tst_QDialogButtonBox::hideAndShowButton()
 }
 #endif
 
+void tst_QDialogButtonBox::hideAndShowStandardButton()
+{
+    QDialogButtonBox buttonBox;
+    buttonBox.setStandardButtons(QDialogButtonBox::Ok | QDialogButtonBox::Cancel);
+    buttonBox.show();
+    QVERIFY(QTest::qWaitForWindowExposed(&buttonBox));
+    auto *button = buttonBox.button(QDialogButtonBox::Cancel);
+    QVERIFY(button);
+    button->hide();
+    QVERIFY(QTest::qWaitFor([button](){ return !button->isVisible(); }));
+    QCOMPARE(button, buttonBox.button(QDialogButtonBox::Cancel));
+    button->show();
+    QVERIFY(QTest::qWaitForWindowExposed(button));
+    QCOMPARE(button, buttonBox.button(QDialogButtonBox::Cancel));
+}
+
 void tst_QDialogButtonBox::testDelete()
 {
     QDialogButtonBox buttonBox;