QComboBox: hide the popup on keypress rather than ShortcutOverride

Qt sends a ShortcutOverride to the focus widget to evaluate whether the
widget's key event handling has higher priority than shortcut handling.
A KeyPress is then sent if the ShortcutOverride comes back accepted, or
if the Shortcut event returns ignored.

QComboBox needs to accept the ShortcutOverride for Cancel, so that
hiding the popup has priority over application shortcuts. But it should
only hide the popup when the KeyPress event actually arrives, as
otherwise the the focus widget changes (from popup to combobox), which
breaks event delivery on macOS.

Fixes: QTBUG-108908
Change-Id: Ie9cce1c2041cbe0e41be301686d7c3b5683e9f10
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
(cherry picked from commit a874087504cf5af8bb4171d4137f23f100b7063b)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/widgets/widgets/qcombobox.cpp

@@ -737,7 +737,8 @@ bool QComboBoxPrivateContainer::eventFilter(QObject *o, QEvent *e)
         default:
 #if QT_CONFIG(shortcut)
             if (keyEvent->matches(QKeySequence::Cancel)) {
-                combo->hidePopup();
+                closeOnCancel = true;
+                keyEvent->accept();
                 return true;
             }
 #endif
@@ -784,6 +785,7 @@ bool QComboBoxPrivateContainer::eventFilter(QObject *o, QEvent *e)
 
 void QComboBoxPrivateContainer::showEvent(QShowEvent *)
 {
+    closeOnCancel = true;
     combo->update();
 }
 
@@ -3234,6 +3236,12 @@ void QComboBox::keyPressEvent(QKeyEvent *e)
         break;
 #endif
     default:
+        if (e->matches(QKeySequence::Cancel) && (!d->container || d->container->closeOnCancel)) {
+            hidePopup();
+            e->accept();
+            d->container->closeOnCancel = false;
+        }
+
         if (!d->lineEdit) {
             if (!e->text().isEmpty())
                 d->keyboardSearchString(e->text());

src/widgets/widgets/qcombobox_p.h

@@ -221,6 +221,7 @@ private:
     QComboBoxPrivateScroller *bottom = nullptr;
     QElapsedTimer popupTimer;
     bool maybeIgnoreMouseButtonRelease = false;
+    bool closeOnCancel = false;
 
     friend class QComboBox;
     friend class QComboBoxPrivate;