How to highlight the menu?

Question

Task: to implement the ability to hide and show the main menu by pressing Alt, as well as highlight the menu after the appearance (such as the FireFox menu also works). Actually, I know how to hide / show, but the menu is always highlighted only by the second Alt press after the menu is shown. I tried to move the focus to menuBar and to a specific menu, tried menuBar()->actions()[0].hover() , tried to activateWindow() , setActiveAction() , activate(QAction::Hover)

We intercept the message on the pressed Alt

 bool MainWindow::event(QEvent *event){ if (event->type() == QEvent::KeyPress) { QKeyEvent *ke = static_cast<QKeyEvent*>(event); if (ke->key() == Qt::Key_Alt) { keyReleaseEvent(ke); return true; } } return QMainWindow::event(event); }

Process Alt

 void MainWindow::keyReleaseEvent (QKeyEvent* event) { if (event->key() == Qt::Key_Alt){ if (menuBar()->isHidden()){ menuBar()->show(); menuBar()->setFocus(Qt::MenuBarFocusEvent); //Здесь пробовал всё вышеперечисленное } else{ menuBar()->hide(); { } }

Please provide the code that performs the specified functions
My little research has shown that the menu is highlighted in a very tricky way.
The QMenuBar object temporarily registers itself with the event filter of the application object, that is, literally qApp->installEventFilter(this) .
In this filter, it handles keystrokes (it does a lot of things in general) and, via Alt, enters the keyboard control mode, which, in fact, means backlighting.
The solution was to send a fictitious event about pressing Alt, but in connection with the chemistry described above it is not clear where to send this event.
@Cerbo Thanks for the hint, in fact, you need to send two dummy messages: keyPressed and keyReleased, then the backlight works.
I did it like this: QApplication::sendEvent(menuBar(), altPress);

Dimanesson Dimanesson 88 7 · Accepted Answer · 2015-07-22T11:52:09

A crutch solution found. First you need to make sure that the focusPolicy parameter of all widgets is Qt::StrongFocus .

Next, you need to write your focus switching handler so that QMenu processed as part of the QMenuBar

 void MainWindow::onFocusChanging(QWidget* old, QWidget* now){ if(now != menuBar() && now != menuBar()->findChild<QMenu*>() && old == menuBar()) { menuBar()->hide(); } else{ QKeyEvent* altPress = new QKeyEvent(QEvent::KeyPress, Qt::Key_Alt, Qt::NoModifier); QKeyEvent* altRelease = new QKeyEvent(QEvent::KeyRelease, Qt::Key_Alt, Qt::NoModifier); QApplication::sendEvent(menuBar(), altPress); QApplication::sendEvent(menuBar(), altRelease); } }

and link it with the QApplication signal about switching focus, I did it in right in main:

 QObject::connect(&a, SIGNAL(focusChanged(QWidget*, QWidget*)), &w, SLOT(onFocusChanging(QWidget*, QWidget*)));

Well, then everything was as it was:

We intercept the message on the pressed Alt

 bool MainWindow::event(QEvent *event){ if (event->type() == QEvent::KeyPress) { QKeyEvent *ke = static_cast<QKeyEvent*>(event); if (ke->key() == Qt::Key_Alt) { keyReleaseEvent(ke); return true; } } return QMainWindow::event(event); }

Process Alt

 void MainWindow::keyReleaseEvent (QKeyEvent* event) { if (event->key() == Qt::Key_Alt){ if (menuBar()->isHidden()){ menuBar()->show(); menuBar()->setFocus(); } } else menuBar()->hide(); }

I hope those who look will forgive me such an ugly solution and a bad description, but this is the only thing that I managed to come up with to solve this problem.

Why not send bogus messages right after menuBar()->setFocus()
@Cerbo application crashes with StackOverflow, I don’t know why, but it also creates a huge number of threads.

How to highlight the menu?

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