Keyboard stops responding

[smacchia]

I am running Qt embedded on an arm based linux distribution (common os). The device has keyboard input. When I first run the application, the keyboard works fine. But after 2 minutes or so, the keyboard stops sending events. If I restart the application, this scenario is repeated.

The application calls grabKeyboard() on the main window to get keyboard input. I don't have QWS_KEYBOARD set to anything and I don't think that this is needed.

Does anyone know how I can keep the keyboard alive, or, worst case, wake it up somehow?

[stampede]

Do you mean that QKeyEvents are not generated ? Install event filter on QApplication object to check if key events are generated.

[smacchia]

I mean I don't get events with the type KeyPress or KeyRelease, only ShortcutOverride. I tried an event filter and still no key press or key release events. I also tried implementing the protected virtual keyPressEvent and keyReleaseEvent methods in the QWidget child windows. They never get called. It's really weird. Only if I call grabKeyboard do I see these events.

What I have is a QMainWindow derivation, who calls grabKeyboard(). It then gets all KeyPress and KeyRelease events for all windows in the system (in it's ::event method). We're using a panel stack pattern and the main window is the panel stack. It gets all events from the joystick and from the keyboard device and translates them to "meaningful" events which get signaled to child windows in the stack for handling.

On X11 this works perfectly without the grabKeyboard() call.

On the embedded device (QWS), without the grabKeyboard() call, only key events with a type of ShortcutOverride are sent. So I tried implementing an event filter in the main window to catch all events from the child windows. Still only ShortcutOverride key events come in. Then I tried implementing the keyPressEvent() and keyReleaseEvent() methods in the child windows; they never get called.

If the main window (panel stack) calls grabKeyboard(), events with a type of KeyPress and KeyRelease are sent to the main window.

But, when you boot the device, if you let it sit for about 2 minutes (with no activity), key events of any kind are no longer sent to the main window. As an interim solution (hack if you ask me), I implemented a timer which fires at a set interval. The slot connected to the timeout() signal accesses QWSServer::instance() and closes the keyboard, then re-opens the keyboard. This seems to keep the keyboard from shutting down and key events are delivered to the app as expected. But I don't like this solution at all. I want to understand why the keyboard stops sending events.