Is there a way to restore the Ctrl+C handler?

[al-martyn1]

I want to run TV Application multiple times from the my console application. Each time I will display misc dialogs to specify missing command line arguments. But after the first launch of my TApplication I lose the ability to handle Ctrl+C. Is there a way to restore Ctrl+C handler to state which took state before the first launch?

[magiblot]

Hi @al-martyn1!

Excuse me for the late reply. The desired behaviour is that the Ctrl+C handler should be restored properly. Is your application running on Windows or Unix? The Ctrl+C you cannot handle anymore, are you talking about handling Ctrl+C from the Turbo Vision application or from the command shell? If your application does anything special, would you mind sharing a sample of code which reproduces the issue?

Cheers.

[al-martyn1]

In Windows console application I want to install Ctrl+C handler after running TV app.

In main:

   //...
    bool showPortDialog = !appConfig.portInfo.isValid() || appConfig.showPortDialog;

    if (showPortDialog)
    {
        if (!unicont::tui::portSelect(appConfig.portInfo))
        {
            LOG_ERR << "No valid port taken\n";
            return 1;
        }

        //unicont::tui::tuiFinalize();
    }


#if defined(WIN32) || defined(_WIN32)
    // SetConsoleCtrlHandler - https://learn.microsoft.com/ru-ru/windows/console/setconsolectrlhandler
    if (!SetConsoleCtrlHandler( &HandlerRoutineCtrlC, TRUE ))
    {
        LOG_ERR << "Failed to install Ctrl+C handler\n";
    }
#else

#endif
   //...

unicont::tui::portSelect looks like this:

class TPortSelectApp : public TApplication
{

    constexpr static const int cmPortSelectCmd  = 101;


public:

    ComPortInfo  portInfo;

    TPortSelectApp() :
        TProgInit( &TPortSelectApp::initStatusLine,
                   &TPortSelectApp::initMenuBar,
                   &TPortSelectApp::initDeskTop
                 )
    {
        putCommand(cmPortSelectCmd);
    }


    virtual void handleEvent( TEvent& event ) override
    {
        // TApplication::handleEvent( event );
        if( event.what == evCommand )
        {
            switch( event.message.command )
            {
                case cmPortSelectCmd:
                    onPortSelect();
                    endModal( cmQuit );
                    clearEvent( event );
                    //break;
                    return;
                default:
                    break;
            }
        }
    
        TApplication::handleEvent( event );
    }


    static TMenuBar *initMenuBar( TRect r )
    {
    
        r.b.y = r.a.y+1;
    
        return new TMenuBar( r,
                             *new TSubMenu( "~F~ile", kbAltF ) +
                                 *new TMenuItem( "E~x~it", cmQuit, cmQuit, hcNoContext, "Alt+X" )
                           );
    }

    static TStatusLine *initStatusLine( TRect r )
    {
        r.a.y = r.b.y-1;
        return new TStatusLine( r,
            *new TStatusDef( 0, 0xFFFF ) +
                *new TStatusItem( "~Alt+X~ Exit", kbAltX, cmQuit ) +
                *new TStatusItem( 0, kbF10, cmMenu )
                );
    }


    //virtual void idle();

    void onPortSelect()
    {
        TComPortDialog *portDlg = (TComPortDialog*) validView( new TComPortDialog(portInfo, ComPortDialogInfo(), "Port Settings") );
        if (portDlg)
        {
            if (portDlg->showModal()==cmOK)
            {
                portInfo = portDlg->portInfo;
            }
        }
        destroy(portDlg);
    }


}; // class TPortSelectApp




inline
bool portSelect(ComPortInfo &pi)
{
    TPortSelectApp portSelectApp;
    portSelectApp.portInfo = pi;

    portSelectApp.run();

    pi = portSelectApp.portInfo;

    return pi.isValid();
}

[magiblot]

Okay, thanks for the details.

What's preventing the handler from working is most likely the ENABLE_PROCESSED_INPUT flag, which gets disabled while initializing the TApplication:

tvision/source/platform/win32con.cpp

Line 34 in 1277a7a

consoleMode &= ~ENABLE_PROCESSED_INPUT; // Report CTRL+C and SHIFT+Arrow events.

This is needed for input handling to work properly, since Turbo Vision is unable to handle certain key events otherwise.

However, the console state gets restored when the process finishes (during destruction of static objects) or when calling TApplication::suspend (such as when using the DOS Shell menu entry in tvdemo).

So, if I am not missing anything, you would have to do the following:

1. Make sure that ENABLE_PROCESSED_INPUT flag is set.
2. Call suspend() in TPortSelectApp's destructor (or after the invocation to run()). If TPortSelectApp might be run several times, then you also need to call resume() in the constructor (or before the invocation to run()).

Or, if you don't need to handle Ctrl+C and Shift+Arrow events from within the Turbo Vision application, you can just re-enable ENABLE_PROCESSED_INPUT once after running TPortSelectApp.

Let me know if it worked.