Home / Questions / 26932
Accepted
Sergio Ramos
Asked: 2020-10-12 00:33:42 +0800 CST 2020-10-12 00:33:42 +0800 CST

Help with mouse events in QT

  • 772

Hi, I'm like doing certain events with my mouse. Now what I want is to return the value of the instance but I don't know how: cpp code:

#include "mouselogger.h"
#include <QDebug>

MouseLogger &MouseLogger::instance()
{
    static MouseLogger _instance;
    return _instance;
}

MouseLogger::MouseLogger(QObject *parent) : QObject(parent)
{
    HINSTANCE hInstance = GetModuleHandle(NULL);

    // Set hook
    mouseHook = SetWindowsHookEx(WH_MOUSE_LL, mouseProc, hInstance, 0);
    // Check hook is correctly
    if (mouseHook == NULL) {
        qWarning() << "Mouse Hook failed";
    }
}

LRESULT CALLBACK MouseLogger::mouseProc(int Code, WPARAM wParam, LPARAM lParam)
{
    Q_UNUSED(Code);

    // Having an event hook, we nned to cast argument lParam
    // to the structure of the mouse is the hook.
    MOUSEHOOKSTRUCT * pMouseStruct = (MOUSEHOOKSTRUCT *)lParam;

    // Next, we check to see what kind of event occurred,
    // if the structure is not a pointer to nullptr
    if(pMouseStruct != nullptr) {
        switch (wParam) {
        case WM_MOUSEMOVE:
            qDebug() << "WM_MOUSEMOVE";
            break;
        case WM_LBUTTONDOWN:
            qDebug() << "WM_LBUTTONDOWN";
            break;
        case WM_LBUTTONUP:
            qDebug() << "WM_LBUTTONUP";
            break;
        case WM_RBUTTONDOWN:
            qDebug() << "WM_RBUTTONDOWN";
            break;
        case WM_RBUTTONUP:
            qDebug() << "WM_RBUTTONUP";
            break;
        case WM_MBUTTONDOWN:
            qDebug() << "WM_MBUTTONDOWN";
            break;
        case WM_MBUTTONUP:
            qDebug() << "WM_MBUTTONUP";
            break;
        case WM_MOUSEWHEEL:
            qDebug() << "WM_MOUSEWHEEL";
            break;
        default:
            break;
        }
        emit instance().mouseEvent();
    }

    // After that you need to return back to the chain hook event handlers
    return CallNextHookEx(NULL, Code, wParam, lParam);
}

main() code:

//#include <QCoreApplication>

//int main(int argc, char *argv[])
//{
   // QCoreApplication a(argc, argv);

    //return a.exec();
//}

#include <QCoreApplication>
#include <QDebug>
#include "mouselogger.h"

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    QObject::connect(&MouseLogger::instance(), &MouseLogger::mouseEvent,
                     [](){

        //retornar el valor
        qDebug() << s;
    });

    return a.exec();
}

I need this for a job, thank you.

c++

1 Answers

  1. Best Answer

    Assuming you intend to fetch s, the bad news is that you won't be able to do it with a lambda. However, nothing prevents you from using a class to manage the information:

    class SignalReceiver : public QObject
{
  Q_OBJECT

  private:
    /* falta el tipo */ s;

  public:
    SignalReceiver& Instance()
    {
      static SignalReceiver instance;
      return instance;
    }

    s GetS() const
    { return s; }

  public slots:
    void Event(/* Argumentos de MouseLogger::mouseEvent */)
    {
      s = /* lo que sea */
    }
};

int main(int argc, char *argv[])
{
  QCoreApplication a(argc, argv);

  SignalReceiver::Instance().connect(&MouseLogger::instance(), &MouseLogger::mouseEvent, &SignalReceiver::Event);

  return a.exec();
}

    To know the value of sit is enough to call (from any part of the code) SignalReceiver::Instance().GetS().

    It's not a particularly elegant design, but it gets the job done. Of course, each event that enters will crush the value of s. If you do not provide more information it is difficult to give a more accurate answer.

    All the best.

    • 1