shortcut.cpp

#include "shortcut.h"
#include <QKeyEvent>
#include <QCoreApplication>
#include <QDebug>

Shortcut::Shortcut(QObject *parent)
    : QObject(parent)
    , m_keySequence()
    , m_keypressAlreadySend(false)
{
    qApp->installEventFilter(this);
}

void Shortcut::setKey(QVariant key)
{
    QKeySequence newKey = key.value<QKeySequence>();
    if(m_keySequence != newKey) {
        m_keySequence = key.value<QKeySequence>();
        emit keyChanged();
    }
}

bool Shortcut::eventFilter(QObject *obj, QEvent *e)
{
    if(e->type() == QEvent::KeyPress && !m_keySequence.isEmpty()) {
        QKeyEvent *keyEvent = static_cast<QKeyEvent*>(e);
        // Just mod keys is not enough for a shortcut, block them just by returning.
        if (keyEvent->key() >= Qt::Key_Shift && keyEvent->key() <= Qt::Key_Alt) {
            return QObject::eventFilter(obj, e);
        }

        int keyInt = keyEvent->modifiers() + keyEvent->key();

        // The m_keypressAlreadySend seems redundant because of ->isAutoRepeat(),
        // however without it, multiple events are still sent for each press/release.
        if(QKeySequence(keyInt) == m_keySequence) {
            if (keyEvent->isAutoRepeat())
                emit pressedAndHold();
            else if (!m_keypressAlreadySend)
            {
                m_keypressAlreadySend = true;
                emit pressed();
            }
        }
        e->accept();
    }
    else if(e->type() == QEvent::KeyRelease) {
        QKeyEvent *keyEvent = static_cast<QKeyEvent*>(e);
        if (!keyEvent->isAutoRepeat() && m_keypressAlreadySend)
        {
            m_keypressAlreadySend = false;
            emit released();
        }
        e->accept();
    }
    return QObject::eventFilter(obj, e);
}

shortcut.h

#pragma once
#include <QObject>
#include <QKeySequence>
#include <QVariant>

class Shortcut : public QObject
{
    Q_OBJECT
    Q_PROPERTY(QVariant key READ key WRITE setKey NOTIFY keyChanged)
public:
    explicit Shortcut(QObject *parent = 0);

    void setKey(QVariant key);
    QVariant key() { return m_keySequence; }

    bool eventFilter(QObject *obj, QEvent *e);

signals:
    void keyChanged();
    void pressed();
    void released();
    void pressedAndHold();

public slots:

private:
    QKeySequence m_keySequence;
    bool m_keypressAlreadySend;
};