• Specific times press:

Reimplement mousePressEvent and mouseReleaseEvent.

Use a self increasing counter to count times of pressed in mouseReleaseEvent. Check if it reached the specific times. If reached, do what you want to do there.

Use a timer to garantee time interval. Start the timer in mousePressEvent when first tap, Stop the timer and clear the counter when time out.

some code snap:
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#include "widget.h"
#include "ui_widget.h"

Widget::Widget(QWidget *parent) :
QWidget(parent),
ui(new Ui::Widget),
isPressed(false),
timesOfPressed(0),
isFistPressed(true),
isTimerTimeout(false)
{
ui->setupUi(this);

timer = new QTimer(this);
timer->setInterval(2000);
connect(timer, SIGNAL(timeout()),this, SLOT(pressTimeOut()));

}

Widget::~Widget()
{
delete ui;
}

void Widget::mousePressEvent(QMouseEvent *event)
{
if(event->button() == Qt::LeftButton) {
isPressed = true;
if (isFistPressed) {
isFistPressed = false;
timer->start();
isTimerTimeout = false;
}
}
}

void Widget::mouseReleaseEvent(QMouseEvent *event)
{
if (event->button() == Qt::LeftButton && isPressed) {
timesOfPressed++;
isPressed = false;
checkPressed();
}
}

void Widget::checkPressed()
{
qDebug() << "You have pressed: " << timesOfPressed << "times";

if (timesOfPressed == 5) {
    timesOfPressed = 0;
    timer->stop();
    isFistPressed = true;

    qDebug() << "Finally get here, do something...";
    // call another application with QProcess.
}

if (isTimerTimeout) {
    timesOfPressed = 0;
    qDebug() << "This round already time out, clear counter ";
}

}

void Widget::pressTimeOut()
{
qDebug() << "This round time out,recounting.";
timer->stop();
isTimerTimeout = true;
timesOfPressed = 0;
isFistPressed = true;
}
@

• Long time press:

Start a timer in mousePressEvent.

Stop the timer in mouseReleaseEvent.

Once the timer time out, stop the timer and do what you want to do.

some code snap:
@
...
longPressTimer = new QTimer(this);
longPressTimer->setInterval(1000);
connect(longPressTimer, SIGNAL(timeout()), this, SLOT(doSomething()));
...

void QWidget::mousePressEvent(QMouseEvent *event)
{
if (event->button() == Qt::LeftButton) {
longPressTimer->start();
}
}

void QWidget::mouseReleaseEvent(QMouseEvent *event)
{
if (event->button() == Qt::LeftButton) {
longPressTimer->stop();
}
}

void QWidget::doSomething()
{
longPressTimer->stop();
// something...
}
@