How to emit a signal from a QPushButton when the mouse hovers over it?

Question

Recently, I wanted that QPushButton can emit a signal, when the mouse pointer enters. How can I make it?

I know that QPushButton has some already defin

Answer 1

So QT deal with mouse hovering using the "event" enterEvent (https://doc.qt.io/qt-5/qevent.html look for "QEvent::Enter"). This isn't about the Signal/Slot functionality (https://doc.qt.io/qt-5/signalsandslots.html), this is about Events (https://doc.qt.io/qt-5/eventsandfilters.html) We find enterEvent as a protected method at QWidget class (https://doc.qt.io/qt-5/qwidget.html) which is a base class for QPushButton class (https://doc.qt.io/qt-5/qpushbutton.html).

So what you have to do: to create a new class derived from QPushButton and override the protected method "enterEvent" that QPushButton inherited from QWidget.

Creating the new class:
QT Creator - File - New File or Project...
File and Classes - C++
C++ Class
Choose...
Base class - Custom - QPushButton
Next
define a name for your new class like MyPushButton

In mypushbutton.h:

#ifndef MYPUSHBUTTON_H
#define MYPUSHBUTTON_H

#include 

class MyPushButton: public QPushButton
{
    Q_OBJECT
public:
    using QPushButton::QPushButton;  //inherits the QPushButton constructors

signals:
    void myPushButtonMouseHover();

protected:
    void enterEvent(QEvent *event);
};

#endif // MYPUSHBUTTON_H

In mypushbutton.cpp:

#include "mypushbutton.h"
#include 

void MyPushButton::enterEvent(QEvent *event)
{
    QMessageBox::warning(this, "Mouse hover", "Mouse hovered MyPushButton"); //popping a message box

    emit myPushButtonMouseHover();  //emitting signal 

    QPushButton::QWidget::enterEvent(event);  //calling the "natural" enterEvent

}