How to draw a frame over an image hovered - c++

Question

I was thinking a little about title cause I had a problem how to name it. I am programming in Qt and C++ and I can use clearly basic structure. Now I want to do something more efective but I don't know what can be the best solution. So I have an image in main window. How can I solve that:
If I move cursor of my mouse for the specific area of the image then program should drawn yellow frame around this area. If I move mouse to other section of this image then this frame should disappear. In pseudo-code:
if(mouse_X >= 100 && mouse_X <=150 &&
mouse_Y >= 250 && mouse_Y <= 300)
drawFrame();
Any suggestion?

Answer 1

There are a lot of ways of solving the issue.
One of them could be to use an event filter as #nwp stated in your question. But it is also necessary to track the mouse movement in your image.
I don't know how you are loading the image, so the next code is just an example supposing that you are loading the image in a QLabel. You must to adapt the idea to your own project.
main.cpp
#include "mywindow.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
MyWindow myWindow;
myWindow.show();
return app.exec();
}
mywindow.h
#ifndef _MAINWINDOW_H
#define _MAINWINDOW_H
#include <QMainWindow>
#include <QLabel>
#include <QDebug>
class MyWindow: public QWidget {
Q_OBJECT
public:
MyWindow();
~MyWindow();
bool eventFilter(QObject *object, QEvent *event);
private:
QLabel *imageLabel;
};
#endif
mywindow.cpp
#include "mywindow.h"
#include <QPixmap>
#include <QEvent>
#include <QMouseEvent>
MyWindow::MyWindow()
{
imageLabel = new QLabel(this);
imageLabel->setPixmap(QPixmap(":icon"));
imageLabel->resize(imageLabel->pixmap()->size());
qDebug() << imageLabel->pixmap()->size();
imageLabel->setMouseTracking(true);
imageLabel->installEventFilter(this);
}
MyWindow::~MyWindow()
{
}
bool MyWindow::eventFilter(QObject *object, QEvent *event)
{
if (object == imageLabel && event->type() == QEvent::MouseMove) {
/*
* We know the image is 60x60 px.
*/
QMouseEvent *mouseEvent = static_cast<QMouseEvent*>(event);
if(mouseEvent->x() >= 0 && mouseEvent->x() <=30 &&
mouseEvent->y() >= 0 && mouseEvent->y() <= 30)
{
qDebug() << "drawFrame()";
} else {
qDebug() << "!drawFrame()";
}
return false;
}
return false;
}