'How to create make not visible range so when user clicks near point, the point will be chosen

I have a set of vector points, with each click on my window I add pair to the vector. I want to add an invisible radius on my point which will help me to detect if a point was clicked. The point is basically 1 pixel in size so the user is not able to click on it directly. How can I achieve this? Do I need to use any math formulas for this?

std::vector<QPoint> pointSet;

void MyWindow::mousePressEvent(QMouseEvent *event)
{
    if(event->button() == Qt::LeftButton)
    {
        x0 = event->x();
        y0 = event->y();
        QPoint data;
        data.setX(x0);
        data.setY(y0);
        pointSet.push_back(data);
    
    }
  //I want to be able to do it like below
  if(event->button() == Qt::RightButton)
    {
        //if(pointClicked) { cout << "point with x,y clicked"; }
    }
    update();
}
c++qt


Solution 1:[1]

If I understand your question correctly, you just need to run through your vector and check if any of the saved points are within a range of the clicked point. So something like this should work:

    if (event->button() == Qt::RightButton)
    {
        int radius = <something>
        QRectF range(event->x() - radius, event->y() - radius, radius * 2, radius * 2);

        for (auto &p in pointSet) 
        {
            if (range.contains(p)) 
            { 
                cout << "point with" << p.x() << "," << p.y() << "clicked"; 
                break;
            }
        }
    }

Solution 2:[2]

You can create an off-screen bitmap the size of your window. Whenever you add a point to your vector, you can draw a filled circle with a color equal, for example, to the index of that point in your vector. Then on any mouse click event, you can get a color of the clicked point and get to your vector element.

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1 JarMan
Solution 2 Vlad Feinstein

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