I am trying to implement a snap-to-grid/snap-to-guideline functionality to a QSplitter.

The idea is:

1. Integer values are set onto the QSplitter (or possibly its parent widget or another ancestor) representing vertical/horizontal lines or a grid.
2. Moving the splitter’s handle works as usual when the mouse button (LMB) is pressed…
3. … except when the mouse cursor comes within a few pixels of a line, in which case the handle is moved to it and, importantly, stays stuck to it.
4. When the mouse is moved away from the line (while the LMB is still held down), the handle is moved back to where the mouse is and the tracking resumes.

I was expecting such functionality to already exist in Qt but I could not find a clue in the assistant.
On a related note, QSplitter seems to ignore the size increment values of a widget, although it does respect the minimum size.

My PoC code is as follows; the middle widget in the splitter had a custom paint event to make it easier to track its width:

#include <QtWidgets/QApplication>
#include <QtGui/QPainter>
#include <QtWidgets/QSplitter>
#include <QtWidgets/QVBoxLayout>

class MyWidget : public QWidget {
public:
    MyWidget(QWidget* parent = nullptr) : QWidget(parent)
    { 
        setMinimumWidth(60);
        setSizeIncrement(QSize(20, 0));
    }
protected:
    void paintEvent(QPaintEvent*) override
    {
        QPainter painter(this);
        for (int x = 10; x < width(); x += 20) {
            painter.drawLine(x, 0, x, height());
        }
    }
};

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QWidget w;
    w.setMinimumSize(800, 600);
    QVBoxLayout l;
    QSplitter splitter(&w);
    l.addWidget(&splitter);
    w.setLayout(&l);
    
    MyWidget constrainedWidget(&splitter);

    splitter.addWidget(new QWidget(&splitter));
    splitter.addWidget(&constrainedWidget);
    splitter.addWidget(new QWidget(&splitter));

    w.setStyleSheet("QFrame { background: dodgerblue; }");
    w.show();
    return a.exec();
}

Assuming I have not missed a class/method in the documentation, what would the best way to go with the implementation of this functionality be?