How to set a thumbnail to my custom file for a preview in Windows Explorer?

Question

In my Qt application, I can save project files of my own type. I would like those files to have a nice preview in Windows explorer, just like picture and video files do by default. Is there a way to do that? I am using Qt, but maybe there is another way.

In other words, if my code for saving a file is as follows, I would like to know what to do in line 5 to make it work:

void saveFile(const QString& fileName, const QImage& thumbnail) {
    QFile file(fileName);
    file.open(QFile::WriteOnly);
    writeInFile(file); // Custom function that saves the project
    //file.setPreview(thumbnail); <- What I wish I could simply do
    file.close();
}

Answer 1

Setting thumbnail for your own file type is not a Qt thing. It's job of Windows shell, and the behavior is controlled using registery.

Check this if you want to assign a custom icon file.

If you want to generate different preview for each file, just like image file, then check this.

Note they are Windows specific.