How to save the image in clipboard in variable and restore it to clipboard later?

Question

I connect a slot to the dataChanged signal of QClipboard to store the image in the clipboard to a variable mimedata(reference):

void MyWin::clipboardDataChanged()
{
    const QMimeData * m=QApplication::clipboard()->mimeData();
    mimedata = new QMimeData();

    foreach(QString format, m->formats())
    {
        QByteArray data = m->data(format);
        if(format.startsWith("application/x-qt"))
        {
            int index1 = format.indexOf('"') + 1;
            int index2 = format.indexOf('"', index1);
            format = format.mid(index1, index2 - index1);
        }
        mimedata->setData(format, data);
    }
}

And restore mimedata to clipboard as follows:

void MyWin::onrestore()
{
     QApplication::clipboard()->setMimeData(mimedata);
}

However, the data set to the clipboard seems corrupted. If I paste from the clipboard to Paint, it says "The information on the Clipboard can't be inserted into Paint." I printed the format of the data in the clipboard, i.e., "application/x-qt-image". So I think it is not a format that is supported by other applications. Is this a bug of Qt or the code is flawed?

Answer 1

I think you'd be better save the whole clipboard content, so you can safely restore it when needed, i.e.

void MyWin::clipboardDataChanged()
{
    const QMimeData * m = QApplication::clipboard()->mimeData();
    mimedata = new QMimeData();

    for(auto format : m->formats())
    {
        mimedata->setData(format, m->data(format));
    }
}

Alternatively, convert the application/x-qt-image data into a QImage, then use QMimeData::setImageData to store it:

void MyWin::clipboardDataChanged()
{
    const QMimeData * m = QApplication::clipboard()->mimeData();
    mimedata = new QMimeData();

    for(auto format : m->formats())
    {
        if(format == "application/x-qt-image")
        {
            QImage image;

            QByteArray data = m->data(format);
            QBuffer buffer(&data);
            image.load(&buffer, nullptr);
            mimedata->setImageData(image);
        }
    }
}