Maximum size of QMimeData (Windows Drag and Drop vs Clipboard) - windows

Question

I have a problem regarding QMimeData using drag and drop and QClipboard.
Scenario:
I have a medical image in SVG format (no file, only buffer) and different options for the user to export the image in different file formats (e.g. jpg, tiff, png, ...).
The user can select the resolution (in page format (e.g. DIN A7- DIN A3) and DPI (up to 600 DPI))
Drag and Drop/Clipboard is implemented with a subclassed QMimeData class and the following MIME header entries:
"application/x-qt-image"
"FileContents"
"FileGroupDescriptorW"
"FileName"
"FileNameW"
This allows drag and drop to the file system and to other apps (e.g. Powerpoint).
The implementation does only provide the necessary data (e.g. file system drags only need header/data 2-5 and drags to e.g. Powerpoint only need header/data 1). No intermediate files are used.
Construction of the MIME datatype (mimeData) is done in the following fashion:
void SCImageWidget::createDragAndDropData(QString mimeType)
{
if(mimeType == "application/x-qt-image" && !mimeData->gotImage)
{
...
QImage img;
this->renderSvgImage(img, ...)
mimeData->setImageData(img);
mimeData->gotImage = true;
...
}
else if(mimeType == "FileName" && !mimeData->gotFileName)
{
QString DDFileName = ... ;
mimeData->setData("FileName", DDFileName.toLatin1());
mimeData->gotFileName = true;
}
else if(mimeType == "FileNameW" && !mimeData->gotFileNameW)
{
QString DDFileName = ... ;
mimeData->setData("FileNameW", QByteArray((const char*) (DDFileName.utf16()), DDFileName.size() * 2));
mimeData->gotFileNameW = true;
}
else if(mimeType == "FileContents" && !mimeData->gotFileContent)
{
...
QByteArray data;
QBuffer buffer(&data);
buffer.open(QIODevice::WriteOnly);
this->renderSvgImageToDevice(buffer, ...);
buffer.close();
mimeData->setData("FileContents", data);
mimeData->gotFileContent = true;
...
}
else if(mimeType == "FileGroupDescriptorW" && !mimeData->gotFileDesc)
{
QString DDFileName = ...;
FILEGROUPDESCRIPTOR desc;
desc.cItems = 1;
desc.fgd[0].dwFlags = FD_PROGRESSUI;
wcscpy_s(desc.fgd[0].cFileName, DDFileName.toStdWString().c_str());
mimeData->setData("FileGroupDescriptorW", QByteArray((const char*)&desc,
sizeof(FILEGROUPDESCRIPTOR)));
mimeData->gotFileDesc = true;
}
return;
}
Problem:
Drag and drop of bigger data entries (> 11 MB) to the filesystem does not work (error copying data/folder. Not enough space available) but does work via the clipboard (up to a certain point of approximately 50 MB).
Image data > 200 DPI cannot be dragged to Powerpoint (even small compressed pngs) with no error. Using the clipboard even A3/600 DPI tiffs work.
Question: Is there any limitation on Windows (besides the typical 1/16th of RAM for the clipboard) for clipboard and drag and drop actions? I could not really find any good information about this topic. Maybe anyone is aware of some hard-coded limits in Qt.
System Information: Dev. platform: Win 7 64/32GB RAM, Qt 5.3
SSCCE is not really possible - sorry.