The printing is quite simple:

• create QPrinter object (mainwidget.cpp l691)
• opens a QPrinterDialog.exec(mainwidget.cpp l701; KPrintDialog is only a small wrapper around the qt version)
• opens the wizzard (mainwidget.cpp l705)
• run Style.print (f.ex. detailedstyle.cpp l279)
• creates a QtextDocument with html (detailedstyle.cpp l303)
• print via Qtextdocument.print(printer) (detailedstyle.cpp l307)

--> so there is nearly no KDE code added, everything is inside qt.

checked the textDocument, that looks good:

QTextEdit *edit(new QtextEdit);
edit->setDocument(&document);
edit->show();
QEventLoop loop;
loop.exec();

so the problem is the the printer object.

Checked the settings and relaised, that these settings are not updated.

KDEPrint is only a small wrapper, that does not modified printer at all.