When the text is too large(>50MB),QPrintPreviewDialog can not preview the text.

After i load a large text(>50MB) using QPlainTextEdit,i use  QPrintPreviewDialog to view the print preview,but the result is empty.

When i use qt source debugging ,i find that in the QTextDocument::print() function,the pageCount() returns a negative value.i think this is abnormal.

You can verify the above statement with the attached code.