Comment 5 for bug 1477696

Sigh, the copy to clipboard code in the viewer is literally five lines of absolutely trivial code, go see for yourself: https://github.com/kovidgoyal/calibre/blob/master/src/calibre/gui2/viewer/documentview.py#L687

Feel free to find the bugs in that. Or perhaps you want to argue that the bug is in Qt, the graphics toolkit that calibre uses, if so, then feel free to open a bug report with them.