@DiapDealer...Thanks for your response and solutions.
Regarding my plugin -- I thought that I had made it clear in the first paragraph of my Description in my release notes that this plugin only applied to standard epub or epub 2. But of course you're right -- it's best to initially use version detection early on using bk.epub_version() to raise an error if someone uses the plugin for epub 3.
Regarding the button and checkbox display problems, I'm simply using standard grids to arrange both these entities in the dialog which has worked fairly well on other plugins that I've released. The poster before you -- PandathePanda, using Ubuntu Linux -- said that there were no problems with my displays. I'm afraid that I'm clueless about the fine nuances and differences between Ubuntu Linux and Arch Linux so I really don't know how to remedy that one. I am soon hoping to move over to Qt5 for my future plugin windowing -- still learning. I really hope and pray that Qt5 has a better cross-platform capability than Tkinter.
I'm also thinking of putting Linux Mint on a partition on my laptop soon which might help. At least that will allow me to test my plugins on Linux. Well, sort of...
