epubveri for calibre 0.4.1 — the background glitch thiago.eec found, and one it led to.
https://github.com/veripublica/epubv...calibre-v0.4.1
thiago.eec — thank you, that is a real one and the cause is worth stating, because it is why I could not see it. The panel told the tree what colour to be with a palette. A palette is a request that a platform style may decline for an item view, and Windows declines it: the theme engine paints item views itself. The dock is an ordinary widget, so it obeyed; the tree is the one item view in the panel, so it did not. On macOS both obey, under Fusion and under calibre's own style, which is why 0.4.0 shipped with this in it and why the tests did not catch it either — they checked the palette, and the palette was set correctly the whole time.
It is now said twice: the palette as before, plus a style sheet naming the same two colours, which Qt draws itself rather than handing to the platform theme. The severity colours and the selection highlight are unaffected by the second instruction — that part I could measure here.
So this one needs your eyes rather than mine. I cannot reproduce the fault on this machine, which means I cannot confirm the fix on it either; it is reasoned from where the two platforms differ. If Always dark now paints the whole panel on Windows, that closes it.
A second one, which nobody reported and which I found while looking into the first: choosing Always dark and then going back to Follow calibre did not undo anything. The panel stayed dark until calibre was restarted, and the severity colours stayed dark with it, since they are chosen by reading the panel's own background back. One panel is built per editor session and reused, so declining to paint a background was not the same as taking one off. Both directions work now.