This is a rather invoved PR. I first looked at putting a splitter in book details, and decided to in the process fix something that has bothered me for years. On Windows in light mode I can't see the splitter handles. In dark mode I can, but I run in light mode and don't want to change. This PR adds a custom QSplitterHandle class that draws the handle depending on the palatte. The PR includes changes for the splitters in classes I know how to test: the main UI, Pinned columns, QuickView, Edit metadata, tweak books, single download metadata, Check library, Book info, and (of course) Book details.
calibre

calibre is an e-book manager. It can view, convert, edit and catalog e-books in all of the major e-book formats. It can also talk to e-book reader devices. It can go out to the internet and fetch metadata for your books. It can download newspapers and convert them into e-books for convenient reading. It is cross platform, running on Linux, Windows and macOS.
For more information, see the calibre About page.
Screenshots
Usage
See the User Manual.
Development
Setting up a development environment for calibre.
A tarball of the source code for the current calibre release.
Bugs
Bug reports and feature requests should be made in the calibre bug tracker at Launchpad. GitHub is only used for code hosting and pull requests.
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calibre is a result of the efforts of many volunteers from all over the world. If you find it useful, please consider contributing to support its development. Donate to support calibre development.
Building calibre binaries
See Build instructions for instructions on how to build the calibre binaries and installers for all the platforms calibre supports.