Signal handling fixes #3669
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Signal handling fixes #3669
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The previous implementation was not async-signal-safe and could cause lots of hard to debug issues. The common ways to handle that include * Self-pipe and non-allocating lock-free set of pending signals in the main thread (see `g_unix_signal_source_new` for example). * A dedicated signal handling thread calling `sigtimedwait`. * Linux-specific solution with `signalfd(2)`. * FreeBSD-specific solution with `EVFILT_SIGNAL` filter for `kqueue`. `GUnixSignalSource` intentionally supports a very limited set of signals, making it a bad fit for us. There's also no benefit in maintaining a set of platform-dependent solutions. Therefore, extending an existing `signalThread` code seems to be the best option. All the threads and child processes inherit the signal mask we set in `UnixSignalHandler::start()`, and now we block a few more signals. That requires an extra care when forking and starting new processes. Thankfully, `waybar::util::command` already does everything necessary and appears to be used consistently across the source.
Repeated calls to `Client::main()` result in unnecessary work and duplication of several event handlers. A common consequence of that is the bug with multiple bars being created (Alexays#3344). This change ensures that the `main` is called only once and makes reload logic much simpler.
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First draft. Tested on Linux with glibc only.
See individual commit descriptions for details.
TODOs:
Time to dig out my old work on reducing the number of
wl_display_roundtrips in the code.CssReloadHelperdoes not handle appearance changes and.reset()on reloads can be optimized.Fixes: #3344