Disclaimer: It's 6:51am. I'm trying to be as understandable as possible.
What was happening previously was this:
* Press Alt
* Extended event generated and processed: state is now Alt down once
* Core event generated
- keyboard switched: inherited state is Alt down once
- event processed: Alt down twice
* Release Alt
* Extended event generated and processed: state is now null
* Core event generated and processed: Alt down once
If we switch the order:
* Press Alt
* Core event generated:
- keyboard switched: inherited state is null
- event processed: Alt down once
* Extended event generated and processed: state is now Alt down once
* Release Alt
* Core event generated and processed: state is now null
* Extended event generated and processed: state is now null
When we carry over the previous state, it needs to be the _previous_ state
(state and modifiersPerKey), assuming that we're going to catch now-core
events for any of these. For example, if Ctrl is held down as we pivot, we
need to carry Ctrl over with a count of one, for which an extended + core
release will then clear. Carrying over the union of the previous state _and
the state resulting from the immediate action_ was what broke things.
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