RFR: 8087700: [KeyCombination, Mac] KeyCharacterCombinations behave erratically

[Martin Fox]

On Mon, 14 Aug 2023 16:28:20 GMT, Martin Fox <mfox at openjdk.org> wrote:

> A KeyCharacterCombination should match a key if the target character is printed on that key. For example, the user should be able to invoke the `Shortcut+'+' ` combination by holding down the Shortcut key and pressing a key that has '+' printed on it. This should work even if '+' is a shifted symbol but the user doesn't hold down the Shift key. 
> 
> The Mac implements KeyCharacterCombinations by monitoring keystrokes to discover the relationship between keys and characters. Currently the system only records the character the user typed and no other characters on the same key. This means a shortcut targeting a shifted character may not work until the user types that character using Shift so the system learns the relationship.
> 
> This PR keeps the same mechanism in place but always records the shifted and unshifted character for each keystroke.
> 
> For the Mac the KeyboardTest app was modified to remove tests for characters accessed using Option. We don't look for these characters because under the hood just about every key has some symbol assigned to the Option modifier that the user probably isn't even aware of. For these character we fall back to the existing logic; once the user types the character it will start working as a shortcut.

I can reproduce this on 13.6. The `charactersByApplyingModifiers` call is modifying the event in some way which is disturbing the IME. This is surprising given how that call is documented and that it's been around since 10.15. It looks like the fix is to do all this processing after we call `handleEvent:` on the NSTextInputContext.

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PR Comment: https://git.openjdk.org/jfx/pull/1209#issuecomment-1826521844