RFR: 8089373: Translation from character to key code is not sufficient

[John Hendrikx]

On Fri, 5 May 2023 19:45:53 GMT, John Hendrikx <jhendrikx at openjdk.org> wrote:

>> Note: the Java-side changes in this PR are also in #694 which fixes the same issue (and more) on Linux. Unfortunately the Linux Robot code is not working making it difficult to test on that platform (see #718).
>> 
>> KeyCharacterCombinations allow the specification of accelerators based on characters whose KeyCodes vary across keyboard layouts. For example, the + character is on KeyCode.EQUALS on a U.S. English layout, KeyCode.PLUS on a German layout, and KeyCode.DIGIT1 on a Mac Swiss German layout. KeyCharacterCombinations finds the correct KeyCode by calling `Toolkit.getKeyCodeForChar`.
>> 
>> `getKeyCodeForChar` can only return one KeyCode for a given character so it can't easily handle characters which appear in more than one location, like + which is on the main keyboard and the numeric keypad. It's also reliant on KeyCodes which prevents KeyCharacterCombinations from working on keys with no codes (e.g. the base character contains a diacritic). It also relies on the platform to map from a character to a key which is the reverse of how key mapping normally works making it slow and/or imprecise to implement on Mac and Linux (Windows is the only platform with a system call to do this).
>> 
>> This PR introduces a new way for a platform to pass key information to the Java core. `View.notifyKeyEx` takes an additional platform-specific `hardwareCode` which identifies the key and is tracked in a private field in the KeyEvent. This is opt-in; a platform can continue to call the old `View.notifyKey` method and allow the `hardwareCode` to default to -1.
>> 
>> On the back-end `KeyCharacterCombination.match` calls the new routine `Toolkit.getKeyCanGenerateCharacter` which unpacks the KeyEvent information and sends it on to the Application. This is also opt-in; the default implementation falls back to the Application's `getKeyCodeForChar` call. Platforms which call `View.notifyKeyEx` will be handed the `hardwareCode` for the key in addition to the Java KeyCode.
>> 
>> The new `View.notifyKeyEx` returns a boolean indicating whether the event was consumed or not. This plays no role here but will be used later to fix [JDK-8087863](https://bugs.openjdk.org/browse/JDK-8087863).
>> 
>> For testing I've included the manual KeyboardTest app that also appears in PR #425. Tests with keypad combinations should now work.
>> 
>> Note: this PR only fixes Windows. Fixes for Mac and Linux but can't be submitted until #425 and #718 are integrated.
>
> modules/javafx.graphics/src/main/java/com/sun/javafx/tk/Toolkit.java line 709:
> 
>> 707:      * The default implementation bridges into the existing getKeyCodeForChar call.
>> 708:      */
>> 709:     public boolean getKeyCanGenerateCharacter(KeyEvent event, String character) {
> 
> I think this method can be narrowed a bit to accept a `KeyCode` instead of `KeyEvent`, making it bit more generally useful (and easier to test).  Also I think perhaps it can be named a bit more direct, like `canKeyGenerateCharacter`.

I forgot the `KeyEvent` is needed to extract the hardware code. Depending on whether this hardware code remains a hidden variable this may be for the best (or can pass both `KeyCode` and the hardware code).

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PR Review Comment: https://git.openjdk.org/jfx/pull/1126#discussion_r1186474970