RFR: 8259680: Need API to query states of CAPS LOCK and NUM LOCK keys

[Kevin Rushforth]

On Sat, 23 Jan 2021 15:40:04 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

> The JavaFX API does not provide a way to get the state of CAPS LOCK or NUM LOCK on the keyboard. Being able to read the lock state would allow an application to inform the user that caps lock was enabled for passwords or other usages where the keyboard input might not be echoed. It would also allow an application to do spell checking / auto-correction that might ordinarily be skipped when typing all upper-case letters.
> 
> We need an equivalent JavaFX API to the existing AWT `java.awt.ToolKit::getLockingKeyState` method. A natural place to put this in JavaFX is in the `javafx.application.Platform` class, so we propose to create a new `Platform::isKeyLocked` method, which will take a `KeyCode` -- either `CAPS` or `NUM_LOCK` -- and return an `Optional<Boolean>` indicating whether or not that key is in the locked or "on" state. If we can't read the key state on a particular platform, we will return `Optional.empty()`, rather than throwing a runtime exception as AWT does.
> 
> I have provided both an automated Robot test and a manual test. The latter is needed primarily because we can't set the CAPS lock on Mac using Robot, but also because we want  way to test the case where the user has enabled CAPS lock before the program starts.

modules/javafx.graphics/src/main/native-glass/gtk/glass_key.cpp line 361:

> 359:     switch (keyCode) {
> 360:         case com_sun_glass_events_KeyEvent_VK_CAPS_LOCK:
> 361:             lockState = gdk_keymap_get_caps_lock_state(keyMap);

It seems that `gdk_keymap_get_caps_lock_state` isn't reliable on GTK 3 either. At least not when I test it on a Linux VM. I may end up using raw Xlib calls instead (which would have the added benefit of removing the "ifdef" for GTK 3).

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PR: https://git.openjdk.java.net/jfx/pull/385