[squeak-dev] Please try out | Cross-platform mapping for virtual key codes :-)

Marcel Taeumel marcel.taeumel at hpi.de
Tue Apr 27 14:40:56 UTC 2021

Hi all!

Please find attached a changeset that adds mapping tables for virtual keys (or scan codes) for macOS, X11, and Windows. You can find them in EventSensor class >> #virtualKeysOn*

You can try out if they work through the KeyboardExerciser. Please take a look at the balloon text (i.e. tool tip) to better understand the data.

There is also a new preference:
[x] Simplify Virtual-key codes

... because of Windows who dares to couple codes to the input language (e.g. US vs. DE), which Squeak knows nothing about. macOS is better in this regard. :-)

Biggest mess is on Linux/X11. For key-down/up events, the Linux VM delivers actual character codes instead of scan codes, which makes a basic mapping to physical keys almost impossible. See EventSensor class >> #virtualKeysOnX11. We MUST fix that! Please. Somebody. Can I haz scan codes? ^__^



The good news: KeyboardEvent >> #key (and UserInputEvent >> #modifiers) now gives you cross-platform stable information about physical keys to be used in keyboard handlers. Yes, for both key-stroke and key-down/up events.

Or at least, that is the plan. That's why it would be great if you could help testing! :-)

Why key-stroke events too? Aren't they for typing text only?

1. Almost all keyboard shortcuts in current Squeak are based on key-stroke events.
2. Using the #keyCharacter is tricky because SHIFT changes lower-case to upper-case, which makes "anEvent shiftPressed" hard to understand.
3. CTRL combinations might not do the expected thing. How would you handle CTRL+C? The #keyCharacter could arrive as $c or Character enter. See the preference "Map non-printable characters to printable characters. Now, #key will always answer $C in such a case. Regardless of that preference.

Can't we just use #keyCharacter in key-down/up events?

No. Those are undefined. Never do that. key-down/up events carry virtual-key codes in their #keyValue. We might want to change #keyCharacter to answer "nil" for those events.


Q: What is a "physical key" or "physical modifier"?
A: The label that can be presented to the user so that he or she feels at home when using Squeak. Thus, looks platform-specific.

Q: What is a "virtual key" or "virtual modifier"?
A: The information to be processed in your application's key handlers. Thus, looks platform-independent. If you have still no clue how to talk to keyboard events, please read the commentary in KeyboardEvent >> #checkCommandKey.


Happy testing! :-) And thank you all in advance!


P.S.: You might want to disable the preference "synthesize mouse-wheel events from keyboard-events" to get CTRL+ArrowUp and CTRL+ArrowDown ;-)
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