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Re: [OpenSmalltalk/opensmalltalk-vm] Keyboard Event issues on Windows (#42)

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David T Lewis

Re: [OpenSmalltalk/opensmalltalk-vm] Keyboard Event issues on Windows (#42)

Note about Ctrl+A/Z: AFAIU, it's what the console app were expected in the ages, so our OS still carry this tribute to legacy...

See how we have to workaround on linux:
https://github.com/OpenSmalltalk/opensmalltalk-vm/blob/abf05549bd377106f27600a293d79f75a59e705e/platforms/unix/vm-display-X11/sqUnixX11.c#L2065

Who is turning the keysym into 1 to: 26 charCode?
https://github.com/OpenSmalltalk/opensmalltalk-vm/blob/abf05549bd377106f27600a293d79f75a59e705e/platforms/unix/vm-display-X11/sqUnixX11.c#L2049
See https://linux.die.net/man/3/xlookupstring

I also mentionned this in issue #396

So we might want to do something similar on Windows? (and Mac OS?)
For Win32, see https://docs.microsoft.com/en-us/windows/win32/learnwin32/keyboard-input

MSDN page above explicitely explains that CTRL+A/Z are translated to ASCII control character in the VM_CHAR event (as I suggested in preliminary comment, for legacy console app).
It also does not recommend handling CTRL+... or ALT+... thru WM_CHAR event, this is not the idiomatic handling on this platform.
And the doc is right - see why below.

The equivalent of linux keysym is the virtual key code (VK_*) passed thru wParam in WM_KEYDOWN event.
https://github.com/OpenSmalltalk/opensmalltalk-vm/blob/d58235ca011b9a8f8344814b66d9f9d6428c963f/platforms/win32/vm/sqWin32Window.c#L1262

The problem is that we effectively get the keycode in case of WM_KEYDOWN event, but not in case of VM_CHAR event: msg->wParam holds an UTF-16 Unicode character the doc says...

So, IMO, we should better generate an extra OpenSmalltalk EventKeyChar event in response to WM_KEYDOWN event when we detect a CTRL down status, and filter out the event in case of VM_CHAR with CRTL down...

Note that Pharo VM uses MapVirtualKey with MAPVK_VSC_TO_VK to handle ctrl+char
https://github.com/OpenSmalltalk/opensmalltalk-vm/blob/d58235ca011b9a8f8344814b66d9f9d6428c963f/platforms/win32/vm/sqWin32Window.c#L1319
https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-mapvirtualkeya
Though it's not clear where the usage of msg->lParam comes from (MapVirtualKey expects a scan code, which is low level keyboard code and will return a VK code that fortunately matches ASCII for A to Z keys...), I've not seen it documented in official MSDN, it would be good to have a link documenting it.
It's not the way that MSDN (and I) recommended above, but might eventually work (I'm not in a position to understand if there are other side effects...)

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