bug(windows): when serialised input is off, rotas and ralt don't work

[mcdurdin]

Describe the bug

When serialised input is off:

• rotas now don't work properly any more. The following normally lets me press SHIFT LCTRL LALT K_1 once to produce ½, twice to produce ⅓, and three times to produce ¼:

   + [SHIFT LCTRL LALT K_1] > '½'
   '½' + [SHIFT LCTRL LALT K_1] > '⅓'
   '⅓' + [SHIFT LCTRL LALT K_1] > '¼' 

But with the new Registry key this produces a string of all three, ½⅓¼, which is of course not what we want.

• In addition, any RALT key combinations don't work any more. They just don't produce anything.

Per https://community.software.sil.org/t/using-autohotkeys-with-keyman/3620/3

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Keyman for Windows/macOS/Linux:

• OS: Windows 10 20H2 x64
• Keyman version: 14.0.270

[mcdurdin]

Can confirm this is still a problem in 15.0.265. Am testing with the attached keyboard: no_serial_key.zip

+ [SHIFT LCTRL LALT K_1] > '½'
'½' + [SHIFT LCTRL LALT K_1] > '⅓'
'⅓' + [SHIFT LCTRL LALT K_1] > '¼' 

+ [RALT K_A] > 'aaah'

+ 'x' > 'Keyboard is functioning'

+ [K_2] > '½'
'½' + [K_2] > '⅓'
'⅓' + [K_2] > '¼' 

This is actually not related to rotas as such. It's a problem with the modifier keys when serialized input is off:

• x to generate Keyboard is functioning works
• 2 to rotate through ½, ⅓, ¼ works
• Ralt+a in notepad opens the Help menu?!
• Shift+Lctrl+Lalt+1 generates ½ but deletes text as well. Similarly with continuing rotas.

[mcdurdin]

See also an issue when serialized input is on:

• #7716