Environment

Windows build number: 10.0.19042.0

Steps to reproduce

1. Add the "US" keyboard layout within the "English (United States)" language
2. Add the "United Kingdom Extended" layout within the "English (United Kingdom)" language
3. Run the following code:

   #define NOMINMAX
   #include <Windows.h>
   #include <cstdio>
   
   int main() {
       while (true) {
           printf("0x%x\n", LOBYTE(VkKeyScanW(0)));
           Sleep(1000);
       }
       return 0;
   }

4. Change the keyboard layout using Win+Space or similar

Expected behavior

VkKeyScanW(0) prints 0x32 if the US and 0x40 if the UK layout is selected. The value changes during runtime if the layout is changed.

Actual behavior

VkKeyScanW(0) will continue to return its initial value and not change if the keyboard layout is changed during runtime. MapVirtualKeyW appears similarly affected. (I haven't tried to reproduce this yet though.)

This has far reaching implications due to the widespread use of these functions in this code base and manifests itself in key combinations either not working at all, or producing incorrect VT sequences. The only way to fix the issue is by restarting the application.