In Keyman for Windows a number of key combinations involving keys such ALT, ALTGR are not sent through for processing unless they are preserved. Preserved in this case meaning we register certain combinations to be sent through to for processing.
To achieve this a new API call will need to be added to the common/core processor that will provide the ability to get an array of all the keys defined in the group rules of a keyboard. Then the Windows engine will be updated to use this list to register the preserved keys for the keyboard.