Karabiner: how to prevent Shift+Alt from being sent?

Question

Can Karabiner's JSON configuration indicate that Shift+Alt should not be sent when typing Shift+Alt+other_key?

The use case is as follows, from inside Microsoft Remote Desktop connected to Windows:

• Let's say I want to type Shift+Alt+) and insert "]" in the Windows app (as is usual with the French keyboard).
• Now, when I start by typing Shift+Alt, Windows switches keyboard layouts. I want to keep this feature on the remote machine, but it should not interfere with Shift+Alt+other_key combinations.

Thus, I would like to produce "]" on the Windows remote machine when I type Shift+Alt+), without Shift+Alt switching between keyboard layouts.

It is not obvious that this could work, as Shift+Alt must be pressed first, which might necessarily trigger the keyboard layout switching. However, things could in principle work if Karabiner would not send anything to Windows when Shift+Alt is pressed, and then only send either "]" if ")" is pressed, or activate the layout switching when Shift+Alt is released.

My current configuration for having Shift+Alt+) produce "]" in Microsoft Remote Desktop (from a French-keyboard MacBook) is:

{
    "conditions": [
        {
            "bundle_identifiers": [
                "com\\.microsoft\\.rdc\\.(mac|osx|macos)"
            ],
            "type": "frontmost_application_if"
        }
    ],
    "from": {
        "key_code": "hyphen",
        "modifiers": {
            "mandatory": [
                "option",
                "shift"
            ]
        }
    },
    "to": [
        {
            "key_code": "close_bracket"
        }
    ],
    "type": "basic"
}

Answer 1

In pure Windows, Shift+Alt by itself does nothing as long as you keep pressing both keys. It will only take effect when the keys are freed. Therefore I find it hard to understand why you have an immediate action when you only press the keys (but then I'm not on the Mac).

A possible solution would be to use on Windows the keyboard remapper AutoHotkey.

The following AutoHotkey script might block Shift+Alt by itself, but will convert Shift+Alt+( to ]. It worked for me on English Windows 10, and should also work in your environment.

!Shift::return
!+):: Send, ]

It might be worth testing if the script can work without the last line.

After installing AutoHotKey, put the above text in a .ahk file and double-click it to test. You may stop the script by right-click on the green H icon in the traybar and choosing Exit. To have it run on login, place it in the Startup group at C:\Users\USER-NAME\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup.

AutoHotkey references:

• Remapping Keys
• Hotkeys - Definition & Usage
• List of Keys
• Send Keys & Clicks