Karabiner-elements: Switch left_ctrl and fn on K380 cause f5 key not working

Created on 28 Jun 2020 · 4Comments · Source: pqrs-org/Karabiner-Elements

Karabiner-Elements is a great tool to remap the keyboard. I used a configuration from an online tutorial and set the home and end key on the K380 keyboard.
The original configuration is this.

{
    "global": {
        "check_for_updates_on_startup": true,
        "show_in_menu_bar": true,
        "show_profile_name_in_menu_bar": false
    },
    "profiles": [
        {
            "complex_modifications": {
                "parameters": {
                    "basic.simultaneous_threshold_milliseconds": 50,
                    "basic.to_delayed_action_delay_milliseconds": 500,
                    "basic.to_if_alone_timeout_milliseconds": 1000,
                    "basic.to_if_held_down_threshold_milliseconds": 500,
                    "mouse_motion_to_scroll.speed": 100
                },
                "rules": [
                    {
                        "description": "Change left arrow + fn to home",
                        "manipulators": [
                            {
                                "from": {
                                    "key_code": "left_arrow",
                                    "modifiers": {
                                        "mandatory": [
                                            "left_option",
                                            "left_shift"
                                        ]
                                    }
                                },
                                "to": [
                                    {
                                        "key_code": "home"
                                    }
                                ],
                                "type": "basic"
                            }
                        ]
                    },
                    {
                        "description": "Change right arrow + fn to end",
                        "manipulators": [
                            {
                                "from": {
                                    "key_code": "right_arrow",
                                    "modifiers": {
                                        "mandatory": [
                                            "left_option",
                                            "left_shift"
                                        ]
                                    }
                                },
                                "to": [
                                    {
                                        "key_code": "end"
                                    }
                                ],
                                "type": "basic"
                            }
                        ]
                    },
                    {
                        "description": "Change up arrow + fn to page up",
                        "manipulators": [
                            {
                                "from": {
                                    "key_code": "up_arrow",
                                    "modifiers": {
                                        "mandatory": [
                                            "left_option"
                                        ]
                                    }
                                },
                                "to": [
                                    {
                                        "key_code": "page_up"
                                    }
                                ],
                                "type": "basic"
                            }
                        ]
                    },
                    {
                        "description": "Change down arrow + fn to page down",
                        "manipulators": [
                            {
                                "from": {
                                    "key_code": "down_arrow",
                                    "modifiers": {
                                        "mandatory": [
                                            "left_option"
                                        ]
                                    }
                                },
                                "to": [
                                    {
                                        "key_code": "page_down"
                                    }
                                ],
                                "type": "basic"
                            }
                        ]
                    }
                ]
            },
            "devices": [
                {
                    "disable_built_in_keyboard_if_exists": false,
                    "fn_function_keys": [],
                    "identifiers": {
                        "is_keyboard": true,
                        "is_pointing_device": false,
                        "product_id": 45890,
                        "vendor_id": 1133
                    },
                    "ignore": false,
                    "manipulate_caps_lock_led": false,
                    "simple_modifications": []
                },
                {
                    "disable_built_in_keyboard_if_exists": false,
                    "fn_function_keys": [],
                    "identifiers": {
                        "is_keyboard": true,
                        "is_pointing_device": false,
                        "product_id": 636,
                        "vendor_id": 1452
                    },
                    "ignore": false,
                    "manipulate_caps_lock_led": true,
                    "simple_modifications": []
                }
            ],
            "fn_function_keys": [
                {
                    "from": {
                        "key_code": "f1"
                    },
                    "to": {
                        "consumer_key_code": "display_brightness_decrement"
                    }
                },
                {
                    "from": {
                        "key_code": "f2"
                    },
                    "to": {
                        "consumer_key_code": "display_brightness_increment"
                    }
                },
                {
                    "from": {
                        "key_code": "f3"
                    },
                    "to": {
                        "key_code": "mission_control"
                    }
                },
                {
                    "from": {
                        "key_code": "f4"
                    },
                    "to": {
                        "key_code": "launchpad"
                    }
                },
                {
                    "from": {
                        "key_code": "f5"
                    },
                    "to": {
                        "key_code": "illumination_decrement"
                    }
                },
                {
                    "from": {
                        "key_code": "f6"
                    },
                    "to": {
                        "key_code": "illumination_increment"
                    }
                },
                {
                    "from": {
                        "key_code": "f7"
                    },
                    "to": {
                        "consumer_key_code": "rewind"
                    }
                },
                {
                    "from": {
                        "key_code": "f8"
                    },
                    "to": {
                        "consumer_key_code": "play_or_pause"
                    }
                },
                {
                    "from": {
                        "key_code": "f9"
                    },
                    "to": {
                        "consumer_key_code": "fastforward"
                    }
                },
                {
                    "from": {
                        "key_code": "f10"
                    },
                    "to": {
                        "consumer_key_code": "mute"
                    }
                },
                {
                    "from": {
                        "key_code": "f11"
                    },
                    "to": {
                        "consumer_key_code": "volume_decrement"
                    }
                },
                {
                    "from": {
                        "key_code": "f12"
                    },
                    "to": {
                        "consumer_key_code": "volume_increment"
                    }
                }
            ],
            "name": "Default profile",
            "parameters": {
                "delay_milliseconds_before_open_device": 1000
            },
            "selected": true,
            "simple_modifications": [],
            "virtual_hid_keyboard": {
                "country_code": 0,
                "mouse_key_xy_scale": 100
            }
        }
    ]
}

Then because the fn key and the left ctrl key are placed in a different order with MacBookPro, so I try to switch these two keys on K380. But after I set the simple modifications, the function keys, for example, f5 is not working as usual. But fn + f5 is working as f5.
By the way, this option is not working. I still have to press fn + f5 to perform f5.

Source

Seraphli

Most helpful comment

Yeah, that's because on the internal MacBook keyboard the function key send a keycode to the operating system. However, the function key on external keyboard generally don't do this. See this for more information. That also means that any modification you make with the function keys will not show up. You can test this as well in karabiner event viewer—they won't show up, which I know as I have the same keyboard. Just like the yellow f1, f2, f3 keys won't show up as they don't send a code to the OS (which I dislike about this keyboard). Unfortunately this also means that you can't remap it. If you install the Logitech Options software, you'll see no option to remap the fn key to something else, either, which is unfortunate.

My suggestion would be to switch the keys on your MacBook and get used to the layout, so that you can use your K380 and your internal keyboard the same way, since you can't change the layout on the K380. Or you can use control + arrow keys to do what you want, because the OS will never know you're pressing the fn key on the external keyboard. Or use Command + arrow keys which I think give similar behavior.