Unix commands to overrun OS X Finder shortcut cmd-opt-esc

Question

I need to temporarily block the sequence cmdoptesc: I developed a formal examination test app for my students, and I need them to not get out of the test other than clicking a button in the test window.

BetterTouchTool accepts any shortcut except that (it seems to me, but I might make mistakes) I tried any combination, but always the forced quit window appears, as well as it happens in System Preferences > Keyboard > etc as suggested in "MacBook Pro, Yosemite: change Finder shortcuts".

I run Yosemite 10.10.5 and intend to stay with it until further upgrades will keep my Adobe suite working.

Answer 1

To get this to work you have to use a third party tool: Karabiner.

In the example below the key combination cmdoptesc darkens the monitor.

1. Download, install and open Karabiner
2. Open in the menulet Karabiner -> Preferences
3. Open the tab Misc & Uninstall
4. Hit the button Open private.xml
5. Open the file private.xml with an appropriate editor

6. Enter the customized keycode

   <?xml version="1.0"?>
   <root>
       <item>
           <name>Disable Command Option Escape</name>
           <identifier>disable_cmd_alt_esc</identifier>
           <autogen>__KeyToKey__ KeyCode::ESCAPE, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_OPTION, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_COMMAND, ConsumerKeyCode::BRIGHTNESS_DOWN</autogen>
      </item>
   </root>
   

7. Save the file

8. Open in the menulet Karabiner -> Preferences the tab Change Key
9. Hit the ReloadXML button
10. Enable the remapping. It should be listed at the beginning.

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You may refine the customized key code by adding a shortcut to brighten the monitor again to avoid a totally darkened screen and a helpless student sitting in front of it - unable to continue the test:

<?xml version="1.0"?>
<root>
    <item>
        <name>Disable Command Option Escape</name>
        <identifier>disable_cmd_alt_esc</identifier>
        <autogen>__KeyToKey__ KeyCode::ESCAPE, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_OPTION, ModifierFlag::COMMAND_L, ConsumerKeyCode::BRIGHTNESS_DOWN</autogen>
        <autogen>__KeyToKey__ KeyCode::ESCAPE, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_OPTION, ModifierFlag::COMMAND_R, ConsumerKeyCode::BRIGHTNESS_UP</autogen>
   </item>
</root>

In the first configuration each key combination (cmd_l/ralt_l/resc) darkens the screen. In the second configuration cmd_lalt_l/resc darkens and cmd_ralt_l/resc brightens the screen.

Karabiner also allows you to define application-only key codes. By adding your app to /Applications/Karabiner.app/Contents/Resources/appdef.xml or to private.xml you can restrict the customized key code to your app's realm. Below the <identifier> tag you have to add a line <only>Your_App's_Name</only> then.

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Depending on your app you probably have to disable some other shortcuts too: e.g. cmdQ. Additionally you may have to hide Karabiner in the menubar.