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Important: This document is part of the Legacy section of the ADC Reference Library. This information should not be used for new development.

Current information on this Reference Library topic can be found here:

Reserved Key Combinations


Q: I've noticed that when I type certain key combinations (particularly those involving the Shift and Option keys), nothing comes through to my application's event loop. These key combinations don't seem to be documented as reserved. What's happening?

A: You're probably running your app while a multi-byte script system's input method is active. It turns out that certain key combinations are reserved as meta-keys for communication with input methods, in addition to the usual assortment of reserved keys.

No, these input method meta-keys have not been documented before now.

So that the information will all be in one place, here is a complete list of key combinations we know of which may require avoidance or special handling on the part of an application:

key combination

reserved by/for

effect/purpose

notes

Option-Shift
and
Option-Control
multi-byte script system input methods
meta-communication between the user and the input method

You can avoid conflicts with input methods by choosing not to pass the relevant key combinations to TSMEvent. However, this means input method users may not be able to perform essential tasks.

Option
some third-party input methods
meta-communication between the user and the input method

This is not an error; some third-party input methods do indeed use key combinations involving the Option key with no other modifier key.

Option-Control-Shift-Tab
Kotoeri (Japanese) input method
shows About Box

This behavior will be removed in a future release.

Command-Tab
Mac OS 8.5
and later
switches to the next application

In Mac OS 8.5, the Application Switcher system extension reserves this combination, but in the future it may be built into the System file.

Command-Space
System 7.0
and later
rotates to the default keyboard layout or input method in the next script

For details, see: Tech Info Library Articles 16481, Keyboard Layouts: Availability and Installation, and 16378, Command-Option-Space bar Application Conflict

Command-Option-Space
System 7.0
and later
rotates to the next keyboard layout or input method in the active script

For details, see: Tech Info Library Articles 16481, Keyboard Layouts: Availability and Installation, and 16378, Command-Option-Space bar Application Conflict

Command-Option-Escape
System 7.0
and later
performs "force quit" on current application

For details, see: Tech Info Library Article 7110, How to Quit from an Application That Hangs

Command-Shift-<digit>
Mac OS
(all versions)
invokes system function or Fkey code resource

For details, see: Inside Macintosh / Macintosh Toolbox Essentials / Chapter 2 - Event Manager / Using the Event Manager / Responding to Keyboard Events

Command-/
and
Command-?
System 7.0
and later
invokes Apple Guide

 

Control-[, ], @, \ or +
Kotoeri (Japanese) input method
none
Due to a problem with 'itlk' resources in Mac OS-J, these control key combinations do not always generate events. The 'itlk' resources will be fixed in a future release.



This document deliberately omits mention of the Power key because:

  • Third-party applications don't need or want to respond to it, nor should they.
  • Responding to it doesn't involve keyDown events.

[May 17 1999]


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