Technical Q&As


TB41 - Reserved Key Combinations (30-July-98)




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-Spacebar
         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-Spacebar
         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

      		
   











This document deliberately omits mention of the Power key
because:















   

      
         
Pete Gontier

      		
      
         
--

      		
      
         
Worldwide Developer Technical Support

      		
   

   

      
         
Yasuo Kida

      		
      
         
--

      		
      
         
Mac OS International Engineering

      		
   



 



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