On the Mac, Emacs can use either the option key or the command key as the META key. If the value of the variable mac-command-key-is-meta is non-nil (its default value), Emacs uses the command key as the META key. Otherwise it uses the option key as the META key.
Most people should want to use the command key as the META key, so that dead-key processing with the option key will still work. This is useful for entering non-ASCII Latin characters directly from the Mac keyboard, for example.
Emacs recognizes the setting in the Keyboard control panel and supports international and alternative keyboard layouts (e.g., Dvorak). Selecting one of the layouts from the keyboard layout pull-down menu will affect how the keys typed on the keyboard are interpreted.
The Mac OS intercepts and handles certain key combinations (e.g., command-SPC for switching input languages). These will not be passed to Emacs.
The Mac keyboard ordinarily generates characters in the Mac Roman encoding. To use it for entering ISO Latin-1 characters directly, set the value of the variable mac-keyboard-text-encoding to kTextEncodingISOLatin1. Note that not all Mac Roman characters that can be entered at the keyboard can be converted to ISO Latin-1 characters.
To enter ISO Latin-2 characters directly from the Mac keyboard, set the value of mac-keyboard-text-encoding to kTextEncodingISOLatin2. Then let Emacs know that the keyboard generates Latin-2 codes, by typing C-x RET k iso-latin-2 RET. To make this setting permanent, put this in your .emacs init file: