Tags: patch

[Creating a separate feature request from bug#43866]

>> How about making a new input method for those?  It seems to me that
>> C-x 8 is already too "fat".
>
> That may be useful, but it has a drawback compared with C-x 8.
>
> It is inconvenient to change input methods just for one character and
> then change back.

The following patch addresses such issues of the current input method
implementation by providing a new feature of transient input methods.

A transient input method is enabled temporarily for entering a key sequence,
and is disabled automatically afterwards.

The command that temporarily activates an one-off transient input method
is bound to the mnemonic key 'C-x \'.  A prefix key is used to select
the default transient input method, e.g.:

C-u C-x \ compose RET   - selects the 'compose' input method
                          as the default transient input method;
C-x \ E =   - activates the default transient input method,
              inserts the EURO SIGN character,
              and disables the transient input method;
C-x \ ^ 3   - inserts the character SUPERSCRIPT THREE.

The same with the help of the 'TeX' input method:

C-u C-x \ TeX RET
C-x \ \ e u r o   - inserts the character EURO SIGN

Also it's possible to create a new input method from the existing
'C-x 8' keymap, and set it as the default method, e.g.:

C-u C-x \ iso-transl RET
C-x \ * E   - inserts the character EURO SIGN