An editor buffer ideally should have an appropriate external format (or encoding) set before you write it to a file. Otherwise an external format specified in the value of the editor variable output-format-default is used. If the value of output-format-default is not an external-format specifier, then the external format is chosen similarly to the way
cl:open
does it. By default this chosen external format will be the Windows code page on Microsoft Windows, and Latin-1 on other platforms.
When using the Editor tool, use Set External Format to set interactively the external format for the current buffer, or set Preferences... > Environment > File Encodings > Output (which in turn sets the editor variable output-format-default) to provide a global default value.
In an application which writes editor buffers to file, you can do this to set the external format of a given buffer:
(setf (editor:buffer-external-format
buffer
)
ef-spec
)
You can also set a global default external format for editor buffers:
(setf (editor:variable-value 'editor:output-format-default
:global)
ef-spec )
Then ef-spec will be used when a buffer itself does not have an external format.