Submode

Utilities for a major mode to manage multiple major modes as submodes in the same buffer.

Two main functions are introduced submode-construct-submode and submode-construct-main-mode.

Submode-construct-submode

Constructs a submode from a major mode with a number of keywords specifying how the major mode will be applied and operate as a submode.

Example:

 (defconst *--the-major-mode-as-submode
   (submode-construct-submode
    'the-major-mode
    :name "(The Major Mode)"
    :relative-indent 'block
    :syntax-propertize-rules
    (syntax-propertize-precompile-rules
     ("<start-tag>"
      (0 (ignore
          (goto-char (match-end 0))
          (submode-syntax-propertize *--the-major-mode-as-submode end)))))
    :end-tag "<end-tag>"
    :syntax-table the-major-mode-syntax-table
    :propertize #'the-major-mode-syntax-propertize
    :keymap the-major-mode-map))

The function will apply the mode and capture buffer-local variables.

Submode-construct-main-mode

Constructs a main-mode with a colletion of submodes and a number of keywords specifying how submodes will be applied and indented etc.

This function is supposed to be called in the corresponding major mode hook to activate the major mode as main mode.

Example:

 (add-hook 'the-main-major-mode-hook
  (lambda ()
    (submode-construct-main-mode
     :name '("The Main Major Mode" (:eval (submode-lighter)))
     :indent-basic c-basic-offset
     :submodes '(*--the-major-mode-as-submode))))

Acknowledgments

This library is inspired from the mhtml-mode introduced in Emacs 26.1.