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;;; company-tng.el --- company-mode configuration for single-button interaction
;; Copyright (C) 2017-2021 Free Software Foundation, Inc.
;; Author: Nikita Leshenko
;; This file is part of GNU Emacs.
;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; GNU General Public License for more details.
;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs. If not, see <>.
;;; Commentary:
;; company-tng (Tab and Go) allows you to perform completion using just TAB.
;; Pressing it will both select the next completion candidate in the list and
;; insert it into the buffer (or make it look like it's inserted, in fact).
;; It cycles the candidates like `yank-pop' or `dabbrev-expand' or Vim:
;; Pressing TAB selects the first item in the completion menu and inserts it in
;; the buffer. Pressing TAB again selects the second item and replaces the
;; "inserted" item with the second one. This can continue as long as the user
;; wishes to cycle through the menu. You can also press S-TAB to select the
;; previous candidate, of course.
;; The benefits are that you only have to use one shortcut key and there is no
;; need to confirm the entry.
;; Usage:
;; Enable `company-tng-mode' with:
;; (add-hook 'after-init-hook 'company-tng-mode)
;; in your init script. It will set up the required frontend, as well as make a
;; number of recommended configuration changes described below.
;; To avoid these changes, if you want to tweak everything yourself, customize
;;`company-tng-auto-configure' to nil.
;; We recommend to bind TAB to `company-select-next', S-TAB to
;; `company-select-previous', and unbind RET and other now-unnecessary
;; keys from `company-active-map':
;; (define-key company-active-map (kbd "TAB") 'company-select-next)
;; (define-key company-active-map (kbd "<backtab>") 'company-select-previous)
;; (define-key company-active-map (kbd "RET") nil)
;; Note that it's not necessary to rebind keys to use this frontend,
;; you can use the arrow keys or M-n/M-p to select and insert
;; candidates. You also need to decide which keys to unbind, depending
;; on whether you want them to do the Company action or the default
;; Emacs action (for example C-s or C-w).
;; We recommend to disable `company-require-match' to allow free typing at any
;; point.
;; By default, company-tng doesn't work well with backends that insert function
;; arguments into the buffer and (optionally) expand them into a snippet
;; (usually performed in `post-completion' using yasnippet or company-template).
;; In company-tng, completion candidates
;; are inserted into the buffer as the user selects them and the completion is
;; finished implicitly when the user continues typing after selecting a
;; candidate. Modifying the buffer (by expanding a snippet) when the user
;; continues typing would be surprising and undesirable, since the candidate was
;; already inserted into the buffer.
;; For this reason `company-tng-mode' by default disables arguments insertion
;; for a number of popular backends. If the backend you are using is not among
;; them, you might have to configure it not to do that yourself.
;; YASnippet and company-tng both use TAB, which causes conflicts. The
;; recommended way to use YASnippet with company-tng is to choose a different
;; key for expanding a snippet and moving to the next snippet field:
;; (define-key yas-minor-mode-map "\C-j" 'yas-expand)
;; (define-key yas-keymap "\C-j" 'yas-next-field-or-maybe-expand)
;; (dolist (keymap (list yas-minor-mode-map yas-keymap))
;; (define-key keymap (kbd "TAB") nil)
;; (define-key keymap [(tab)] nil))
;;; Code:
(require 'company)
(require 'cl-lib)
(defvar-local company-tng--overlay nil)
(defun company-tng-frontend (command)
"When the user changes the selection at least once, this
frontend will display the candidate in the buffer as if it's
already there and any key outside of `company-active-map' will
confirm the selection and finish the completion."
(cl-case command
(let ((ov (make-overlay (point) (point))))
(setq company-tng--overlay ov)
(overlay-put ov 'priority 2)))
(let* ((ov company-tng--overlay)
(selected (and company-selection
(nth company-selection company-candidates)))
(prefix (length company-prefix)))
(move-overlay ov (- (point) prefix) (point))
(overlay-put ov
(if (= prefix 0) 'after-string 'display)
(when company-tng--overlay
(delete-overlay company-tng--overlay)
(kill-local-variable 'company-tng--overlay)))
(when (and company-selection
(not (company--company-command-p (this-command-keys))))
(setq this-command 'company-complete-selection)))))
(defvar company-clang-insert-arguments)
(defvar company-semantic-insert-arguments)
(defvar company-rtags-insert-arguments)
(defvar lsp-enable-snippet)
(defgroup company-tng nil
"Company Tab and Go."
:group 'company)
(defcustom company-tng-auto-configure t
"Automatically apply default configure when enable `company-tng-mode'."
:type 'boolean)
(define-obsolete-function-alias 'company-tng-configure-default 'company-tng-mode "0.9.14"
"Applies the default configuration to enable company-tng.")
(declare-function eglot--snippet-expansion-fn "eglot")
(defvar company-tng-map
(let ((keymap (make-sparse-keymap)))
(set-keymap-parent keymap company-active-map)
(define-key keymap [return] nil)
(define-key keymap (kbd "RET") nil)
(define-key keymap [tab] 'company-select-next)
(define-key keymap (kbd "TAB") 'company-select-next)
(define-key keymap [backtab] 'company-select-previous)
(define-key keymap (kbd "S-TAB") 'company-select-previous)
(define-minor-mode company-tng-mode
"This minor mode enables `company-tng-frontend'."
:init-value nil
:global t
(setq company-frontends
(add-to-list 'company-frontends 'company-tng-frontend))
(when company-tng-auto-configure
(setq company-frontends '(company-tng-frontend
(setq company-require-match nil
company-clang-insert-arguments nil
company-semantic-insert-arguments nil
company-rtags-insert-arguments nil
lsp-enable-snippet nil)
(advice-add #'eglot--snippet-expansion-fn :override #'ignore)
(setq company-active-map company-tng-map))
(setq company-selection-default nil))
(setq company-frontends
(when company-tng-auto-configure
(setq company-require-match 'company-explicit-action-p
company-clang-insert-arguments t
company-semantic-insert-arguments t
company-rtags-insert-arguments t
lsp-enable-snippet t)
(advice-remove #'eglot--snippet-expansion-fn #'ignore)
(setq company-active-map (keymap-parent company-tng-map)))
(setq company-selection-default 0))))
(provide 'company-tng)
;;; company-tng.el ends here