;;; company-tng.el --- company-mode configuration for single-button interaction
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;; Copyright (C) 2017 Free Software Foundation, Inc.
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;; Author: Nikita Leshenko
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;; This file is part of GNU Emacs.
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;; GNU Emacs is free software: you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation, either version 3 of the License, or
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;; (at your option) any later version.
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;; GNU Emacs is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;; You should have received a copy of the GNU General Public License
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;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
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;;; Commentary:
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;;
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;; company-tng (Tab and Go) allows you to perform completion using just TAB.
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;; Pressing it will both select the next completion candidate in the list and
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;; insert it into the buffer (or make it look like it's inserted, in fact).
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;;
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;; It cycles the candidates like `yank-pop' or `dabbrev-expand' or Vim:
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;; Pressing TAB selects the first item in the completion menu and inserts it in
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;; the buffer. Pressing TAB again selects the second item and replaces the
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;; "inserted" item with the second one. This can continue as long as the user
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;; wishes to cycle through the menu. You can also press S-TAB to select the
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;; previous candidate, of course.
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;;
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;; The benefits are that you only have to use one shortcut key and there is no
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;; need to confirm the entry.
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;;
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;; Usage:
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;;
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;; To apply the default configuration for company-tng call
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;; `company-tng-configure-default' from your init script.
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;;
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;; You can also configure company-tng manually:
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;;
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;; Add `company-tng-frontend' to `company-frontends':
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;;
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;; (add-to-list 'company-frontends 'company-tng-frontend)
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;;
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;; We recommend to bind TAB to `company-select-next', S-TAB to
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;; `company-select-previous', and unbind RET and other now-unnecessary
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;; keys from `company-active-map':
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;;
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;; (define-key company-active-map (kbd "TAB") 'company-select-next)
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;; (define-key company-active-map (kbd "<backtab>") 'company-select-previous)
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;; (define-key company-active-map (kbd "RET") nil)
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;;
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;; Note that it's not necessary to rebind keys to use this frontend,
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;; you can use the arrow keys or M-n/M-p to select and insert
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;; candidates. You also need to decide which keys to unbind, depending
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;; on whether you want them to do the Company action or the default
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;; Emacs action (for example C-s or C-w).
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;;
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;; We recommend to disable `company-require-match' to allow free typing at any
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;; point.
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;;; Code:
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(require 'company)
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(require 'cl-lib)
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(defvar-local company-tng--overlay nil)
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;;;###autoload
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(defun company-tng-frontend (command)
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"When the user changes the selection at least once, this
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frontend will display the candidate in the buffer as if it's
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already there and any key outside of `company-active-map' will
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confirm the selection and finish the completion."
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(cl-case command
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(show
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(let ((ov (make-overlay (point) (point))))
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(setq company-tng--overlay ov)
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(overlay-put ov 'priority 2))
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(advice-add 'company-select-next :before-until 'company-tng--allow-unselected)
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(advice-add 'company-fill-propertize :filter-args 'company-tng--adjust-tooltip-highlight))
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(update
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(let ((ov company-tng--overlay)
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(selected (nth company-selection company-candidates))
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(prefix (length company-prefix)))
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(move-overlay ov (- (point) prefix) (point))
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(overlay-put ov
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(if (= prefix 0) 'after-string 'display)
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(and company-selection-changed selected))))
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(hide
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(when company-tng--overlay
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(delete-overlay company-tng--overlay)
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(kill-local-variable 'company-tng--overlay))
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(advice-remove 'company-select-next 'company-tng--allow-unselected)
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(advice-remove 'company-fill-propertize 'company-tng--adjust-tooltip-highlight))
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(pre-command
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(when (and company-selection-changed
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(not (company--company-command-p (this-command-keys))))
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(company--unread-this-command-keys)
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(setq this-command 'company-complete-selection)
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(advice-add 'company-call-backend :before-until 'company-tng--supress-post-completion)))))
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;;;###autoload
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(defun company-tng-configure-default ()
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"Applies the default configuration to enable company-tng."
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(setq company-require-match nil)
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(setq company-frontends '(company-tng-frontend
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company-pseudo-tooltip-frontend
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company-echo-metadata-frontend))
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(let ((keymap company-active-map))
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(define-key keymap [return] nil)
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(define-key keymap (kbd "RET") nil)
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(define-key keymap [tab] 'company-select-next)
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(define-key keymap (kbd "TAB") 'company-select-next)
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(define-key keymap [backtab] 'company-select-previous)
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(define-key keymap (kbd "S-TAB") 'company-select-previous)))
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(defun company-tng--allow-unselected (&optional arg)
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"Advice `company-select-next' to allow for an 'unselected'
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state. Unselected means that no user interaction took place on the
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completion candidates and it's marked by setting
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`company-selection-changed' to nil. This advice will call the underlying
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`company-select-next' unless we need to transition to or from an unselected
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state.
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Possible state transitions:
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- (arg > 0) unselected -> first candidate selected
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- (arg < 0) first candidate selected -> unselected
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- (arg < 0 wrap-round) unselected -> last candidate selected
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- (arg < 0 no wrap-round) unselected -> unselected
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There is no need to advice `company-select-previous' because it calls
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`company-select-next' internally."
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(cond
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;; Selecting next
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((or (not arg) (> arg 0))
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(unless company-selection-changed
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(company-set-selection (1- (or arg 1)) 'force-update)
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t))
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;; Selecting previous
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((< arg 0)
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(when (and company-selection-changed
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(< (+ company-selection arg) 0))
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(company-set-selection 0)
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(setq company-selection-changed nil)
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(company-call-frontends 'update)
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t)
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)))
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(defun company-tng--adjust-tooltip-highlight (args)
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"Prevent the tooltip from highlighting the current selection if it wasn't
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made explicitly (i.e. `company-selection-changed' is true)"
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(unless company-selection-changed
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;; The 4th arg of `company-fill-propertize' is selected
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(setf (nth 3 args) nil))
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args)
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(defun company-tng--supress-post-completion (command &rest args)
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"Installed as a :before-until advice on `company-call-backend' and
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prevents the 'post-completion command from being delivered to the backend
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for the next iteration. post-completion do things like expand snippets
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which are undesirable because completions are implicit in company-tng and
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visible side-effects after the completion are surprising."
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(when (eq command 'post-completion)
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(advice-remove 'company-call-backend 'company-tng--supress-post-completion)
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t))
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(provide 'company-tng)
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;;; company-tng.el ends here
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