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131 lines
4.2 KiB
131 lines
4.2 KiB
;;; avy.el --- set-based completion -*- lexical-binding: t -*- |
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;; Copyright (C) 2015 Free Software Foundation, Inc. |
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;; Author: Oleh Krehel |
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;; This file is part of GNU Emacs. |
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;; This file 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, or (at your option) |
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;; any later version. |
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;; This program 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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;; For a full copy of the GNU General Public License |
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;; see <http://www.gnu.org/licenses/>. |
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;;; Commentary: |
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;; |
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;; This package provides a generic completion method based on building |
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;; a balanced decision tree with each candidate being a leaf. To |
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;; traverse the tree from the root to a desired leaf, typically a |
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;; sequence of `read-char' can be used. |
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;; |
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;; In order for `read-char' to make sense, the tree needs to be |
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;; visualized appropriately, with a character at each branch node. So |
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;; this completion method works only for things that you can see on |
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;; your screen, all at once: |
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;; |
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;; * character positions |
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;; * word or subword start positions |
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;; * line beginning positions |
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;; * link positions |
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;; * window positions |
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;; |
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;; If you're familiar with the popular `ace-jump-mode' package, this |
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;; package does all that and more, without the implementation |
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;; headache. |
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;;; Code: |
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(require 'cl-lib) |
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(defmacro avy-multipop (lst n) |
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"Remove LST's first N elements and return them." |
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`(if (<= (length ,lst) ,n) |
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(prog1 ,lst |
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(setq ,lst nil)) |
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(prog1 ,lst |
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(setcdr |
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(nthcdr (1- ,n) (prog1 ,lst (setq ,lst (nthcdr ,n ,lst)))) |
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nil)))) |
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(defun avy-tree (lst keys) |
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"Coerce LST into a balanced tree. |
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The degree of the tree is the length of KEYS. |
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KEYS are placed appropriately on internal nodes." |
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(let ((len (length keys))) |
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(cl-labels |
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((rd (ls) |
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(let ((ln (length ls))) |
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(if (< ln len) |
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(cl-pairlis keys |
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(mapcar (lambda (x) (cons 'leaf x)) ls)) |
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(let ((ks (copy-sequence keys)) |
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res) |
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(dolist (s (avy-subdiv ln len)) |
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(push (cons (pop ks) |
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(if (eq s 1) |
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(cons 'leaf (pop ls)) |
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(rd (avy-multipop ls s)))) |
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res)) |
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(nreverse res)))))) |
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(rd lst)))) |
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(defun avy-subdiv (n b) |
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"Distribute N in B terms in a balanced way." |
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(let* ((p (1- (floor (+ (log n b) 1e-6)))) |
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(x1 (expt b p)) |
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(x2 (* b x1)) |
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(delta (- n x2)) |
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(n2 (/ delta (- x2 x1))) |
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(n1 (- b n2 1))) |
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(append |
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(make-list n1 x1) |
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(list |
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(- n (* n1 x1) (* n2 x2))) |
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(make-list n2 x2)))) |
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(defun avy-traverse (tree walker &optional recur-key) |
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"Traverse TREE generated by `avy-tree'. |
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WALKER is a function that takes KEYS and LEAF. |
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RECUR-KEY is used in recursion. |
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LEAF is a member of LST argument of `avy-tree'. |
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KEYS is the path from the root of `avy-tree' to LEAF." |
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(dolist (br tree) |
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(let ((key (cons (car br) recur-key))) |
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(if (eq (cadr br) 'leaf) |
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(funcall walker key (cddr br)) |
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(avy-traverse (cdr br) walker key))))) |
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(defun avy-read (tree display-fn cleanup-fn) |
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"Select a leaf from TREE using consecutive `read-char'. |
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DISPLAY-FN should take CHAR and LEAF and signify that LEAFs |
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associated with CHAR will be selected if CHAR is pressed. This is |
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commonly done by adding a CHAR overlay at LEAF position. |
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CLEANUP-FN should take no arguments and remove the effects of |
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multiple DISPLAY-FN invokations." |
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(catch 'done |
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(while tree |
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(avy-traverse tree display-fn) |
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(let ((char (read-char)) |
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branch) |
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(funcall cleanup-fn) |
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(if (setq branch (assoc char tree)) |
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(if (eq (car (setq tree (cdr branch))) 'leaf) |
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(throw 'done (cdr tree))) |
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(signal 'user-error (list "No such candidate" char)) |
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(throw 'done nil)))))) |
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(provide 'avy) |
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;;; avy.el ends here
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