Variable: reference-point-alist
reference-point-alist is a variable defined in composite.el.gz.
Value
Large value
((tl . 0)
(tc . 1)
(tr . 2)
(Bl . 3)
(Bc . 4)
(Br . 5)
(bl . 6)
(bc . 7)
(br . 8)
(cl . 9)
(cc . 10)
(cr . 11)
(top-left . 0)
(top-center . 1)
(top-right . 2)
(base-left . 3)
(base-center . 4)
(base-right . 5)
(bottom-left . 6)
(bottom-center . 7)
(bottom-right . 8)
(center-left . 9)
(center-center . 10)
(center-right . 11)
(ml . 3)
(mc . 10)
(mr . 5)
(mid-left . 3)
(mid-center . 10)
(mid-right . 5))
Documentation
Alist of symbols vs integer codes of glyph reference points.
A glyph reference point symbol is to be used to specify a composition
rule in COMPONENTS argument to such functions as compose-region.
The meaning of glyph reference point codes is as follows:
0----1----2 <---- ascent 0:tl or top-left
| | 1:tc or top-center
| | 2:tr or top-right
| | 3:Bl or base-left 9:cl or center-left
9 10 11 <---- center 4:Bc or base-center 10:cc or center-center
| | 5:Br or base-right 11:cr or center-right
--3----4----5-- <-- baseline 6:bl or bottom-left
| | 7:bc or bottom-center
6----7----8 <---- descent 8:br or bottom-right
Glyph reference point symbols are to be used to specify a composition rule of the form (GLOBAL-REF-POINT . NEW-REF-POINT), where GLOBAL-REF-POINT is a reference point in the overall glyphs already composed, and NEW-REF-POINT is a reference point in the new glyph to be added.
For instance, if GLOBAL-REF-POINT is br (bottom-right) and
NEW-REF-POINT is tc (top-center), the overall glyph is updated as
follows (the point * corresponds to both reference points):
+-------+--+ <--- new ascent
| | |
| global| |
| glyph | |
-- | | |-- <--- baseline (doesn't change)
+----+--*--+
| | new |
| |glyph|
+----+-----+ <--- new descent
A composition rule may have the form (GLOBAL-REF-POINT NEW-REF-POINT XOFF YOFF), where XOFF and YOFF specify how much to shift NEW-REF-POINT from GLOBAL-REF-POINT. In this case, XOFF and YOFF are integers in the range -100..100 representing the shifting percentage against the font size.
Probably introduced at or before Emacs version 21.1.
Source Code
;; Defined in /usr/src/emacs/lisp/composite.el.gz
;;; composite.el --- support character composition -*- lexical-binding: t; -*-
;; Copyright (C) 2001-2024 Free Software Foundation, Inc.
;; Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007,
;; 2008, 2009, 2010, 2011
;; National Institute of Advanced Industrial Science and Technology (AIST)
;; Registration Number H14PRO021
;; Author: Kenichi Handa <handa@gnu.org>
;; (according to ack.texi)
;; Keywords: mule, multilingual, character composition
;; Package: emacs
;; 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
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; 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 <https://www.gnu.org/licenses/>.
;;; Commentary:
;;; Code:
(defconst reference-point-alist
'((tl . 0) (tc . 1) (tr . 2)
(Bl . 3) (Bc . 4) (Br . 5)
(bl . 6) (bc . 7) (br . 8)
(cl . 9) (cc . 10) (cr . 11)
(top-left . 0) (top-center . 1) (top-right . 2)
(base-left . 3) (base-center . 4) (base-right . 5)
(bottom-left . 6) (bottom-center . 7) (bottom-right . 8)
(center-left . 9) (center-center . 10) (center-right . 11)
;; For backward compatibility...
(ml . 3) (mc . 10) (mr . 5)
(mid-left . 3) (mid-center . 10) (mid-right . 5))
"Alist of symbols vs integer codes of glyph reference points.
A glyph reference point symbol is to be used to specify a composition
rule in COMPONENTS argument to such functions as `compose-region'.
The meaning of glyph reference point codes is as follows:
0----1----2 <---- ascent 0:tl or top-left
| | 1:tc or top-center
| | 2:tr or top-right
| | 3:Bl or base-left 9:cl or center-left
9 10 11 <---- center 4:Bc or base-center 10:cc or center-center
| | 5:Br or base-right 11:cr or center-right
--3----4----5-- <-- baseline 6:bl or bottom-left
| | 7:bc or bottom-center
6----7----8 <---- descent 8:br or bottom-right
Glyph reference point symbols are to be used to specify a composition
rule of the form (GLOBAL-REF-POINT . NEW-REF-POINT), where
GLOBAL-REF-POINT is a reference point in the overall glyphs already
composed, and NEW-REF-POINT is a reference point in the new glyph to
be added.
For instance, if GLOBAL-REF-POINT is `br' (bottom-right) and
NEW-REF-POINT is `tc' (top-center), the overall glyph is updated as
follows (the point `*' corresponds to both reference points):
+-------+--+ <--- new ascent
| | |
| global| |
| glyph | |
-- | | |-- <--- baseline (doesn't change)
+----+--*--+
| | new |
| |glyph|
+----+-----+ <--- new descent
A composition rule may have the form (GLOBAL-REF-POINT
NEW-REF-POINT XOFF YOFF), where XOFF and YOFF specify how much
to shift NEW-REF-POINT from GLOBAL-REF-POINT. In this case, XOFF
and YOFF are integers in the range -100..100 representing the
shifting percentage against the font size.")