Function: xterm-register-default-colors

xterm-register-default-colors is a byte-compiled function defined in xterm.el.gz.

Signature

(xterm-register-default-colors COLORS)

Documentation

Register the default set of colors for xterm or compatible emulator.

This function registers the number of colors returned by display-color-cells for the currently selected frame. The first (16) colors are taken from COLORS, which see, while the rest are computed assuming either the 88- or 256-color standard color scheme supported by latest versions of xterm.

Source Code

;; Defined in /usr/src/emacs/lisp/term/xterm.el.gz
(defun xterm-register-default-colors (colors)
  "Register the default set of colors for xterm or compatible emulator.

This function registers the number of colors returned by `display-color-cells'
for the currently selected frame.  The first (16) colors are taken from
COLORS, which see, while the rest are computed assuming
either the 88- or 256-color standard color scheme supported by latest
versions of xterm."
  (let* ((ncolors (display-color-cells))
	 (color (car colors)))
    (if (> ncolors 0)
	;; Clear the 8 default tty colors registered by startup.el
	(tty-color-clear))
    ;; Only register as many colors as are supported by the display.
    (while (and (> ncolors 0) colors)
      (tty-color-define (car color) (cadr color)
			(mapcar #'xterm-rgb-convert-to-16bit
				(car (cddr color))))
      (setq colors (cdr colors)
	    color (car colors)
	    ncolors (1- ncolors)))
    ;; We've exhausted the colors from `colors'.  If there
    ;; are more colors to support, compute them now.
    (when (> ncolors 0)
      (cond
       ((= ncolors 16777200) ; 24-bit xterm
	;; all named tty colors
	(let ((idx (length xterm-standard-colors)))
	  (mapc (lambda (color)
		  (unless (assoc (car color) xterm-standard-colors)
		    (tty-color-define (car color) idx (cdr color))
		    (setq idx (1+ idx))))
		color-name-rgb-alist)))
       ((= ncolors 240)	; 256-color xterm
	;; 216 non-gray colors first
	(let ((r 0) (g 0) (b 0))
	  (while (> ncolors 24)
	    ;; This and other formulas taken from 256colres.pl and
	    ;; 88colres.pl in the xterm distribution.
	    (tty-color-define (format "color-%d" (- 256 ncolors))
			      (- 256 ncolors)
			      (mapcar #'xterm-rgb-convert-to-16bit
				      (list (if (zerop r) 0 (+ (* r 40) 55))
					    (if (zerop g) 0 (+ (* g 40) 55))
					    (if (zerop b) 0 (+ (* b 40) 55)))))

	    (setq b (1+ b))
	    (if (> b 5)
		(setq g (1+ g)
		      b 0))
	    (if (> g 5)
		(setq r (1+ r)
		      g 0))
	    (setq ncolors (1- ncolors))))
	;; Now the 24 gray colors
	(while (> ncolors 0)
	  (setq color (xterm-rgb-convert-to-16bit (+ 8 (* (- 24 ncolors) 10))))
	  (tty-color-define (format "color-%d" (- 256 ncolors))
			    (- 256 ncolors)
			    (list color color color))
	  (setq ncolors (1- ncolors))))
       ((= ncolors 72)  ; 88-color xterm
	;; 64 non-gray colors
	(let ((levels '(0 139 205 255))
	      (r 0) (g 0) (b 0))
	  (while (> ncolors 8)
	    (tty-color-define (format "color-%d" (- 88 ncolors))
			      (- 88 ncolors)
			      (mapcar #'xterm-rgb-convert-to-16bit
				      (list (nth r levels)
					    (nth g levels)
					    (nth b levels))))
	    (setq b (1+ b))
	    (if (> b 3)
		(setq g (1+ g)
		      b 0))
	    (if (> g 3)
		(setq r (1+ r)
		      g 0))
	    (setq ncolors (1- ncolors))))
	;; Now the 8 gray colors
	(while (> ncolors 0)
	  (setq color (xterm-rgb-convert-to-16bit
		       (floor
			(if (= ncolors 8)
			    46.36363636
			  (+ (* (- 8 ncolors) 23.18181818) 69.54545454)))))
	  (tty-color-define (format "color-%d" (- 88 ncolors))
			    (- 88 ncolors)
			    (list color color color))
	  (setq ncolors (1- ncolors))))
       (t (error "Unsupported number of xterm colors (%d)" (+ 16 ncolors)))))
    ;; Modifying color mappings means realized faces don't use the
    ;; right colors, so clear them.
    (clear-face-cache)))