1 files changed, 79 insertions, 9 deletions
diff --git a/bl b/bl
index a88eebe..4ebff00 100755
--- a/bl
+++ b/bl
@@ -1,4 +1,6 @@
-#!/bin/sh
+#!/bin/zsh
+# vim: set ft=sh:
+#shellcheck shell=sh
 
 # This software is released into the public domain.
 # It is provided "as is", without warranties or conditions of any kind.
@@ -6,8 +8,9 @@
 
 # backlight brightness configuration utility
 #
-# Requirements: POSIX sh, backlight in /sys/class/backlight/*,
-#               write permission for $BACKLIGHT/brightness
+# Requirements: POSIX sh or zsh, backlight in /sys/class/backlight/*,
+#               write permission for $BACKLIGHT/brightness,
+#               one of zsh, bc or qalc (only for -c)
 
 set -eu
 
@@ -81,13 +84,57 @@ is_num() {
 	return 1
 }
 
+raw_to_num() {
+	case "$math" in
+		"")
+			: $(( num = (raw + (raw_max / 2 / max)) * max / raw_max ))
+			;;
+		zsh)
+			: $(( num = int(0.5 + (100 - ((1.0 * raw * max / raw_max - 100) / 10) ** 2)) ))
+			;;
+		zshcmd)
+			num="$(zsh -c "zmodload zsh/mathfunc && echo \$(( int(0.5 + (100 - ((1.0 * $raw * $max / $raw_max - 100) / 10) ** 2)) )) || :")"
+			;;
+		bc)
+			num="$(printf "%s\n" "100.5 - ((($raw * $max / $raw_max) - 100) / 10) ^ 2" | bc -l)"
+			num="${num%.*}"
+			;;
+		qalc)
+			num="$(qalc -t "round((100 - ((($raw * $max / $raw_max) - 100) / 10) ** 2))")"
+			;;
+	esac
+}
+
+num_to_raw() {
+	case "$math" in
+		"")
+			: $(( raw = num * raw_max / max ))
+			;;
+		zsh)
+			: $(( raw = int(0.5 + ((100 - 10 * sqrt(100 - 1.0 * num)) * raw_max / max)) ))
+			;;
+		zshcmd)
+			raw="$(zsh -c "zmodload zsh/mathfunc && echo \$(( int(0.5 + ((100 - 10 * sqrt(100 - 1.0 * $num)) * $raw_max / $max)) )) || :")"
+			;;
+		bc)
+			raw="$(printf "%s\n" "0.5 + (100 - 10 * sqrt(100 - $num)) * $raw_max / $max" | bc -l)"
+			raw="${raw%.*}"
+			;;
+		qalc)
+			raw="$(qalc -t "round((100 - 10 * sqrt(100 - $num)) * $raw_max / $max)")"
+			;;
+	esac
+}
+
 get_brightness() {
 	read_num "$bldir/max_brightness"
 	raw_max="$num"
 	read_num "$bldir/brightness"
 	raw_curr="$num"
 	max=100
-	curr=$(( (raw_curr + (raw_max / 2 / max)) * max / raw_max ))
+	raw="$raw_curr"
+	raw_to_num
+	curr="$num"
 
 	# brightness 0 tends to completely turn off the backlight
 	raw_min=1
@@ -126,7 +173,9 @@ get_raw_new() {
 			;;
 	esac
 	if [ -n "$new" ]; then
-		: $(( raw_new = new * raw_max / max ))
+		num="$new"
+		num_to_raw
+		raw_new="$raw"
 		if [ "$new" -lt "$curr" ] && [ "$raw_new" -ge "$raw_curr" ]; then
 			: $(( raw_new = raw_curr - 1 ))
 		elif [ "$new" -gt "$curr" ] && [ "$raw_new" -le "$raw_curr" ]; then
@@ -150,7 +199,7 @@ set_brightness() {
 
 usage() {
 	prog="$(basename "$0")"
-	printf "%s: usage: %s OPERATOR\n" "$prog" "$prog"
+	printf "%s: usage: %s [OPTION]... OPERATOR\n" "$prog" "$prog"
 	printf "\n"
 	printf "Operators:\n"
 	printf "  (none)      print current brightness in percentages\n"
@@ -163,12 +212,32 @@ usage() {
 	printf "  =-VAL       decrease brightness by VAL raw value\n"
 	printf "  -L, --list  list all found backlights\n"
 	printf "\n"
+	printf "Options:\n"
+	printf "  -c          modify percentage curve to emphasize low raw values\n"
+	printf "\n"
 	printf "Environment variables:\n"
 	printf "  BACKLIGHT   the backlight to use (absolute path or a folder\n"
 	printf "              in %s or %s)\n" "$sys_backlight" "$sys_leds"
 }
 
 main() {
+	math=
+	if [ "${1:-}" = "-c" ]; then
+		if [ -n "${ZSH_VERSION:-}" ]; then
+			zmodload zsh/mathfunc
+			math="zsh"
+		elif command -v zsh >/dev/null; then
+			math="zshcmd"
+		elif command -v bc >/dev/null; then
+			math="bc"
+		elif command -v qalc >/dev/null; then
+			math="qalc"
+		else
+			printf "no supported math option (zsh, bc, qalc) found\n" >&2
+			return 1
+		fi
+		shift
+	fi
 	if [ $# -gt 1 ]; then
 		usage >&2
 		exit 2
@@ -181,6 +250,7 @@ main() {
 		list_backlights
 		exit
 	fi
+
 	get_bldir
 	get_brightness
 	op="${1:-}"
@@ -190,11 +260,11 @@ main() {
 		-[0-9]*)  set_brightness -    "${op#-}" ;;
 		[0-9]*)   set_brightness ""   "$op" ;;
 		=) printf "%d\n" "$raw_curr" ;;
-		=+[0-9]*) set_brightness "=+" "${op#=+}" ;;
+		"="+[0-9]*) set_brightness "=+" "${op#=+}" ;;
 		#+=[0-9]*) set_brightness "=+" "${op#+=}" ;;
-		=-[0-9]*) set_brightness "=-" "${op#=-}" ;;
+		"="-[0-9]*) set_brightness "=-" "${op#=-}" ;;
 		#-=[0-9]*) set_brightness "=-" "${op#-=}" ;;
-		=[0-9]*)  set_brightness "="  "${op#=}" ;;
+		"="[0-9]*)  set_brightness "="  "${op#=}" ;;
 		*)
 			printf "invalid operator: '%s'\n" "$op" >&2
 			exit 2