Feat: adds xbrightness

diff --git a/xbrightness b/xbrightness
new file mode 100755 (executable)
index 0000000..c15c131
--- /dev/null
+++ b/xbrightness
@@ -0,0 +1,203 @@
+#!/usr/bin/env bash
+# Change the screen brightness.
+# See the output of "$0 -h" for details.
+
+# Exit immediately on each error and unset variable;
+# see: https://vaneyckt.io/posts/safer_bash_scripts_with_set_euxo_pipefail/
+#set -Eeuo pipefail
+set -Eeu
+
+APP_NAME="Screen Brightness Changer"
+cmd=${1:-get}
+bl_dir=/sys/class/backlight/intel_backlight
+
+function print_help() {
+
+    script_name="$(basename "$0")"
+    echo "${APP_NAME} - Allows to change the screen brightness."
+    echo "It may do so using the hardware backlight or through software manipulation of pixel values sent to the screen."
+    echo
+    echo "Usage:"
+    echo "  $script_name [OPTIONS] COMMAND"
+    echo "Commands:"
+    echo "  [on|off]         set the brightness to either 100% or 0%"
+    echo "  [0.0, 1.0]       set the brightness to the given fraction"
+    echo "  [+-][0.0, 1.0]   increase/decrease the brightness by the given fraction"
+    echo "  [0, 100]%        set the brightness to the given percentage"
+    echo "  [+-][0, 100]%    increase/decrease the brightness by the given percentage"
+    echo "Options:"
+    echo "  -h, --help              Print this usage help and exit"
+    echo "Examples:"
+    echo "  $script_name            # Returns the current brightness"
+    echo "  $script_name 1.0        # Set to full brightness"
+    echo "  $script_name 100%       # Set to full brightness"
+    echo "  $script_name +0.1       # Increase brightness by 10%"
+    echo "  $script_name -10%       # Reduce brightness by 10%"
+    echo "  $script_name --help     # Print this usage help and exit"
+}
+
+# read command-line args
+POSITIONAL=()
+while [[ $# -gt 0 ]]
+do
+    arg="${1}"
+    shift # $2 -> $1, $3 -> $2, ...
+
+    case "${arg}" in
+        -h|--help)
+            print_help
+            exit 0
+            ;;
+        *) # non-/unknown option
+            POSITIONAL+=("${arg}") # save it in an array for later
+            ;;
+    esac
+done
+set -- "${POSITIONAL[@]}" # restore positional parameters
+
+# Check if first number is larger then the second.
+# This can do floating-point comparison.
+function _isLarger() {
+    return "$(awk -v n1="$1" -v n2="$2" \
+        'BEGIN { if (n1 >= n2) { print("0") } else { print("1") } }')"
+}
+
+# Convert potentially relative (+|-X) into new absolute value.
+# If relative=false, return the value.
+# Else, return current +|- the value.
+function _makeAbs() {
+    local _cur="$1"
+    local _rel="$2"
+    local _rel_sign="$3"
+    local _val="$4"
+    local _new=""
+    if $_rel
+    then
+        _new=$(printf "%.3f" "$(awk "BEGIN { print($_cur + ($_rel_sign * $_val)) }")")
+    else
+        _new="$_val"
+    fi
+    echo -n "$_new"
+}
+
+# Limits the input value (float) to the range [0.0, 1.0] (inclusive).
+function _limit01() {
+    local _val="$1"
+    local _new=""
+    if _isLarger "$_val" 1
+    then
+        _new="1.0"
+    elif _isLarger 0 "$_val"
+    then
+        _new="0.0"
+    else
+        _new="$_val"
+    fi
+    echo -n "$_new"
+}
+
+# Post-process/parse the input command/value.
+val_rel=$(echo "$cmd" | grep -q '^[+-]' && echo -n "true" || echo -n "false")
+val_rel_sign=$(echo "$cmd" | grep -q '^+' && echo -n "1" || echo -n "-1")
+cmd=$(echo "$cmd" | sed -e 's|^[+-]||')
+
+# Calculate the (float) fractional value -
+# absolute or relative -
+# indicated by the given command.
+if   [ "$cmd" == "on" ]; then
+    # turn fully bright
+    val_new=1.0
+elif [ "$cmd" == "off" ]; then
+    # turn the screen backlight off
+    val_new=0.0
+elif echo "$cmd" | grep -q '%$'; then
+    val_new=${cmd/\%/}
+    val_new=$(printf "%.3f" "$(awk "BEGIN { print($val_new / 100) }")")
+elif _isLarger "$cmd" 0 && _isLarger 1 "$cmd"; then
+    val_new=$cmd
+elif [ "$cmd" == "get" ]; then
+    val_new="0"
+    val_rel="true"
+    val_rel_sign="1"
+else
+    >&2 echo "Invalid command '$cmd'!"
+    exit 1
+fi
+
+# Evaluate which backlight/brightness changeing method to use
+
+mth_xbacklight=false
+mth_bare=false
+mth_xrandr=false
+if which xbacklight > /dev/null 2>&1 && xbacklight -get > /dev/null 2>&1
+then
+    echo "Using 'xbacklight' (hardware) ..."
+    # This requires the `xbacklight` utility installed
+    # and the systems backlight to be suported by it.
+    # This method actually changes the backlight brightness (hardware).
+    mth_xbacklight=true
+elif [ -d "$bl_dir" ] && [ "$EUID" -eq 0 ]
+then
+    echo "Using '$bl_dir' (hardware) ..."
+    # This requires the $bl_dir directory to be present
+    # and this script to be run with root priviledges
+    # in order to be able to write ot that dir.
+    # This method actually changes the backlight brightness (hardware).
+    mth_bare=true
+elif which xrandr > /dev/null 2>&1
+then
+    echo "Using xrandr (software) ..."
+    # This has no prerequisite; it should always work.
+    # This method only manipulates the pixel values sent to the screen, imitating more/less brightness (software).
+    mth_xrandr=true
+else
+    >&2 echo "No low-level-method chosen!"
+    exit 1
+fi
+
+# Fetch the current brightness value as fraction in [0.0, 1.0]
+if $mth_xbacklight
+then
+    val_cur_perc=$(xbacklight -get)
+    val_cur=$(printf "%.3f" "$(awk "BEGIN { print($val_cur_perc / 100) }")")
+elif $mth_bare
+then
+    val_max=$(cat "$bl_dir/max_brightness")
+    val_cur_abs=$(cat "$bl_dir/brightness")
+    val_cur=$(printf "%.3f" "$(awk "BEGIN { print(1.0 * $val_cur_abs / $val_max) }")")
+elif $mth_xrandr
+then
+    val_cur=$(xrandr --verbose | grep -i "brightness" | sed -e 's|.*: ||')
+else
+    >&2 echo "No low-level-method chosen!"
+    exit 1
+fi
+
+# Calculate the new brightness value as fraction in [0.0, 1.0]
+val_new=$(_limit01 "$(_makeAbs "$val_cur" "$val_rel" "$val_rel_sign" "$val_new")")
+val_new_perc=$(printf "%.0f" "$(awk "BEGIN { print($val_new * 100) }")")
+
+# Just print the (new == old) current brightness percentage and exit
+if [ "$cmd" == "get" ]
+then
+    echo "${val_new_perc}%"
+    exit 0
+fi
+
+# Set the new brightness value
+if $mth_xbacklight
+then
+    xbacklight -set "$val_new_perc"
+elif $mth_bare
+then
+    val_max=$(cat "$bl_dir/max_brightness")
+    val_new_abs=$(printf "%.0f" "$(awk "BEGIN { print($val_new * $val_max) }")")
+    echo -n "$val_new_abs" | tee "$bl_dir/brightness"> /dev/null
+elif $mth_xrandr
+then
+    display=$(xrandr -q | grep " connected" | sed -e 's| .*||')
+    xrandr --output "$display" --brightness "$val_new"
+else
+    >&2 echo "No low-level-method chosen!"
+    exit 1
+fi