Como faço para escurecer janelas inativas

Então, inspirado pelos comentários, procurei extensões gnome adequadas e encontrei duas úteis:

Sombrear Windows inativo e efeitos de desfoque do Windows

Eu me conformei com o segundo, pois é mais configurável.

No entanto, percebi rapidamente que, embora isso seja uma grande ajuda quando estou alternando rapidamente entre as janelas, é um incômodo em outros momentos. Não querendo abrir o aplicativo de extensões para habilitar/desabilitar a extensão toda vez, fiz algumas pesquisas e encontrei este script que modifiquei da seguinte forma:

#! /usr/bin/env bash

#   Copyright (C) 2016
#       Alexandru Catalin Petrini <[email protected]>
#  This script is intended to usefully manage gnome-shell extensions,
#  in compatible Gnome Shell versions.

# Install this script by running this command:
# $ sudo wget https://raw.githubusercontent.com/cyberalex4life/gnome-shell-extension-cl/master/gnome-shell-extension-cl -O /usr/local/bin/gnome-shell-extension-cl && sudo chmod +x /usr/local/bin/gnome-shell-extension-cl


# -------------------------------------------------------------------------------

function get_enabled_extensions() {
    enabled_extensions=( $(gsettings get org.gnome.shell enabled-extensions | \
                               sed -e 's|^@as ||g' | tr -d "[",",","]","\'") )
}


function print_enabled_extensions(){
    get_enabled_extensions
    for enabled_extension in "${enabled_extensions[@]}"
    do
        echo "$enabled_extension"
    done
}


# -------------------------------------------------------------------------------

function get_installed_extensions() {
    global_installed_extensions=( $(find "/usr/share/gnome-shell/extensions/" \
                                         -maxdepth 1 -type d -name "*@*" -exec \
                                         /usr/bin/basename {} \;) )
    local_installed_extensions=( $(find "$HOME/.local/share/gnome-shell/extensions/" \
                                        -maxdepth 1 -type d -name "*@*" -exec \
                                        /usr/bin/basename {} \;) )

    if [ ${#local_installed_extensions[@]} -gt ${#global_installed_extensions[@]} ]
    then
        installed_extensions=( ${local_installed_extensions[@]} )
        test_extensions=( ${global_installed_extensions[@]} )
    else
        installed_extensions=( ${global_installed_extensions[@]} )
        test_extensions=( ${local_installed_extensions[@]} )
    fi
    for test_extension in "${test_extensions[@]}"
    do
        test_extension_not_doubled=true
        for installed_extension in "${installed_extensions[@]}"
        do
            if [ "$test_extension" = "$installed_extension" ]
            then
                test_extension_not_doubled=false
                break
            fi
        done
        if  [ $test_extension_not_doubled = true ]
        then
            test_extension=( $test_extension )
            installed_extensions=( "${installed_extensions[@]}" "${test_extension[@]}" )
            #echo ${test_extension[@]}
        fi
    done
    echo "${installed_extensions[@]}"
}


function print_installed_extensions() {
    installed_extensions=( $(get_installed_extensions) )
    for installed_extension in "${installed_extensions[@]}"
    do
        [ "$(check_extension_is_enabled "$installed_extension")" = true ] && \
            status="enabled" || status="disabled";
        printf "%-65s - %-10s \n" "$installed_extension" "$status"
    done
}


# -------------------------------------------------------------------------------

function check_extension_is_enabled() {
    extension_to_check=$1
    enabled_extensions=( $(gsettings get org.gnome.shell enabled-extensions | \
                               sed -e 's|^@as ||g' | tr -d "[",",","]","\'") )
    for enabled_extension in "${enabled_extensions[@]}"
    do
        if [ "$enabled_extension" = "$extension_to_check" ]
        then
            echo true
            return
        fi
    done
    echo false
}


function check_extension_in_all_extensions() {
    extension_to_check=$1
    installed_extensions=( $(get_installed_extensions) )
    for installed_extension in "${installed_extensions[@]}"
    do
        if [ "$installed_extension" = "$extension_to_check" ]
        then
            echo true
            return
        fi
    done
    echo false
}


function version_greater() {
    minimal_version=3.18.0
    our_version=$(gnome-shell --version | awk '{print $3}')
    if [ "$(echo "$our_version $minimal_version" | tr " " "\n" | sort -V | head -n 1)" != "$our_version" ]
    then
        echo true
    else
        echo false
    fi
}


function disable_extension() {

    arguments=("$@")
    unset "arguments[0]"

    for extension_to_disable in "${arguments[@]}"
    do

        if  [ "$(check_extension_in_all_extensions "$extension_to_disable")" = false ]
        then
            echo "'$extension_to_disable' is not installed."
            continue
        fi
        if  [ "$(check_extension_is_enabled "$extension_to_disable")" = false ]
        then
            echo "'$extension_to_disable' is already disabled."
            continue
        fi
        if [ "$(version_greater)" = true ]
        then
            gnome-shell-extension-tool -d "$extension_to_disable"
            continue
        fi
        enabled_extensions=( $(gsettings get org.gnome.shell enabled-extensions | \
                                   tr -d "[",",","]","\'") )
        enabled_extensions_string=""
        for enabled_extension in "${enabled_extensions[@]}"
        do
            if [ "$enabled_extension" != "$extension_to_disable" ]
            then
                enabled_extensions_string="$enabled_extensions_string '$enabled_extension', "
            fi
        done
        enabled_extensions_string=${enabled_extensions_string:1:-2}
        enabled_extensions_string="[ $enabled_extensions_string ]"

        dbus-launch gsettings set org.gnome.shell enabled-extensions "$enabled_extensions_string"

    done
    return
}


function enable_extension() {

    arguments=("$@")
    unset "arguments[0]"

    for extension_to_enable in "${arguments[@]}"
    do

        if  [ "$(check_extension_in_all_extensions "$extension_to_enable")" = false ]
        then
            echo "'$extension_to_enable' is not installed."
            continue
        fi
        if  [ "$(check_extension_is_enabled "$extension_to_enable")" = true ]
        then
            echo "'$extension_to_enable' is already enabled."
            continue
        fi
        if [ "$(version_greater)" = true ]
        then
            gnome-shell-extension-tool -e "$extension_to_enable"
            continue
        fi
        enabled_extensions_string=$(gsettings get org.gnome.shell enabled-extensions | tr -d "]")
        [ "$enabled_extensions_string" != "@as [" ] && delimiter=,
        enabled_extensions_string="${enabled_extensions_string}${delimiter} '$extension_to_enable' ]"

        gsettings set org.gnome.shell enabled-extensions "$enabled_extensions_string"

    done
    return
}


# -------------------------------------------------------------------------------

function disable_all_extensions() {
    get_enabled_extensions
    for enabled_extension in "${enabled_extensions[@]}"
    do
        # Don't disable user-theme extensions to avoid breaking them
        if [ "$enabled_extension" != "user-theme" ] && \
               [ "$enabled_extension" != "user-themes" ] && \
               [ "$enabled_extension" != "[email protected]" ]
        then
            disable_extension "this element will be ignored" "$enabled_extension"
        else
            continue
        fi
    done
}
# -------------------------------------------------------------------------------

function toggle_extension() {

    arguments=("$@")
    unset "arguments[0]"

    for extension_to_enable in "${arguments[@]}"
    do

        if  [ "$(check_extension_in_all_extensions "$extension_to_enable")" = false ]
        then
            echo "'$extension_to_enable' is not installed."
            continue
        fi
        if  [ "$(check_extension_is_enabled "$extension_to_enable")" = true ]
        then
            disable_extension "$@"
        else
            enable_extension "$@"
        fi
    done
    return
}
# -------------------------------------------------------------------------------

function print_help() {

    printf "
GNOME Shell Extension Control Tool:

usage: gnome-shell-extensions <option> [extension name]

Options
    -h,   --help                                Display help message.
    -e,   --enable-extension <extension name>   Enable extension.
    -d,   --disable-extension <extension name>  Disable extension.
    -da,  --disable-all-extensions              Disables all extensions.
    -le,  --list-enabled                        List enabled extensions.
    -l,   --list                                List all extensions + state info.
    -s,   --status <extension name>             Show status of extension.
    -t,   --toggle-extension                    Toggle extension.
\n"

}


# -------------------------------------------------------------------------------

case $1 in
    -h|--help)
        print_help
        ;;
    -e|--enable-extension)
        enable_extension "$@"
        ;;
    -d|--disable-extension)
        disable_extension "$@"
        ;;
    -t|--toggle-extension)
        toggle_extension "$@"
        ;;
    -da|--disable-all-extensions)
        disable_all_extensions
        ;;
    -le|--list-enabled)
        print_enabled_extensions
        ;;
    -l|--list)
        print_installed_extensions
        ;;
    -s|--status)
        if  [ "$(check_extension_is_enabled "$2")" = true ]
        then
            echo "enabled"
        else
            echo "disabled"
        fi
        ;;
    *)
        print_help
        ;;
esac

Então, corri gnome-shell-extension-cl -lpara pegar a lista de extensões.

Por fim, adicionei um atalho de teclado para executar o gnome-shell-extension-cl -t [email protected]. Eu usei Super+ Alt+ B, mas qualquer combinação de teclado poderia servir.