_lp_explain_theme_activate() {
    # Disable tyographic marks without meaning.
    LP_MARK_DEV_OPEN=
    LP_MARK_DEV_CLOSE=
    LP_MARK_DEV_MID=
    LP_MARK_MODULES_OPEN=
    LP_MARK_MODULES_SEP=
    LP_MARK_MODULES_CLOSE=
    LP_MARK_ENV_VARS_OPEN=
    LP_MARK_ENV_VARS_SEP=
    LP_MARK_ENV_VARS_CLOSE=

    # A prompt starting on the third line looks weird,
    # so we duplicate the mark and put it on a new line.
    LP_MARK_PREFIX=${LP_MARK_PREFIX:-$'\n'}

    # Light gray as a default.
    lp_terminal_format 239 -1
    LP_COLOR_EXPLAIN=${LP_COLOR_EXPLAIN:-"$lp_terminal_format"}

    _lp_default_theme_activate
}

_lp_explain_theme_directory() {
    _lp_default_theme_directory
}

_lp_explain_theme_prompt() {
    _lp_default_theme_prompt_data
    _lp_explain_theme_prompt_template
}


# Add a boxed section of the prompt, along with the corresponding variable name.
# Interpret "name" as an LP_* variable, and show lowercase names.
# E.G. `_box PWD` will show the content of $LP_PWD under the name "pwd".
_box() { # name [color]
    local name="${1-}"
    name_len=${#name}
    # printf "$name\n"
    if _lp_create_link "https://liquidprompt.readthedocs.io/en/stable/theme/default.html#LP_${name}" "${name,,}" ; then
        name_link="$lp_link"
    else
        name_link="${name,,}"
    fi

    # Get LP_ variable from name.
    local varname="LP_${name}"
    local var=${!varname} # Get indirection.
    # Trim spaces from content,
    # since they are useless here
    # (added by the default theme,
    # that uses them as separators).
    shopt -s extglob
    local what="${var##+([[:space:]])}"
    what="${what%%+([[:space:]])}"

    # Get length from text without color/link escapes.
    __lp_strip_escapes "$what"
    local raw_data="$ret"
    local raw_data_len=${#raw_data}

    # If no color, use global var.
    local color="${2:-$LP_COLOR_EXPLAIN}"

    if [[ -n "$what" ]]; then
        local i
        box_top+="┬"
        box_mid+="${color}│${NO_COL}$what"
        box_bot+="┴"

        __lp_strip_escapes "$box_mid"
        local raw_mid="$ret"

        # Fill in missing spaces, using box_mid as reference.
        __lp_strip_escapes "$box_hyp"
        local raw_hyp="$ret"
        for (( i=${#raw_hyp}; i < ${#raw_mid}-raw_data_len; i++ )) ; do
            box_hyp+=" "
        done
        # printf "${#box_sup} -> ${#raw_mid}\n"
        __lp_strip_escapes "$box_sup"
        local raw_sup="$ret"
        for (( i=${#raw_sup}; i < ${#raw_mid}-raw_data_len; i++ )) ; do
            box_sup+=" "
        done
        __lp_strip_escapes "$box_top"
        local raw_top="$ret"

        # Add names.
        if (( name_len > raw_data_len )); then
            # printf "On sup/hyp line\n"
            local top_len=${#raw_top}
            local cursor="${raw_sup:top_len:1}"
            # printf "$raw_top\n"
            # printf "${top_len}«${cursor}»\n"

            if [[ "$cursor" != " " && "$cursor" != "" ]] ; then
                # printf "On hyp line\n"
                box_hyp+="┌$name_link"
                box_top+="┴"
            else
                # printf "On sup line\n"
                box_sup+="┌$name_link"
                box_top+="┴"
            fi
        else
            # printf "On top line\n"
            box_top+="$name_link"
        fi

        # Fill in missing spaces, using box_mid as reference.
        __lp_strip_escapes "$box_top"
        local raw_top="$ret"
        for (( i=${#raw_top}; i < ${#raw_mid}; i++ )) ; do
            box_top+="─"
        done
        __lp_strip_escapes "$box_bot"
        local raw_bot="$ret"
        for (( i=${#raw_bot}; i < ${#raw_mid}; i++ )) ; do
            box_bot+="─"
        done

    fi

    # __lp_strip_escapes "$box_hyp"
    # printf "$ret\n"
    # __lp_strip_escapes "$box_sup"
    # printf "$ret\n"
    # __lp_strip_escapes "$box_top"
    # printf "$ret\n"
    # __lp_strip_escapes "$box_mid"
    # printf "$ret\n"
    # __lp_strip_escapes "$box_bot"
    # printf "$ret\n"
}


_lp_explain_theme_prompt_template() {
    if [[ -f "${LP_PS1_FILE-}" ]]; then
        # shellcheck source=liquid.ps1
        source "$LP_PS1_FILE"
    fi

    if [[ -z "${LP_PS1-}" ]]; then
        # Initial global variables.
        box_hyp=""
        box_sup=""
        box_top=""
        box_mid=""
        box_bot=""

        # Add title escape time, battery, load, temperature, RAM, disk, wifi, jobs.
        _box PS1_PREFIX
        _box TIME
        _box BATT
        _box LOAD
        _box TEMP
        _box RAM
        _box DISK
        _box WIFI
        _box JOBS

        # Add multiplexer brackets, user, host, permissions colon, working directory, dirstack, proxy, watched environment variables and nested shell level.

        _box BRACKET_OPEN
        _box USER
        _box HOST
        _box PERM
        _box PWD
        _box DIRSTACK
        _box BRACKET_CLOSE
        _box PROXY
        _box ENVVARS
        _box SHLVL

        # Add the list of development environments/config/etc.
        _box DEV_ENV
        # Add VCS infos
        # If root, the info has not been collected unless LP_ENABLE_VCS_ROOT
        # is set.
        _box VCS
        # Add last runtime, return code & meaning, prompt mark and user-defined postfix.
        _box RUNTIME
        _box ERR
        _box ERR_MEANING

        # prefix/mark/suffix will be shown twice.
        _box MARK_PREFIX
        _box MARK
        _box PS1_POSTFIX

        # End last segment with an arrow shape.
        box_hyp+=" "
        box_sup+=" "
        box_top+="🮢"
        box_mid+="${LP_COLOR_EXPLAIN}🮥${NO_COL}"
        box_bot+="🮠"

        # Show hyp/sup lines only if needed.
        PS1="${LP_COLOR_EXPLAIN}"
        if [[ -n ${box_hyp// } ]] ; then # If not just spaces.
            PS1+="${box_hyp}\n"
        fi
        if [[ -n ${box_sup// } ]] ; then
            PS1+="${box_sup}\n"
        fi

        # Assemble, and add mark+prompt on a new line.
        PS1+="${box_top}${NO_COL}\n${box_mid}\n${LP_COLOR_EXPLAIN}${box_bot}${NO_COL}${LP_MARK_PREFIX}${LP_MARK}${LP_PS1_POSTFIX}"

        # Get the core sections without prompt escapes and make them into a title.
        _lp_formatted_title "${LP_PS1_PREFIX}${LP_BRACKET_OPEN}${LP_USER}${LP_HOST}${LP_MARK_PERM}${lp_path-}${LP_BRACKET_CLOSE}${LP_MARK_PREFIX}${LP_MARK}${LP_PS1_POSTFIX}"
    else
        PS1=$LP_PS1
    fi
}