Preface

Goal: Manage Herbstclient process trigerred by idle event

Focusing in "herbstclient --idle". 

HerbstluftWM: Tag Status

This is the next Part, of the previous Tutorial. This tutorial cover Lemonbar. In order to use Dzen2, any reader could use the source code in github.


Reading

Before you jump off to scripting, you might desire to read this overview.

All The Source Code:

Impatient coder like me, like to open many tab on browser.

The PipeHandler Source File:

Let’s have a look at pipehandler.sh in github.


HerbstluftWM Idle Event in Many Languages

This article is one part of a collection. All integrated, on related to another. So we can compare each other quickly.

Tutorial/ Guidance/ Article: [ Idle Event Overview ] [ BASH ] [ Perl ] [ Python ] [ Ruby ] [ PHP ] [ Lua ] [ Haskell ]

Dzen2 Source Code Directory: [ BASH ] [ Perl ] [ Python ] [ Ruby ] [ PHP ] [ Lua ] [ Haskell ]

Lemonbar Source Code Directory: [ BASH ] [ Perl ] [ Python ] [ Ruby ] [ PHP ] [ Lua ] [ Haskell ]


Statusbar Screenshot

Dzen2

Statusbar: Dzen2 Screenshot

Lemonbar

Statusbar: Lemonbar Screenshot


Without Idle event

Let’s have a look at our main panel.sh in github. At the end of the script, we finally call lemonbar with detach_lemon function.

# remove all lemonbar instance
pkill lemonbar

# run process in the background
detach_lemon $monitor $lemon_parameters

View Source File:

Run Lemon, Run !

This detach_lemon function. is just a function that enable the lemonbar running process to be detached, using fork &.

function detach_lemon() { 
    monitor=$1
    shift
    parameters=$@
    
    run_lemon $monitor $parameters &
}

The real function is run_lemon.

function run_lemon() { 
    monitor=$1
    shift
    parameters=$@
    
    command_out="lemonbar $parameters -p"
    
    {
       content_init $monitor
    } | $command_out
}

Note: that we want to ignore idle event for a while. And append the -p for a while, to make the statusbar persistent.

Statusbar Initialization

Here we have the content_init. It is just an initialization of global variable. We are going to have some loop later in different function, to do the real works.

function content_init() {
    monitor=$1

    set_tag_value $monitor
    set_windowtitle ''

    get_statusbar_text $monitor
    echo $buffer
}

Now is time to try the panel, on your terminal. Note: that we already reach this stage in our previous article. These two functions, set_tag_value and set_windowtitle, have already been discussed.

View Source File:

Simple version. No idle event. Only statusbar initialization.


With Idle event

Consider this content_walk call, after content_init call, inside the run_lemon.

function run_lemon() { 
    monitor=$1
    shift
    parameters=$@
    
    command_out="lemonbar $parameters"
    
    {
       content_init $monitor
       content_walk $monitor # loop for each event
    } | $command_out
}

Wrapping Idle Event into Code

content_walk is the heart of this script. We have to capture every event, and process the event in event handler.

Walk step by step, Process event by event

After the event handler, we will get the statusbar text, in the same way, we did in content_init.

function content_walk() {
    monitor=$1

    # start a pipe
    command_in='herbstclient --idle'

    # wait for each event     
    $command_in | while read event; do
        handle_command_event $monitor "$event"
        
        get_statusbar_text $monitor
        echo $buffer
    done    
}

The Event Handler

For each idle event, there are multicolumn string. The first string define the event origin.

HerbstluftWM: Tag Status

The origin is either reload, or quit_panel, tag_changed, or tag_flags, or tag_added, or tag_removed, or focus_changed, or window_title_changed. More complete event, can be read in herbstclient manual.

All we need is to pay attention to this two function. set_tag_value and set_windowtitle.

function handle_command_event() {
    local monitor=$1
    shift
    local event=$@    
    
    # find out event origin
    IFS=$'\t' column=($event);
    origin=${column[0]}
    
    # find out event origin
    case $origin in
        reload)
            pkill lemonbar
            ;;
        quit_panel)
            exit
            ;;
        tag*)
            set_tag_value $monitor
            ;;
        focus_changed|window_title_changed)            
            [[ ${#column[@]} > 2 ]] && title=${column[2]} || title=''
            set_windowtitle "$title"
            ;;
    esac 
}

Actually that’s all we need to have a functional lemonbar. This is the minimum version.

View Source File:

With idle event. The heart of the script.


Lemonbar Clickable Areas

This is specific issue for lemonbar, that we don’t have in dzen2.

Consider have a look at output.sh.

    # clickable tags
    local text_name=''
    text_name+="%{A:herbstclient focus_monitor \"$monitor\" && "
    text_name+="herbstclient use \"$tag_index\":} $tag_name %{A} "

Issue: Lemonbar put the output on terminal instead of executing the command.

HerbstluftWM: Tag Status

Consider going back to pipehandler.sh.

We need to pipe the lemonbar output to shell. It means Lemonbar read input and write output at the same time.

function run_lemon() { 
    monitor=$1
    shift
    parameters=$@
    
    command_out="lemonbar $parameters"
    
    {
       content_init $monitor
       content_walk $monitor # loop for each event
    } | $command_out | sh
}

How does it work ?

All we need to do is to pipe the output to sh. And voilla !! The magic happened. Now we have real clickable areas.

View Source File:

Piping lemonbar output to shell, implementing lemonbar clickable area.


Interval Based Event

We can put custom event other than idle event in statusbar panel. This event, such as date event, called based on time interval in second. Luckily we can treat interval as event.

It is a little bit tricky, because we have to make, a combined event that consist of, idle event (asynchronous) and interval event (synchronous). Merging two different paralel process into one.

This is an overview of what we want to achieve.

HerbstluftWM: Custom Event

In real code later, we do not need the timestamp. interval string is enough to trigger interval event.

View Testbed Source File:

Before merging combined event into main code, consider this test in an isolated fashion.


Combined Event

Preparing The View

This is what it looks like, an overview of what we want to achieve.

Statusbar: Event Screenshot

Consider make a progress in output.sh.

segment_datetime='';    # empty string

function get_statusbar_text() {
    ...

    # draw date and time
    text+='%{c}'
    output_by_datetime
    text+=$buffer

    ...
}


function output_by_datetime() {
    buffer=$segment_datetime
}

function set_datetime() {
    ...

    segment_datetime="$date_text  $time_text"
}

And a few enhancement in pipehandler.sh.

function handle_command_event() {
    ...

    case $origin in
        ...
        interval)
            set_datetime
            ;;
    esac 
}

function content_init() {
    ...
    set_windowtitle ''
    set_datetime

    ...
}

Expanding The Event Controller

All we need to do is to split out content_walk into

  • content_walk: combined event.

  • content_event_idle: HerbstluftWM idle event. Forked, as background processing.

  • content_event_interval : Custom date time event. Forked, as background processing.

function content_event_idle() {
    # wait for each event     
    herbstclient --idle
}
function content_event_interval() {
    # endless loop
    while :; do 
      echo "interval"
      sleep 1
    done
}
function content_walk() {
    monitor=$1
    
    {
        content_event_idle &
        pid_idle=$!
    
        content_event_interval &
        pid_interval=$!
    
    }  | while read event; do
            handle_command_event $monitor "$event"
        
            get_statusbar_text $monitor
            echo $buffer
        done
}

This above is the most complex part. We are almost done.

View Source File:

Combined event consist of both, synchronous interval event and asynchronous idle event.


Dual Bar

The idea of this article comes from the fact that herbsclient --idle is asynchronous event. If you need another bar, just simply use Conky instead.

  • Dzen2: HerbstluftWM: Dzen2 Conky

  • Lemonbar: HerbstluftWM: Lemonbar Conky

We only need one function to do this in pipehandler.pm.

function detach_lemon_conky() {    
    parameters=$@

    command_out="lemonbar $parameters"
    
    {
        dirname=$(dirname $(readlink -f "$0"))
        path="$dirname/../conky"
        conky -c "$path/conky.lua"
    } | $command_out &
}

And execute the function main script in panel.pl.

#!/usr/bin/env bash

# libraries

DIR=$(dirname "$0")

. ${DIR}/gmc.sh
. ${DIR}/helper.sh
. ${DIR}/output.sh
. ${DIR}/pipehandler.sh

# main

panel_height=24
get_monitor ${@}

pkill lemonbar
herbstclient pad $monitor $panel_height 0 $panel_height 0

# run process in the background

get_params_top $monitor $panel_height
detach_lemon $monitor $lemon_parameters

get_params_bottom $monitor $panel_height
detach_lemon_conky $lemon_parameters

View Source File:

Dual Bar, detach_lemon_conky function.


Avoid Zombie Apocalypse

Zombie are scary, and fork does have a tendecy to become a zombie. Application that utilize several forks should be aware of this threat. The reason why I use fork instead of thread is, because the original herbstluftwm configuration coming from bash, and this bash script is using fork.

However, you can use this short script to reduce zombie population. It won’t kill all zombie, but works for most case. You might still need htop, and kill -9 manually.

function kill_zombie() {
    pkill -x dzen2
    pkill -x lemonbar
    pkill -x cat
    pkill conky
    pkill herbstclient
}

Putting Them All Together

I also created compact for version, for use with main HerbstluftWM configuration, in ~/.config/herbstluftwm/ directory. After reunification, they are not very long scripts after all.


Desktop Screenshot

Fullscreen, Dual Panel, Zero Gap.

HerbstluftWM: Screenshot Dual Panel


Enjoy the statusbar ! Enjoy the window manager !