Scripting Guide

Overview

Mepo has advanced scripting capabilities through mepolang by way of primarily two mechanisms: 1) via interactive scripting through STDIN and 2) via the shellpipe_{sync,async} mepolang mechanism from binding commands.

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1. Scripting via Interactive STDIN

Mepo has the capability of being scripted interactively via feeding mepolang commands continually into the application's STDIN filedescriptor. This functionality can be enabled via using the -i commandline flag which indicates to the application logic to continually read commands from STDIN.

One example might be:

echo "prefset_n crosshair_size 200;" | mepo -i

Or continually:

mkfifo foo
cat foo | mepo -i &
echo "prefset_n crosshair_size 200;" > foo

Or to interactively debug similar to a REPL (note -e enables debug messages):

tee | mepo -i -e

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2. Scripting via Mepolang bindings and shellpipe_sync / shellpipe_async

Many commands for mepolang, and binding commands in particular accept a mepolang expression themselves to run, for example: bind_button, bind_key, and bind_gesture. Using these binding commands, in coordination with shellpipe_sync as your mepolang expression to run, you may bind a shellscript on a keybinding, clicking a button, or performing a gesture for example. This is done often in the default base configuration (which is a great example to study from), but may be done as well by end-users in their configuration as well.

The script or program to run for shellpipe_{sync,async} may be written in any language (though shellscript is simplest/best) and the only requirement is your script needs to write mepolang plain text to STDOUT. To make this more practical, for example, to bind a keybinding for Control-j to set the crosshair size sequentially to 3 different sizes, you might in your mepolang configuration write:

bind_key c j [shellpipe_sync crosshair.sh];

And then save in your $PATH, the script crosshair.sh as:

#!/usr/bin/env sh

echo "prefset_n crosshair_size 30;"
sleep 2
echo "prefset_n crosshair_size 100;"
sleep 2
echo "prefset_n crosshair_size 15;"

See the below tutorial or screencast for a more in-depth examples.

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Demo Video Screencast: Adding a script and running via a UI button

The following demo video example shows a full walkthrough of creating a mepolang script from scratch and adding a UI button to run the script via bind_button and shellpipe_sync.

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Tutorial: Writing a repositioning script and running via keybinding

The following tutorial demonstrates an example script for a usecase where the user might want to select between three different locations to reposition the map to on pressing a keybinding.

As you will recall for shellpipe_sync scripts, whatever appears in STDOUT is run as mepolang. Accordingly the below script simply prompts the user for a location using the mepo_ui_helper_menu.sh helper script (which calls to zenity), and then as a result prints to STDOUT via echo to use the prefset_n mepolang command to set the picked location's latitude and longitude.

#!/usr/bin/env sh
PLACES="NYC: 40.71273 -74.00602
Anchorage: 61.21631 -149.89485
Paris: 48.85889 2.32004"

PICKED="$(echo "$PLACES" | PROMPT="Location" mepo_ui_helper_menu.sh)"
LAT="$(echo "$PICKED" | cut -d ' ' -f2)"
LON="$(echo "$PICKED" | cut -d ' ' -f3)"

echo "prefset_n lat $LAT;"
echo "prefset_n lon $LON;"

Place the following above script in $PATH as mepo_ui_locationjump.sh and then you can edit your config to run the script via bind_key for example as:

bind_key c j [shellpipe_sync locationjump.sh];

Or alternatively for quick testing, you could bootup mepo with this binding via:

echo "bind_key c j [shellpipe locationjump.sh];" | mepo -i

Either way now when you press Control-j the script will be run.