Scripting Guide


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.

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

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];

And then save in your $PATH, the script 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.

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.

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 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""
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 and then you can edit your config to run the script via bind_key for example as:

bind_key c j [shellpipe_sync];

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

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

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