mepo/doc/mepolang.md -rw-r--r-- 4.4 KiB
e75a4eafMiles Alan Update docs/error messages for 0.8.1 8 days ago


Note: This document is a working draft and will be finalized upon tagging the 1.0 release of Mepo. Expect there to be breaking changes between pre 1.0 tagged releases.


  • Mepolang is Mepo's command language API for IPC that can be sent to its process via STDIN continually.
  • Through this mechanism you can control Mepo: using an external script, by simply piping in a configuration on boot, or by using a FIFO.
    • E.g. ./my_script | mepo
    • Or cat config | mepo
    • Or mkfifo foo; cat foo | mepo
  • Upon the 1.0 release it is planned that there will be two commands included to run Mepo: mepo_raw and mepo wherein mepo will just be a script that runs cat default_config | mepo_raw.
    • The default config provides some nice mobile & desktop friendly settings, however things are entirely customizable through mepolang by providing your own config.
  • Many of Mepo's commands play nice together. A good place to look to understand mepolang's utilization is the default config.
    • For example bind_key actually also takes mepolang text to run as an argument.
    • Similarly the result of shellpipe, runs mepolang text given the STDOUT result of a (user) shellscript.



commandname textarg [multi word arg] 2;
commandname2 arg 8.373 anothertextarg;


  • Each statement is made up of multiple tokens.
  • Each mepolang command should be terminated by a semicolon.
  • The first token in a statement is always the command name.
  • Tokens should be separated by whitespace.
  • Each token is either:
    • Text
      • Just plain text, by default assumed to be a single word.
      • If you want to use a space within an argument use [ square brackets ] to create a multiword token.
      • If you want to have a text token that looks like a number, use square brackets like [-3]
    • Number
      • A floating point number, either decimal (e.g. 3.77) or whole (e.g. 3).
      • Can be negative like -22.22 or positive like 22.22


  • bind_key [mod:text] [key:text] [mepolang:text]:
    • Binds pressing a keyboard key to run another mepolang command.
  • center_on_coords [lat:number] [lon:number]:
    • Navigates to the given latitude and longitude placing point in center of the screen.
  • center_on_mouse:
    • Reposition the viewport to be centered on the current position of the mouse.
  • download_bbox [a_lat:number] [a_lon:number] [b_lat:number] [b_lon:number] [zoom_min:number] [zoom_max:number]:
    • Queues for downloading all tiles within the bounding box denoted between a lat/lon and b lat/lon for zoom levels between zoom_min/zoom_max
  • move_relative [x:number] [y:number]:
    • Move the viewport by the given x and y relative numbers.
  • pin_add [lat:number] [lon:number] [name:text]:
    • Add a pin at the given latitude and longitude with the given name.
  • pin_cycle [index:number]:
    • Focus the next or previous pin based on the index (relative). Repositions the viewport's center to lie ontop of the pin.
  • pin_deactivate:
    • Deactivate pin-selection mode.
  • pin_purge:
    • Clear all currently added pins.
  • prefset [prefname:text] [value:text_or_number]:
    • Sets the preference named text to the value. Currently supported preferences:
    • prefname type description
      debug_global number Shows (1) or hides (0) global debug text.
      debug_tiles number Shows (1) or hides (0) per-tile debug text.
      zoom number Sets the zoom level of the map.
      crosshair_on number Show (1) or hides (0) the center crosshair.
      crosshair_size number Determines the size pixels of the center crosshair.
      tile_cache_dir text Determines the directory for downloaded tites to be saved to.
      tile_cache_url text Determines the URL of the tileserver to pull from.
  • shellpipe [path_to_script:text]:
    • Executes the script given in a subshell; the result given to STDOUT may optionally be mepolang command(s) which are then subsequently run. See examples.
  • zoom_relative [index:number]:
    • Adjust the current zoom level by the given index.