Map Markers

This is a Python 3 script that reconciles dynmap markers in a specified world against Minecraft map items in that world. It creates a "pin" marker named after the map ID number in the centre of each map's render region.

This script assumes an environment running the mark2 server wrapper to send commands to the server console.

Principle of Operation

The dynmap plugin stores all markers in plugins/dynmap/markers.yml. Minecraft maps are stored in worlds/world/data/map_<n>.dat for each map ID, <n>.

The script works out the highest (most recent) map ID number at each (x,z) coordinate pair, discards information about older (obsoleted) maps centred on those coordinates and adjusts the dynmap markers by issuing /dmarker delete and /dmarker add commands in the server console using mark2 send -n <server>. In Minecraft 1.16, dynmap breaks if you issue /dynmap reload, so directly updating the markers.yml file and reloading it is out of the question.

To ensure that map files are up-to-date on disk, the script issues a /save-all command and then waits a few seconds before reading map files.

Usage

Usage: mapmarkers.py <server> <world> <maps-dir> <markers-file> <marker-set>

Add dynmap markers in the specified world for all Minecraft maps in that world.
Markers are named after the map number. They are created by issuing console
commands with "mark2 send -n <server>".

<maps-dir> is the path to the directory containing "map_<n>.dat" files, e.g.
"/servers/pve/worlds/world/data".

<markers-file> is the path to the dynmap markers configuration file, e.g.
"/servers/pve/plugins/dynmap/markers.yml".

<marker-set> is the name of the set of markers to update, e.g. "markers".

Configuration

The script should be configured to run every few minutes. The easiest way to do this is with the mark2 scheduling facility, scripts.txt:

# scripts.txt

*/5     *    *    *    *    $python3 /home/minecraft/scripts/mapmarkers.py pve27 mapworld /servers/pve/worlds/world/data /servers/pve/plugins/dynmap/markers.yml markers

Python Dependencies

To install library dependencies, run these commands:

pip3 install PyYAML
pip3 install nbtlib

Bugs/Quirks

Intermittently, map markers will not appear for some map items placed in item frames. This is because the corresponding map_<n>.dat file does not list the map as having been placed in an item frame. This is a bug in Mojang or Spigot/Paper code.