Theme inspector

[hyperknot]

Hi,

I'm trying to find the differences between OpenAndroMaps and MapsForge Prebuilt Maps (from ftp-stud.hs-esslingen.de). Particularly, I'm developing themes for paragliding pilots and high voltage power cables seems to be not visible on the MapsForge maps.

In Maplibre/Mapbox world, there are the inspector themes, which show this "X-Ray" view of all data visible on maps.

Is this possible to have this view in the Mapsforge ecosystem? I tried both Cruiser, but didn't find an option for this) and VTM playgrounds (but couldn't start it on Apple M1 Macbook).

I'm looking for any option to debug this.

[devemux86]

There are 2 map libraries:

• Mapsforge map library
• VTM (OpenGL) map library

OpenAndroMaps themes are created for the Mapsforge map library.
VTM (OpenGL) can read them, but there may be some incompatibilities.

---

About your question, there is no such tool, unless an app implements it.

[hyperknot]

I don't yet understand the difference between Mapsforge and VTM. I'm familiar with Maplibre and OpenMapTiles. What is their analogue in the Mapsforge/VTM/Cruiser ecosystem of libraries?

Practically speaking I have two questions:

1. What would you recommend to develop/debug map themes, which are rendered in an Android app which uses VTM? I'd like to develop these themes on macOS.
2. Can you point me to the "schema" file of MapsForge Prebuilt Maps? I'd like to see if the electric cables are missing or just renamed compared to OpenAndroMaps.

[devemux86]

What is included in Mapsforge maps depends on the tag-mapping during the map creation.
Each map provider may include different map content:

• Mapsforge tag-mapping
• OpenAndroMaps tag-mapping

To develop map themes for a map library, you can start with one of their default themes and modify it.

• Mapsforge render theme documentation
• VTM render theme documentation

VTM uses OpenGL and can read Mapsforge maps and themes.
But it uses a slightly different syntax of theme rules.

[hyperknot]

Thanks, I've developed a theme once, now I'd like to update it, to run on recent VTM versions and support MapsForge Prebuilt Maps.

This my map theme, made for paragliding pilots:
https://github.com/hyperknot/hyperpilot

I didn't know VTM has a different syntax. So if Cruiser runs on my computer, can I just use it to develop the theme? I had trouble compiling VTM playgrounds.

About the tag mapping, powerlines in particular:

OAM has this, along a bunch of other power line related bits:

<osm-tag key='power' value='line' zoom-appear='12' />
<osm-tag key='power' value='minor_line' zoom-appear='12' />

Mapsforge Prebuilt only has this:

<osm-tag key="power" value="generator" zoom-appear="17"/>
<osm-tag key="power" value="tower" zoom-appear="17"/>

Can I conclude that Mapsforge Prebuilt then has no way of displaying power lines?

[devemux86]

Desktop Cruiser does not support OpenGL anymore.

OpenGL on desktop has issues and no help to build its native libraries, for example:

• Desktop: Apple ARM support #1004

On desktop you should use VTM playground to develop themes, find it here:

• VTM playground devemux86/cruiser#743

Mapsforge maps only contain the OSM tags that exist in its tag-mapping.

[hyperknot]

Thanks, I was finally able to run VTM using your guide. I wrote about the additional steps needed for Apple Silicon macOS:
devemux86/cruiser#743 (comment)

[hyperknot]

OK, I managed to start this:

java \
  -jar vtm-playground-master-SNAPSHOT-jar-with-dependencies.jar \
  ../_old/HGT/ \
  ./hungary_oam.map

It displays the map then.

But the moment I add a theme.xml like vtm-themes/resources/assets/vtm/motorider.xml, it shows a blank page and outputs this to terminal:

Jun 16, 2025 5:50:46 PM org.oscim.gdx.GdxMap create
INFO: Type: OpenGL
Version: 2:1:0
Vendor: Apple
Renderer: Apple M1 Pro
Exception in thread "LWJGL Application" java.lang.NullPointerException: Cannot read field "boundingBox" because the return value of "org.oscim.tiling.source.mapfile.MapFileTileSource.getMapInfo()" is null
	at org.oscim.tiling.source.mapfile.MultiMapFileTileSource.getBoundingBox(MultiMapFileTileSource.java:68)
	at org.oscim.test.MapsforgeTest.createLayers(MapsforgeTest.java:121)
	at org.oscim.gdx.GdxMap.create(GdxMap.java:107)
	at com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop(LwjglApplication.java:150)
	at com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:127)

[hyperknot]

OK, I was able to solve it, by changing the order of arguments.

This is the full command which works:

export JAVA_HOME=$(/usr/libexec/java_home -v 21)

java \
  -jar vtm-playground-master-SNAPSHOT-jar-with-dependencies.jar \
    ./themes/lightpilot/lightpilot-transp.xml \
  ../_old/HGT/ \
  ./maps/hungary_oam.map

[devemux86]

@hyperknot The order of the arguments is described in the documentation:

https://github.com/mapsforge/vtm/blob/master/docs/desktop.md

[MotoUKRider]

Hello @hyperknot
I help maintain the themes that are used in "Cruiser", so have a vested interest in this topic!

Having added a "quick n dirty"declaration of power-lines in a VTM theme, I can confirm that OpenAndroMaps have them, but Mapsforge maps do not. This might be something to add to the Cruiser themes so that the basic theme "rules" make their way back to developers/tweakers like yourself - there is a similar "issue" with "Contour Lines" as they are not present within a Mapsforge map. However, we include a Layer which makes them visible with the right map provider, eg: Freiz, OAMaps.

[hyperknot]

Thank you. I'm thinking, that for the very specific use case of aircraft/pilots, it might make sense to compile a specific tag mapping for the world. A lot of the data is simply not needed (most POIs, etc.) whereas some object like power lines should be visible on even lower zoom levels compared to OAM, not only z=14.

@devemux86, in mapsforge-creator, what is your input data/script? Do you read this JSON from Geofabrik and run it for each osm.pbf?
https://download.geofabrik.de/index-v1-nogeom.json

[devemux86]

@hyperknot Mapsforge creator is open source here: https://github.com/mapsforge/mapsforge-creator

It downloads OSM data from Geofabrik and creates the maps and poi using the default tag mappings.
It uses the .poly files that are available for each region.

[hyperknot]

@devemux86 I saw that, nice project! What my question was referring to, is the $1 variables. It processes a single country.

To create the Prebuilt maps, I guess you run it through a batch file or similar, which does all countries in the world. How do you do that? Do you just parse https://download.geofabrik.de/index-v1-nogeom.json and call it in a for loop?

[devemux86]

@hyperknot There is a collection of scripts for all regions:

https://github.com/mapsforge/mapsforge-creator/tree/master/regions

[hyperknot]

@hyperknot There is a collection of scripts for all regions:

https://github.com/mapsforge/mapsforge-creator/tree/master/regions

I understand it now, thank you!