What is the decision of external and internal themes in different maps?

[ColdAutumn]

How do these external and internal themes are correctly identified?
Is it possible to cause errors?

[john_percy]

Your first picture is themes for LoMaps and version 3 Mapsforge maps, the second one is for version 4 or 5 Mapsforge maps, such as those from OpenAndroMaps. The maps identify themselves as what version they are; Locus offers the corresponding themes, which identify themselves in their header.


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[ColdAutumn]

wow...you are really a top expert. If possible, I still want to further seek help from you.
I think you still remember your reply:
https://forum.locusmap.eu/index.php?topic=7643.msg65917#msg65917

Your two themes doesn't seem to be Locus built-in, so we can write our own themes ?
Because everyone has different interests.

I really appreciate your guidance of overlay, it is really great.
Many thanks.

[john_percy]

The external themes are XML text files and can be edited by any text editor. I use Notepad++ on a PC and Quickedit on Android.
Sadly I don't think there is an overall guide to how to write a theme. I suggest you start with an existing theme and tweak it according to what you want to change.
Locus has its own help here (for its themes for LoMaps): https://docs.locusmap.eu/doku.php?id=manual:advanced:map_tools:theming
A good reference to the tags for both LoMaps and Mapsforge v4+ maps is here: https://www.openandromaps.org/en/oam-forums/topic/mapsforge-rendertheme-reference#post-2830