[Script] Any hint on how to change the game's popup message on new routes, ONLY the first time you step on that route?

[EduEpsilon]

The game saves which locations have we discovered and which ones we haven't, since you can see them in the map. Where can I find this data? And how could I use it to add some text to the popup with the route name only the first time you enter in the route? For example, the first time you enter un route 1, I want the game to show the popup saying 'Route 101 *New location discovered*', and from that point, it should always say 'Route 101'.
Any hint on how to achieve this? I was thinking that this could be a good way to tell the player when can they capture a pokemon in a nuzlocke for example, just in case they forgot which routes have they already visited.

 

[Lunos]

The game saves which locations have we discovered and which ones we haven't, since you can see them in the map.

The game sets flags as soon as you enter each town/city you can fly to by using a map script. That's how it tracks which flight points the Player should be able to use.
https://github.com/pret/pokeemerald/blob/master/include/constants/flags.h#L1364-L1380
https://github.com/pret/pokeemerald/blob/master/data/maps/LittlerootTown/scripts.inc#L42-L43
https://github.com/pret/pokeemerald/blob/master/data/maps/OldaleTown/scripts.inc#L9-L11
https://github.com/pret/pokeemerald/blob/master/src/region_map.c#L1178-L1223
https://github.com/pret/pokeemerald/blob/master/src/region_map.c#L1956-L1970

You could define new flags in include/constants/flags.h (note that this is a savefile breaking change) for each map and set them in the same manner.
By default, there's 120 bytes in the SaveBlock1 where the flags are also stored, which is enough space to add 960 flags to use as you please, not to mention there a handful of unused flags you can also use.

And how could I use it to add some text to the popup with the route name only the first time you enter in the route? For example, the first time you enter un route 1, I want the game to show the popup saying 'Route 101 *New location discovered*', and from that point, it should always say 'Route 101'.
Any hint on how to achieve this? I was thinking that this could be a good way to tell the player when can they capture a pokemon in a nuzlocke for example, just in case they forgot which routes have they already visited.

Well, for that, you'll probably need to do some code changes involving the src/map_name_popup.c file.
Unfortunately, I can't give you hints on that myself, but I imagine you have to create a window inside ShowMapNamePopUpWindow and fill it with content in the same manner the map name popup itself is made.

 

[EduEpsilon]

Thanks! That's a lot of info! I'll look into it