TileLayer on IOs phones "breaks" and don't show parts when you zoom in/out multiple times [BUG]

[fabionfd]

What is the bug?

I download some zip files, unzip them on the phone and use it to source some TileLayers on my app, I use the same pattern of {z}-{x}-{y} but locally so the layers will work offline. When you zoom in and out the Layers starts to bug and don't show correctly as it does on Android. I've upgraded to the last version(4.0.0) and the bug persists, and only occurs on IOs phones(just tested on android and ios phones).

How can we reproduce it?

In my usecase I have up to 8 local tilelayers showing at once, it's quite simple to reproduce, just zoom in and out several times on an iphone and the layers start to lose some parts. I couldn't reproduce it on ios emulator so you need a real device to see the bug.

              String url = '';
              url = "${dir.path}/{z}-{x}-{y}.sigma";
                layers.add(
                  TileLayer(
                    maxNativeZoom: 15,
                    tileProvider: FileTileProvider(),
                    urlTemplate: url,
                    tms: true,
                    backgroundColor: Colors.transparent,
                  ),
                );

this is a sample of a tile that I use on my app, it's inside a for loop for each of the directories of tiles.
I don't know if I could be clear but if you can't undestant something just ask me and I can provide more context to the problem, also I'm not a native english speaker so, sorry about any mistakes of that sort.

Do you have a potential solution?

No response

Platforms

IOs 16.4.1(but other versions seems to have the same problem)

Severity

Obtrusive: Prevents normal functioning but causes no errors in the console

[JaffaKetchup]

Hi @fabionfd,

This sounds like the OS restricting the number of files openable at once, especially as you are using 8 file tile layers.

Can you try executing ulimit -S -n 2048 in a console in your app directory, then running normally? You can also try increasing that number if 2048 doesn't appear to have an effect.
This used to be a part of this library's much older README, but we removed it because I assumed it was out of date. Original source from Flutter SDK: flutter/flutter#18225.

[fabionfd]

Hi, thanks for the quick reply!

Definitely there are more than 2048 files in the directoriesof the tiles( I use zoom 9 to 15 and the files are all inside the same folder for each tile), but I could not quite understand how, or where, to execute this ulimit command, can you give me a little guidance? Just open the terminal and type it at the app folder?

[JaffaKetchup]

No problem.
I don't think it matters how many tiles total there are, I think that's just the number of open file handlers that can be alive at once.
You should just be able to open up the app folder, open a terminal in it, then run that (on a Mac I guess). Never tried it before, so not 100% sure.

[fabionfd]

I've tried the method but it only increases the amount of open file handlers within mac, the problem is occuring on the Iphones that installed the app from the store. Even with only one tile enabled the problem still happens, I'd need to change this config on the project itself, or something like that. Funny thing is that it don't occur inside emulators, neither ios and android(my guess is that the PC/Mac/Android have more handlers than IOs phones, if that is the problem), and don't occur on Android devices too.

[fabionfd]

I've published a video of the bug, so you can better understand the problem. In the video there are 3 tiles enabled, but we tested with only one, and the problem happens too

https://veed.io/view/c0ee51e6-85ca-401a-b740-7c86ced45cb6

[JaffaKetchup]

Unfortunately, I'm not really sure what can be done here then. We can't bypass OS restrictions!

[mohammedX6]

I had this problem before, if i kill the app the problem goes away but it will come back

[fabionfd]

Well, this is very odd but after I comment my openstreet layer the bug didn't happen anymore, even with several of my own layers active.

TileLayer(
  urlTemplate:
  'https://tile.openstreetmap.org/{z}/{x}/{y}.png',
  userAgentPackageName: 'blabla',
),

[mohammedX6]

So OpenStreetMap causing this problem !!
This is very strange

[ibrierley]

Isn't that just because you are removing a layer, hence less tiles loaded ? (I may be misunderstanding tho)

[JaffaKetchup]

Closing for now due to lack of information and some discussion on a similar matter on the Discord server. We're still keeping an eye on this!

[fabionfd]

Isn't that just because you are removing a layer, hence less tiles loaded ? (I may be misunderstanding tho)

I think you are right, the bug happened again. there are just too many files open I guess.

[mohammedX6]

I am able to fix the issue by setting bounds to the tile layer, so unnecessary tiles don't strain the file OS