proj.db access fails when embedded into the app folder and installed from MSIX

[creatio-ua]

Problem description

1. When I run my app installed to "%Program Files%", the embedded proj.db is loaded normally and everything works fine.
2. When I run the same app installed as an MSIX Windows package (inside the installed folder, the folder tree is the same), the proj.db access fails in some cases (the screenshot below hopefully explains what I mean).
3. If I copy proj\proj.db to "%LocalAppData%", it'll work even for the MSIX package installation.
4. If I set a read-only attribute to %LocalAppData%\proj\proj.db, it still works even from an MSIX package installation.

This is how it looks in case of the write access failure (see ACCESS DENIED):

And here's an example of the normal operation:

Expected Output

I don't want to overwrite the shared version of proj.db installed by some other software (into "%LocalAppData%"), and also I don't want my version to ever be overwritten. So I'd like to have a bundled version of proj.db working even when it's installed from MSIX package.

Environment Information

• OS:
  Edition Windows 11 Pro
  Version 24H2
  OS build 26100.4652

• PROJ: 9.5.1 (static lib)

• GDAL: 3.10.0 (static lib)

• libSQLite3: 3.46.0 (shared lib)

[chikle9090]

Hi, I’m trying to understand this issue.
From what I see, the problem happens because PROJ tries to open proj.db in read-write mode, but MSIX packages only allow read-only access. This causes SQLite to return ACCESS DENIED, so the bundled proj.db cannot be used inside MSIX.

I would like to work on this issue.
Could you please guide me if there is any preferred approach for opening proj.db in read-only mode in MSIX environments?

[jjimenezshaw]

@chikle9090 I am very surprised that proj.db is open in write mode. Are your sure?
BTW, since 9.6.0 you can embed proj.db (and other files next to it) in the library with a compile option: https://proj.org/en/stable/install.html#cmdoption-arg-EMBED_RESOURCE_FILES

[chikle9090]

Yes, I can confirm that the issue comes from the MSIX environment.
Inside an MSIX package, the installation directory is read-only.
When PROJ (through SQLite) tries to create journal or lock files next to proj.db, SQLite requests write access and MSIX blocks it, which results in the ACCESS DENIED error.

When the same application is installed normally, or when proj.db is placed under %LocalAppData%, everything works because the directory allows writing.

This issue is happening with PROJ 9.5.1, so the 9.6.0 embedding option is not available in this setup.

[creatio-ua]

@chikle9090 Thanks for checking this issue and confirming it.

@jjimenezshaw thank you for the idea with EMBED_RESOURCE_FILES.

I'll try to upgrade my code to 9.6.0 to see how it works with EMBED_RESOURCE_FILES option.