Bug: Photo folder path not resolved correctly on Windows when using forward slashes in @project_home expression

[GvdDool]

In my current project, I have to store images in four different tables, in four different folders, and while following the documentation:
https://merginmaps.com/docs/layer/photos/#how-to-set-up-a-custom-folder-for-storing-photos
I noticed that the camera was not able to locate the folder I created and pointed to by using the following expression:
@project_home + '/photos/thema01/'
But when changing to:
@project_home + \\photos\\thema01\\
the camera finds the folder and saves the image.

Platform: Windows 10/11, QGIS desktop project synced to Mergin Maps mobile.

PHOTO_FILE stored value: When using backslashes, the file is written to the table as filename only (e.g. JPEG_20260309_....jpg), the application correctly resolves the file and shows the correct gallery based on the active theme.

Expected behaviour: The documentation examples use forward slashes but do not mention Windows path separator behaviour. Either the expression should be normalised automatically regardless of OS, or the documentation should explicitly note that Windows requires backslashes in the @project_home path expression.

[tomasMizera]

Hi @GvdDool let me transfer the issue to the mobile app repository. We'll investigate what is going on and update you.

[GvdDool]

Thanks, @tomasMizera - the behaviour is very erratic, and I have not found a reliable method across all four instances that ensures stable image capture. Happy to walk you, or the team, through my specific setup (as a test case) if that's helpful.

[GvdDool]

Update - to be more precise and identify where the workflow breaks, so you can try to reproduce the error.

I have tested many different settings and combinations, and in all configurations I tried, it's possible to create one picture. However, after syncing back to the server, it's no longer possible to save a picture to the form. You can attach an image from the gallery (meaning you can take a picture outside MM and then attach that image), but as soon as you sync to the server, the camera capture stops working. Hope this is helpful @gabriel-bolbotina (@tomasMizera).

This might still be a human error, so I am happy to learn the correct way to manage multiple images on a single record.

[Withalion]

Hello @GvdDool, we forwarded your issue to our support team. They'll reach out if they find some solution.

[GvdDool]

Thanks @Withalion, I think I have found a solution. It’s not the design I originally envisioned, but it should work for now: one table, one attachment field. It seems that having multiple attachments confuses the camera and causes it to lose the ability to save an image, even when a file (zero size) is created. I can't confirm it works yet, as I don't want to risk upsetting the project by initiating a project, syncing to the phone, then syncing back to the server, and syncing back to the phone again — as this was another instance where the camera lost its rights to save at the specified path.