Hi,
I’m new to Sailfish OS, finally took the plunge last weekend and installed it. I like the nextcloud integration by default, since my whole life is organized with nextcloud (calendar, contacts, tasks, notes).
Now I do miss the tasks, and I’ve started to write an app for it. I’d like some pointers on the nextcloud calendar integration though, since ideally my app would use that to get the VTODO’s from the calendars. However, a brief excursion leads me to think that is not possible. I’ve found the dbus service org.nemomobile.calendardataservice, but looking at the code behind that it seems it does not provide the VTODO’s, and also I seem to only be able to get from that service.
I’m currently developing under the assumption that there is no way to leverage the built-in nextcloud account, and I will implement my own account mgmt and caldav interaction for now. However, if that assumption is incorrect, please do let me know!
Also, any pointers on where to find the actual nextcloud integration code and calendar could would be appreciated. I’m still finding my way around Sailfish OS. Perhaps I will consider trying to enhance the integrated nextcloud functionality to provide VTODO’s afterall.
My first baby-steps are here: https://cvs.sonologic.net/gmc/harbour-tasks, it really doesn’t do anything yet, just getting my feet wet 
It’s a project in my time off, as I do have a day job to pay the bills.
A bit of background on myself: I’ve been a software engineer for well over 20 years now, been programming one way or the other for at least 30 years. Ranging from the low level like vhdl/verilog, assembly through mid-level c/c++ and more higher level stuff like java, python, c#. I’m currently working as a software architect in the embedded space. I’m really impressed at the Sailfish project, the level of maturity it has reached without the billions of euro’s big tech can throw at such a project. There’s a lot of room for refinement though, and I’m a great believer in open source so happy to contribute.