How do I use custom fields in Mantis' Roadmap?

I'd like to have an effort estimate for upcoming versions of my software in its Roadmap in Mantis Bug Tracker.

I could figure out easily 开发者_如何学运维how to add a custom fields (integer type, called "days to complete") to issues, and how to show it on the "view issues" page. But I couldn't find out how to add something to the roadmap showing the sum of days to complete for non-resolved issues.

Is there a built-in way to do this? My guess is no, that would take some php coding inside Mantis. But maybe someone did that already?

Edit: I had a look at the Time Tracking feature. It doesn't look like what I want.

The display of the Roadmap is driven by a Custom Function, which you can override in any way you see fit (and yes that means writing some PHP code, but without altering the MantisBT core).

To achieve what you want, you should override custom_function_default_roadmap_print_issue().

Please refer to the MantisBT documentation for further details.