Microsoft's Surface Duo SDK has received its first update, focused on improving the experience for early developers. As well as various bug fixes, the company has made several changes to make dual-screen development easier.
This includes additions to the DisplayMask API. It now sports a bounding rectangle relative to the display metrics based on app context. An empty list with no interaction will be returned when it's running in a single screen, while dual-screen usage will show a bounding rectangle that displays the position of the hardware hinge.
Speaking of DisplayMetrics, Microsoft has resolved some of those weird issues with the way size is reported to an app. It spotted inconsistencies in the reporting of activity, window, and display metrics, and has made similar changes for variable behavior based on single or dual-screen span. The size returned should now be appropriate to the displays an app is on.
Finally, the image refresh turns this into a USER build rather than the previous USERDEBUG. In real terms, that means devs should experience less logging and faster image access. Despite all this, ADB commands should work as usual without needing to fiddle with developer settings.
This update is marked as 02022020 and should be available to all now. Microsoft is looking for further feedback to inform its next move, which can be reported on the official forum. Microsoft doesn't say specifically, but I assume these changes will also be available to developers on macOS. You don't have to be a developer to download the Duo SDK and emulator, so you can download here to have a play.