In particular: mus/ozone displays need to be reconfigurable once they have been created.

kylechar@: fixing this would benefit/require your CL to make the window resizable.

The PlatformWindow for Ozone X11 is resizable? You can currently drag and resize it. Nothing at a higher level than the PlatformWindow is listening to that resize so mash doesn't resize the content inside the window. 

It's ash::DisplayManager and ui::DisplayConfigurator that handle resizing the window now I believe? Those classes don't exist as part of mus though. There is a very different mus::ws::DisplayManager.

Is there a design doc for PlatformScreen? If not, what is the interaction between mus::ws::PlatformScreen, mus::ws::DisplayManager and ui::NativeDisplayDelegate supposed to look like?

Actually, I take that back that window resizing isn't hook up with mash. It sort of works, some of the time.

When the X11WindowOzone is resized it triggers mus::ws::DefaultPlatformDisplay::OnBoundsChanged, which calls mus::ws::Display::OnViewportMetricsChanged which updates sizes of various sub windows. It's just very buggy.

There isn't a design doc for PlatformScreen but I plan on writing one for display management.

I attempted to resize the X11 window and things didn't work as desired: it resized and painted but events stopped being delivered.

ScreenManager has functionality to add/remove/configure displays. I think this can be closed and any further changes to configure displays falls under https://bugs.chromium.org/p/chromium/issues/detail?id=686848.