Function resolved_surface_mode 

pub fn resolved_surface_mode() -> ResolvedSurfaceMode

Read the resolved surface mode — ResolvedSurfaceMode::Unknown until a shell publishes one (no surface yet, or a shell with no Mode B seam, e.g. the desktop preview).

A poll, not a subscription: reading this never wakes a frame, and a change here never marks anything dirty on its own. Read it during a rebuild (the same place theme_override-style process-global state is read) and branch; see the module docs’ The RESOLVED slot for the full contract.