komorebi/docs/dev/backend-switch.md

Windows: which call sites go through backend()

Step 8 of the unified-binaries plan. komorebi::windows_backend::backend() returns the shared komorebi_backend::Backend (a stateless WindowsBackend over WindowsApi and Window). The daemon is switched one cluster at a time; each switch is its own revision marked BEHAVIOUR.

What every switched call changes in the Windows daemon: WindowsBackend first asks IsWindow and fails with Error::WindowGone for a dead window (hide, restore, minimize, maximize and the other () returning operations are then skipped: before, Window::hide of a dead window still ran ShowWindow on it, a no-op, and recorded its handle in HIDDEN_HWNDS), and a failure of a window that died meanwhile is reported as WindowGone (the error text changes from the Win32 one). Call sites use ? or ignore the result; none inspects the error. frame is the exception: it does not ask IsWindow first, so the Win32 error is what callers get.

Switched

Cluster	Operation	Sites	Notes	e2e needed
focus	focus(id, mouse_follows)	40 (process_event, process_command, workspace, window_manager, focus_manager, stackbar)	animation/transition.rs calls Window::focus from the slide-in code Window::focus defers to: left	commands, focus, focus_follows_mouse, stacking, workspaces, lifecycle
frame write	set_rect(id, rect)	2 (workspace layout update, stackbar tab click)	top = false only	commands, resize, layouts, stacking, scrolling, workspaces
frame read	frame(id)	about 55, one revision per file: stackbar_manager (2 files), animation (snapshot, ghost_dispatcher, ghost test), live_resize, pan, scrolling, process_command, process_event, window_manager, border_manager (2 files)	frame is a provided method added to the trait for this (WindowsBackend: Window::window_rect, one DWM call; error kept). Window::window_rect/WindowsApi::window_rect remain only inside window.rs (the implementation, and Window::set_position/move_to_area/center/focus internals)	resize, layouts, stacking, scrolling, borders, animation, commands, lifecycle
hide / show	hide, restore (plain forms)	23		commands, workspaces, stacking, lifecycle_hidden
hide / show	minimize, close, raise	1 + 1 + 4 (process_command), 4 minimize (monitor_reconciliator)		commands, monitor reconciliation, lifecycle
maximize	maximize(id, bool)	5 (workspace.rs)	capability query already in the trait (supports(Capability::Maximize), true here)	maximizing, commands, workspaces

Left on purpose (platform-owned subsystems, seam.md rule 5)

• set_position(.., true) (window.rs move_to_area, center, workspace maximize area): the raise-to-front flag is a Windows detail of the layout/animation code, the shared set_rect has none.
• hide_with_border, restore_with_border: borders are a platform subsystem (own windows and threads).
• animation/transition.rs, animation/ghost*.rs (except the frame reads above): the DWM ghost and slide-in machinery.
• set_opacity: the adapter writes the plain alpha, Window::transparent/opaque take the alpha from the transparency manager and animate.

Not switched, and what the trait would need (for step 9)

Operation	Why it stays on the platform API	What the trait would need
foreground_window	WindowsApi::foreground_window() -> Result<isize>: a null handle is an Err whose message callers pass on; the trait has Option<WindowId>	a Result variant (Error::Platform for "no foreground window"), or accept losing the message
cursor_pos	Result<POINT> vs Option<(i32, i32)>; callers ? it	same: a Result return
monitors / window	monitors() rebuilds MonitorInfo and drops the Monitor fields the daemon needs (device id, serial, device, work-area offsets); window() asks title, class, exe, path	the daemon-side Monitor fields in MonitorInfo (or a platform extension), and for step 9 the monitor model moving to the core
monitor_from_point	never None on Windows (MONITOR_DEFAULTTONEAREST), None outside every monitor on KDE and macOS	an explicit "nearest" flag or two methods

What is left in window_manager.rs, workspace.rs, monitor.rs (checked call by call)

Switched in the last batch: center_cursor_in_rect (3, window_manager), disable_focus_follows_mouse (1), restore_window as unminimize (1, workspace). The rest names WindowsApi for a reason the trait does not cover yet:

Call (sites)	Why it stays
foreground_window (10 in window_manager, 3 workspace, 1 monitor)	Result<isize>, a null handle is an Err the callers ? on; trait has Option<WindowId>
cursor_pos, window_at_cursor_pos, monitor_from_window, monitor_from_point	Result/never-None semantics, see the table above; window_at_cursor_pos and monitor_from_window have no trait equivalent
raise_and_focus_window(desktop_window) (4)	Backend::focus is Window::focus, which skips when the window is already foreground and defers while it slides in; the direct call always raises and focuses
position_window(hwnd, rect, false, true) (2)	a different flag combination than set_rect (top = false, the second flag is the layered/shadow handling), not expressible
load_monitor_information, load_workspace_information	start-up enumeration into a WindowManager; seam.md 9: windows() cannot match the core's filter
monitor(hmonitor), monitor_rects, monitors_have_same_dpi	the Monitor fields (device id, DPI) the trait's MonitorInfo drops
set_wallpaper	wallpaper stays KDE-only in the trait (D36)
focus_follows_mouse (query)	the trait has the setter only