Overlay Placement

Global shell overlays should be positioned against the core workspace rectangle, not blindly against the full browser viewport.

Why

When Alma is enabled, part of the browser viewport belongs to the assistant rail. Centering Switchbar, command overlays, or future modals against the full viewport makes them look visually off-center relative to the actual work area.

Core Workspace Rect

The shell marks the desktop work area with:

data-os-core-workspace

The hook useCoreWorkspaceRect reads that element and falls back to the full viewport when the workspace element is not available.

Current file:

apps/os-shell/src/shell/overlays/useCoreWorkspaceRect.ts

Current Consumers

• Prox Switchbar centers on the core workspace.
• Floating Surface stacks against the core workspace edge.
• Slidepad positions its corner panel inside the core workspace boundary.

Future Migration

Command palette, generic modal placement, app-specific command overlays, and additional app action surfaces can migrate to the same helper gradually. This should be done incrementally so existing shell dialogs do not regress.