Skip to content

ADR 0046: Cockpit CDS - policy layouts (CockpitPresentationLayoutPolicy) and P/F/M invariants

Status: Accepted · Implemented
Date: 2026-04-14

ADR Role
0017 presentation, multi-window
0021 PFD/MFD Attention Model
0044 UI is not the source of truth in meaning
0047 Instrument, slots
0036 CDS → composer → surface

Implementation snapshot

Element Meaning
— P/F/M and coercion intent invariants in VM; CockpitPresentationLayoutPolicy / CASCOPE003 - see § "Solution"

Context

presentation in settings.toml specifies not only the decorative geometry, but also the semantic layout of the cockpit: where the PFD, Forward and MFD are located.

Problem before fixing the rules:

  • different inputs (menu, MCP, changing UI mode, reactive changes) changed the visibility of panels differently;
  • it was possible to get a state that contradicts the anchors of the first screen;
  • closing MfdHostWindow visually affected the layout as if the preset had changed.

This broke the cockpit model: the user saw a “floating UI” rather than a stable P/F/M scheme.

Solution

  1. The canon of rules is placed in the CDS layer: CockpitPresentationLayoutPolicy (CascadeIDE.Cockpit.Cds).
  2. The source of truth for the rules is the parsed PresentationParseResult (first screen). Static PresentationLayoutAuthority from Services/Presentation cleared; at the shell boundary, only a thin intent record remains (partial MainWindowViewModel, Apply* methods - “I want” semantics, no duplication of policy).
  3. For the first screen, the following invariants apply:
  4. if there is an anchor P, you cannot hide the left column (IsSolutionExplorerVisible);
  5. if there is an anchor M, you cannot collapse the right column of the MFD to zero (IsChatPanelExpanded = false);
  6. Forward is interpreted as a mandatory central zone; a separate explicit toggle to disable forward is not introduced.
  7. Any way to change the layout must go through the coercion policy; displaying main grid columns - through the surface composer (MainWindowShellSurfaceCompositor, ADR 0036 p.3):
  8. relay commands;
  9. MCP visibility commands;
  10. application of UI mode;
  11. reactive-callbacks properties to intercept direct assignments.
  12. Closing/opening the second TopLevel (MfdHostWindow) only changes the surface of the M-content placement, but does not recalculate the presentation semantics.

Consequences

  • The behavior of UI, MCP and modes becomes deterministic and consistent.
  • "Impossible" states do not accumulate: policy returns them to the valid area.
  • Any new commands that affect P/F/M must be consistent with the same coercion policy in CDS and not bypass the composer surface.
  • On the assembly: Roslyn CASCOPE003 (CascadeIDE.ArchitectureAnalyzers) - direct assignments IsSolutionExplorerVisible / IsChatPanelExpanded (and backing fields) outside the white list of files; new points - via Apply* / expanding the list in the analyzer.

Rejected alternatives

  • Allow each input (menu/MCP/mode) to have its own rules: causes logic drift.
  • Consider presentation only a "layout hint", and not an invariant: contradicts the cockpit model.
  • Fix only UI commands, without reactive coercion: direct assignments still bypass the rules.