05 — Shell and apps (L4 / L5)¶

L4 — src/Nps.Shell¶

Shared Avalonia-adjacent helpers. No [DllImport] (the only mentions in SH/Controls/MainWindowShell.axaml.cs:6 are comments). Calls only Nps.EngineHost (NpsAbi, handles via controllers).

MainWindowShell region composition¶

3-row × 5-column MainGrid (RowDefinitions="Auto,*,Auto", MainWindowShell.axaml:13):

Shell-owned routing objects: Activity (MainWindowShell.axaml.cs:40) and Panels (:41). Pointer events on the viewport host are re-raised verbatim as ViewportPointerPressed/Moved/Released (:35-37) — the shell does no camera math. IsPlaybackTabVisible (default true, :123-131) is set to False by Slicer, which hides and never registers the playback tab.

ViewportController public API¶

All methods call NpsAbi exports; the shell never declares ABI itself.

CameraState field order is RotationXRadians, RotationZRadians, PanX, PanY, Zoom (ViewportController.cs:72-77). Overlay-mode wire ids come from NpsAbi.OverlayModeId.*; the default is motion-type (:162).

Painters (stateless sinks)¶

Both painters append to the canvas and never clear it — the app's RenderViewport clears and re-invokes them after any camera / layer / overlay / sim-index change.

Status paths: StatusSink vs StatusText¶

Two fully separate paths, written independently by each app's Status() helper (SA/MainWindow.axaml.cs:665-669 / SI/MainWindow.axaml.cs:851-858):

• Visible status bar — MainWindowShell.StatusText styled property (MainWindowShell.axaml.cs:90-97), presented in the StatusRegion.
• Process output — StatusSink.Emit (StatusSink.cs:57-62) writes "[SlicerUI] {message}" (Prefix :36) to both stdout and stderr; the smoke hook greps this stream.

L5 — Apps¶

Both apps: thin hosts. Pattern:

1. Program.Main → ABI gate + CLI preflight → Avalonia bootstrap
2. MainWindow ctor → shell chrome + EngineSession.CreateAndInitialize() + ViewportController.CreateAndInitialize() (Simulator also constructs MeshController over the session — SI/MainWindow.axaml.cs:109 — and a MeshCanvasPainter)
3. Button Load + Gen + Analyze → primary user path

App boot differences¶

Shared primary path (OnLoadAnalyzeClick)¶

Code: SA/MainWindow.axaml.cs:155 / SI/MainWindow.axaml.cs:205.

FixtureLocator.FindPrimaryBenchy3Mf()           // FixtureLocator.cs:60
  → EngineSession.LoadModel(path)               // EngineSession.cs:202
  → [Simulator] MeshController.Reload()         // MeshController.cs:131 — snapshot plates + palette
  → present plates/palette/counts in Status + MeshInfoLabel
  → GenerateDemoToolpath(GcodeGenOptions)       // EngineSession.cs:253 — DEMO TOOLPATH
  → ViewportController.SetMoves(LastMovesPointer, LastMovesCount)   // ViewportController.cs:240
  → SetLayerVisibility + SetCamera + BuildBuffers
  → Analyze(MaterialProfileOptions("PLA", 210, 60))                 // EngineSession.cs:332
  → LoadFindings()                              // 16B summary rows first
  → force thermal overlay + ApplyCurrentOverlay()
  → RenderViewport()                            // Simulator: MeshCanvasPainter underlay first (SI:732)

Status text explicitly says DEMO TOOLPATH — not a production slice (SA:315-317 / SI:313).

FixtureLocator.FindPrimaryBenchy3Mf resolution order¶

SH/FixtureLocator.cs:60-90; target PrimaryBenchyFileName = "4-colors+Benchy+AMS+test-v2.3mf" (:41), the repo-root golden fixture (1 plate / 16562 verts / 33097 tris / 4 palette colors):

1. Start at AppContext.BaseDirectory (:62); walk up to MaxWalkDepth = 12 levels (:51, :63):
2. probe dir + filename (:65-69) — return on File.Exists;
3. probe the level's parent directory (:76-80) — return on exists;
4. dir = parent (:82).
5. Fallback: BaseDirectory + "../../../../../../" + filename (:89) — the src/<App>/bin/Debug/net8.0/ → repo-root hop; may not exist, callers must check File.Exists (SA:163 / SI:213).

Slicer vs Simulator¶

Shared identically: LayerSlider + LayerLabel, all 10 ViewportToolbar event lambdas, OverlayPanel/FindingsPanel wiring + findings cache contract, camera orbit/pan handlers, Ctrl+L inspector toggle, thermal overlay forced after each load, StatusSink dual-write, shell chrome.

Neither app declares DllImport. No MVVM / no ICommand / no RelayCommand anywhere — all interaction is code-behind events. The per-app OnActivityTabClick(object?, RoutedEventArgs) handlers (SA:504 / SI:454) are dead code — tab clicks route through Activity.HandleClick → TabClicked instead.

User interactions (both)¶

• Load + Gen + Analyze button → full pipeline above
• Finding click → cached/GetFindingDetail → status + highlight (Sim: seek)
• Overlay mode → ApplyOverlay(session, mode) → re-render
• Playback (P, Sim only) → timer advances SimMoveIndex → SetSimulationState → re-render
• Pointer drag → orbit (left) / pan (other) → SetCamera → re-render. No mouse-wheel zoom anywhere — zoom is camera presets + Zoom to Fit only.

Keybindings — exact set¶

ShellKeybindings.Handle(e, actions) (ShellKeybindings.cs:82-113) handles exactly four keys, each setting e.Handled = true:

Actions is a public readonly struct (ShellKeybindings.cs:58). Anything unhandled returns false so apps can chain. The TabOverlays tooltip "Overlays (T/S/C/W)" (MainWindowShell.axaml:86) is misleading text — T/S/C/W hotkeys do not exist.

Forbidden in apps¶

• No mesh/G-code parsing
• No second ABI
• No fake golden counts — fixture file must exist

See also¶

• user-flows.md — sequence diagrams
• engine-host.md — the L3 façade these apps call
• docs/ui-shell-and-viewport.md