fs-skia-scene

name	fs-skia-scene
description	Build pure scene descriptions in a generated FS.Skia.UI product.

Scene Capability

Scope

Use this skill for product code that builds pure Scene / SceneNode descriptions: HUD regions, gameplay geometry, markers, and text. Scene values are plain data — they perform no window, render, or screenshot I/O themselves.

Public Contract

The signatures you consume are bundled with this product at docs/api-surface/Scene/Scene.fsi. Read them to confirm any union case's exact field order locally — no DLL reflection needed. Prefer the self-describing constructors (Scene.filledRectangle, Scene.textAt, Scene.circle) over the positional tuple cases to avoid an arity slip.

Usage

open FS.Skia.UI.Scene

let panel = { Red = 40uy; Green = 90uy; Blue = 200uy; Alpha = 255uy }
let ink = { Red = 255uy; Green = 255uy; Blue = 255uy; Alpha = 255uy }

// A pure scene: a HUD bar plus a label. No I/O happens here.
let hud : Scene =
    Scene.group
        [ Scene.filledRectangle { X = 0.0; Y = 0.0; Width = 320.0; Height = 48.0 } panel
          Scene.textAt { X = 12.0; Y = 30.0 } "tally: 0" ink ]

Common pitfalls

• Consumer geometry records colliding with framework Point/Rect. Scene exposes Point = { X: float; Y: float } and Rect = { X: float; Y: float; Width: float; Height: float }. If your product also defines a geometry record with the same field names (a common type Vec2 = { X: float; Y: float }), F# label resolution binds a bare { X = ...; Y = ... } to whichever record type is in scope last, which produces a misleading error cascade at unrelated call sites. Disambiguate explicitly at the boundary — annotate the type or qualify the fields — and convert your record into the framework type when you call Scene:

  type Vec2 = { X: float; Y: float }                     // product geometry
  let toPoint (v: Vec2) : Point = { X = v.X; Y = v.Y }   // explicit conversion
  let p : Point = { Point.X = 0.0; Point.Y = 0.0 }       // or qualify fields inline
  

Build Commands

Run ./fake.sh build -t Dev then ./fake.sh build -t Verify in this product.

Test Commands

Run ./fake.sh build -t Test to exercise product-owned scene examples.

Evidence

Record scene and bounds evidence under this product's readiness/ paths. Do not copy framework readiness reports into the product.

Package Boundary

Scene must not reference Elmish, the viewer host, layout, or widgets. Keep host wiring in fs-skia-skiaviewer and control authoring in fs-skia-ui-widgets.

Generated Product

Scene is the base capability in every profile; build product geometry from these primitives and feed the resulting SceneNode to your View.

Persistent problems

When a problem outlasts reasonable in-repo attempts, extensive external research is mandatory — consult official online docs first (the F#/.NET docs and the driven library's own documentation/API reference), then community sources (forums, Reddit, Q&A sites, issue trackers and changelogs). Record the findings and resolving links in the feature's specs/<feature>/feedback/ folder and, for durable lessons, in this skill's Sources line. Offline, the mandate degrades to recording "research blocked — " rather than hard-failing the phase.

Related

• [[fs-skia-skiaviewer]] — render the SceneNode this skill builds at the host boundary.
• [[fs-skia-ui-widgets]] — compose higher-level controls that ultimately emit scenes.

Sources / links

• F#/.NET docs: https://learn.microsoft.com/en-us/dotnet/fsharp/
• SkiaSharp (driven render library): https://github.com/mono/SkiaSharp