FS.GG.UI.Layout 0.6.0

FS.GG.UI.Layout

Pure layout and graph scene builders for FS.GG.UI.

FS.GG.UI.Layout is one of the FS.GG.UI distribution packages — an F# / Elmish UI and 2D scene-graph framework for .NET 10 desktop, rendered through Vulkan + SkiaSharp.

Install

dotnet add package FS.GG.UI.Layout

Or scaffold a full governed project that wires the FS.GG.UI packages together:

dotnet new install FS.GG.UI.Template
dotnet new fs-gg-ui -o MyApp

Usage

open FS.GG.UI.Layout

// Stack two children into an 800x600 region.
let panel =
    Layout.verticalStack
        (Defaults.stackConfig 800.0 600.0)
        [ Defaults.child headerScene
          Defaults.child bodyScene ]

// Evaluate a node tree, then hit test the computed bounds.
let root = Defaults.layoutNode "root"
let result = Layout.evaluate (Defaults.availableSpace 800.0 600.0) root
let snap = Defaults.pixelSnapPolicy 1.0

match Layout.hitTestComputed snap result 120.0 64.0 with
| Some nodeId -> printfn "hit %s" nodeId
| None -> ()

// Build and probe a directed graph scene.
let graph =
    { Config = Defaults.graphConfig Directed 400.0 300.0
      Nodes = [ { Id = "a"; Label = "A"; Style = None }
                { Id = "b"; Label = "B"; Style = None } ]
      Edges = [ { Source = "a"; Target = "b"; Weight = None; Label = None } ] }

match Graph.layout graph with
| Ok placed -> Graph.hitTest placed 50.0 50.0 |> ignore
| Error issues -> issues |> List.iter (printfn "%A")

API at a glance

• Layout.evaluate / Layout.evaluateIncremental — compute (or incrementally recompute) a LayoutResult for a LayoutNode tree against an AvailableSpace.
• Layout.horizontalStack / Layout.verticalStack / Layout.dock — build a Scene from LayoutChild lists using StackConfig / DockConfig; measureHorizontal / measureVertical return the child LayoutBounds.
• Layout.renderComputed, Layout.snapBounds, Layout.hitTestComputed — turn a computed result into a Scene, apply a PixelSnapPolicy, and resolve a point to a LayoutNodeId.
• Layout.constraints, Layout.measureProtocol, Layout.intrinsicQuery, Layout.evaluateIntrinsic, Layout.cacheEntry, and Layout.contentExtent — Feature150's explicit constraints-down, sizes-up and intrinsic-query contract. These records expose deterministic identities and dependency keys so containers can request natural size without inspecting rendered descendants.
• Layout.initWorkflow / Layout.updateWorkflow / Layout.interpretWorkflowEffect — Elmish-style LayoutWorkflowModel / LayoutWorkflowMsg / LayoutWorkflowEffect loop for host-resize and invalidation handling.
• Graph.layout / Graph.directed / Graph.undirected — lay out or render a GraphDefinition, returning a Result with GraphValidationIssue lists on failure; Graph.hitTest resolves a point to a GraphTarget.
• GraphValidation.validate / hasCycle / disconnectedComponents — inspect a GraphDefinition for duplicate ids, missing endpoints, self-loops, cycles, and connectivity.
• Defaults — constructors for the core records (layoutNode, availableSpace, pixelSnapPolicy, stackConfig, dockConfig, graphConfig, child, plus default padding / layoutIntent / sizing).

Intrinsic Layout Protocol

Feature150 keeps Yoga as the default evaluator and adds explicit protocol records around it: parents create LayoutConstraints, participants produce MeasuredLayoutResult values with child placements, and containers that need natural sizes issue IntrinsicQuery values. Layout.contentExtent is the reference helper for fixed viewports such as ScrollViewer; it returns content width/height, max offsets, extent source, diagnostics, and dependency keys.

P8 Layout Readiness

Feature151 accepts the P8 layout bar without adding a new public surface. The readiness package under specs/151-complete-p8-layout/readiness/ records the representative corpus, invalid and fallback diagnostics, measured and intrinsic dependency identities, stale-rejection evidence, and full/incremental parity. Consumers should treat the Feature150 protocol helpers as the stable public entry points for P8 evidence.

Versioning

All FS.GG.UI.* libraries share one version and move together. In a generated project a single <FsGgUiVersion> in Directory.Packages.props pins every package — upgrading is one edit; see docs/UPGRADING.md. Pre-release versions use a -preview.N suffix.

Links

• Repository & issues: https://github.com/FS-Skia-UI/FS-Skia-UI
• License: MIT