Share Snippet

Share / Snippet round-trip

Three ways to share a fiddle. They differ in fidelity — this is the part that bites.

Shaders travel in all three. That is the shaders skill's territory — point there, don't re-document.

The fidelity contract (the snippet codec)

SnippetExpander and SnippetReverter are exact inverses around a fixed scaffold (a FiddleGame : Game skeleton). Only what fits a SnippetModel field survives the trip; anything the scaffold can't represent is dropped. The codec is symmetric: every line the expander injects is a line the reverter must strip, or sharing-then-resharing bloats.

• Scaffold-owned boilerplate. The expander owns the constructor and a GraphicsDeviceManager graphics; field, plus the canonical method-body lines (base.Initialize/Update/Draw, GraphicsDevice.Clear(...)). The reverter strips exactly these back out (InjectedMembers set + the IsInjected* statement predicates). Keep the two sides in lockstep when editing either.
• Constructor handoff (issue #83 — the crux). A custom constructor used to be dropped outright. Now SnippetModel.Constructor carries it: when present, the expander steps aside — emits neither its own graphics field nor the default ctor and reproduces the user's verbatim. The reverter captures the ctor body only when it differs from the canonical scaffold ctor (IsScaffoldConstructor, compared on whitespace-collapsed text), so scaffold-shaped snippets stay compact. Subtlety: once a custom ctor is captured, a user field literally named graphics must be kept rather than mistaken for the injected one.
• Presets are inferred from using directives. IsGum/IsAposShapes/IsMonoGameExtended are detected on revert from the namespaces present (not stored explicitly), and each injects its members + method-body lines on expand / is stripped on revert. The flag set drives which injected lines the reverter recognizes.

Call-site gotcha (Index.razor.cs)

The SnippetModel is built field-by-field from _revertResult in two places — RecomputeSnippetPreview (the live preview URL) and CopyShareUrl (the actual copied link). A new SnippetModel field wired into only one is silently dropped from the shared URL. This nearly sank the #83 fix; grep both before adding a field.

Why these classes live in XnaFiddle.Core

The codec is browser-free so the net10.0 test project can exercise it. The test project cannot reference net10.0-browser BlazorGL (same split as the shaders skill / issue #26), so SnippetReverter/SnippetExpander/SnippetModel were moved to Core in the #83 fix. Tests: XnaFiddle.Tests/SnippetRoundTripTests.cs.

Shallow pointers (did not cause confusion — leave shallow)

• URL gzip+base64 codec: XnaFiddle.Core/UrlCodec.cs.
• &assets= and &shaders= fragments, gist import/export: Index.razor.cs fragment builders; shaders -> shaders skill.

Files