# Gum Runtime Topology > Gum Runtime Topology - Skill: `vchelaru/gum-runtime-topology` (Agent Skill) - Install (CLI): `npx skillmds@latest add vchelaru/gum-runtime-topology` - Raw SKILL.md: https://api.skillmd.com/api/skills/vchelaru/gum-runtime-topology/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: vchelaru (https://skillmd.com/u/vchelaru) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/vchelaru/gum-runtime-topology --- # Gum Runtime Topology Gum has **no single "runtime" assembly**. The same `RenderingLibrary.*` / `GumCommon` source is compiled into many assemblies via three different source-sharing mechanisms, and is also consumed by FlatRedBall (FRB), a **separate repo**. A refactor that builds clean in `AllLibraries.sln` can still break the WPF runtime or FRB. Before moving/renaming/deleting any shared file, check it against every surface below. > FRB is a separate git repo, but Gum and FRB are always checked out side by side (`GitHub/Gum` and `GitHub/FlatRedBall`), so `../FlatRedBall/...` reaches FRB from the Gum repo root. ## Compilation surfaces — rebuild/verify ALL for a runtime-level refactor | Surface | What it is | Notes | |---|---|---| | `AllLibraries.sln` | All render backends + `GumCommon` + shapes + themes + CLI + ProjectServices + tests | **Must compile on Mac**, so it EXCLUDES Windows-only projects. The broad verify command — but not complete. | | `Runtimes/SkiaGum.Wpf/SkiaGum.Wpf.csproj` | WPF host for the Skia runtime | **NOT in AllLibraries** (WPF can't build on Mac). Build separately on Windows. The single easiest runtime to forget. | | `GumFull.sln` | The Gum tool (KNI-based) + plugins | Tool work; `$(SolutionDir)` post-builds require the solution, not a bare csproj. | | `GumCoreShared.shproj` | Gum-side shared project (imports `GumCoreShared.projitems`) | Source-shares Gum core into FRB. The file lists live in the `.projitems`. | | `../FlatRedBall/FRBDK/Glue/GumPlugin/GumPlugin/GumCoreShared.FlatRedBall.shproj` | FRB-side core consumer | FRB multi-targets down to **net6.0** — gate net7+ BCL APIs. | | `../FlatRedBall/Engines/Forms/FlatRedBall.Forms/FlatRedBall.Forms.Shared/FlatRedBall.Forms.Shared.shproj` | FRB-side Forms consumer | Picks up `MonoGameGum/Forms/**` files individually; new/renamed Forms files must be registered here. | ## Render backends XNA-family (`MonoGameGum`, `KniGum`, `FnaGum`), `RaylibGum`, `SkiaGum` (+ hosts `SkiaGum.Maui`, `SkiaGum.Wpf`), `SokolGum`. For the per-runtime file-sharing/unification pattern see [gum-cross-platform-unification](../gum-cross-platform-unification/SKILL.md). ### Shapes are NOT MonoGame/Skia-only — no backend is the outlier Shape runtimes (`RectangleRuntime`/`CircleRuntime` — corner radius, two-slot fill/stroke, drop shadows, dashed strokes, gradients) are **unified across all backends, and every backend reaches full capability** via its recommended renderable; only the contained renderable differs: | Backend | Contained renderable (recommended path) | |---|---| | raylib / Sokol | `LineRectangle` / `LineCircle` | | Skia | `RoundedRectangle` (#2818) | | XNA-family **+ Apos.Shapes** (`MonoGameGumShapes`/`KniGumShapes`, recommended) | Apos `RoundedRectangle` | | XNA-family, no Apos | `SolidRectangle`+`LineRectangle` split — degraded fallback, no real radius/shadow | The no-Apos XNA split is a **degraded fallback, not a separate tier or an outlier**. Two traps that produced wrong conclusions here: - ⚠ **Don't infer capability from type names.** raylib's `LineRectangle`/`LineCircle` are full filled + rounded + drop-shadowed shapes (they mirror Apos/Skia — see the `` in `Runtimes/RaylibGum/Renderables/`), despite the outline-suggesting names. A directory listing is not the API surface — read the renderable. - ⚠ The `MonoGameGumShapes`/`KniGumShapes` ↔ `SkiaGum` **"pair"** (in [gum-cross-platform-unification](../gum-cross-platform-unification/SKILL.md)) is only a *source-sharing* link for the **Apos-specific** `RoundedRectangleRuntime`/`ColoredCircleRuntime` types — **not** a claim that shape support is MonoGame/Skia-only or that raylib lacks it. Consequence for themes: a rounded/shadowed theme's visual code (`new RectangleRuntime { CornerRadius = …, HasDropshadow = … }`) is portable to raylib at the type level — the shape layer is a non-issue. ## Three source-sharing mechanisms (each is a separate landmine) 1. **GumCommon project reference.** `GumCommon` is the runtime-agnostic core (net8.0, no XNA/WPF). It cherry-picks files from `RenderingLibrary/`, `GumDataTypes/`, `ToolsUtilities/` via `` **and globs its own folder**. MonoGame/Raylib/Skia/Sokol reference it as a project. 2. **Cross-project file links.** `GueDeriving` runtimes are canonical in `MonoGameGum/GueDeriving/` and ``-ed into the Raylib/Skia/Sokol csprojs. These are **deliberately excluded** from `GumCoreShared.projitems` (FRB generates its own runtime classes). 3. **FRB shared projects** (the two `../FlatRedBall/...shproj` above) — source-sharing for an out-of-repo consumer on a net6 floor. ## Landmines - **`RenderingLibrary` is not a built assembly.** It's a source directory distributed by links/projitems, so `RenderingLibrary.*` types exist in *several* compiled assemblies at once. - **Same-FQN forks.** Because of the above, two files can define the same `RenderingLibrary.X` type for different consumers and silently diverge. Confirmed example: `GumCommon/Content/LoaderManager.cs` (XNA-free; used by every GumCommon-referencing runtime) vs `RenderingLibrary/Content/LoaderManager.cs` (XNA-coupled — `InvalidTexture`, `Initialize`, `LoadOrInvalid`; compiled only by `GumCoreShared.projitems` + FRB `GumPlugin.csproj`). Editing one does not touch the other; placing both in one compilation is a duplicate-type error. - **Moving a file between a glob'd folder and a linked location requires a csproj edit.** GumCommon and the runtime projects glob their own folders; external shared files are explicit links. (E.g. relocating the shared `LoaderManager` into `GumCommon/Content/` meant dropping its explicit `` link and removing SkiaGum's ``.) - **projitems / Forms / net6 sync.** Adding/renaming/deleting files under `GumCommon/` or `MonoGameGum/` (and Forms files) has sync obligations to the FRB shared projects, with explicit exceptions (the LoaderManager fork, `GueDeriving`). These rules are authoritative in the coder agent (`.claude/agents/coder.md`) — follow them there, don't restate. ## Cross-references - [gum-cross-platform-unification](../gum-cross-platform-unification/SKILL.md) — per-runtime file unification (`#if`/links). - `.claude/agents/coder.md` — projitems/Forms/net6 sync rules (authoritative).