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+# OpenDecal - Project Context
+
+## What This Is
+Open-source rebuild of **Decal**, the plugin framework for Asheron's Call.
+The original v2.9.8.3 is closed-source. This project produces a fully open-source
+drop-in replacement with identical COM interfaces and GUIDs for plugin compatibility.
+
+## Current Status: All 5 Phases Complete (Skeleton)
+
+The solution compiles with **25 C# projects, 0 errors**. Most COM server methods
+are **stubs** that need real implementations. See `docs/PLAN.md` for the full plan.
+
+### What's built:
+- **Phase 1**: 14 decompiled .NET projects (Interop.*, Adapter, FileService, DecalUtil)
+- **Phase 2**: 10 native DLLs rewritten as C# COM servers with matching GUIDs
+- **Phase 3**: C++ shims — Inject.DLL (D3D9 hooking) + LauncherHook.DLL
+- **Phase 4**: DenAgent WinForms tray app replacing the MFC original
+- **Phase 5**: WiX installer + build script
+
+### What's next (Phase 6):
+Bottom-up verification — swap one original DLL at a time with our C# version,
+test against a running AC client, fix what breaks. See `docs/PLAN.md` "Phase 6".
+
+## Key Files
+- `Managed/Decal.sln` — Main solution (25 projects)
+- `Managed/Directory.Build.props` — Shared build settings (net472, x86)
+- `Managed/Decal.Interop.*/` — COM interface contracts (the spec for everything)
+- `Native/InjectModern/` — Inject.DLL C++ source (~530 lines)
+- `Native/LauncherHookModern/` — LauncherHook.DLL C++ source (~330 lines)
+- `Native/` — Old C++ source (reference for algorithms, NOT part of the build)
+- `Installer/Package.wxs` — WiX v5 MSI package
+- `build.cmd` — Top-level build script
+- `docs/PLAN.md` — Full project plan with all phases and next steps
+
+## Build Commands
+```bash
+# Managed (.NET) — works on Linux/WSL or Windows
+dotnet build Managed/Decal.sln
+
+# Native C++ — Windows only, requires VS 2022
+cd Native
+cmake -G "Visual Studio 17 2022" -A Win32 -B build
+cmake --build build --config Release
+```
+
+## Architecture
+- **10 COM servers** (C#): DecalDat, DHS, SpellFilter, DecalInput, DecalNet,
+  DecalFilters, Decal.Core, DecalControls, DecalRender, D3DService
+- **2 native DLLs** (C++): Inject.DLL (D3D9 vtable hooking), LauncherHook.DLL
+- **1 tray app** (C# WinForms): DenAgent
+- All COM servers use `[ComVisible]`, `[Guid]`, `[ClassInterface]`, `[ProgId]`
+- Original CLSIDs preserved exactly for plugin compatibility
+
+## Common Pitfalls
+- `record` types need IsExternalInit — unavailable in net472, use class instead
+- `CollectionsMarshal.AsSpan` unavailable in net472
+- LongValueKey enum: correct names are `keyStackCount`, `keyContainer`
+- tagPOINT defined in Interop.Inject, needed by Interop.Render → add ProjectReference
+- ICommandEvents delegates ambiguous between Interop.Controls and Interop.Inject → use `using` aliases
+
+## Goal
+**Pixel-perfect drop-in replacement** for closed-source Decal v2.9.8.3,
+targeting the original AC client.exe. Existing community plugins (VTank,
+Mag-Tools, etc.) should load and work without modification.