openDecal/CLAUDE.md

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: Phase 6 — Verification In Progress

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 (Phases 1-5):

• 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

Phase 6 Progress:

• DecalDat: WORKING — 13/13 tests pass against real AC DAT files
• COM Registration: PASS — 50/50 CLSIDs register and verify (0 GUID mismatches)
• Tools: tools/Test-ComRegistration.ps1 — regasm + registry verification
• Tests: Managed/Decal.DecalDat.Tests/ — console app smoke tests

What's next:

• Smoke test DenAgent tray app
• Integration test — swap one DLL at a time vs original Decal
• Plugin compatibility (VTank, Mag-Tools)

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)
• Managed/Decal.DecalDat.Tests/ — Smoke tests for DAT file I/O
• tools/Test-ComRegistration.ps1 — COM registration verification (regasm + registry check)
• 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

# 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
• GenerateAssemblyInfo=False → use [assembly: InternalsVisibleTo()] attribute, not MSBuild items
• AppendTargetFrameworkToOutputPath=false → DLLs at bin\Release\, NOT bin\Release\net472\
• 32-bit regasm registers to WOW6432Node on 64-bit Windows — check both registry views
• DAT file BTree root is at offset 0x160, NOT 0x148 (old C++ code was wrong)
• BTree entries are 24 bytes (not 12) — see dat-format.md in memory

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.