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TwinShim

HKLM and Window Scaler wrapper

Wrapper for proxying and redirecting HKLM registry queries to local sqlite storage, and upscaling window mode renderers (mainly via dgVoodoo)

Binaries

  • twinshim.exe: GUI launcher/injector (no console window when launched from GUI tools).
  • twinshim_cli.exe: console launcher/injector (recommended for --debug from cmd/PowerShell).
  • twinshim_shim.dll: hooked registry + scaling layer.
  • hklmreg.exe: CLI for local DB add/delete/export/import/dump.

Default DB name: HKLM.sqlite (in the current directory).

Workspace switching (recommended)

Use the workspace file that matches your task:

  • TwinShim-native.code-workspace
    • macOS/Linux native development and fast unit-test iteration.
  • TwinShim-windows-mingw.code-workspace
    • Win32-target IntelliSense/cross-build on macOS/Linux. Cross-build doesn't build dgvoodoo features.

Practical flow:

  1. Work mostly in the native workspace.
  2. Switch to the MinGW workspace when editing Win32 shim/hooking code.
  3. Validate runtime behavior natively on Windows before release.

Build

This repo uses CMake presets and vcpkg (sqlite3 comes from vcpkg.json).

macOS: native hklmreg build

Build only the local hklmreg CLI on macOS (no wrapper/shim/injector targets):

cmake --preset macos-hklmreg-release
cmake --build --preset macos-hklmreg-release

Helper script:

./scripts/build-macos-hklmreg.sh

Expected artifact:

  • build/macos-hklmreg-release/hklmreg

macOS/Linux: cross-compile Windows x86 (MinGW)

Install host tools:

  • macOS: brew install cmake ninja git pkg-config mingw-w64
  • Ubuntu/Debian: sudo apt-get update && sudo apt-get install -y build-essential cmake ninja-build git curl zip unzip tar pkg-config mingw-w64

Set up vcpkg:

git clone https://github.com/microsoft/vcpkg.git ~/vcpkg
~/vcpkg/bootstrap-vcpkg.sh
export VCPKG_ROOT=~/vcpkg

Configure/build:

cmake --preset windows-x86-mingw-release
cmake --build --preset windows-x86-mingw-release

Staging output:

cmake --preset windows-x86-mingw-release-stage
cmake --build --preset windows-x86-mingw-release-stage
cmake --build --preset windows-x86-mingw-release-stage-install

Expected runtime artifacts in stage/bin:

  • twinshim.exe
  • twinshim_cli.exe
  • twinshim_shim.dll
  • hklmreg.exe

Windows native (MSVC x86)

Helper scripts:

scripts\cmake-msvc-x86.cmd --preset windows-x86-msvc-release
scripts\cmake-msvc-x86.cmd --build --preset windows-x86-msvc-release

Staging helper:

scripts\build-windows-msvc-x86.cmd

If third_party/dgvoodoo_addon_sdk is present (with Inc/Addon headers and Lib/x86/dgVoodooAddon.lib), the staging helper auto-enables the dgVoodoo AddOn build and stages SampleAddon.dll into stage/bin.

Tests

Native host tests (macOS/Linux)

cmake --preset native-tests
cmake --build --preset native-tests
ctest --preset native-tests

Native Windows tests

scripts\cmake-msvc-x86.cmd --preset native-tests-windows
scripts\cmake-msvc-x86.cmd --build --preset native-tests-windows
ctest --preset native-tests-windows

One-shot helper:

scripts\test-windows-msvc-x86.cmd

Override the base directory by setting TWINSHIM_TEST_TMP_BASE (or the legacy HKLM_WRAPPER_TEST_TMP_BASE).

This suite includes a Windows-only workflow test that launches twinshim_cli.exe --debug all around a probe process and verifies both hook debug trace output and persisted SQLite-backed registry data.

Run

Usage:
  twinshim_cli.exe [--db <path>] [--debug <api1,api2,...|all>] [--readthrough] [--scale <1.1-100>] [--scale-method <point|bilinear|bicubic|cr|catmull-rom|lanczos|lanczos3>] <target_exe> [target arguments...]

Use twinshim.exe for normal GUI-driven launches. Use twinshim_cli.exe when launching from cmd/PowerShell, especially with --debug, so the shell blocks until the wrapped process finishes.

Examples:

twinshim.exe C:\Path\To\TargetApp.exe
twinshim.exe --db .\HKLM.sqlite C:\Path\To\TargetApp.exe
twinshim.exe --readthrough C:\Path\To\TargetApp.exe
twinshim_cli.exe --debug RegOpenKey,RegQueryValue C:\Path\To\TargetApp.exe
twinshim_cli.exe --debug all C:\Path\To\TargetApp.exe

Registry virtualization scope:

  • Only HKEY_LOCAL_MACHINE paths are virtualized. Other root hives pass through to the real registry unchanged.
  • By default, HKLM reads and writes stay inside the local SQLite-backed store.
  • --readthrough changes reads to overlay mode: consult the local store first, then fall through to the real HKLM key/value data when the local store misses. Local tombstones still hide the real registry.

dgVoodoo (scaling)

This repo has two scaling approaches:

  • Shim hooks (default): best-effort surface scaling for native D3D9 and system DirectDraw paths.
  • dgVoodoo AddOn (recommended for dgVoodoo): intended path when running under dgVoodoo, where the wrapper may render through non-D3D9 backends (e.g. D3D12) and backbuffer/swapchain hooking is fragile.

When --scale is active, the injected shim also installs a small mouse-coordinate mapping layer so that client-space mouse positions and mouse messages are translated back into the app's pre-scale coordinate space. This avoids the common "cursor moves too fast / hits the edge early" symptom when the window is physically resized but the game still clamps input to its native render size.

Debugging:

  • Set TWINSHIM_MOUSE_DEBUG=1 (or legacy HKLM_WRAPPER_MOUSE_DEBUG=1) to emit limited trace output about scale mapping registration and coordinate transforms.
  • The shim remaps GetCursorPos while the cursor is inside the scaled window client area (common for games that poll cursor position instead of using WM_MOUSEMOVE).

Building the dgVoodoo AddOn DLL

  1. Unpack the dgVoodoo SDK under:
  • third_party/dgvoodoo_addon_sdk/ (expected layout includes Inc/Addon and Lib/x86)
  1. Configure with:
  • -DHKLM_WRAPPER_ENABLE_DGVOODOO_ADDON=ON
    (automatically done if using build script.)

If your SDK is in a different location or you need a different arch library path, set:

  • -DDGVOODOO_ADDON_SDK_DIR=<path>
  • -DDGVOODOO_ADDON_LIB_DIR=<path-to-Lib/x86>

The AddOn implementation scaffold lives in src/dgvoodoo_addon/addon_main.cpp.

dgVoodoo currently loads an add-on DLL only by the fixed name SampleAddon.dll, typically from the same directory as the dgVoodoo graphics DLLs. The build produces SampleAddon.dll when the add-on target is enabled.

hklmreg quick examples

hklmreg add HKLM\Software\MyApp /v Test /t REG_SZ /d hello /f
hklmreg delete HKLM\Software\MyApp /v Test /f
hklmreg export out.reg HKLM\Software\MyApp
hklmreg dump HKLM\Software\MyApp > out.reg
hklmreg import out.reg

(Optional override)
hklmreg --db .\SomeOther.sqlite dump HKLM\Software\MyApp

SQLite schema (direct DB format)

The local store uses two tables:

keys

Tracks key-level existence/tombstones.

CREATE TABLE keys(
  key_path   TEXT PRIMARY KEY,
  is_deleted INTEGER NOT NULL DEFAULT 0,
  updated_at INTEGER NOT NULL
);
  • key_path: canonical key path (for example HKLM\\Software\\MyApp).
  • is_deleted: soft-delete flag (0 active, 1 deleted/tombstone).
  • updated_at: Unix epoch seconds.

values_tbl

Stores registry values and value-level tombstones.

CREATE TABLE values_tbl(
  key_path   TEXT NOT NULL,
  value_name TEXT NOT NULL,
  type       INTEGER NOT NULL,
  data       BLOB,
  is_deleted INTEGER NOT NULL DEFAULT 0,
  updated_at INTEGER NOT NULL,
  PRIMARY KEY(key_path, value_name)
);
CREATE INDEX idx_values_key ON values_tbl(key_path);
  • value_name: empty string means the default value ((Default)).
  • type: Win32 registry type value (common: REG_SZ=1, REG_BINARY=3, REG_DWORD=4, REG_QWORD=11).
  • data: raw bytes for that type:
    • REG_SZ: UTF-16LE bytes including terminating NUL.
    • REG_DWORD: 4-byte little-endian integer.
    • REG_QWORD: 8-byte little-endian integer.
  • is_deleted/updated_at: same semantics as keys.

Deletes are modeled as tombstones (is_deleted=1) rather than hard row removal.

Direct SQLite examples

Examples below use the sqlite3 CLI directly.

Insert a REG_SZ value (Test=hello)

INSERT INTO keys(key_path, is_deleted, updated_at)
VALUES ('HKLM\\Software\\MyApp', 0, strftime('%s','now'))
ON CONFLICT(key_path) DO UPDATE SET
  is_deleted=0,
  updated_at=excluded.updated_at;

INSERT INTO values_tbl(key_path, value_name, type, data, is_deleted, updated_at)
VALUES (
  'HKLM\\Software\\MyApp',
  'Test',
  1,
  X'680065006C006C006F000000',
  0,
  strftime('%s','now')
)
ON CONFLICT(key_path, value_name) DO UPDATE SET
  type=excluded.type,
  data=excluded.data,
  is_deleted=0,
  updated_at=excluded.updated_at;

Query active values under a key

SELECT
  key_path,
  value_name,
  type,
  hex(data) AS data_hex,
  datetime(updated_at, 'unixepoch') AS updated_utc
FROM values_tbl
WHERE key_path = 'HKLM\\Software\\MyApp'
  AND is_deleted = 0
ORDER BY value_name;

Insert/query a REG_DWORD value (Flags=123)

123 decimal = 0x7B, stored little-endian as X'7B000000'.

INSERT INTO values_tbl(key_path, value_name, type, data, is_deleted, updated_at)
VALUES ('HKLM\\Software\\MyApp', 'Flags', 4, X'7B000000', 0, strftime('%s','now'))
ON CONFLICT(key_path, value_name) DO UPDATE SET
  type=excluded.type,
  data=excluded.data,
  is_deleted=0,
  updated_at=excluded.updated_at;

SELECT
  value_name,
  hex(data) AS dword_le_hex
FROM values_tbl
WHERE key_path='HKLM\\Software\\MyApp'
  AND value_name='Flags'
  AND type=4
  AND is_deleted=0;

Notes / limitations

  • Wrapper and shim DLL bitness must match target process bitness.
  • For native MSVC x86 builds, use scripts\cmake-msvc-x86.cmd (or scripts\build-windows-msvc-x86.cmd) so the Visual Studio toolchain is initialized with -arch=x86. Running CMake directly from an x64 dev shell can produce x64 binaries, which will fail to inject into x86 targets.
  • Native MSVC builds default to static runtime (/MT) via HKLM_WRAPPER_MSVC_STATIC_RUNTIME=ON to avoid conflicts with app-local MSVCP140.dll/vcruntime in injected target processes.
  • Hook mode is runtime-selectable with TWINSHIM_HOOK_MODE (or legacy HKLM_WRAPPER_HOOK_MODE):
    • default (unset) / all / full / extended: enable full ANSI + wide hook set
    • core/minimal/wide/unicode: wide-only core + legacy/key-info/enum hooks
    • off/none/disabled: inject shim but skip hook installation (diagnostics/fallback)
  • Optional windowed scaling (Direct3D9 and some DirectDraw paths) is controlled by target command-line options:
    • --scale <1.1-100>: scaling factor (e.g. --scale 2 for 2x)
    • --scale-method <point|bilinear|bicubic>: sampling method (default: point)
    • Use twinshim_cli.exe --debug (-|all) ... to see [shim:d3d9] / [shim:ddraw] probe output.
  • macOS/Linux cross-build validates compile/link only for non-dgVoodoo functionality; runtime injection/hooking must be validated natively on Windows.
  • Hooks a small set of APIs (both *W and *A where applicable):
    • Open/create keys: RegOpenKey(Ex), RegCreateKey(Ex)
    • Close key handles: RegCloseKey
    • Read/write values: RegQueryValue(Ex), RegSetValue(Ex), RegSetKeyValue
    • Delete keys/values: RegDeleteValue, RegDeleteKey (and RegDeleteKeyEx if present)
    • Enumerate/query metadata: RegEnumValue, RegEnumKey(Ex), RegQueryInfoKey
  • No ACL/security descriptor handling.
  • In --debug mode, tracing stays active for the full target process lifetime (wrapper waits for target exit).

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Wrapper for proxying and redirecting HKLM registry queries to local sqlite storage, and upscaling window mode renderers (mainly via dgVoodoo)

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