Architecture Overview

This page describes the high-level architecture of the PadForge codebase: solution structure, project layout, design philosophy, threading model, dependencies, and build system.

Solution Structure

PadForge is a two-project .NET 8 solution:

Project	Target	Role
PadForge.App	`net8.0-windows` (WPF, WinExe)	Main application: UI, input pipeline, virtual controllers, services
PadForge.Engine	`net8.0-windows` (Class Library)	Shared data types, SDL3 P/Invoke, device wrappers, input state structures

PadForge.App references PadForge.Engine. The Engine assembly contains no WPF dependencies and is designed to be reusable.

Project Layout

PadForge.App

PadForge.App/
  App.xaml / App.xaml.cs              # Application entry, auto-elevation, global exception handling
  MainWindow.xaml / MainWindow.xaml.cs # Shell window: sidebar navigation, page hosting, event wiring
  Properties/
    AssemblyInfo.cs                   # Version, metadata (GenerateAssemblyInfo=false)

  Common/
    ControllerIcons.cs                # SVG path data for controller type icons (Xbox, DS4, vJoy)
    DriverInstaller.cs                # InstallVJoy(), UninstallVJoy() -- SetupAPI-based driver management
    HidHideController.cs              # HidHide IOCTL API: blacklist/whitelist/cloaking via \\.\HidHide
    SettingsManager.cs                # XML serialization, slot management, PadSetting defaults, profile CRUD
    StartupHelper.cs                  # Run-at-startup registry helper (HKCU\...\Run)
    VirtualKey.cs                     # Windows VK code → display name lookup table

    Input/
      InputManager.cs                 # Core partial class: fields, Start/Stop, PollingLoop, IDisposable
      InputManager.Step1.UpdateDevices.cs       # Device enumeration (SDL3 + Raw Input)
      InputManager.Step2.UpdateInputStates.cs   # Input state reading + force feedback
      InputManager.Step3.UpdateOutputStates.cs  # Mapping engine (descriptor → Gamepad)
      InputManager.Step4.CombineOutputStates.cs # Multi-device merge per slot
      InputManager.Step4b.EvaluateMacros.cs     # Macro trigger/action state machine
      InputManager.Step5.VirtualDevices.cs      # ViGEm + vJoy virtual controller lifecycle
      InputManager.Step6.RetrieveOutputStates.cs # Copy combined states for UI display
      Xbox360VirtualController.cs     # IVirtualController for ViGEm Xbox 360
      DS4VirtualController.cs         # IVirtualController for ViGEm DualShock 4
      VJoyVirtualController.cs        # IVirtualController for vJoy (direct P/Invoke)
      InputEventArgs.cs               # Event args for input state change notifications
      InputException.cs               # Custom exception for input pipeline errors
      InputExceptionEventArgs.cs      # Event args wrapping InputException

  Services/
    InputService.cs                   # Bridge between InputManager (engine thread) and UI (30Hz timer)
    SettingsService.cs                # Manages settings load/save, applies PadSettings to InputManager
    DeviceService.cs                  # Device list UI synchronization (ObservableCollection from UserDevices)
    DsuMotionServer.cs                # UDP server on port 26760 implementing DSU/Cemuhook motion protocol
    ForegroundMonitorService.cs       # Polls GetForegroundWindow at 30Hz for per-app profile switching
    RecorderService.cs                # Input mapping recorder (records physical input → assigns descriptors)
    WebControllerServer.cs              # Embedded HTTP+WebSocket server for browser-based virtual controllers

  ViewModels/
    ViewModelBase.cs                  # Base class with INotifyPropertyChanged (CommunityToolkit.Mvvm)
    MainViewModel.cs                  # Shell VM: navigation, sidebar items, profile list
    DashboardViewModel.cs             # Per-slot status cards, virtual controller status
    PadViewModel.cs                   # Per-slot mapping/settings/deadzone/macro configuration
    DevicesViewModel.cs               # Physical device list with live input visualization
    DeviceRowViewModel.cs             # Single device card in the Devices page
    SettingsViewModel.cs              # App-level settings (polling rate, driver status, etc.)
    MappingItem.cs                    # Single axis/button mapping row in the PadPage
    MacroItem.cs                      # Macro definition: trigger, actions, repeat mode, state machine
    StickConfigItem.cs                # Thumbstick dead zone / anti-dead zone / linear config
    TriggerConfigItem.cs              # Trigger dead zone / anti-dead zone / max range config
    VJoySlotConfig.cs                 # vJoy HID descriptor config: axis/button/POV/stick/trigger counts

  Views/
    DashboardPage.xaml(.cs)           # Card-based dashboard with per-slot status and 3D/2D preview
    PadPage.xaml(.cs)                 # Mapping page: axis/button mapping grid, dead zone sliders, macros
    DevicesPage.xaml(.cs)             # Physical device list with live input visualization
    SettingsPage.xaml(.cs)            # App settings: polling rate, driver install, DSU toggle
    ProfilesPage.xaml(.cs)            # Profile management: save/load/delete profiles
    AboutPage.xaml(.cs)               # Version, credits, license information
    ControllerModelView.xaml(.cs)     # 3D controller visualization (HelixToolkit viewport)
    ControllerModel2DView.xaml(.cs)   # 2D controller overlay visualization (Canvas-based)
    ControllerSchematicView.xaml(.cs) # Schematic controller diagram (vector-based)
    CopyFromDialog.xaml(.cs)          # Dialog for copying mappings from another slot
    ProfileDialog.xaml(.cs)           # Dialog for saving a new profile (name + exe list)

  Models3D/
    ControllerModelBase.cs            # Abstract base for 3D controller models (OBJ loading, part animation)
    ControllerModelXbox360.cs         # Xbox 360 3D model parts and animation bindings
    ControllerModelDS4.cs             # DualShock 4 3D model parts and animation bindings

  Models2D/
    ControllerOverlayLayout.cs        # 2D overlay positioning data (button/stick coordinates)

  2DModels/
    DS4/                              # DualShock 4 PNG sprite assets (Gamepad-Asset-Pack, MIT)
    XBOX360/                          # Xbox 360 PNG sprite assets

  3DModels/
    DS4/                              # DualShock 4 OBJ mesh files (from Handheld Companion, CC BY-NC-SA 4.0)
    XBOX360/                          # Xbox 360 OBJ mesh files

  Controls/
    RangeSlider.cs                    # Custom dual-thumb range slider control (dead zone min/max)

  Converter/
    AxisToPercentConverter.cs         # short → "N%" display string
    BoolToColorConverter.cs           # bool → SolidColorBrush
    BoolToInstallTextConverter.cs     # bool → "Install" / "Uninstall" text
    BoolToOpacityConverter.cs         # bool → 1.0 / 0.35 opacity
    BoolToVisibilityConverter.cs      # bool → Visible / Collapsed
    NormToCanvasConverter.cs          # Normalized float → Canvas pixel coordinate
    NormToTriggerHeightConverter.cs   # Trigger value → bar height
    NormToTriggerSlideConverter.cs    # Trigger value → slide offset
    NullToCollapsedConverter.cs       # null → Collapsed, non-null → Visible
    PercentToSizeConverter.cs         # Percentage → pixel size
    PovToAngleConverter.cs            # POV centidegrees → rotation angle
    StatusToColorConverter.cs         # Online/offline status → color
    StringToGeometryConverter.cs      # SVG path string → WPF Geometry
    StringToVisibilityConverter.cs    # Non-empty string → Visible, empty → Collapsed

  Resources/
    ControllerIcons.xaml              # XAML resource dictionary with controller icon geometries
    PadForge.ico                      # Application icon
    SDL3/x64/SDL3.dll                 # SDL3 native library (custom fork)
    SDL3/x64/libusb-1.0.dll           # libusb for HIDAPI backend (Switch 2 support)
    ViGEmBus_1.22.0_x64_x86_arm64.exe # Embedded ViGEmBus installer
    HidHide_1.5.230_x64.exe           # Embedded HidHide installer
    vJoyDriver.zip                     # Embedded vJoy driver files (vjoy.sys, vjoy.inf, etc.)
    vJoySetup_v2.2.2.0_Win10_Win11.exe # Optional standalone vJoy installer

  WebAssets/
    index.html                        # Landing page with Xbox 360 and DS4 layout cards
    controller.html                   # Controller UI shell (dynamic overlay layout)
    css/controller.css                # Responsive dark theme with touch-optimized zones
    js/controller_client.js           # WebSocket client, touch handling, layout renderer
    js/nipplejs.min.js                # Virtual joystick library for analog sticks

  Themes/
    Generic.xaml                      # Custom control default styles (RangeSlider)

PadForge.Engine

PadForge.Engine/
  Properties/
    AssemblyInfo.cs

  Common/
    SDL3Minimal.cs              # SDL3 P/Invoke declarations (init, joystick, gamepad, haptic, sensor)
    ISdlInputDevice.cs          # Interface: GetCurrentState(), GetDeviceObjects(), rumble
    SdlDeviceWrapper.cs         # Joystick/Gamepad open, state reading, GUID construction, haptic
    SdlKeyboardWrapper.cs       # Keyboard via Raw Input, ISdlInputDevice adapter
    SdlMouseWrapper.cs          # Mouse via Raw Input with delta accumulation, ISdlInputDevice adapter
    RawInputListener.cs         # Hidden HWND_MESSAGE window, RIDEV_INPUTSINK, per-device state
    CustomInputState.cs         # API-agnostic input snapshot: axes[24], sliders[8], povs[4], buttons[256], gyro[3], accel[3]
    CustomInputHelper.cs        # Diff computation between two CustomInputState snapshots
    CustomInputUpdate.cs        # Describes a single input change (axis delta, button press/release)
    DeviceObjectItem.cs         # Metadata for one axis/button/hat on a device (SDL GetObjects equivalent)
    DeviceEffectItem.cs         # Metadata for a force feedback effect on a device
    ForceFeedbackState.cs       # Per-device rumble management: change detection, haptic effect lifecycle
    GamepadTypes.cs             # Gamepad struct (XInput layout), VJoyRawState, Vibration, MotionSnapshot
    InputTypes.cs               # Enums: DeviceObjectTypeFlags, ObjectAspect, MapType, ObjectGuid, InputDeviceType
    VirtualControllerTypes.cs   # VirtualControllerType enum, IVirtualController interface
    RumbleLogger.cs             # Diagnostic logger for rumble/FFB debugging (disabled by default)
    InputHookManager.cs         # WH_KEYBOARD_LL / WH_MOUSE_LL hooks for mapped input suppression
    WebControllerDevice.cs      # Virtual input device from browser clients (implements ISdlInputDevice)

  Data/
    PadSetting.cs               # Per-device mapping configuration: button/axis descriptors, dead zones, vJoy mappings
    UserDevice.cs               # Physical device record: GUID, name, capabilities, runtime state
    UserSetting.cs              # Links a UserDevice (InstanceGuid) to a pad slot (MapTo) with a PadSetting

tools/

tools/
  DsuDiag/                      # Standalone DSU client for motion data diagnostics
  vJoy/
    Test/                       # vJoy axis/button/POV test tool with WinMM readback
    FfbTest/                    # SharpDX-based DirectInput FFB test tool
  capture_screenshots.ps1       # Automated screenshot capture script
  cleanup_vjoy.ps1              # vJoy device node cleanup utility
  dump_ui_tree.ps1              # WPF visual tree dump for debugging
  overlay_positions.py          # 2D controller overlay coordinate generator

Design Philosophy

SDL3-Only Input

All physical controller input (including Xbox/XInput controllers) flows through SDL3. There is no separate XInput code path for reading controller state. The native XInput P/Invoke in Step 5 (xinput1_4.dll) is used exclusively for detecting which XInput slot a newly created ViGEm virtual controller occupies — it never reads input.

Key SDL3 configuration:

SDL_SetHint(SDL_HINT_JOYSTICK_XINPUT, "1");             // Enables Xbox enumeration
SDL_SetHint(SDL_HINT_JOYSTICK_ALLOW_BACKGROUND_EVENTS, "1"); // Background input
// NEVER set SDL_HINT_JOYSTICK_RAWINPUT -- conflicts with XInput enumeration

MVVM with CommunityToolkit.Mvvm

ViewModels use ObservableObject from CommunityToolkit.Mvvm as their base class, providing [ObservableProperty] and [RelayCommand] source generators. The ViewModelBase class in the project extends this base.

Command + Event Decoupling

ViewModels expose commands and raise events. They do not directly call services or touch the input pipeline. Instead:

VMs raise events (e.g., MappingChanged, SlotAdded)
MainWindow.xaml.cs or service classes subscribe to these events
Event handlers call into InputService, SettingsService, etc.

This keeps VMs testable and decoupled from the engine thread.

No DI Container

Dependencies are wired manually as singletons in App.xaml.cs and MainWindow.xaml.cs. The typical lifecycle:

App.OnStartup()
  -> new MainWindow()
    -> Creates InputService, SettingsService, DeviceService
    -> Creates ViewModels with injected services
    -> Starts InputManager polling loop

Threading Model

PadForge uses up to five distinct threads:

1. Engine Thread (InputManager, ~1000Hz)

_pollingThread = new Thread(PollingLoop)
{
    Name = "PadForge.InputManager",
    IsBackground = true,
    Priority = ThreadPriority.AboveNormal
};

Runs the 6-step pipeline (see Input Pipeline). Uses a hybrid sleep/spin-wait loop:

>1.5ms remaining: Thread.Sleep(1) — real sleep, near-zero CPU
<=1.5ms remaining: Thread.SpinWait(1) — precise busy-wait via CPU PAUSE instructions

timeBeginPeriod(1) is set for the lifetime of the polling loop to support multimedia timer resolution across SDL, ViGEm, and the UI dispatcher.

Timing target is recalculated each cycle from the runtime-adjustable PollingIntervalMs property (default: 1ms).

2. UI Thread (WPF Dispatcher, 30Hz)

InputService creates a DispatcherTimer at ~33ms interval that:

Reads RetrievedOutputStates[] from the engine for dashboard/schematic display
Reads UserDevice.InputState for the Devices page live visualization
Pushes macro snapshots to MacroSnapshots[] for engine consumption
Updates SlotControllerTypes[], SlotVJoyConfigs[], SlotVJoyIsCustom[]

All WPF data binding occurs on this thread. Engine thread results are exposed via arrays that use atomic reference swap (Volatile.Read/write) or value copy semantics.

3. Raw Input Thread (Hidden HWND_MESSAGE Window)

public static class RawInputListener

A dedicated background thread creates a message-only window (CreateWindowExW with HWND_MESSAGE parent) and runs a GetMessageW pump. Registered for:

HID_USAGE_GENERIC_KEYBOARD with RIDEV_INPUTSINK (background capture)
HID_USAGE_GENERIC_MOUSE with RIDEV_INPUTSINK

Per-device state is tracked via RAWINPUT.header.hDevice using concurrent dictionaries. The engine thread reads this state in Step 2 via RawInputListener.GetKeyboardState() / ConsumeMouseDelta().

4. DSU Receive Thread

DsuMotionServer uses UdpClient.ReceiveAsync() on a background task to receive subscription packets from DSU clients (e.g., Cemu, Dolphin). Motion data is broadcast by the engine thread in the polling loop after Step 2.

5. Input Hook Thread (InputHookManager, on demand)

_hookThread = new Thread(() => HookThreadProc(ready))
{
    Name = "InputHookManager",
    IsBackground = true
};

Created only when devices have "Consume mapped inputs" enabled. Installs WH_KEYBOARD_LL and WH_MOUSE_LL low-level hooks and runs a GetMessageW message pump. Suppression sets (which VKeys/mouse buttons to consume) are updated via volatile reference swap from the UI thread. The thread is stopped and hooks are removed when the engine stops or hiding is disabled.

6. Web Controller Server Thread

_acceptThread = new Thread(AcceptLoop)
{
    Name = "WebControllerServer",
    IsBackground = true
};

Created when the web controller server is enabled on the Dashboard. Runs an HttpListener accept loop. WebSocket connections spawn async tasks for per-client I/O. Each connected browser client creates a WebControllerDevice (implements ISdlInputDevice) that appears in the Step 1 device enumeration pipeline. The server also handles HTTP requests for static assets (HTML/CSS/JS/PNG) and a /api/layout JSON endpoint.

Thread Safety Summary

Shared State	Written By	Read By	Sync Mechanism
`UserDevices.Items`	Engine (Step 1)	UI thread, Engine	`SyncRoot` lock
`UserSettings.Items`	UI thread	Engine (Steps 2-5)	`SyncRoot` lock
`UserDevice.InputState`	Engine (Step 2)	UI timer	Atomic reference swap
`CombinedOutputStates[]`	Engine (Step 4)	Engine (Step 5, 6)	Single-thread write
`RetrievedOutputStates[]`	Engine (Step 6)	UI timer	Value copy (struct)
`VibrationStates[]`	ViGEm callback thread	Engine (Step 2)	Volatile fields
`MacroSnapshots[]`	UI timer	Engine (Step 4b)	Atomic reference swap
`SlotControllerTypes[]`	UI timer	Engine (Step 5)	Volatile read
`MotionSnapshots[]`	Engine (polling loop)	DSU broadcast	Same thread
`RawInputListener` key/mouse state	Raw Input thread	Engine (Step 2)	ConcurrentDictionary
`InputHookManager` suppression sets	UI thread	Hook thread callbacks	Volatile reference swap
`WebControllerDevice.InputState`	WebSocket receive task	Engine (Step 2)	Atomic reference swap

NuGet Dependencies

Package	Version	Purpose
ModernWpfUI	0.9.6	Fluent Design theme for WPF (Windows 11-style UI)
HelixToolkit.Core.Wpf	2.27.3	3D viewport for controller model visualization
CommunityToolkit.Mvvm	8.2.2	MVVM infrastructure: ObservableObject, RelayCommand, source generators
Nefarius.ViGEm.Client	1.21.256	ViGEmBus client for creating virtual Xbox 360 and DS4 controllers

SDL3 is loaded via direct P/Invoke ([DllImport("SDL3")]) from SDL3Minimal.cs — there is no SDL3 NuGet package. The SDL3.dll binary is a custom fork (with Switch 2 Pro Controller support) placed in Resources/SDL3/x64/.

vJoy is loaded via direct P/Invoke ([DllImport("vJoyInterface.dll")]) with NativeLibrary.TryLoad fallback from C:\Program Files\vJoy\.

Build System

PadForge must be built with dotnet publish, not dotnet build. The publish command produces a single-file self-contained executable:

dotnet publish PadForge.App/PadForge.App.csproj -c Release

Key publish properties (from PadForge.App.csproj):

<RuntimeIdentifier>win-x64</RuntimeIdentifier>
<PublishSingleFile>true</PublishSingleFile>
<SelfContained>true</SelfContained>
<IncludeNativeLibrariesForSelfExtract>true</IncludeNativeLibrariesForSelfExtract>
<EnableCompressionInSingleFile>true</EnableCompressionInSingleFile>

Output location: PadForge.App/bin/Release/net8.0-windows/win-x64/publish/PadForge.exe

The SDL3.dll and libusb-1.0.dll are copied to the output directory via <Content> items with CopyToOutputDirectory=PreserveNewest. They are not embedded in the single-file exe — they must be adjacent to PadForge.exe at runtime.

Embedded resources (extracted at install time or runtime):

ViGEmBus_1.22.0_x64_x86_arm64.exe — ViGEmBus installer
HidHide_1.5.230_x64.exe — HidHide installer
vJoyDriver.zip — vJoy driver files (vjoy.sys, vjoy.inf, vjoy.cat, hidkmdf.sys, vJoyInterface.dll)
3DModels/**/*.obj — 3D controller mesh assets
2DModels/**/*.png — 2D controller sprite assets (included as <Resource>, not <EmbeddedResource>)

Key Static / Singleton Classes

Class	Location	Lifetime	Role
`SettingsManager`	`Common/SettingsManager.cs` + partial in Step1	Static	XML persistence, slot arrays, UserDevices/UserSettings collections
`RawInputListener`	`Engine/Common/RawInputListener.cs`	Static	Per-device keyboard/mouse input via hidden window
`RumbleLogger`	`Engine/Common/RumbleLogger.cs`	Static	Diagnostic logger (disabled by default, `Enabled=true` to activate)
`InputManager`	`Common/Input/InputManager.cs`	Singleton instance	Polling loop, 6-step pipeline, virtual controller lifecycle
`InputService`	`Services/InputService.cs`	Singleton instance	UI↔Engine bridge, 30Hz timer, macro snapshot push
`SettingsService`	`Services/SettingsService.cs`	Singleton instance	Settings load/save, PadSetting application

Slot System

PadForge supports up to 16 virtual controller slots (MaxPads = 16). All three output types share this global limit (MaxXbox360Slots = MaxDS4Slots = MaxVJoySlots = 16). There is no per-type cap.

The "Add Controller" button disappears when all 16 slots are in use.

API visibility note: The XInput API can only address 4 controllers (slots 0-3). Xbox 360 virtual controllers beyond the first 4 still function but may not be visible to XInput-only games. Games using DirectInput, SDL, or raw HID can see all 16. DualShock 4 and vJoy controllers are not affected by the XInput limit.

Per-slot state arrays in SettingsManager:

public static bool[] SlotCreated;   // Slot exists in config
public static bool[] SlotEnabled;   // Slot is active (user toggle)

Per-slot state arrays in InputManager:

public Gamepad[] CombinedOutputStates;          // Step 4 output
public VJoyRawState[] CombinedVJoyRawStates;    // Step 4 output (custom vJoy)
public Gamepad[] RetrievedOutputStates;          // Step 6 output (UI display)
public Vibration[] VibrationStates;              // ViGEm feedback
public MotionSnapshot[] MotionSnapshots;         // DSU motion data
public MacroItem[][] MacroSnapshots;             // Macro definitions
public VirtualControllerType[] SlotControllerTypes;  // Configured type
internal VJoyVirtualController.VJoyDeviceConfig[] SlotVJoyConfigs;  // vJoy HID config
internal bool[] SlotVJoyIsCustom;                // Custom vs gamepad preset

Architecture Overview

Architecture Overview

Solution Structure

Project Layout

PadForge.App

PadForge.Engine

tools/

Design Philosophy

SDL3-Only Input

MVVM with CommunityToolkit.Mvvm

Command + Event Decoupling

No DI Container

Threading Model

1. Engine Thread (InputManager, ~1000Hz)

2. UI Thread (WPF Dispatcher, 30Hz)

3. Raw Input Thread (Hidden HWND_MESSAGE Window)

4. DSU Receive Thread

5. Input Hook Thread (InputHookManager, on demand)

6. Web Controller Server Thread

Thread Safety Summary

NuGet Dependencies

Build System

Key Static / Singleton Classes

Slot System

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