PowerToys Runner

Overview

The PowerToys Runner is the main executable (PowerToys.exe) that serves as the host process for all PowerToys modules. It manages module lifecycle, hotkey registration, the system tray icon, and communication with the Settings UI.

Core Responsibilities

┌─────────────────────────────────────────────────────────┐
│                   PowerToys Runner                      │
│                                                         │
│  ┌───────────────────────────────────────────────┐    │
│  │  Tray Icon & Menu                             │    │
│  │  • Right-click menu                           │    │
│  │  • Left-click (Quick Access Flyout)           │    │
│  │  • Double-click (Settings Dashboard)          │    │
│  └───────────────────────────────────────────────┘    │
│                                                         │
│  ┌───────────────────────────────────────────────┐    │
│  │  Module Manager                               │    │
│  │  • Load DLLs from modules/ folder             │    │
│  │  • Call powertoy_create() on each             │    │
│  │  • Track enabled/disabled state               │    │
│  │  • Apply GPO policies                         │    │
│  └───────────────────────────────────────────────┘    │
│                                                         │
│  ┌───────────────────────────────────────────────┐    │
│  │  Centralized Keyboard Hook                    │    │
│  │  • Low-level keyboard hook (WH_KEYBOARD_LL)   │    │
│  │  • Hotkey registration per module             │    │
│  │  • Performance optimizations                  │    │
│  │  • Dispatch to module on_hotkey()             │    │
│  └───────────────────────────────────────────────┘    │
│                                                         │
│  ┌───────────────────────────────────────────────┐    │
│  │  Settings Bridge                              │    │
│  │  • Named pipe IPC to Settings UI              │    │
│  │  • JSON message protocol                      │    │
│  │  • Configuration dispatch to modules          │    │
│  └───────────────────────────────────────────────┘    │
│                                                         │
│  ┌───────────────────────────────────────────────┐    │
│  │  Update Management                            │    │
│  │  • Check for updates                          │    │
│  │  • Download and install                       │    │
│  │  • Restart coordination                       │    │
│  └───────────────────────────────────────────────┘    │
└─────────────────────────────────────────────────────────┘

Initialization Sequence

The Runner follows a specific initialization order to ensure all components are ready before modules are enabled.

1. Process Initialization

// From src/runner/main.cpp:181-200
int runner(bool isProcessElevated, bool openSettings, 
           std::string settingsWindow, bool openOobe, 
           bool openScoobe, bool showRestartNotificationAfterUpdate)
{
    Logger::info("Runner is starting. Elevated={}", isProcessElevated);
    
    // Enable DPI awareness for proper scaling
    DPIAware::EnableDPIAwarenessForThisProcess();
    
    // Register telemetry provider
    Trace::RegisterProvider();
    
    // Load settings from file before reading them
    load_general_settings();
    auto const settings = get_general_settings();
    
    // ...
}

Reference: src/runner/main.cpp:181

2. Tray Icon Startup

// Start the system tray icon
start_tray_icon(isProcessElevated, settings.showThemeAdaptiveTrayIcon);

// Enable Quick Access flyout if configured
if (settings.enableQuickAccess) {
    QuickAccessHost::start();
}

Reference: doc/devdocs/core/runner.md:37-65

3. Module Loading

// From src/runner/main.cpp and powertoy_module.cpp

// Scan for module DLLs in the modules/ directory
std::vector<std::wstring> module_paths = get_module_paths();

for (const auto& path : module_paths) {
    // Load the DLL
    HMODULE module_dll = LoadLibraryExW(path.c_str(), nullptr, 
                                        LOAD_WITH_ALTERED_SEARCH_PATH);
    
    if (!module_dll) {
        Logger::error(L"Failed to load module: {}", path);
        continue;
    }
    
    // Get the powertoy_create function
    auto create_func = reinterpret_cast<powertoy_create_func>(
        GetProcAddress(module_dll, "powertoy_create")
    );
    
    if (!create_func) {
        Logger::error(L"Module missing powertoy_create: {}", path);
        continue;
    }
    
    // Create the module instance
    PowertoyModuleIface* module = create_func();
    
    if (!module) {
        Logger::error(L"powertoy_create returned null: {}", path);
        continue;
    }
    
    // Store the module
    std::wstring key = module->get_key();
    modules[key] = std::make_unique<PowertoyModule>(module, module_dll);
}

Reference: src/runner/powertoy_module.cpp:13-24

4. Settings Application

// Load module-specific settings and apply GPO policies
for (auto& [name, module] : modules) {
    // Check GPO policy
    auto gpo_policy = module->gpo_policy_enabled_configuration();
    
    if (gpo_policy == powertoys_gpo::gpo_rule_configured_disabled) {
        Logger::info(L"Module {} disabled by GPO", name);
        continue;
    }
    
    // Load settings from file
    auto settings_file = get_module_settings_path(name);
    if (std::filesystem::exists(settings_file)) {
        auto config = load_json_file(settings_file);
        module->set_config(config.c_str());
    }
    
    // Enable if configured
    if (module->is_enabled() || 
        gpo_policy == powertoys_gpo::gpo_rule_configured_enabled) {
        module->enable();
    }
}

Reference: doc/devdocs/core/runner.md:130-138

5. Keyboard Hook Registration

// Initialize low-level keyboard hook
start_lowlevel_keyboard_hook();

// Register hotkeys from all modules
register_hotkeys();

Reference: doc/devdocs/core/runner.md:120-128

System Tray Icon

The system tray icon is the primary UI element of the Runner, providing quick access to settings and module controls.

Implementation

// From src/runner/tray_icon.cpp

void start_tray_icon(bool is_elevated, bool theme_adaptive_icon)
{
    // Create notification icon data
    NOTIFYICONDATAW nid = {};
    nid.cbSize = sizeof(NOTIFYICONDATAW);
    nid.hWnd = tray_icon_hwnd;
    nid.uID = tray_icon_id;
    nid.uFlags = NIF_ICON | NIF_MESSAGE | NIF_TIP;
    nid.uCallbackMessage = WM_ICON_NOTIFY;
    nid.hIcon = LoadIcon(hinstance, MAKEINTRESOURCE(APPICON));
    wcscpy_s(nid.szTip, L"PowerToys");
    
    // Register with system tray
    Shell_NotifyIconW(NIM_ADD, &nid);
    
    // Register for taskbar recreate message
    // (to restore icon after explorer.exe restart)
    wm_taskbar_created = RegisterWindowMessageW(L"TaskbarCreated");
}

Reference: doc/devdocs/core/runner.md:49-56, src/runner/tray_icon.cpp

Window Procedure

LRESULT CALLBACK tray_icon_window_proc(HWND hwnd, UINT msg, 
                                       WPARAM wparam, LPARAM lparam)
{
    switch (msg)
    {
    case WM_ICON_NOTIFY:
        switch (lparam)
        {
        case WM_LBUTTONUP:
            // Single left-click: Show Quick Access flyout
            on_tray_icon_left_click();
            break;
            
        case WM_LBUTTONDBLCLK:
            // Double left-click: Open Settings Dashboard
            open_settings_window(ESettingsWindowNames::Dashboard);
            break;
            
        case WM_RBUTTONUP:
            // Right-click: Show context menu
            show_tray_icon_menu();
            break;
        }
        break;
        
    case WM_COMMAND:
        // Handle menu item selections
        handle_menu_command(LOWORD(wparam), lparam);
        break;
    }
    
    return DefWindowProc(hwnd, msg, wparam, lparam);
}

Reference: doc/devdocs/core/runner.md:57-61

Tray Icon Actions

Left Click - Quick Access Flyout:

void on_tray_icon_left_click()
{
    if (!settings_window) {
        return;
    }
    
    // Get tray icon position for flyout placement
    POINT cursor_pos;
    GetCursorPos(&cursor_pos);
    
    // Send IPC message to Settings UI
    json::JsonObject message;
    message.SetNamedValue(L"ShowYourself", json::value(L"flyout"));
    message.SetNamedValue(L"x_position", json::value(cursor_pos.x));
    message.SetNamedValue(L"y_position", json::value(cursor_pos.y));
    
    current_settings_ipc->send(message.Stringify().c_str());
}

Reference: doc/devdocs/core/runner.md:66-68, doc/devdocs/core/runner.md:103-112 Double Click - Dashboard:

void open_settings_window(ESettingsWindowNames page)
{
    json::JsonObject message;
    message.SetNamedValue(L"ShowYourself", 
                         json::value(ESettingsWindowNames_to_string(page)));
    current_settings_ipc->send(message.Stringify().c_str());
}

Reference: doc/devdocs/core/runner.md:71-74 Right Click - Context Menu: The context menu is defined in resource files:

// From src/runner/runner.rc
IDM_TRAY_MENU MENU
BEGIN
    POPUP "PowerToys"
    BEGIN
        MENUITEM "Settings",                ID_SETTINGS_MENU_COMMAND
        MENUITEM SEPARATOR
        MENUITEM "Run at startup",          ID_RUN_AT_STARTUP_MENU_COMMAND
        MENUITEM SEPARATOR
        MENUITEM "Exit",                    ID_EXIT_MENU_COMMAND
    END
END

Reference: doc/devdocs/core/runner.md:114-119

Module Management

Module Discovery

The Runner scans for module DLLs in the modules/ directory:

std::vector<std::wstring> get_module_paths()
{
    std::vector<std::wstring> paths;
    
    // Get modules directory path
    std::wstring modules_dir = get_module_folderpath();
    
    // Scan for DLLs
    for (const auto& entry : std::filesystem::directory_iterator(modules_dir)) {
        if (entry.path().extension() == L".dll") {
            // Exclude certain patterns (like *ModuleInterface.dll)
            std::wstring filename = entry.path().filename().wstring();
            if (filename.find(L"ModuleInterface") != std::wstring::npos) {
                paths.push_back(entry.path().wstring());
            }
        }
    }
    
    return paths;
}

Note: WinUI 3 applications are located in a separate WinUI3Apps/ folder to avoid DLL conflicts. Reference: doc/devdocs/core/runner.md:17-19

Module Lifecycle

class PowertoyModule
{
private:
    PowertoyModuleIface* module_;
    HMODULE dll_handle_;
    
public:
    PowertoyModule(PowertoyModuleIface* module, HMODULE dll_handle)
        : module_(module), dll_handle_(dll_handle)
    {
    }
    
    ~PowertoyModule()
    {
        if (module_) {
            module_->destroy();
            module_ = nullptr;
        }
        if (dll_handle_) {
            FreeLibrary(dll_handle_);
            dll_handle_ = nullptr;
        }
    }
    
    // Delegate all interface methods to the module
    void enable() { module_->enable(); }
    void disable() { module_->disable(); }
    bool is_enabled() { return module_->is_enabled(); }
    // ... etc
};

Reference: src/runner/powertoy_module.h, src/runner/powertoy_module.cpp

Centralized Keyboard Hook

The Runner uses a low-level keyboard hook to intercept hotkey presses for all modules. This centralized approach prevents performance issues from multiple hooks.

Implementation

// From src/runner/centralized_kb_hook.cpp

namespace
{
    HHOOK keyboard_hook_handle = nullptr;
    std::map<size_t, std::vector<Hotkey>> module_hotkeys;
}

LRESULT CALLBACK LowLevelKeyboardProc(int nCode, WPARAM wParam, LPARAM lParam)
{
    if (nCode == HC_ACTION)
    {
        KBDLLHOOKSTRUCT* kb_data = reinterpret_cast<KBDLLHOOKSTRUCT*>(lParam);
        
        // Performance optimization: ignore keystrokes generated by PowerToys
        if (kb_data->dwExtraInfo == CENTRALIZED_KEYBOARD_HOOK_DONT_TRIGGER_FLAG) {
            return CallNextHookEx(keyboard_hook_handle, nCode, wParam, lParam);
        }
        
        // Only process key down events
        if (wParam == WM_KEYDOWN || wParam == WM_SYSKEYDOWN)
        {
            // Check if this matches any registered hotkey
            for (auto& [module_id, hotkeys] : module_hotkeys)
            {
                for (size_t i = 0; i < hotkeys.size(); ++i)
                {
                    const auto& hotkey = hotkeys[i];
                    
                    // Match modifier keys and virtual key code
                    bool win_pressed = (GetAsyncKeyState(VK_LWIN) & 0x8000) || 
                                      (GetAsyncKeyState(VK_RWIN) & 0x8000);
                    bool ctrl_pressed = (GetAsyncKeyState(VK_CONTROL) & 0x8000);
                    bool alt_pressed = (GetAsyncKeyState(VK_MENU) & 0x8000);
                    bool shift_pressed = (GetAsyncKeyState(VK_SHIFT) & 0x8000);
                    
                    if (hotkey.win == win_pressed &&
                        hotkey.ctrl == ctrl_pressed &&
                        hotkey.alt == alt_pressed &&
                        hotkey.shift == shift_pressed &&
                        hotkey.key == kb_data->vkCode)
                    {
                        // Found matching hotkey - notify module
                        auto module = get_module_by_id(module_id);
                        if (module && module->is_enabled())
                        {
                            // Call module's hotkey handler
                            bool handled = module->on_hotkey(i);
                            
                            // If handled, swallow the keystroke
                            if (handled) {
                                return 1;
                            }
                        }
                    }
                }
            }
        }
    }
    
    return CallNextHookEx(keyboard_hook_handle, nCode, wParam, lParam);
}

void start_lowlevel_keyboard_hook()
{
    keyboard_hook_handle = SetWindowsHookExW(
        WH_KEYBOARD_LL,
        LowLevelKeyboardProc,
        GetModuleHandle(nullptr),
        0
    );
}

Performance Optimizations:

Early Exit on PowerToys-Generated Input
- Uses dwExtraInfo flag to ignore synthetic keystrokes
- Prevents infinite loops and unnecessary processing
No Key Press Detection
- Returns immediately if no keys are actually pressed
- Avoids processing modifier-only events
Metadata Caching
- Caches hotkey information to avoid repeated lookups
- Uses efficient data structures for fast matching

Important: The hook handler must execute very quickly as it’s called on every keystroke system-wide. Reference: doc/devdocs/core/runner.md:120-128

Hotkey Registration

Modules report their hotkeys to the Runner, which registers them with the centralized keyboard hook.

Hotkey Collection

void register_hotkeys()
{
    module_hotkeys.clear();
    
    for (auto& [name, module] : modules)
    {
        if (!module->is_enabled()) {
            continue;
        }
        
        // Get hotkeys from module
        std::vector<Hotkey> hotkeys;
        
        // Try new GetHotkeyEx method first
        auto hotkey_ex = module->GetHotkeyEx();
        if (hotkey_ex.has_value()) {
            // Convert HotkeyEx to Hotkey
            Hotkey hk;
            hk.win = (hotkey_ex->modifiersMask & MOD_WIN) != 0;
            hk.ctrl = (hotkey_ex->modifiersMask & MOD_CONTROL) != 0;
            hk.alt = (hotkey_ex->modifiersMask & MOD_ALT) != 0;
            hk.shift = (hotkey_ex->modifiersMask & MOD_SHIFT) != 0;
            hk.key = static_cast<unsigned char>(hotkey_ex->vkCode);
            hotkeys.push_back(hk);
        }
        else {
            // Fall back to legacy get_hotkeys method
            const size_t max_hotkeys = 16;
            Hotkey buffer[max_hotkeys];
            size_t count = module->get_hotkeys(buffer, max_hotkeys);
            
            for (size_t i = 0; i < count; ++i) {
                hotkeys.push_back(buffer[i]);
            }
        }
        
        // Store hotkeys for this module
        if (!hotkeys.empty()) {
            size_t module_id = get_module_id(name);
            module_hotkeys[module_id] = std::move(hotkeys);
        }
    }
}

Reference: src/modules/interface/powertoy_module_interface.h:111-124

Hotkey Conflict Detection

The Settings UI checks for hotkey conflicts across modules:

Each module implements get_hotkeys() or GetHotkeyEx()
Settings UI collects all hotkeys via Runner IPC
Conflicts are displayed in the Settings UI with warnings
User can resolve conflicts by changing hotkeys

Reference: doc/devdocs/core/settings/settings-implementation.md:74-108

IPC with Settings UI

The Runner communicates with the Settings UI process via Windows Named Pipes using a bidirectional JSON protocol.

Pipe Initialization

// From src/runner/settings_window.cpp

void initialize_settings_window()
{
    // Generate unique pipe names
    std::wstring runner_to_settings_pipe = 
        L"\\\\.\\pipe\\powertoys_runner_" + std::to_wstring(GetCurrentProcessId());
    std::wstring settings_to_runner_pipe = 
        L"\\\\.\\pipe\\powertoys_settings_" + std::to_wstring(GetCurrentProcessId());
    
    // Create two-way pipe
    current_settings_ipc = new TwoWayPipeMessageIPC(
        runner_to_settings_pipe,
        settings_to_runner_pipe,
        [](const std::wstring& message) {
            // Handle messages from Settings UI
            dispatch_json_message_to_main_thread(message);
        }
    );
    
    current_settings_ipc->start();
}

Reference: doc/devdocs/core/runner.md:76-91, src/runner/settings_window.cpp

Message Types

Runner → Settings UI:

// Show Settings window
current_settings_ipc->send(L"{\"ShowYourself\":\"Dashboard\"}");

// Show specific page
current_settings_ipc->send(L"{\"ShowYourself\":\"FancyZones\"}");

// Show Quick Access flyout with position
json::JsonObject msg;
msg.SetNamedValue(L"ShowYourself", json::value(L"flyout"));
msg.SetNamedValue(L"x_position", json::value(1234));
msg.SetNamedValue(L"y_position", json::value(567));
current_settings_ipc->send(msg.Stringify().c_str());

// Update available notification
current_settings_ipc->send(L"{\"UpdateAvailable\":{\"version\":\"0.75.0\"}}");

Settings UI → Runner:

// General settings changed
{
  "general": {
    "startup": true,
    "theme": "dark",
    "run_elevated": false
  }
}

// Module settings changed
{
  "powertoy": "FancyZones",
  "properties": {
    "fancyzones_shiftDrag": { "value": true },
    "fancyzones_zoneCount": { "value": 3 }
  }
}

// Module enabled/disabled
{
  "action": {
    "FancyZones": {
      "action_name": "enable",
      "value": true
    }
  }
}

Reference: doc/devdocs/core/settings/runner-ipc.md:16-20

Message Processing

void dispatch_json_message_to_main_thread(const std::wstring& message)
{
    // Parse JSON message
    auto json_msg = json::JsonObject::Parse(message);
    
    if (json::has(json_msg, L"general")) {
        // General settings update
        auto general = json_msg.GetNamedObject(L"general");
        apply_general_settings(general);
    }
    else if (json::has(json_msg, L"powertoy")) {
        // Module settings update
        std::wstring module_name = json_msg.GetNamedString(L"powertoy");
        auto properties = json_msg.GetNamedObject(L"properties");
        
        // Find module and update settings
        auto module_it = modules.find(module_name);
        if (module_it != modules.end()) {
            // Serialize to JSON string
            std::wstring config = json_msg.Stringify();
            module_it->second->set_config(config.c_str());
        }
    }
    else if (json::has(json_msg, L"action")) {
        // Module enable/disable action
        auto action = json_msg.GetNamedObject(L"action");
        for (const auto& [module_name, action_obj] : action) {
            auto module_it = modules.find(module_name.c_str());
            if (module_it != modules.end()) {
                bool enable = action_obj.GetObjectW()
                    .GetNamedBoolean(L"value", false);
                
                if (enable) {
                    module_it->second->enable();
                } else {
                    module_it->second->disable();
                }
            }
        }
    }
}

Reference: doc/devdocs/core/runner.md:157, src/runner/tray_icon.cpp:157

Update Management

The Runner handles automatic update checking and installation.

Update Checking

// From src/runner/UpdateUtils.cpp

void check_for_updates()
{
    std::thread([]() {
        try {
            // Check GitHub releases API
            auto latest_version = get_latest_release_version();
            auto current_version = get_current_version();
            
            if (latest_version > current_version) {
                // Notify Settings UI of available update
                json::JsonObject msg;
                msg.SetNamedValue(L"UpdateAvailable", 
                    json::JsonObject().
                        SetNamedValue(L"version", 
                            json::value(latest_version.to_wstring())));
                
                current_settings_ipc->send(msg.Stringify().c_str());
            }
        }
        catch (const std::exception& e) {
            Logger::error("Update check failed: {}", e.what());
        }
    }).detach();
}

Reference: doc/devdocs/core/runner.md:196

Update Installation

When the user approves an update from the Settings UI:

Download installer to temp directory
Verify digital signature
Close all PowerToys processes
Launch installer with elevation
Exit Runner (installer will restart after completion)

Reference: src/runner/UpdateUtils.cpp

Key Source Files

File	Purpose	Reference
`main.cpp`	Entry point, initialization, message loop	`src/runner/main.cpp:150`
`powertoy_module.h/cpp`	Module loading and management	`src/runner/powertoy_module.cpp:153`
`tray_icon.cpp`	System tray icon and menu	`src/runner/tray_icon.cpp:156`
`settings_window.cpp`	Settings UI communication	`src/runner/settings_window.cpp:160`
`general_settings.cpp`	General settings loading/saving	`src/runner/general_settings.cpp:163`
`centralized_kb_hook.cpp`	Keyboard hook implementation	`src/runner/centralized_kb_hook.cpp:184`
`centralized_hotkeys.cpp`	Hotkey registration logic	`src/runner/centralized_hotkeys.cpp:181`
`UpdateUtils.cpp`	Update checking and installation	`src/runner/UpdateUtils.cpp:196`
`trace.cpp`	Telemetry implementation	`src/runner/trace.cpp:172`

Next Steps

Module Interface

Learn how to implement a PowerToys module

Settings System

Understand the settings architecture and IPC

Architecture Overview

High-level system architecture

Common Libraries

Shared utilities and helper functions

Architecture

Development Guide

Plugin Development

Overview

Core Responsibilities

Initialization Sequence

1. Process Initialization

2. Tray Icon Startup

3. Module Loading

4. Settings Application

5. Keyboard Hook Registration

System Tray Icon

Implementation

Window Procedure

Tray Icon Actions

Module Management

Module Discovery

Module Lifecycle

Centralized Keyboard Hook

Implementation

Hotkey Registration

Hotkey Collection

Hotkey Conflict Detection

IPC with Settings UI

Pipe Initialization

Message Types

Message Processing

Update Management

Update Checking

Update Installation

Key Source Files

Next Steps

Module Interface

Settings System

Architecture Overview

Common Libraries

Build docs developers (and LLMs) love

Architecture

Development Guide

Plugin Development

​Overview

​Core Responsibilities

​Initialization Sequence

​1. Process Initialization

​2. Tray Icon Startup

​3. Module Loading

​4. Settings Application

​5. Keyboard Hook Registration

​System Tray Icon

​Implementation

​Window Procedure

​Tray Icon Actions

​Module Management

​Module Discovery

​Module Lifecycle

​Centralized Keyboard Hook

​Implementation

​Hotkey Registration

​Hotkey Collection

​Hotkey Conflict Detection

​IPC with Settings UI

​Pipe Initialization

​Message Types

​Message Processing

​Update Management

​Update Checking

​Update Installation

​Key Source Files

​Next Steps

Module Interface

Settings System

Architecture Overview

Common Libraries

Build docs developers (and LLMs) love

Overview

Core Responsibilities

Initialization Sequence

1. Process Initialization

2. Tray Icon Startup

3. Module Loading

4. Settings Application

5. Keyboard Hook Registration

System Tray Icon

Implementation

Window Procedure

Tray Icon Actions

Module Management

Module Discovery

Module Lifecycle

Centralized Keyboard Hook

Implementation

Hotkey Registration

Hotkey Collection

Hotkey Conflict Detection

IPC with Settings UI

Pipe Initialization

Message Types

Message Processing

Update Management

Update Checking

Update Installation

Key Source Files

Next Steps