feat(native): C# input/capture sidecar replacing the PowerShell helper

Implements ADR-008. native/input-helper is a self-contained .NET 9 console exe
speaking the identical JSON-over-stdin/stdout protocol as the old PowerShell
helper (ping/cursor/runtime/focus/click/scroll/bounds/capture), so the
InputHelperService interface is unchanged.

- Win32 interop compiled once (native exe), not per call.
- PerMonitorV2 DPI via manifest so click/capture coordinates stay correct on
  mixed-DPI multi-monitor setups.
- capture returns base64 PNG bytes inline (imageBase64) instead of writing a
  temp file per frame; the client handles both base64 and the PowerShell path.
- InputHelperClient prefers the exe and falls back to the embedded PowerShell
  helper when the exe is absent, so the app still runs without the .NET build.
- main.ts resolves the exe (INPUT_HELPER_EXE env -> packaged resources/input-helper
  -> native/input-helper/bin/publish). electron-builder ships it via extraResources.
- npm run helper:build; README documents the build + fallback.

Verified end-to-end through the compiled client: sidecar spawns, runtime info
and a base64 primary-screen capture return correctly. Build stays green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

README.md

@@ -34,6 +34,20 @@ npm run dev
 
 Use the Electron app window for scanner work. The browser preview does not expose the local capture bridge.
 
+### Input/Capture helper (C# sidecar)
+
+Input automation and screen capture run through a compiled C# sidecar
+(`native/input-helper`, see ADR-008). Build it once:
+
+```powershell
+npm run helper:build   # requires the .NET SDK; produces a self-contained exe
+```
+
+The app auto-detects the exe (`INPUT_HELPER_EXE` env override → packaged
+`resources/input-helper` → `native/input-helper/bin/publish`). If the exe is not
+present it falls back to the embedded PowerShell helper, so the app still runs
+without the .NET build - just slower and with the old per-frame temp-file capture.
+
 ### Automatischer Scan: als Administrator starten
 
 Genshin läuft erhöht (Administrator). Windows (UIPI) verwirft dann alle simulierten Maus-Eingaben aus einer nicht-erhöhten App - SendInput meldet dabei trotzdem Erfolg. Für den automatischen Scan muss die App deshalb ebenfalls erhöht laufen:

electron/main.ts

@@ -1,5 +1,6 @@
 import { app, BrowserWindow, Menu, desktopCapturer, globalShortcut, nativeImage, screen, type NativeImage } from "electron";
 import fs from "node:fs/promises";
+import { existsSync } from "node:fs";
 import http, { type Server } from "node:http";
 import path from "node:path";
 import { fileURLToPath } from "node:url";
@@ -70,6 +71,25 @@ function getInputHelperService() {
   return inputHelperService;
 }
 
+// Locate the compiled C# input/capture sidecar (ADR-008). Falls back to null so
+// the service uses the embedded PowerShell helper when the exe was never built.
+function resolveInputHelperExePath(): string | null {
+  const candidates = [
+    process.env.INPUT_HELPER_EXE,
+    path.join(process.resourcesPath, "input-helper", "InputHelper.exe"),
+    path.join(app.getAppPath(), "native", "input-helper", "bin", "publish", "InputHelper.exe"),
+  ].filter((candidate): candidate is string => Boolean(candidate));
+
+  for (const candidate of candidates) {
+    try {
+      if (existsSync(candidate)) return candidate;
+    } catch {
+      // Unreadable path; try the next candidate.
+    }
+  }
+  return null;
+}
+
 function getRepositoryContext() {
   if (!repositoryContext) {
     throw new Error("Repository context has not been initialized.");
@@ -1032,7 +1052,7 @@ function initializeAppLifecycle() {
     artifactStoreRepository = repositoryContext.artifactStoreRepository;
     reviewSamplesRepository = repositoryContext.reviewSamplesRepository;
     scannerLearningRepository = repositoryContext.scannerLearningRepository;
-    inputHelperService = createInputHelperService({ userDataPath });
+    inputHelperService = createInputHelperService({ userDataPath, exePath: resolveInputHelperExePath() });
 
     registerIpcHandlers({
       focusMainWindow: () => focusMainWindow(),

electron/services/inputHelper.ts

@@ -382,7 +382,7 @@ class InputHelperClient {
   private starting: Promise<void> | null = null;
   private disposed = false;
 
-  constructor(private readonly scriptUserDataPath: string) {}
+  constructor(private readonly options: { scriptUserDataPath: string; exePath?: string | null }) {}
 
   private async ensureStarted() {
     if (this.child) return;
@@ -396,14 +396,31 @@ class InputHelperClient {
   }
 
   private async start() {
-    const scriptPath = path.join(this.scriptUserDataPath, "input-helper.ps1");
+    // Prefer the compiled C# sidecar (ADR-008). If it is missing or fails to
+    // start, fall back to the embedded PowerShell helper so the app keeps working
+    // on machines where the native exe was never built.
+    if (this.options.exePath) {
+      try {
+        await this.startWith(spawn(this.options.exePath, [], { windowsHide: true, stdio: ["pipe", "pipe", "pipe"] }));
+        return;
+      } catch {
+        this.teardownChild();
+      }
+    }
+    await this.startWith(await this.spawnPowershell());
+  }
+
+  private async spawnPowershell() {
+    const scriptPath = path.join(this.options.scriptUserDataPath, "input-helper.ps1");
     await fs.mkdir(path.dirname(scriptPath), { recursive: true });
     await fs.writeFile(scriptPath, INPUT_HELPER_SCRIPT, "utf8");
-
+    return spawn("powershell.exe", ["-NoProfile", "-ExecutionPolicy", "Bypass", "-File", scriptPath], {
-    const child = spawn("powershell.exe", ["-NoProfile", "-ExecutionPolicy", "Bypass", "-File", scriptPath], {
       windowsHide: true,
       stdio: ["pipe", "pipe", "pipe"],
     });
+  }
+
+  private async startWith(child: ChildProcessWithoutNullStreams) {
     child.stdout.setEncoding("utf8");
     child.stdout.on("data", (chunk: string) => this.handleStdout(chunk));
     child.stderr.setEncoding("utf8");
@@ -419,10 +436,22 @@ class InputHelperClient {
     });
     this.child = child;
 
-    // First request compiles the Win32 interop; give it extra time.
+    // The C# sidecar answers ping immediately; the PowerShell fallback compiles
+    // Win32 interop on the first request, so give it extra time.
     await this.send("ping", {}, 20000);
   }
 
+  private teardownChild() {
+    const child = this.child;
+    this.child = null;
+    this.buffer = "";
+    try {
+      child?.kill();
+    } catch {
+      // Child was never spawned or already gone.
+    }
+  }
+
   private handleStdout(chunk: string) {
     this.buffer += chunk;
     let newlineIndex = this.buffer.indexOf("\n");
@@ -485,8 +514,8 @@ export interface InputHelperService {
   dispose(): void;
 }
 
-export function createInputHelperService(options: { userDataPath: string }): InputHelperService {
+export function createInputHelperService(options: { userDataPath: string; exePath?: string | null }): InputHelperService {
-  const inputHelper = new InputHelperClient(options.userDataPath);
+  const inputHelper = new InputHelperClient({ scriptUserDataPath: options.userDataPath, exePath: options.exePath ?? null });
 
   async function request(op: string, params: Record<string, unknown> = {}, timeoutMs = 8000) {
     return inputHelper.request(op, params, timeoutMs);
@@ -590,16 +619,24 @@ export function createInputHelperService(options: { userDataPath: string }): Inp
 
   async function capturePrimaryScreenViaGdi() {
     const result = await request("capture", {}, 15000);
-    const capturePath = String(result.path);
+    // The C# sidecar returns PNG bytes inline (no temp file). The PowerShell
-    const buffer = await fs.readFile(capturePath);
+    // fallback writes a temp PNG and returns its path.
-    await fs.unlink(capturePath).catch(() => undefined);
+    let base64: string;
+    if (typeof result.imageBase64 === "string" && result.imageBase64) {
+      base64 = result.imageBase64;
+    } else {
+      const capturePath = String(result.path);
+      const buffer = await fs.readFile(capturePath);
+      await fs.unlink(capturePath).catch(() => undefined);
+      base64 = buffer.toString("base64");
+    }
     const captureTargetRaw = typeof result.captureTarget === "string" ? result.captureTarget : "";
     const captureTarget: "primary-screen" | "genshin-client" = captureTargetRaw === "primary-screen" || captureTargetRaw === "genshin-client"
       ? captureTargetRaw
       : "primary-screen";
 
     return {
-      dataUrl: `data:image/png;base64,${buffer.toString("base64")}`,
+      dataUrl: `data:image/png;base64,${base64}`,
       width: Number(result.width),
       height: Number(result.height),
       originX: Number(result.originX),

native/input-helper/.gitignore

@@ -0,0 +1,4 @@
+# .NET build outputs — the self-contained exe is built via `npm run helper:build`,
+# not committed (it is ~100 MB).
+bin/
+obj/

native/input-helper/InputHelper.csproj

@@ -0,0 +1,23 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net9.0-windows</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <AssemblyName>InputHelper</AssemblyName>
+    <RootNamespace>GenshinAssistant.InputHelper</RootNamespace>
+    <!-- Screen.PrimaryScreen (Forms) + Bitmap/Graphics.CopyFromScreen (Drawing). -->
+    <UseWindowsForms>true</UseWindowsForms>
+    <!-- Single self-contained exe: no .NET install needed on the user's machine. -->
+    <RuntimeIdentifier>win-x64</RuntimeIdentifier>
+    <SelfContained>true</SelfContained>
+    <PublishSingleFile>true</PublishSingleFile>
+    <IncludeNativeLibrariesForSelfExtract>true</IncludeNativeLibrariesForSelfExtract>
+    <InvariantGlobalization>true</InvariantGlobalization>
+    <!-- Per-monitor DPI v2 so SendInput/capture coordinates match a mixed-DPI
+         multi-monitor setup (same reason as the old PowerShell helper). -->
+    <ApplicationManifest>app.manifest</ApplicationManifest>
+  </PropertyGroup>
+
+</Project>

native/input-helper/Program.cs

@@ -0,0 +1,466 @@
+using System.Diagnostics;
+using System.Drawing;
+using System.Drawing.Imaging;
+using System.Runtime.InteropServices;
+using System.Security.Principal;
+using System.Text;
+using System.Text.Json;
+using System.Windows.Forms;
+
+// Long-lived input/capture sidecar for the Genshin Artifact Assistant.
+// Drop-in replacement for the old PowerShell helper (see ADR-008): identical
+// JSON-over-stdin/stdout protocol - one JSON request per line, one JSON response
+// per line - so the Electron-side InputHelperService is unchanged. Win32 interop
+// is compiled once (this is a native exe), and capture returns base64 PNG bytes
+// directly instead of writing a temp file per frame.
+
+namespace GenshinAssistant.InputHelper;
+
+internal static class Program
+{
+    private static IntPtr _genshinHwnd = IntPtr.Zero;
+
+    private static int Main()
+    {
+        // Manifest already declares PerMonitorV2; this is a belt-and-suspenders
+        // call for hosts that ignore the manifest.
+        try { Native.SetProcessDpiAwarenessContext(Native.DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2); }
+        catch { try { Native.SetProcessDpiAwareness(2); } catch { /* oldest fallback */ Native.SetProcessDPIAware(); } }
+
+        Console.OutputEncoding = Encoding.UTF8;
+        var stdout = Console.Out;
+
+        string? line;
+        while ((line = Console.In.ReadLine()) != null)
+        {
+            if (line.Trim().Length == 0) continue;
+
+            var response = new Dictionary<string, object?> { ["id"] = "", ["ok"] = true };
+            try
+            {
+                using var doc = JsonDocument.Parse(line);
+                var root = doc.RootElement;
+                response["id"] = GetString(root, "id");
+                var op = GetString(root, "op");
+                Handle(op, root, response);
+            }
+            catch (Exception ex)
+            {
+                response["ok"] = false;
+                response["error"] = ex.Message;
+            }
+
+            stdout.WriteLine(JsonSerializer.Serialize(response));
+            stdout.Flush();
+        }
+
+        return 0;
+    }
+
+    private static void Handle(string op, JsonElement root, Dictionary<string, object?> response)
+    {
+        switch (op)
+        {
+            case "ping":
+                response["pong"] = true;
+                break;
+
+            case "cursor":
+            {
+                var state = GetCursorState();
+                response["cursorX"] = state.X;
+                response["cursorY"] = state.Y;
+                response["escapePressed"] = state.Escape;
+                response["enterPressed"] = state.Enter;
+                response["f9Pressed"] = state.F9;
+                break;
+            }
+
+            case "runtime":
+            {
+                var hwnd = FindGenshinWindow();
+                var fgHwnd = Native.GetForegroundWindow();
+                response["isElevated"] = IsElevated();
+                response["genshinFound"] = hwnd != IntPtr.Zero;
+                response["genshinHwnd"] = hwnd.ToInt64();
+                response["targetProcess"] = ProcessNameFromHwnd(hwnd);
+                response["foregroundProcess"] = ProcessNameFromHwnd(fgHwnd);
+                response["foregroundHwnd"] = fgHwnd.ToInt64();
+                response["helperPid"] = Environment.ProcessId;
+                break;
+            }
+
+            case "focus":
+            {
+                var info = FocusGenshinWindow();
+                response["focused"] = info.Focused;
+                response["alreadyForeground"] = info.AlreadyForeground;
+                response["foregroundProcess"] = info.ForegroundProcess;
+                response["targetProcess"] = info.TargetProcess;
+                response["genshinFound"] = info.Hwnd != IntPtr.Zero;
+                response["setForegroundResult"] = info.SetForegroundResult;
+                break;
+            }
+
+            case "click":
+            {
+                var info = FocusGenshinWindow();
+                if (info.Focused && !info.AlreadyForeground) Thread.Sleep(120);
+
+                var targetX = GetInt(root, "x");
+                var targetY = GetInt(root, "y");
+                // Bare SetCursorPos then a batched down+up click, matching the
+                // verified Inventory Kamera sequence: no extra move event, no
+                // gap between move and click.
+                Native.SetCursorPos(targetX, targetY);
+                Native.GetCursorPos(out var pt);
+                var onTarget = Math.Abs(targetX - pt.X) <= 2 && Math.Abs(targetY - pt.Y) <= 2;
+                var clickEventsSent = onTarget ? SendMouseClickBatch() : 0u;
+
+                var state = GetCursorState();
+                response["cursorX"] = state.X;
+                response["cursorY"] = state.Y;
+                response["escapePressed"] = state.Escape;
+                response["enterPressed"] = state.Enter;
+                response["f9Pressed"] = state.F9;
+                response["moved"] = onTarget;
+                response["focused"] = info.Focused;
+                response["alreadyForeground"] = info.AlreadyForeground;
+                response["foregroundProcess"] = info.ForegroundProcess;
+                response["targetProcess"] = info.TargetProcess;
+                response["isElevated"] = IsElevated();
+                // Only report a click when the cursor is verifiably on target and
+                // SendInput injected both events; real acceptance is proven later
+                // by the detail-panel fingerprint.
+                response["clicked"] = onTarget && clickEventsSent >= 2;
+                response["inputBlocked"] = onTarget && clickEventsSent < 2;
+                break;
+            }
+
+            case "scroll":
+            {
+                var info = FocusGenshinWindow();
+                if (info.Focused && !info.AlreadyForeground) Thread.Sleep(120);
+
+                if (TryGetInt(root, "x", out var ax) && TryGetInt(root, "y", out var ay))
+                {
+                    Native.SetCursorPos(ax, ay);
+                    Thread.Sleep(30);
+                }
+
+                Native.GetCursorPos(out var pt);
+                response["cursorX"] = pt.X;
+                response["cursorY"] = pt.Y;
+                response["focused"] = info.Focused;
+                response["foregroundProcess"] = info.ForegroundProcess;
+                response["isElevated"] = IsElevated();
+
+                var notches = GetInt(root, "notches");
+                var stepDelta = notches < 0 ? -120 : 120;
+                var count = Math.Min(60, Math.Abs(notches));
+                uint sentTotal = 0;
+                for (var i = 0; i < count; i++)
+                {
+                    sentTotal += SendMouseWheel(stepDelta);
+                    Thread.Sleep(45);
+                }
+                response["notchesSent"] = sentTotal;
+                response["inputBlocked"] = count > 0 && sentTotal == 0;
+                break;
+            }
+
+            case "bounds":
+            {
+                var bounds = GetGenshinClientBounds();
+                if (bounds == null)
+                {
+                    response["found"] = false;
+                }
+                else
+                {
+                    response["found"] = true;
+                    response["left"] = bounds.Value.Left;
+                    response["top"] = bounds.Value.Top;
+                    response["width"] = bounds.Value.Width;
+                    response["height"] = bounds.Value.Height;
+                }
+                break;
+            }
+
+            case "capture":
+            {
+                var bounds = GetGenshinClientBounds();
+                string captureTarget;
+                Rect area;
+                if (bounds == null)
+                {
+                    var screen = Screen.PrimaryScreen!.Bounds;
+                    area = new Rect { Left = screen.Left, Top = screen.Top, Width = screen.Width, Height = screen.Height };
+                    captureTarget = "primary-screen";
+                }
+                else
+                {
+                    area = bounds.Value;
+                    captureTarget = "genshin-client";
+                }
+
+                using var bitmap = new Bitmap(area.Width, area.Height, PixelFormat.Format32bppArgb);
+                using (var graphics = Graphics.FromImage(bitmap))
+                {
+                    graphics.CopyFromScreen(area.Left, area.Top, 0, 0, bitmap.Size, CopyPixelOperation.SourceCopy);
+                }
+
+                using var stream = new MemoryStream();
+                bitmap.Save(stream, ImageFormat.Png);
+                response["imageBase64"] = Convert.ToBase64String(stream.ToArray());
+                response["width"] = area.Width;
+                response["height"] = area.Height;
+                response["originX"] = area.Left;
+                response["originY"] = area.Top;
+                response["captureTarget"] = captureTarget;
+                break;
+            }
+
+            default:
+                response["ok"] = false;
+                response["error"] = "unknown op";
+                break;
+        }
+    }
+
+    private readonly struct Rect
+    {
+        public int Left { get; init; }
+        public int Top { get; init; }
+        public int Width { get; init; }
+        public int Height { get; init; }
+    }
+
+    private struct CursorState
+    {
+        public int X;
+        public int Y;
+        public bool Escape;
+        public bool Enter;
+        public bool F9;
+    }
+
+    private struct FocusInfo
+    {
+        public IntPtr Hwnd;
+        public bool Focused;
+        public bool AlreadyForeground;
+        public string ForegroundProcess;
+        public string TargetProcess;
+        public bool SetForegroundResult;
+    }
+
+    private static CursorState GetCursorState()
+    {
+        Native.GetCursorPos(out var pt);
+        // Only 0x8000 (held right now). The 0x0001 "pressed since last call" bit
+        // is unreliable and fires for ESC presses used to navigate Genshin menus.
+        var esc = (Native.GetAsyncKeyState(0x1B) & 0x8000) != 0;
+        var enter = (Native.GetAsyncKeyState(0x0D) & 0x8000) != 0;
+        var f9 = (Native.GetAsyncKeyState(0x78) & 0x8000) != 0;
+        return new CursorState { X = pt.X, Y = pt.Y, Escape = esc, Enter = enter, F9 = f9 };
+    }
+
+    private static FocusInfo FocusGenshinWindow()
+    {
+        var hwnd = FindGenshinWindow();
+        var info = new FocusInfo
+        {
+            Hwnd = hwnd,
+            ForegroundProcess = "",
+            TargetProcess = ProcessNameFromHwnd(hwnd),
+        };
+        if (hwnd == IntPtr.Zero) return info;
+
+        info.AlreadyForeground = Native.GetForegroundWindow() == hwnd;
+        if (!info.AlreadyForeground)
+        {
+            Native.ShowWindowAsync(hwnd, 9); // SW_RESTORE
+            // No ALT tap: this app and Genshin run at the same (elevated)
+            // integrity level, so SetForegroundWindow succeeds on its own. An ALT
+            // tap would toggle menu-mnemonic mode and swallow the next inputs.
+            info.SetForegroundResult = Native.SetForegroundWindow(hwnd);
+            Thread.Sleep(140);
+        }
+
+        var foreground = Native.GetForegroundWindow();
+        info.Focused = foreground == hwnd;
+        info.ForegroundProcess = ProcessNameFromHwnd(foreground);
+        return info;
+    }
+
+    private static IntPtr FindGenshinWindow()
+    {
+        if (_genshinHwnd != IntPtr.Zero && Native.IsWindow(_genshinHwnd)) return _genshinHwnd;
+
+        foreach (var proc in Process.GetProcesses())
+        {
+            try
+            {
+                var name = proc.ProcessName;
+                if ((name.Contains("GenshinImpact", StringComparison.OrdinalIgnoreCase)
+                     || name.Contains("YuanShen", StringComparison.OrdinalIgnoreCase)
+                     || name.Contains("Genshin", StringComparison.OrdinalIgnoreCase))
+                    && proc.MainWindowHandle != IntPtr.Zero)
+                {
+                    _genshinHwnd = proc.MainWindowHandle;
+                    return _genshinHwnd;
+                }
+            }
+            catch
+            {
+                // Process exited between enumeration and inspection; ignore.
+            }
+        }
+
+        _genshinHwnd = IntPtr.Zero;
+        return _genshinHwnd;
+    }
+
+    private static Rect? GetGenshinClientBounds()
+    {
+        var hwnd = FindGenshinWindow();
+        if (hwnd == IntPtr.Zero) return null;
+        if (!Native.GetClientRect(hwnd, out var rect)) return null;
+
+        var topLeft = new Native.POINT { X = 0, Y = 0 };
+        if (!Native.ClientToScreen(hwnd, ref topLeft)) return null;
+
+        var width = rect.Right - rect.Left;
+        var height = rect.Bottom - rect.Top;
+        if (width <= 0 || height <= 0) return null;
+
+        return new Rect { Left = topLeft.X, Top = topLeft.Y, Width = width, Height = height };
+    }
+
+    private static string ProcessNameFromHwnd(IntPtr hwnd)
+    {
+        if (hwnd == IntPtr.Zero) return "";
+        Native.GetWindowThreadProcessId(hwnd, out var pid);
+        if (pid == 0) return "";
+        try { return Process.GetProcessById((int)pid).ProcessName; }
+        catch { return ""; }
+    }
+
+    private static bool IsElevated()
+    {
+        using var identity = WindowsIdentity.GetCurrent();
+        var principal = new WindowsPrincipal(identity);
+        return principal.IsInRole(WindowsBuiltInRole.Administrator);
+    }
+
+    private static uint SendMouseClickBatch()
+    {
+        var inputs = new Native.INPUT[2];
+        inputs[0].type = 0; // INPUT_MOUSE
+        inputs[0].mi.dwFlags = Native.MOUSEEVENTF_LEFTDOWN;
+        inputs[1].type = 0;
+        inputs[1].mi.dwFlags = Native.MOUSEEVENTF_LEFTUP;
+        return Native.SendInput(2, inputs, Marshal.SizeOf<Native.INPUT>());
+    }
+
+    private static uint SendMouseWheel(int wheelData)
+    {
+        var inputs = new Native.INPUT[1];
+        inputs[0].type = 0;
+        inputs[0].mi.mouseData = unchecked((uint)wheelData);
+        inputs[0].mi.dwFlags = Native.MOUSEEVENTF_WHEEL;
+        return Native.SendInput(1, inputs, Marshal.SizeOf<Native.INPUT>());
+    }
+
+    private static string GetString(JsonElement root, string name)
+        => root.TryGetProperty(name, out var value) ? value.ToString() : "";
+
+    private static int GetInt(JsonElement root, string name)
+        => TryGetInt(root, name, out var value) ? value : 0;
+
+    private static bool TryGetInt(JsonElement root, string name, out int value)
+    {
+        value = 0;
+        if (!root.TryGetProperty(name, out var element)) return false;
+        if (element.ValueKind == JsonValueKind.Number && element.TryGetInt32(out value)) return true;
+        if (element.ValueKind == JsonValueKind.String && int.TryParse(element.GetString(), out value)) return true;
+        return false;
+    }
+}
+
+internal static class Native
+{
+    public const uint MOUSEEVENTF_LEFTDOWN = 0x0002;
+    public const uint MOUSEEVENTF_LEFTUP = 0x0004;
+    public const uint MOUSEEVENTF_WHEEL = 0x0800;
+    public static readonly IntPtr DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2 = new(-4);
+
+    [StructLayout(LayoutKind.Sequential)]
+    public struct POINT { public int X; public int Y; }
+
+    [StructLayout(LayoutKind.Sequential)]
+    public struct RECT { public int Left; public int Top; public int Right; public int Bottom; }
+
+    // Binary-compatible with the Win32 INPUT for mouse-only use on x64:
+    // type(4) + 4 pad + MOUSEINPUT(32) = 40 bytes = sizeof(INPUT).
+    [StructLayout(LayoutKind.Sequential)]
+    public struct MOUSEINPUT
+    {
+        public int dx;
+        public int dy;
+        public uint mouseData;
+        public uint dwFlags;
+        public uint time;
+        public UIntPtr dwExtraInfo;
+    }
+
+    [StructLayout(LayoutKind.Sequential)]
+    public struct INPUT
+    {
+        public int type;
+        public MOUSEINPUT mi;
+    }
+
+    [DllImport("user32.dll")]
+    public static extern bool SetProcessDPIAware();
+
+    [DllImport("shcore.dll")]
+    public static extern int SetProcessDpiAwareness(int value);
+
+    [DllImport("user32.dll")]
+    public static extern bool SetProcessDpiAwarenessContext(IntPtr value);
+
+    [DllImport("user32.dll")]
+    public static extern bool SetCursorPos(int x, int y);
+
+    [DllImport("user32.dll")]
+    public static extern bool GetCursorPos(out POINT lpPoint);
+
+    [DllImport("user32.dll", SetLastError = true)]
+    public static extern bool GetClientRect(IntPtr hWnd, out RECT lpRect);
+
+    [DllImport("user32.dll", SetLastError = true)]
+    public static extern bool ClientToScreen(IntPtr hWnd, ref POINT lpPoint);
+
+    [DllImport("user32.dll")]
+    public static extern short GetAsyncKeyState(int vKey);
+
+    [DllImport("user32.dll", SetLastError = true)]
+    public static extern uint SendInput(uint nInputs, INPUT[] pInputs, int cbSize);
+
+    [DllImport("user32.dll")]
+    public static extern bool SetForegroundWindow(IntPtr hWnd);
+
+    [DllImport("user32.dll")]
+    public static extern bool ShowWindowAsync(IntPtr hWnd, int nCmdShow);
+
+    [DllImport("user32.dll")]
+    public static extern IntPtr GetForegroundWindow();
+
+    [DllImport("user32.dll")]
+    public static extern bool IsWindow(IntPtr hWnd);
+
+    [DllImport("user32.dll")]
+    public static extern uint GetWindowThreadProcessId(IntPtr hWnd, out uint lpdwProcessId);
+}

native/input-helper/app.manifest

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<assembly manifestVersion="1.0" xmlns="urn:schemas-microsoft-com:asm.v1">
+  <assemblyIdentity version="1.0.0.0" name="GenshinAssistant.InputHelper" type="win32" />
+  <application xmlns="urn:schemas-microsoft-com:asm.v3">
+    <windowsSettings>
+      <!-- PerMonitorV2: coordinates stay correct across mixed-DPI monitors. -->
+      <dpiAwareness xmlns="http://schemas.microsoft.com/SMI/2016/WindowsSettings">PerMonitorV2</dpiAwareness>
+      <dpiAware xmlns="http://schemas.microsoft.com/SMI/2005/WindowsSettings">true/pm</dpiAware>
+    </windowsSettings>
+  </application>
+</assembly>

package.json

@@ -15,6 +15,7 @@
     "lint": "tsc --noEmit",
     "test": "vitest run",
     "eval": "vitest run src/eval/ocrEval.test.ts",
+    "helper:build": "dotnet publish native/input-helper/InputHelper.csproj -c Release -o native/input-helper/bin/publish",
     "data:genshin": "node scripts/generate-genshin-data.cjs"
   },
   "dependencies": {
@@ -48,6 +49,15 @@
       "dist-electron/**/*",
       "package.json"
     ],
+    "extraResources": [
+      {
+        "from": "native/input-helper/bin/publish",
+        "to": "input-helper",
+        "filter": [
+          "**/*"
+        ]
+      }
+    ],
     "win": {
       "target": "nsis",
       "requestedExecutionLevel": "requireAdministrator"