Run Apple driver in a worker process

cyanfish#105

NAPS2.App.Mac/Info.plist

@@ -17,6 +17,10 @@
     <key>CFBundleIconFile</key>
     <string>Icon.icns</string>
     <key>NSPrincipalClass</key>
+    <!-- We start as a background application in case we're in worker mode and don't want to show a UI.
+     If we're in GUI mode we dynamically switch to a foreground application (see MacEntryPoint.cs). -->
     <string>NSApplication</string>
+    <key>LSBackgroundOnly</key>
+    <true/>
   </dict>
 </plist>

NAPS2.Lib.Mac/EntryPoints/MacEntryPoint.cs

@@ -20,9 +20,14 @@ public static int Run(string[] args)
         }
         if (args.Length > 0 && args[0] == "worker")
         {
-            return WorkerEntryPoint.Run(args.Skip(1).ToArray(), new MacModule());
+            return MacWorkerEntryPoint.Run(args.Skip(1).ToArray());
         }
 
+        // We start the process as a background process (by setting LSBackgroundOnly in Info.plist) and only turn it
+        // into a foreground process once we know we're not in worker or console mode. This ensures workers don't have
+        // a chance to show in the dock.
+        MacProcessHelper.TransformThisProcessToForeground();
+
         // Initialize Autofac (the DI framework)
         var container = AutoFacHelper.FromModules(
             new CommonModule(), new MacModule(), new RecoveryModule(), new ContextModule());

NAPS2.Lib.Mac/EntryPoints/MacWorkerEntryPoint.cs

@@ -0,0 +1,12 @@
+using NAPS2.Modules;
+
+namespace NAPS2.EntryPoints;
+
+public static class MacWorkerEntryPoint
+{
+    public static int Run(string[] args)
+    {
+        var app = NSApplication.SharedApplication;
+        return WorkerEntryPoint.Run(args, new MacModule(), () => app.Run(), () => app.Terminate(null));
+    }
+}

NAPS2.Lib.Mac/Util/MacProcessHelper.cs

@@ -0,0 +1,26 @@
+namespace NAPS2.Util;
+
+public class MacProcessHelper
+{
+    [DllImport("/System/Library/Frameworks/ApplicationServices.framework/ApplicationServices")]
+    private static extern int TransformProcessType(ref ProcessSerialNumber psn, int type);
+
+    private static ProcessSerialNumber _currentProcess = new() { hi = 0, lo = 2 };
+
+    public static void TransformThisProcessToBackground()
+    {
+        TransformProcessType(ref _currentProcess, 2);
+    }
+
+    public static void TransformThisProcessToForeground()
+    {
+        TransformProcessType(ref _currentProcess, 1);
+    }
+
+    [StructLayout(LayoutKind.Sequential)]
+    private struct ProcessSerialNumber
+    {
+        public int hi;
+        public int lo;
+    }
+}

NAPS2.Sdk/Scan/Internal/ScanBridgeFactory.cs

@@ -13,8 +13,11 @@ public ScanBridgeFactory(ScanningContext scanningContext)
 
     public IScanBridge Create(ScanOptions options)
     {
-        // TODO: Ideally Apple could be run in a worker too for stability. But we would need to set up the worker with
-        // an NSApplication etc. (I assume - trying without gives a Device Offline error)
+        if (options.Driver == Driver.Apple)
+        {
+            // Run ImageCaptureCore in a worker process for added stability
+            return new WorkerScanBridge(_scanningContext, WorkerType.Native);
+        }
         if (options.Driver == Driver.Sane)
         {
             // Run SANE in a worker process for added stability