From 4ba463ddeccddd64135c2856e9d8ae8454425aa8 Mon Sep 17 00:00:00 2001
From: Ben Olden-Cooligan <ben.cyanfish@gmail.com>
Date: Thu, 29 Feb 2024 16:59:21 -0800
Subject: [PATCH] Sdk: Keep SANE initialized for multiple operations

---
 NAPS2.Lib/Scan/ScanPerformer.cs                 |  4 ++++
 .../Scan/Internal/Sane/Native/SaneClient.cs     | 17 ++++++++++++++---
 NAPS2.Sdk/Scan/Internal/Sane/SaneScanDriver.cs  |  4 ++--
 NAPS2.Sdk/Scan/SaneOptions.cs                   |  6 ++++++
 4 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/NAPS2.Lib/Scan/ScanPerformer.cs b/NAPS2.Lib/Scan/ScanPerformer.cs
index eb5836ca08..b0714f0524 100644
--- a/NAPS2.Lib/Scan/ScanPerformer.cs
+++ b/NAPS2.Lib/Scan/ScanPerformer.cs
@@ -238,6 +238,10 @@ private ScanOptions BuildOptions(ScanProfile scanProfile, ScanParams scanParams,
                 IncludeWiaDevices = false
                 // TODO: Consider adding a user option for TwainOptions.ShowProgress instead of our progress window
             },
+            SaneOptions =
+            {
+                KeepInitialized = false
+            },
             KeyValueOptions = scanProfile.KeyValueOptions != null
                 ? new KeyValueScanOptions(scanProfile.KeyValueOptions)
                 : new KeyValueScanOptions(),
diff --git a/NAPS2.Sdk/Scan/Internal/Sane/Native/SaneClient.cs b/NAPS2.Sdk/Scan/Internal/Sane/Native/SaneClient.cs
index edbeb6a412..daa89051df 100644
--- a/NAPS2.Sdk/Scan/Internal/Sane/Native/SaneClient.cs
+++ b/NAPS2.Sdk/Scan/Internal/Sane/Native/SaneClient.cs
@@ -6,6 +6,9 @@ namespace NAPS2.Scan.Internal.Sane.Native;
 internal class SaneClient : SaneNativeObject
 {
     private static readonly object SaneLock = new();
+    private static bool _isInitialized;
+
+    private readonly bool _keepInitialized;
 
     private static SaneNativeLibrary GetNativeLibrary(ISaneInstallation saneInstallation)
     {
@@ -15,10 +18,17 @@ private static SaneNativeLibrary GetNativeLibrary(ISaneInstallation saneInstalla
         }
     }
 
-    public SaneClient(ISaneInstallation saneInstallation) : base(GetNativeLibrary(saneInstallation), IntPtr.Zero)
+    public SaneClient(ISaneInstallation saneInstallation, bool keepInitialized)
+        : base(GetNativeLibrary(saneInstallation), IntPtr.Zero)
     {
+        _keepInitialized = keepInitialized;
+
         Monitor.Enter(SaneLock);
-        Native.sane_init(out _, IntPtr.Zero);
+        if (!_isInitialized)
+        {
+            Native.sane_init(out _, IntPtr.Zero);
+            _isInitialized = true;
+        }
     }
 
     public IEnumerable<SaneDeviceInfo> GetDevices()
@@ -56,9 +66,10 @@ public SaneDevice OpenDevice(string deviceName)
 
     protected override void Dispose(bool disposing)
     {
-        if (disposing)
+        if (disposing && !_keepInitialized)
         {
             Native.sane_exit();
+            _isInitialized = false;
         }
         Monitor.Exit(SaneLock);
     }
diff --git a/NAPS2.Sdk/Scan/Internal/Sane/SaneScanDriver.cs b/NAPS2.Sdk/Scan/Internal/Sane/SaneScanDriver.cs
index 5adee29f45..4d805f1a64 100644
--- a/NAPS2.Sdk/Scan/Internal/Sane/SaneScanDriver.cs
+++ b/NAPS2.Sdk/Scan/Internal/Sane/SaneScanDriver.cs
@@ -50,7 +50,7 @@ void MaybeCallback(SaneDeviceInfo device)
             {
                 // TODO: This is crashing after a delay for no apparent reason.
                 // That's okay because we're in a worker process, but ideally we could fix it in SANE.
-                using var client = new SaneClient(Installation);
+                using var client = new SaneClient(Installation, options.SaneOptions.KeepInitialized);
                 // TODO: We can use device.type and .vendor to help pick an icon etc.
                 // https://sane-project.gitlab.io/standard/api.html#device-descriptor-type
                 if (Installation.CanStreamDevices)
@@ -133,7 +133,7 @@ public Task Scan(ScanOptions options, CancellationToken cancelToken, IScanEvents
             try
             {
                 Installation.Initialize();
-                using var client = new SaneClient(Installation);
+                using var client = new SaneClient(Installation, options.SaneOptions.KeepInitialized);
                 if (cancelToken.IsCancellationRequested) return;
                 _scanningContext.Logger.LogDebug("Opening SANE Device \"{ID}\"", options.Device!.ID);
                 using var device = client.OpenDevice(options.Device.ID);
diff --git a/NAPS2.Sdk/Scan/SaneOptions.cs b/NAPS2.Sdk/Scan/SaneOptions.cs
index 7ed1ce6a49..a46e077157 100644
--- a/NAPS2.Sdk/Scan/SaneOptions.cs
+++ b/NAPS2.Sdk/Scan/SaneOptions.cs
@@ -9,4 +9,10 @@ public class SaneOptions
     /// Limit the devices queried by GetDevices/GetDeviceList to the given SANE backend.
     /// </summary>
     public string? Backend { get; set; }
+
+    /// <summary>
+    /// Whether to keep SANE initialized in memory after the operation is complete. This improves stability when
+    /// doing multiple operations in a single process. Defaults to true.
+    /// </summary>
+    public bool KeepInitialized { get; set; } = true;
 }
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