Add support to config max instances in tray (#244)

docs/diff-tool.md

@@ -53,6 +53,8 @@ This value can be changed:
 
 Setting the `DiffEngine_MaxInstances` environment variable to the number of instances to launch.
 
+This value can also be set using [the DiffEngineTray options dialog](/docs/tray.md#max-instances-to-launch).
+
 
 ### Using code
 
@@ -71,7 +73,7 @@ By default, when a diff is opened, the temp file is on the left and the target f
 
 This value can be changed by setting the `DiffEngine_TargetOnLeft` environment variable to `true`.
 
-This value can also be set using [the DiffEngineTray options dialog](https://github.com/VerifyTests/DiffEngine/blob/main/docs/tray.md#open-on-left).
+This value can also be set using [the DiffEngineTray options dialog](/docs/tray.md#open-on-left).
 
 
 ## Successful verification behavior

docs/mdsource/diff-tool.source.md

@@ -46,6 +46,8 @@ This value can be changed:
 
 Setting the `DiffEngine_MaxInstances` environment variable to the number of instances to launch.
 
+This value can also be set using [the DiffEngineTray options dialog](/docs/tray.md#max-instances-to-launch).
+
 
 ### Using code
 
@@ -58,7 +60,7 @@ By default, when a diff is opened, the temp file is on the left and the target f
 
 This value can be changed by setting the `DiffEngine_TargetOnLeft` environment variable to `true`.
 
-This value can also be set using [the DiffEngineTray options dialog](https://github.com/VerifyTests/DiffEngine/blob/main/docs/tray.md#open-on-left).
+This value can also be set using [the DiffEngineTray options dialog](/docs/tray.md#open-on-left).
 
 
 ## Successful verification behavior

docs/mdsource/tray.source.md

@@ -69,6 +69,11 @@ Runs DiffEngineTray at system startup.
 By default, when a diff is opened, the temp file will be on the left and the target file will be on the right. To invert this, select "Open on left".
 
 
+#### Max instances to launch
+
+Control the [max instances to launch setting](docs/diff-tool.md#maxinstancestolaunch).
+
+
 #### Accept all HotKey
 
 Registers a system wide HotKey to accept pending:

docs/tray.md

@@ -76,6 +76,11 @@ Runs DiffEngineTray at system startup.
 By default, when a diff is opened, the temp file will be on the left and the target file will be on the right. To invert this, select "Open on left".
 
 
+#### Max instances to launch
+
+Control the [max instances to launch setting](docs/diff-tool.md#maxinstancestolaunch).
+
+
 #### Accept all HotKey
 
 Registers a system wide HotKey to accept pending:

src/DiffEngine/DiffRunner.cs

@@ -16,8 +16,7 @@ public static partial class DiffRunner
 
         public static void MaxInstancesToLaunch(int value)
         {
-            Guard.AgainstNegativeAndZero(value, nameof(value));
-            MaxInstance.Set(value);
+            MaxInstance.SetForAppDomain(value);
         }
 
         public static LaunchResult Launch(DiffTool tool, string tempFile, string targetFile)

src/DiffEngine/Guard.cs

@@ -29,7 +29,7 @@ public static void AgainstEmpty(string value, string argumentName)
         }
     }
 
-    public static void AgainstEmpty(object[] value, string argumentName)
+    public static void AgainstEmpty(object?[] value, string argumentName)
     {
         if (value == null)
         {

src/DiffEngine/MaxInstance.cs

@@ -3,15 +3,16 @@
 
 static class MaxInstance
 {
-    static int maxInstancesToLaunch = GetMaxInstances();
+    public static int MaxInstancesToLaunch { get; private set; } = GetMaxInstances();
     static int launchedInstances;
+    const int defaultMax = 5;
 
     static int GetMaxInstances()
     {
         var variable = Environment.GetEnvironmentVariable("DiffEngine_MaxInstances");
         if (string.IsNullOrEmpty(variable))
         {
-            return 5;
+            return defaultMax;
         }
 
         if (ushort.TryParse(variable, out var result))
@@ -22,15 +23,35 @@ static int GetMaxInstances()
         throw new($"Could not parse the DiffEngine_MaxInstances environment variable: {variable}");
     }
 
-    public static void Set(int value)
+    public static void SetForAppDomain(int value)
     {
         Guard.AgainstNegativeAndZero(value, nameof(value));
-        maxInstancesToLaunch = value;
+        MaxInstancesToLaunch = value;
+    }
+
+    public static void SetForUser(int value)
+    {
+        if (MaxInstancesToLaunch == value)
+        {
+            return;
+        }
+        MaxInstancesToLaunch = value;
+        string? envVariable;
+        if (value == defaultMax)
+        {
+            envVariable = null;
+        }
+        else
+        {
+            envVariable = value.ToString();
+        }
+
+        Environment.SetEnvironmentVariable("DiffEngine_MaxInstances", envVariable, EnvironmentVariableTarget.User);
     }
 
     public static bool Reached()
     {
         var instanceCount = Interlocked.Increment(ref launchedInstances);
-        return instanceCount > maxInstancesToLaunch;
+        return instanceCount > MaxInstancesToLaunch;
     }
 }

src/DiffEngine/ResolvedTool.cs

@@ -30,7 +30,7 @@ public string BuildCommand(string tempFile, string targetFile)
 
         string GetArguments(string tempFile, string targetFile)
         {
-            if (TargetPositionHelper.TargetOnLeft)
+            if (TargetPosition.TargetOnLeft)
             {
                 return TargetLeftArguments(tempFile, targetFile);
             }

src/DiffEngine/TargetPositionHelper.cs → src/DiffEngine/TargetPosition.cs

@@ -1,10 +1,10 @@
 using System;
 
-static class TargetPositionHelper
+static class TargetPosition
 {
     public static bool TargetOnLeft { get; private set; }
 
-    static TargetPositionHelper()
+    static TargetPosition()
     {
         TargetOnLeft = ReadTargetOnLeft().GetValueOrDefault(false);
     }
@@ -33,6 +33,11 @@ static TargetPositionHelper()
 
     public static void SetTargetOnLeft(bool value)
     {
+        if (TargetOnLeft == value)
+        {
+            return;
+        }
+
         TargetOnLeft = value;
         string? envVariable;
         if (value)

src/DiffEngineTray.Tests/SettingsHelperTests.ReadWrite.verified.txt

@@ -1,5 +1,6 @@
-{
+{
   AcceptAllHotKey: {
     Key: T
-  }
+  },
+  MaxInstancesToLaunch: 5
 }

src/DiffEngineTray/DiffEngineTray.csproj

@@ -28,7 +28,9 @@
     <None Remove="**\*.png" />
     <EmbeddedResource Include="Images\*.ico" />
     <EmbeddedResource Include="Images\*.png" />
-    <Compile Include="..\DiffEngine\TargetPositionHelper.cs" Link="TargetPositionHelper.cs" />
+    <Compile Include="..\DiffEngine\MaxInstance.cs" Link="MaxInstance.cs" />
+    <Compile Include="..\DiffEngine\TargetPosition.cs" Link="TargetPosition.cs" />
+    <Compile Include="..\DiffEngine\Guard.cs" Link="Guard.cs" />
     <PackageReference Include="Resourcer.Fody" Version="1.8.0" PrivateAssets="all" />
     <PackageReference Include="Fody" Version="6.5.2" PrivateAssets="all" />
     <PackageReference Include="Serilog" Version="2.10.0" />