Added options to configure window name to log into. Change window search mechanism.

Notepad.Extensions.Logging/LoggingBuilderExtensions.cs

@@ -1,10 +1,17 @@
-namespace Microsoft.Extensions.Logging
+using System;
+
+namespace Microsoft.Extensions.Logging
 {
     public static class LoggingBuilderExtensions
     {
         public static ILoggingBuilder AddNotepad(this ILoggingBuilder builder)
+             => AddNotepad(builder, null);
+
+        public static ILoggingBuilder AddNotepad(this ILoggingBuilder builder, Action<NotepadProviderOptions> optionsConfiguration)
         {
-            builder.AddProvider(NotepadLoggerProvider.Instance);
+            var options = NotepadProviderOptions.Default;
+            optionsConfiguration?.Invoke(options);
+            builder.AddProvider(new NotepadLoggerProvider(options));
             return builder;
         }
     }

Notepad.Extensions.Logging/NotepadLogger.cs

@@ -7,14 +7,16 @@ namespace Microsoft.Extensions.Logging
 {
     class NotepadLogger : ILogger
     {
-        public NotepadLogger(ObjectPool<StringBuilder> stringBuilderPool, string categoryName)
+        public NotepadLogger(ObjectPool<StringBuilder> stringBuilderPool, string categoryName, string windowName = null)
         {
             this.stringBuilderPool = stringBuilderPool;
             this.categoryName = categoryName;
+            this.windowName = windowName;
         }
 
         readonly ObjectPool<StringBuilder> stringBuilderPool;
         readonly string categoryName;
+        readonly string windowName;
 
         public IDisposable BeginScope<TState>(TState state) => NullDisposable.Instance;
 
@@ -82,30 +84,33 @@ namespace Microsoft.Extensions.Logging
             _ => throw new ArgumentOutOfRangeException(nameof(logLevel)),
         };
 
-        static void WriteToNotepad(string message)
+        void WriteToNotepad(string message)
         {
             IntPtr hwnd = FindNotepadWindow();
+
+            if (hwnd.Equals(IntPtr.Zero))
+            {
+                return;
+            }
+
             IntPtr edit = NativeMethods.FindWindowEx(hwnd, IntPtr.Zero, "EDIT", null);
             NativeMethods.SendMessage(edit, NativeMethods.EM_REPLACESEL, (IntPtr)1, message);
         }
 
-        static IntPtr FindNotepadWindow()
+        IntPtr FindNotepadWindow()
         {
             IntPtr hwnd;
-            
-            hwnd = NativeMethods.FindWindow(null, "Untitled - Notepad");
-            if (hwnd != IntPtr.Zero)
-            {
-                return hwnd;
-            }
 
-            hwnd = NativeMethods.FindWindow(null, "*Untitled - Notepad");
-            if (hwnd != IntPtr.Zero)
+            hwnd = NativeMethods.FindWindow(null, windowName);
+            if (hwnd.Equals(IntPtr.Zero))
             {
-                return hwnd;
+                // when the file changes, notepad changes the name to "* Window Name", so later created loggers cannot find window
+                var builder = stringBuilderPool.Get();
+                builder.Append("*").Append(windowName);
+                hwnd = NativeMethods.FindWindow(null, builder.ToString());
+                stringBuilderPool.Return(builder);
             }
-
-            return IntPtr.Zero;
+            return hwnd;
         }
     }
 

Notepad.Extensions.Logging/NotepadLoggerProvider.cs

@@ -11,11 +11,15 @@ namespace Microsoft.Extensions.Logging
             stringBuilderPool = poolProvider.CreateStringBuilderPool();
         }
 
-        public static ILoggerProvider Instance { get; } = new NotepadLoggerProvider();
+        internal NotepadLoggerProvider(NotepadProviderOptions options) : this()
+        {
+            this.options = options;
+        }
 
         readonly ObjectPool<StringBuilder> stringBuilderPool;
+        readonly NotepadProviderOptions options;
 
-        public ILogger CreateLogger(string categoryName) => new NotepadLogger(stringBuilderPool, categoryName);
+        public ILogger CreateLogger(string categoryName) => new NotepadLogger(stringBuilderPool, categoryName, options.WindowName);
 
         public void Dispose()
         {

Notepad.Extensions.Logging/NotepadProviderOptions.cs

@@ -0,0 +1,21 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Microsoft.Extensions.Logging
+{
+    public class NotepadProviderOptions
+    {
+        /// <summary>
+        /// Default options for <see cref="NotepadLoggerProvider"/>.
+        /// </summary>
+        public static NotepadProviderOptions Default { get; } = new NotepadProviderOptions
+        {
+            WindowName = "Untitled - Notepad",
+        };
+        /// <summary>
+        /// Name of window to search.
+        /// </summary>
+        public string WindowName { get; set; }
+    }
+}