src/Appender/ColoredConsoleAppender.cs

#region Apache License
//
// Licensed to the Apache Software Foundation (ASF) under one or more
// contributor license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright ownership.
// The ASF licenses this file to you under the Apache License, Version 2.0
// (the "License"); you may not use this file except in compliance with
// the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
#endregion

// MONO 1.0 Beta mcs does not like #if !A && !B && !C syntax

// .NET Compact Framework 1.0 has no support for Win32 Console API's
#if !NETCF
// .Mono 1.0 has no support for Win32 Console API's
#if !MONO
// SSCLI 1.0 has no support for Win32 Console API's
#if !SSCLI
// We don't want framework or platform specific code in the CLI version of log4net
#if !CLI_1_0

using System;
using System.Globalization;
using System.Runtime.InteropServices;

using log4net.Layout;
using log4net.Util;

namespace log4net.Appender
{
	/// <summary>
	/// Appends logging events to the console.
	/// </summary>
	/// <remarks>
	/// <para>
	/// ColoredConsoleAppender appends log events to the standard output stream
	/// or the error output stream using a layout specified by the
	/// user. It also allows the color of a specific type of message to be set.
	/// </para>
	/// <para>
	/// By default, all output is written to the console's standard output stream.
	/// The <see cref="Target"/> property can be set to direct the output to the
	/// error stream.
	/// </para>
	/// <para>
	/// NOTE: This appender writes directly to the application's attached console
	/// not to the <c>System.Console.Out</c> or <c>System.Console.Error</c> <c>TextWriter</c>.
	/// The <c>System.Console.Out</c> and <c>System.Console.Error</c> streams can be
	/// programmatically redirected (for example NUnit does this to capture program output).
	/// This appender will ignore these redirections because it needs to use Win32
	/// API calls to colorize the output. To respect these redirections the <see cref="ConsoleAppender"/>
	/// must be used.
	/// </para>
	/// <para>
	/// When configuring the colored console appender, mapping should be
	/// specified to map a logging level to a color. For example:
	/// </para>
	/// <code lang="XML" escaped="true">
	/// <mapping>
	/// 	<level value="ERROR" />
	/// 	<foreColor value="White" />
	/// 	<backColor value="Red, HighIntensity" />
	/// </mapping>
	/// <mapping>
	/// 	<level value="DEBUG" />
	/// 	<backColor value="Green" />
	/// </mapping>
	/// </code>
	/// <para>
	/// The Level is the standard log4net logging level and ForeColor and BackColor can be any
	/// combination of the following values:
	/// <list type="bullet">
	/// <item><term>Blue</term><description></description></item>
	/// <item><term>Green</term><description></description></item>
	/// <item><term>Red</term><description></description></item>
	/// <item><term>White</term><description></description></item>
	/// <item><term>Yellow</term><description></description></item>
	/// <item><term>Purple</term><description></description></item>
	/// <item><term>Cyan</term><description></description></item>
	/// <item><term>HighIntensity</term><description></description></item>
	/// </list>
	/// </para>
	/// </remarks>
	/// <author>Rick Hobbs</author>
	/// <author>Nicko Cadell</author>
	public class ColoredConsoleAppender : AppenderSkeleton
	{
		#region Colors Enum

		/// <summary>
		/// The enum of possible color values for use with the color mapping method
		/// </summary>
		/// <remarks>
		/// <para>
		/// The following flags can be combined together to
		/// form the colors.
		/// </para>
		/// </remarks>
		/// <seealso cref="ColoredConsoleAppender" />
		[Flags]
		public enum Colors : int
		{
			/// <summary>
			/// color is blue
			/// </summary>
			Blue = 0x0001,

			/// <summary>
			/// color is green
			/// </summary>
			Green = 0x0002,

			/// <summary>
			/// color is red
			/// </summary>
			Red = 0x0004,

			/// <summary>
			/// color is white
			/// </summary>
			White = Blue | Green | Red,

			/// <summary>
			/// color is yellow
			/// </summary>
			Yellow = Red | Green,

			/// <summary>
			/// color is purple
			/// </summary>
			Purple = Red | Blue,

			/// <summary>
			/// color is cyan
			/// </summary>
			Cyan = Green | Blue,

			/// <summary>
			/// color is intensified
			/// </summary>
			HighIntensity = 0x0008,
		}

		#endregion // Colors Enum

		#region Public Instance Constructors

		/// <summary>
		/// Initializes a new instance of the <see cref="ColoredConsoleAppender" /> class.
		/// </summary>
		/// <remarks>
		/// The instance of the <see cref="ColoredConsoleAppender" /> class is set up to write
		/// to the standard output stream.
		/// </remarks>
		public ColoredConsoleAppender()
		{
		}

		/// <summary>
		/// Initializes a new instance of the <see cref="ColoredConsoleAppender" /> class
		/// with the specified layout.
		/// </summary>
		/// <param name="layout">the layout to use for this appender</param>
		/// <remarks>
		/// The instance of the <see cref="ColoredConsoleAppender" /> class is set up to write
		/// to the standard output stream.
		/// </remarks>
		[Obsolete("Instead use the default constructor and set the Layout property")]
		public ColoredConsoleAppender(ILayout layout) : this(layout, false)
		{
		}

		/// <summary>
		/// Initializes a new instance of the <see cref="ColoredConsoleAppender" /> class
		/// with the specified layout.
		/// </summary>
		/// <param name="layout">the layout to use for this appender</param>
		/// <param name="writeToErrorStream">flag set to <c>true</c> to write to the console error stream</param>
		/// <remarks>
		/// When <paramref name="writeToErrorStream" /> is set to <c>true</c>, output is written to
		/// the standard error output stream.  Otherwise, output is written to the standard
		/// output stream.
		/// </remarks>
		[Obsolete("Instead use the default constructor and set the Layout & Target properties")]
		public ColoredConsoleAppender(ILayout layout, bool writeToErrorStream)
		{
			Layout = layout;
			m_writeToErrorStream = writeToErrorStream;
		}

		#endregion // Public Instance Constructors

		#region Public Instance Properties

		/// <summary>
		/// Target is the value of the console output stream.
		/// This is either <c>"Console.Out"</c> or <c>"Console.Error"</c>.
		/// </summary>
		/// <value>
		/// Target is the value of the console output stream.
		/// This is either <c>"Console.Out"</c> or <c>"Console.Error"</c>.
		/// </value>
		/// <remarks>
		/// <para>
		/// Target is the value of the console output stream.
		/// This is either <c>"Console.Out"</c> or <c>"Console.Error"</c>.
		/// </para>
		/// </remarks>
		virtual public string Target
		{
			get { return m_writeToErrorStream ? ConsoleError : ConsoleOut; }
			set
			{
				string v = value.Trim();

				if (string.Compare(ConsoleError, v, true, CultureInfo.InvariantCulture) == 0)
				{
					m_writeToErrorStream = true;
				}
				else
				{
					m_writeToErrorStream = false;
				}
			}
		}

		/// <summary>
		/// Add a mapping of level to color - done by the config file
		/// </summary>
		/// <param name="mapping">The mapping to add</param>
		/// <remarks>
		/// <para>
		/// Add a <see cref="LevelColors"/> mapping to this appender.
		/// Each mapping defines the foreground and background colors
		/// for a level.
		/// </para>
		/// </remarks>
		public void AddMapping(LevelColors mapping)
		{
			m_levelMapping.Add(mapping);
		}

		#endregion // Public Instance Properties

		#region Override implementation of AppenderSkeleton

		/// <summary>
		/// This method is called by the <see cref="M:AppenderSkeleton.DoAppend(log4net.Core.LoggingEvent)"/> method.
		/// </summary>
		/// <param name="loggingEvent">The event to log.</param>
		/// <remarks>
		/// <para>
		/// Writes the event to the console.
		/// </para>
		/// <para>
		/// The format of the output will depend on the appender's layout.
		/// </para>
		/// </remarks>
#if NET_4_0 || MONO_4_0
		[System.Security.SecuritySafeCritical]
#endif
		[System.Security.Permissions.SecurityPermission(System.Security.Permissions.SecurityAction.Demand, UnmanagedCode = true)]
		override protected void Append(log4net.Core.LoggingEvent loggingEvent)
		{
			if (m_consoleOutputWriter != null)
			{
				IntPtr consoleHandle = IntPtr.Zero;
				if (m_writeToErrorStream)
				{
					// Write to the error stream
					consoleHandle = GetStdHandle(STD_ERROR_HANDLE);
				}
				else
				{
					// Write to the output stream
					consoleHandle = GetStdHandle(STD_OUTPUT_HANDLE);
				}

				// Default to white on black
				ushort colorInfo = (ushort)Colors.White;

				// see if there is a specified lookup
				LevelColors levelColors = m_levelMapping.Lookup(loggingEvent.Level) as LevelColors;
				if (levelColors != null)
				{
					colorInfo = levelColors.CombinedColor;
				}

				// Render the event to a string
				string strLoggingMessage = RenderLoggingEvent(loggingEvent);

				// get the current console color - to restore later
				CONSOLE_SCREEN_BUFFER_INFO bufferInfo;
				GetConsoleScreenBufferInfo(consoleHandle, out bufferInfo);

				// set the console colors
				SetConsoleTextAttribute(consoleHandle, colorInfo);

				// Using WriteConsoleW seems to be unreliable.
				// If a large buffer is written, say 15,000 chars
				// Followed by a larger buffer, say 20,000 chars
				// then WriteConsoleW will fail, last error 8
				// 'Not enough storage is available to process this command.'
				//
				// Although the documentation states that the buffer must
				// be less that 64KB (i.e. 32,000 WCHARs) the longest string
				// that I can write out a the first call to WriteConsoleW
				// is only 30,704 chars.
				//
				// Unlike the WriteFile API the WriteConsoleW method does not
				// seem to be able to partially write out from the input buffer.
				// It does have a lpNumberOfCharsWritten parameter, but this is
				// either the length of the input buffer if any output was written,
				// or 0 when an error occurs.
				//
				// All results above were observed on Windows XP SP1 running
				// .NET runtime 1.1 SP1.
				//
				// Old call to WriteConsoleW:
				//
				// WriteConsoleW(
				//     consoleHandle,
				//     strLoggingMessage,
				//     (UInt32)strLoggingMessage.Length,
				//     out (UInt32)ignoreWrittenCount,
				//     IntPtr.Zero);
				//
				// Instead of calling WriteConsoleW we use WriteFile which
				// handles large buffers correctly. Because WriteFile does not
				// handle the codepage conversion as WriteConsoleW does we
				// need to use a System.IO.StreamWriter with the appropriate
				// Encoding. The WriteFile calls are wrapped up in the
				// System.IO.__ConsoleStream internal class obtained through
				// the System.Console.OpenStandardOutput method.
				//
				// See the ActivateOptions method below for the code that
				// retrieves and wraps the stream.


				// The windows console uses ScrollConsoleScreenBuffer internally to
				// scroll the console buffer when the display buffer of the console
				// has been used up. ScrollConsoleScreenBuffer fills the area uncovered
				// by moving the current content with the background color
				// currently specified on the console. This means that it fills the
				// whole line in front of the cursor position with the current
				// background color.
				// This causes an issue when writing out text with a non default
				// background color. For example; We write a message with a Blue
				// background color and the scrollable area of the console is full.
				// When we write the newline at the end of the message the console
				// needs to scroll the buffer to make space available for the new line.
				// The ScrollConsoleScreenBuffer internals will fill the newly created
				// space with the current background color: Blue.
				// We then change the console color back to default (White text on a
				// Black background). We write some text to the console, the text is
				// written correctly in White with a Black background, however the
				// remainder of the line still has a Blue background.
				//
				// This causes a disjointed appearance to the output where the background
				// colors change.
				//
				// This can be remedied by restoring the console colors before causing
				// the buffer to scroll, i.e. before writing the last newline. This does
				// assume that the rendered message will end with a newline.
				//
				// Therefore we identify a trailing newline in the message and don't
				// write this to the output, then we restore the console color and write
				// a newline. Note that we must AutoFlush before we restore the console
				// color otherwise we will have no effect.
				//
				// There will still be a slight artefact for the last line of the message
				// will have the background extended to the end of the line, however this
				// is unlikely to cause any user issues.
				//
				// Note that none of the above is visible while the console buffer is scrollable
				// within the console window viewport, the effects only arise when the actual
				// buffer is full and needs to be scrolled.

				char[] messageCharArray = strLoggingMessage.ToCharArray();
				int arrayLength = messageCharArray.Length;
				bool appendNewline = false;

				// Trim off last newline, if it exists
				if (arrayLength > 1 && messageCharArray[arrayLength-2] == '\r' && messageCharArray[arrayLength-1] == '\n')
				{
					arrayLength -= 2;
					appendNewline = true;
				}

				// Write to the output stream
				m_consoleOutputWriter.Write(messageCharArray, 0, arrayLength);

				// Restore the console back to its previous color scheme
				SetConsoleTextAttribute(consoleHandle, bufferInfo.wAttributes);

				if (appendNewline)
				{
					// Write the newline, after changing the color scheme
					m_consoleOutputWriter.Write(s_windowsNewline, 0, 2);
				}
			}
		}

		private static readonly char[] s_windowsNewline = {'\r', '\n'};

		/// <summary>
		/// This appender requires a <see cref="Layout"/> to be set.
		/// </summary>
		/// <value><c>true</c></value>
		/// <remarks>
		/// <para>
		/// This appender requires a <see cref="Layout"/> to be set.
		/// </para>
		/// </remarks>
		override protected bool RequiresLayout
		{
			get { return true; }
		}

		/// <summary>
		/// Initialize the options for this appender
		/// </summary>
		/// <remarks>
		/// <para>
		/// Initialize the level to color mappings set on this appender.
		/// </para>
		/// </remarks>
#if NET_4_0 || MONO_4_0
		[System.Security.SecuritySafeCritical]
#endif
		[System.Security.Permissions.SecurityPermission(System.Security.Permissions.SecurityAction.Demand, UnmanagedCode=true)]
		public override void ActivateOptions()
		{
			base.ActivateOptions();
			m_levelMapping.ActivateOptions();

			System.IO.Stream consoleOutputStream = null;

			// Use the Console methods to open a Stream over the console std handle
			if (m_writeToErrorStream)
			{
				// Write to the error stream
				consoleOutputStream = Console.OpenStandardError();
			}
			else
			{
				// Write to the output stream
				consoleOutputStream = Console.OpenStandardOutput();
			}

			// Lookup the codepage encoding for the console
			System.Text.Encoding consoleEncoding = System.Text.Encoding.GetEncoding(GetConsoleOutputCP());

			// Create a writer around the console stream
			m_consoleOutputWriter = new System.IO.StreamWriter(consoleOutputStream, consoleEncoding, 0x100);

			m_consoleOutputWriter.AutoFlush = true;

			// SuppressFinalize on m_consoleOutputWriter because all it will do is flush
			// and close the file handle. Because we have set AutoFlush the additional flush
			// is not required. The console file handle should not be closed, so we don't call
			// Dispose, Close or the finalizer.
			GC.SuppressFinalize(m_consoleOutputWriter);
		}

		#endregion // Override implementation of AppenderSkeleton

		#region Public Static Fields

		/// <summary>
		/// The <see cref="ColoredConsoleAppender.Target"/> to use when writing to the Console
		/// standard output stream.
		/// </summary>
		/// <remarks>
		/// <para>
		/// The <see cref="ColoredConsoleAppender.Target"/> to use when writing to the Console
		/// standard output stream.
		/// </para>
		/// </remarks>
		public const string ConsoleOut = "Console.Out";

		/// <summary>
		/// The <see cref="ColoredConsoleAppender.Target"/> to use when writing to the Console
		/// standard error output stream.
		/// </summary>
		/// <remarks>
		/// <para>
		/// The <see cref="ColoredConsoleAppender.Target"/> to use when writing to the Console
		/// standard error output stream.
		/// </para>
		/// </remarks>
		public const string ConsoleError = "Console.Error";

		#endregion // Public Static Fields

		#region Private Instances Fields

		/// <summary>
		/// Flag to write output to the error stream rather than the standard output stream
		/// </summary>
		private bool m_writeToErrorStream = false;

		/// <summary>
		/// Mapping from level object to color value
		/// </summary>
		private LevelMapping m_levelMapping = new LevelMapping();

		/// <summary>
		/// The console output stream writer to write to
		/// </summary>
		/// <remarks>
		/// <para>
		/// This writer is not thread safe.
		/// </para>
		/// </remarks>
		private System.IO.StreamWriter m_consoleOutputWriter = null;

		#endregion // Private Instances Fields

		#region Win32 Methods

		[DllImport("Kernel32.dll", SetLastError=true, CharSet=CharSet.Auto)]
		private static extern int GetConsoleOutputCP();

		[DllImport("Kernel32.dll", SetLastError=true, CharSet=CharSet.Auto)]
		private static extern bool SetConsoleTextAttribute(
			IntPtr consoleHandle,
			ushort attributes);

		[DllImport("Kernel32.dll", SetLastError=true, CharSet=CharSet.Auto)]
		private static extern bool GetConsoleScreenBufferInfo(
			IntPtr consoleHandle,
			out CONSOLE_SCREEN_BUFFER_INFO bufferInfo);

//		[DllImport("Kernel32.dll", SetLastError=true, CharSet=CharSet.Unicode)]
//		private static extern bool WriteConsoleW(
//			IntPtr hConsoleHandle,
//			[MarshalAs(UnmanagedType.LPWStr)] string strBuffer,
//			UInt32 bufferLen,
//			out UInt32 written,
//			IntPtr reserved);

		//private const UInt32 STD_INPUT_HANDLE = unchecked((UInt32)(-10));
		private const UInt32 STD_OUTPUT_HANDLE = unchecked((UInt32)(-11));
		private const UInt32 STD_ERROR_HANDLE = unchecked((UInt32)(-12));

		[DllImport("Kernel32.dll", SetLastError=true, CharSet=CharSet.Auto)]
		private static extern IntPtr GetStdHandle(
			UInt32 type);

		[StructLayout(LayoutKind.Sequential)]
		private struct COORD
		{
			public UInt16 x;
			public UInt16 y;
		}

		[StructLayout(LayoutKind.Sequential)]
		private struct SMALL_RECT
		{
			public UInt16 Left;
			public UInt16 Top;
			public UInt16 Right;
			public UInt16 Bottom;
		}

		[StructLayout(LayoutKind.Sequential)]
		private struct CONSOLE_SCREEN_BUFFER_INFO
		{
			public COORD      dwSize;
			public COORD      dwCursorPosition;
			public ushort     wAttributes;
			public SMALL_RECT srWindow;
			public COORD      dwMaximumWindowSize;
		}

		#endregion // Win32 Methods

		#region LevelColors LevelMapping Entry

		/// <summary>
		/// A class to act as a mapping between the level that a logging call is made at and
		/// the color it should be displayed as.
		/// </summary>
		/// <remarks>
		/// <para>
		/// Defines the mapping between a level and the color it should be displayed in.
		/// </para>
		/// </remarks>
		public class LevelColors : LevelMappingEntry
		{
			private Colors m_foreColor;
			private Colors m_backColor;
			private ushort m_combinedColor = 0;

			/// <summary>
			/// The mapped foreground color for the specified level
			/// </summary>
			/// <remarks>
			/// <para>
			/// Required property.
			/// The mapped foreground color for the specified level.
			/// </para>
			/// </remarks>
			public Colors ForeColor
			{
				get { return m_foreColor; }
				set { m_foreColor = value; }
			}

			/// <summary>
			/// The mapped background color for the specified level
			/// </summary>
			/// <remarks>
			/// <para>
			/// Required property.
			/// The mapped background color for the specified level.
			/// </para>
			/// </remarks>
			public Colors BackColor
			{
				get { return m_backColor; }
				set { m_backColor = value; }
			}

			/// <summary>
			/// Initialize the options for the object
			/// </summary>
			/// <remarks>
			/// <para>
			/// Combine the <see cref="ForeColor"/> and <see cref="BackColor"/> together.
			/// </para>
			/// </remarks>
			public override void ActivateOptions()
			{
				base.ActivateOptions();
				m_combinedColor = (ushort)( (int)m_foreColor + (((int)m_backColor) << 4) );
			}

			/// <summary>
			/// The combined <see cref="ForeColor"/> and <see cref="BackColor"/> suitable for
			/// setting the console color.
			/// </summary>
			internal ushort CombinedColor
			{
				get { return m_combinedColor; }
			}
		}

		#endregion // LevelColors LevelMapping Entry
	}
}

#endif // !CLI_1_0
#endif // !SSCLI
#endif // !MONO
#endif // !NETCF