ConsoleInGame.cs

using UnityEngine;
using System;
using System.Collections.Generic;

/// <summary>
/// A console that displays the contents of Unity's debug log.
/// </summary>
/// <remarks>
/// Developed by Matthew Miner (www.matthewminer.com)
/// Forked by Joseph Cassano (jplc.ca) from Console to ConsoleInGame so the console can work from other scripts.
/// Fork adds ExampleSceneScript.cs to show how to use this class in another script.
/// Permission is given to use this script however you please with absolutely no restrictions.
/// </remarks>
public static class ConsoleInGame
{
	public static readonly Version version = new Version(1, 0);

	struct ConsoleMessage
	{
		public readonly string  message;
		public readonly string  stackTrace;
		public readonly LogType	type;

		public ConsoleMessage (string message, string stackTrace, LogType type)
		{
			this.message    = message;
			this.stackTrace	= stackTrace;
			this.type       = type;
		}
	}

	static List<ConsoleMessage> entries = new List<ConsoleMessage>();
	static Vector2 scrollPos;
	static bool collapse;

	// Visual elements:

	static GUIContent clearLabel    = new GUIContent("Clear",    "Clear the contents of the console.");
	static GUIContent collapseLabel = new GUIContent("Collapse", "Hide repeated messages.");
	
	/// <summary>
	/// A window displaying the logged messages.
	/// </summary>
	/// <param name="windowID">The window's ID.</param>
	public static void ConsoleWindow (int windowID)
	{
		scrollPos = GUILayout.BeginScrollView(scrollPos);
			
			// Go through each logged entry
			for (int i = 0; i < entries.Count; i++) {
				ConsoleMessage entry = entries[i];

				// If this message is the same as the last one and the collapse feature is chosen, skip it
				if (collapse && i > 0 && entry.message == entries[i - 1].message) {
					continue;
				}

				// Change the text colour according to the log type
				switch (entry.type) {
					case LogType.Error:
					case LogType.Exception:
						GUI.contentColor = Color.red;
						break;

					case LogType.Warning:
						GUI.contentColor = Color.yellow;
						break;

					default:
						GUI.contentColor = Color.white;
						break;
				}

				GUILayout.Label(entry.message);
			}

			GUI.contentColor = Color.white;

		GUILayout.EndScrollView();

		GUILayout.BeginHorizontal();

			// Clear button
			if (GUILayout.Button(clearLabel)) {
				entries.Clear();
			}
			
			// Collapse toggle
			collapse = GUILayout.Toggle(collapse, collapseLabel, GUILayout.ExpandWidth(false));

		GUILayout.EndHorizontal();

		// Set the window to be draggable by the top title bar
		GUI.DragWindow(new Rect(0, 0, 10000, 20));
	}

	/// <summary>
	/// Logged messages are sent through this callback function.
	/// </summary>
	/// <param name="message">The message itself.</param>
	/// <param name="stackTrace">A trace of where the message came from.</param>
	/// <param name="type">The type of message: error/exception, warning, or assert.</param>
	public static void HandleLog (string message, string stackTrace, LogType type)
	{
		ConsoleMessage entry = new ConsoleMessage(message, stackTrace, type);
		entries.Add(entry);
	}
}

ExampleSceneScript.cs

using UnityEngine;

/// <summary>
/// An example of a script for a Unity scene that uses ConsoleInGame to make a debug log console.
/// </summary>
/// <remarks>
/// Forked by Joseph Cassano (jplc.ca) from Matthew Miner (www.matthewminer.com)'s Console.cs.
/// Fork splits Console.cs into ConsoleInGame.cs for the main console code and ExampleSceneScript
/// to show how one would use ConsoleInGame from another script.
/// Permission is given to use this script however you please with absolutely no restrictions.
/// </remarks>

public class ExampleSceneScript : MonoBehaviour
{
	// Variables for use with the console.
	KeyCode consoleToggleKey;
	int consoleMargin;
	Rect consoleWindowRect;
	bool consoleShow;
	
	void OnEnable()
	{
		// Tying the Log messages to the console.
		Application.RegisterLogCallback(ConsoleInGame.HandleLog);
	}
	
	void OnDisable()
	{
		// Removing the link between the Log and the console.
		Application.RegisterLogCallback(null);
	}
	
	// Use this for initialization
	void Start()
	{
		consoleToggleKey = KeyCode.BackQuote;
		consoleMargin = 20;
		consoleWindowRect = new Rect(consoleMargin, consoleMargin, Screen.width - (2 * consoleMargin), Screen.height - (2 * consoleMargin));
	
		// Example of Log message created before Update() still being shown in the console
		Debug.Log("Start Log message.");
	}
	
	// Update is called once per frame
	void Update()
	{
		// Input for displaying/dismissing the console.
		if (Input.GetKeyDown(consoleToggleKey))
		{
			consoleShow = !consoleShow;
		}
		
		// Creating a Log message to show that the console works.
		if (Input.GetKeyDown(KeyCode.Space))
		{
			Debug.Log("Example Log message.");
		}
		
		// Insert the code for your scene below.
		// Also add to any other methods as necessary (like Start()).
		// ...
	}
	
	void OnGUI()
	{
		// Displaying/dismissing the console.
		if (!consoleShow) {
			return;
		}

		consoleWindowRect = GUILayout.Window(123456, consoleWindowRect, ConsoleInGame.ConsoleWindow, "Console");
	}
}