Called when the window gets keyboard focus.

	// Simple script that lets you preview your main camera in Orthographic view
	// when selected.
	
	class OrthographicPreviewer extends EditorWindow {
		var renderTexture : RenderTexture;
		var camera = Camera.main;
		@MenuItem("Example/Camera Selector")
		static function Init() {
			var window = GetWindow(OrthographicPreviewer);
			window.Show();
		}
		function Awake () {
			renderTexture = 
				new RenderTexture(position.width, position.height, RenderTextureFormat.ARGB32 );
		}
		function OnInspectorUpdate() {
			this.Repaint();
		}
		function OnGUI() {
			if(GUILayout.Button("Close")) {
				camera.orthographic = false;
				this.Close();
			}
			GUI.DrawTexture(Rect( 0.0f, 50.0f, position.width, position.height), renderTexture);
		}
		function OnFocus() {
			Selection.activeTransform = camera.transform;
			camera.orthographic = true;
		}
		function Update() {
			if(camera != null) {
				camera.targetTexture = renderTexture;
				camera.Render();
				camera.targetTexture = null;	
			}
			if(renderTexture.width != position.width || renderTexture.height != position.height)
				renderTexture = new RenderTexture(position.width, 
										position.height, 
										RenderTextureFormat.ARGB32 );
		}
		function OnLostFocus() {
			camera.orthographic = false;
		}
	}