ColorConverter.cs

//
// System.Drawing.ColorConverter
//
// Authors:
//	Gonzalo Paniagua Javier (gonzalo@ximian.com)
//	Ravindra (rkumar@novell.com)
//
// Copyright (C) 2002 Ximian, Inc.  http://www.ximian.com
// Copyright (C) 2004,2006,2008 Novell, Inc (http://www.novell.com)
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
// 
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//

using System.Collections;
using System.ComponentModel;
using System.Globalization;
using System.Text;
using System.ComponentModel.Design.Serialization;
using System.Reflection;

namespace System.Drawing
{
	public class ColorConverter : TypeConverter
	{
		static StandardValuesCollection cached;
		static object creatingCached = new object ();

		public ColorConverter () { }

		public override bool CanConvertFrom (ITypeDescriptorContext context, Type sourceType)
		{
			if (sourceType == typeof (string))
				return true;

			return base.CanConvertFrom (context, sourceType);
		}

		public override bool CanConvertTo (ITypeDescriptorContext context, Type destinationType)
		{
			if (destinationType == typeof (InstanceDescriptor))
				return true;

			return base.CanConvertTo (context, destinationType);
		}

		internal static Color StaticConvertFromString (ITypeDescriptorContext context, string s, CultureInfo culture)
		{
			if (culture == null)
				culture = CultureInfo.InvariantCulture;

			s = s.Trim ();

			if (s.Length == 0)
				return Color.Empty;

			// Try to process both NamedColor and SystemColors from the KnownColor enumeration
			if (Char.IsLetter (s [0])) {
				KnownColor kc;
				try {
					kc = (KnownColor) Enum.Parse (typeof (KnownColor), s, true);
				}
				catch (Exception e) {
					// whatever happens MS throws an basic Exception
					string msg = Locale.GetText ("Invalid color name '{0}'.", s);
					throw new Exception (msg, new FormatException (msg, e));
				}
				return KnownColors.FromKnownColor (kc);
			}

			String numSeparator = culture.TextInfo.ListSeparator;
			Color result = Color.Empty;

			if (s.IndexOf (numSeparator) == -1) {
				bool sharp = (s[0] == '#');
				int start = sharp ? 1 : 0;
				bool hex = false;
				// deal with #hex, 0xhex and #0xhex
				if ((s.Length > start + 1) && (s[start] == '0')) {
					hex = ((s[start + 1] == 'x') || (s[start + 1] == 'X'));
					if (hex)
						start += 2;
				}

				if (sharp || hex) {
					s = s.Substring (start);
					int argb;
					try {
						argb = Int32.Parse (s, NumberStyles.HexNumber);
					}
					catch (Exception e) {
						// whatever happens MS throws an basic Exception
						string msg = Locale.GetText ("Invalid Int32 value '{0}'.", s);
						throw new Exception (msg, e);
					}

					// note that the default alpha value for a 6 hex digit (i.e. when none are present) is 
					// 0xFF while shorter string defaults to 0xFF - unless both # an 0x are specified
					if ((s.Length < 6) || ((s.Length == 6) && sharp && hex))
						argb &= 0x00FFFFFF;
					else if ((argb >> 24) == 0)
						argb |= unchecked((int)0xFF000000);
					result = Color.FromArgb (argb);
				}
			}

			if (result.IsEmpty) {
				Int32Converter converter = new Int32Converter ();
				String [] components = s.Split (numSeparator.ToCharArray ());

				// MS seems to convert the indivual component to int before
				// checking the number of components
				int[] numComponents = new int[components.Length];
				for (int i = 0; i < numComponents.Length; i++) {
					numComponents[i] = (int) converter.ConvertFrom (context,
						culture, components[i]);
				}

				switch (components.Length) {
					case 1:
						result = Color.FromArgb (numComponents[0]);
						break;
					case 3:
						result = Color.FromArgb (numComponents[0], numComponents[1],
							numComponents[2]);
						break;
					case 4:
						result = Color.FromArgb (numComponents[0], numComponents[1],
							numComponents[2], numComponents[3]);
						break;
					default:
						throw new ArgumentException (s + " is not a valid color value.");
				}
			} 

			if (!result.IsEmpty) {
				// Look for a named or system color with those values
				Color known = KnownColors.FindColorMatch (result);
				if (!known.IsEmpty)
					return known;
			}

			return result;
		}


		public override object ConvertFrom (ITypeDescriptorContext context,
						    CultureInfo culture,
						    object value)
		{
			string s = value as string;
			if (s == null)
				return base.ConvertFrom (context, culture, value);

			return StaticConvertFromString (context, s, culture);
		}

		public override object ConvertTo (ITypeDescriptorContext context,
						  CultureInfo culture,
						  object value,
						  Type destinationType)
		{
			if (value is Color) {
				Color color = (Color) value;
				if (destinationType == typeof (string)) {
					if (color == Color.Empty)
						return string.Empty;

					if (color.IsKnownColor || color.IsNamedColor)
						return color.Name;

					String numSeparator = culture.TextInfo.ListSeparator;

					StringBuilder sb = new StringBuilder ();
					if (color.A != 255) {
						sb.Append (color.A);
						sb.Append (numSeparator);
						sb.Append (" ");
					}
					sb.Append (color.R);
					sb.Append (numSeparator);
					sb.Append (" ");

					sb.Append (color.G);
					sb.Append (numSeparator);
					sb.Append (" ");

					sb.Append (color.B);
					return sb.ToString ();
				} else if (destinationType == typeof (InstanceDescriptor)) {
					if (color.IsEmpty) {
						return new InstanceDescriptor (typeof (Color).GetField ("Empty"), null);
					} else if (color.IsSystemColor) {
						return new InstanceDescriptor (typeof (SystemColors).GetProperty (color.Name), null);
					} else if (color.IsKnownColor){
						return new InstanceDescriptor (typeof (Color).GetProperty (color.Name), null);
					} else {
						MethodInfo met = typeof(Color).GetMethod ("FromArgb", new Type[] { typeof(int), typeof(int), typeof(int), typeof(int) } );
						return new InstanceDescriptor (met, new object[] {color.A, color.R, color.G, color.B });
					}
				}
			}

			return base.ConvertTo (context, culture, value, destinationType);
		}

		public override StandardValuesCollection GetStandardValues (ITypeDescriptorContext context)
		{
			lock (creatingCached) {
				if (cached != null)
					return cached;
#if TARGET_JVM
				Color [] colors = new Color [KnownColors.Values.Length - 1];
				Array.Copy (KnownColors.Values, 1, colors, 0, colors.Length);
#else
				Array colors = Array.CreateInstance (typeof (Color), KnownColors.ArgbValues.Length - 1);
				for (int i=1; i < KnownColors.ArgbValues.Length; i++) {
					colors.SetValue (KnownColors.FromKnownColor ((KnownColor)i), i - 1);
				}
#endif

				Array.Sort (colors, 0, colors.Length, new CompareColors ());
				cached = new StandardValuesCollection (colors);
			}

			return cached;
		}

		public override bool GetStandardValuesSupported (ITypeDescriptorContext context)
		{
			return true;
		}

		sealed class CompareColors : IComparer {

			public int Compare (object x, object y)
			{
				return String.Compare (((Color) x).Name, ((Color) y).Name);
			}
		}
	}
}