using System;
using System.Drawing;
using System.Windows.Forms;

using System.Runtime.InteropServices;

namespace AppliStation.Util
{
	public class DisplayDeviceContext : IDeviceContext, IDisposable
	{
		private HandleRef hWnd;
		private IntPtr hDc;
		private bool isGottenDc;
		
		/// <summary>
		/// ディスプレイコンテクストの生成
		/// </summary>
		/// <param name="hWnd">ウィンドウハンドル</param>
		public DisplayDeviceContext(IntPtr hWnd)
			: this(new HandleRef(null, hWnd))
		{
		}

		/// <summary>
		/// ディスプレイコンテクストの生成
		/// </summary>
		/// <param name="hWnd">ウィンドウハンドル</param>
		public DisplayDeviceContext(HandleRef hWnd)
		{
			this.hWnd = hWnd;
			this.hDc = GetDC(hWnd);
			this.isGottenDc = true;
		}
		
		protected DisplayDeviceContext(IntPtr hDc, bool isGottenDc)
		{
			this.hDc = hDc;
			this.isGottenDc = isGottenDc;
		}
		
		public static DisplayDeviceContext FromHdc(IntPtr hDc)
		{
			return new DisplayDeviceContext(hDc, false);
		}
		
		public DisplayDeviceContext CreateCompatibleDisplayDeviceContext()
		{
			return FromHdc(CreateCompatibleDC(hDc));
		}
		
		public IntPtr GetHdc()
		{
			return hDc;
		}
		
		public void ReleaseHdc()
		{
			if (this.isGottenDc) { // GetDC 関数を使って取得した場合
				ReleaseDC(hWnd, hDc);
			} else {
				DeleteObject(hDc);
			}
		}
		
		public void Dispose()
		{
			ReleaseHdc();
		}
		
		/// <summary>
		/// 指定されたデバイスコンテキストのオブジェクトを選択
		/// </summary>
		/// <example><code>
		/// 	context.SelectObject(bitmap.GetHbitmap(Color.FromArgb(0)));
		/// </code></example>
		/// <param name="hGdiObj">選択するオブジェクトのハンドル</param>
		/// <returns>置き換えが発生する前のオブジェクトのハンドル</returns>
		public IntPtr SelectObject(IntPtr hGdiObj)
		{
			return SelectObject(hDc, hGdiObj);
		}
		
		#region DllImport
		
		[DllImport("user32.dll")]
		private static extern IntPtr GetDC(HandleRef hWnd);
		
		[DllImport("user32.dll")]
		private static extern int ReleaseDC(HandleRef hWnd, IntPtr hDC);
		
		[DllImport("gdi32.dll", SetLastError=true)]
		private static extern IntPtr CreateCompatibleDC(IntPtr hdc);
		
		[DllImport("gdi32.dll", ExactSpelling=true, PreserveSig=true, SetLastError=true)]
		private static extern IntPtr SelectObject(IntPtr hdc, IntPtr hgdiobj);
		
		[DllImport("gdi32.dll")]
		private static extern bool DeleteObject(IntPtr hObject);
		
		#endregion
	}
	
	public class SprashScreenLayered : Form
	{
		public static Form CreateSprashScreenLayered(Bitmap bitmap, Color bgColor)
		{
			Form form;
			
			if (OSFeature.Feature.IsPresent(OSFeature.LayeredWindows)) {
				form = new SprashScreenLayered();
				form.BackgroundImage = bitmap;
			} else {
				form = new Form();
				form.BackgroundImage = bitmap;
				form.BackColor = bgColor;
			}
			//form.ShowInTaskbar = false;
			form.ControlBox = false;
			form.FormBorderStyle = FormBorderStyle.None;
			form.StartPosition = FormStartPosition.CenterScreen;
			form.Size = bitmap.Size;
			
			if (form is SprashScreenLayered) {
				((SprashScreenLayered) form).CenterToScreen2();
			}
			
			return form;
		}
		
		public SprashScreenLayered()
		{
		}
		
		protected internal void CenterToScreen2()
		{
			base.CenterToScreen();
		}
		
		protected override CreateParams CreateParams {
			get {
				CreateParams param = base.CreateParams;
				// param.ExStyle |= WS_EX_LAYERED;
				param.ExStyle |= 0x00080000;
				return param;
			}
		}
		
		public override Image BackgroundImage {
			set {
				base.BackgroundImage = value;
				updateLayeredWindow();
			}
		}
				
		#region UpdateLayeredWindow関連
		
		[DllImport("user32.dll", ExactSpelling=true, SetLastError=true)]
		private static extern bool UpdateLayeredWindow(IntPtr hwnd, IntPtr hdcDst,
		                                               [In] ref Point pptDst, [In] ref Size psize,
		                                               IntPtr hdcSrc, [In] ref Point pptSrc,
		                                               uint crKey,
		                                               [In] ref BLENDFUNCTION pblend,
		                                               uint dwFlags);
		
		private Bitmap convertBitmap(Image img)
		{
			if (img is Bitmap) {
				return (Bitmap) img;
			} else {
				Bitmap bitmap = new Bitmap(img.Width, img.Height, img.PixelFormat);
				Graphics.FromImage(bitmap).DrawImage(img, 0, 0);
				return bitmap;
			}
		}
		
		protected void updateLayeredWindow()
		{
			Point ptDest = this.Location;
			Point ptSrc  = Point.Empty;
			Size  size   = BackgroundImage.Size;
			
			BLENDFUNCTION blend = new BLENDFUNCTION();
			blend.BlendOp = 0; // AC_SRC_OVER
			blend.BlendFlags = 0;
			blend.SourceConstantAlpha = 255;
			blend.AlphaFormat = 1; // AC_SRC_ALPHA
			
			using(DisplayDeviceContext screen = new DisplayDeviceContext(IntPtr.Zero))
			using(DisplayDeviceContext mem = screen.CreateCompatibleDisplayDeviceContext())
			using(DisplayDeviceContext hBitmap = DisplayDeviceContext.FromHdc(
				convertBitmap(BackgroundImage).GetHbitmap(Color.FromArgb(0))
			)) {
				IntPtr hOldBitmap = IntPtr.Zero;
				
				try {
					hOldBitmap = mem.SelectObject(hBitmap.GetHdc());
					
					UpdateLayeredWindow(this.Handle, screen.GetHdc(),
			                    ref ptSrc, ref size,
			                    mem.GetHdc(), ref ptDest,
			                    0,
			                    ref blend,
			                    2 /* ULW_ALPHA */);
				} finally {
					if (hBitmap.GetHdc() != IntPtr.Zero) {
						mem.SelectObject(hOldBitmap);
					}
				}
			}
		}
		
		[StructLayout(LayoutKind.Sequential, Pack=1)]
		protected struct BLENDFUNCTION
		{
			public byte BlendOp;
			public byte BlendFlags;
			public byte SourceConstantAlpha;
			public byte AlphaFormat;
		}
		
		#endregion
		
	}
}