using System;
using System.Runtime.InteropServices;
using Vanara.Extensions;

namespace Vanara.PInvoke
{
	public static partial class User32
	{
		/// <summary>Contains information about a notification message.</summary>
		[StructLayout(LayoutKind.Sequential)]
		public struct NMHDR
		{
			/// <summary>A window handle to the control sending the message.</summary>
			public HWND hwndFrom;

			/// <summary>An identifier of the control sending the message.</summary>
			public IntPtr idFrom;

			/// <summary>
			/// A notification code. This member can be one of the common notification codes (see Notifications under General Control
			/// Reference), or it can be a control-specific notification code.
			/// </summary>
			public int code;

			/// <summary>Creates a <see cref="NMHDR"/> structure from an LPARAM value.</summary>
			/// <param name="lParam">The LPARAM value.</param>
			/// <returns>A <see cref="NMHDR"/> structure.</returns>
			public static NMHDR FromLParam(IntPtr lParam) => (NMHDR)Marshal.PtrToStructure(lParam, typeof(NMHDR));

#if ALLOWSPAN
			/// <summary>Creates a reference to an <see cref="NMHDR"/> structure from an LPARAM value.</summary>
			/// <param name="lParam">The LPARAM value.</param>
			/// <returns>A <see cref="NMHDR"/> structure reference.</returns>
			public static ref NMHDR LParamAsRef(IntPtr lParam) => ref lParam.AsRef<NMHDR>();
#endif

			/// <summary>Updates the <see cref="NMHDR"/> value pointed to by an LPARAM value from this instance.</summary>
			/// <param name="lParam">The LPARAM value to update.</param>
			public void UpdateLParam(IntPtr lParam) => Marshal.StructureToPtr(this, lParam, false);
		}
	}
}