#region License
/*
MIT License

Copyright(c) 2020 Petteri Kautonen

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.
*/
#endregion

using System;
using System.ComponentModel;
using System.Runtime.InteropServices;
using System.Windows.Forms;
using ScintillaNET;

namespace ScintillaDiff
{
    /// <summary>
    /// An inherited class from the <see cref="Scintilla"/> which can synchronize vertical scroll bar position with another <see cref="Scintilla"/> control.
    /// Implements the <see cref="ScintillaNET.Scintilla" />
    /// </summary>
    /// <seealso cref="ScintillaNET.Scintilla" />
    public class ScrollSyncScintilla : Scintilla
    {
        // ReSharper disable once CommentTypo
        /// <summary>
        /// The WM_VSCROLL message is sent to a window when a scroll event occurs in the window's standard vertical scroll bar.
        /// This message is also sent to the owner of a vertical scroll bar control when a scroll event occurs in the control.
        /// <remarks>
        /// https://docs.microsoft.com/en-us/windows/desktop/controls/wm-vscroll
        /// </remarks>
        /// </summary>
        // ReSharper disable once InconsistentNaming
        private const int WM_VSCROLL = 0x115;
        // ReSharper disable once CommentTypo
        /// <summary>
        /// The WM_HSCROLL message is sent to a window when a scroll event occurs in the window's standard horizontal scroll bar.
        /// This message is also sent to the owner of a horizontal scroll bar control when a scroll event occurs in the control.
        /// <remarks>
        /// https://docs.microsoft.com/en-us/windows/desktop/controls/wm-hscroll
        /// </remarks>
        /// </summary>
        // ReSharper disable once InconsistentNaming
        private const int WM_HSCROLL = 0x114;
        /// <summary>
        /// The WM_MOUSEWHEEL message is Sent to the focus window when the mouse wheel is rotated.
        /// <remarks>
        /// https://docs.microsoft.com/en-us/windows/win32/inputdev/wm-mousewheel
        /// </remarks>
        /// </summary>
        // ReSharper disable once InconsistentNaming
        private const int WM_MOUSEWHEEL = 0x20a;

        /// <summary>
        /// The SendMessage Win32 function is used to send a specified message to a window or windows.
        /// <remarks>
        /// https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-sendmessage
        /// </remarks>
        /// </summary>
        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        private static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wp, IntPtr lp);

        /// <summary>
        /// Processes Windows messages.
        /// </summary>
        /// <param name="m">The Windows Message to process.</param>
        protected override void WndProc(ref Message m)
        {
            if (m.Msg == WM_MOUSEWHEEL)
            {
                // two casts to make this work with 32 bit and 64 bit params
                var wp = new IntPtr((int)(long)m.WParam < 0 ? 1 : 0);
                SendMessage(this.Handle, WM_VSCROLL, wp, new IntPtr(0));
                return;
            }

            base.WndProc(ref m);

            // vertical scrolling
            if (m.Msg == WM_VSCROLL && ScrollSync != null)
            {
                // get the first visible line of this control..
                int scrollTop = FirstVisibleLine;

                // set the value to the other Scintilla control..
                ScrollSync.FirstVisibleLine = scrollTop;
            }

            // horizontal scrolling
            if (m.Msg == WM_HSCROLL && ScrollSync != null)
            {
                // get the leftmost pixel
                int scrollLeft = XOffset;

                // set the value to the other Scintilla control..
                ScrollSync.XOffset = scrollLeft;
            }
        }

        /// <summary>
        /// Gets or sets the <see cref="Scintilla"/> to synchronize the vertical scroll bar with.
        /// </summary>
        [Browsable(true)]
        [Category("Miscellaneous")]
        [Description("Gets or sets the Scintilla to synchronize the vertical scroll bar with.")]
        public Scintilla ScrollSync { get; set; }
    }
}