//Except where stated all code and programs in this project are the copyright of Jim Blackler, 2008.
//jimblackler@gmail.com
//
//This is free software. Libraries and programs are distributed under the terms of the GNU Lesser
//General Public License. Please see the files COPYING and COPYING.LESSER.

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

namespace MiscControls
{
    /// <summary>
    /// A tab control in which the user can re-order the tabs by dragging the mouse
    /// </summary>
    public partial class ReorderableTabControl : TabControl
    {
        /// <summary>
        /// Make a reorderable tab control
        /// </summary>
        public ReorderableTabControl()
        {
            InitializeComponent();
        }

        bool dragging = false;

        TabPage lastDraggedTabPage;

        private void ReorderableTabControl_MouseDown(object sender, MouseEventArgs e)
        {
            if ((e.Button & MouseButtons.Left) != 0)
            {
                dragging = true;
                lastDraggedTabPage = null;
            }
        }

        private void ReorderableTabControl_MouseMove(object sender, MouseEventArgs e)
        {
            if (!dragging)
                return; // user does not have button held down

            TabPage overTabPage = null;
            int overTabPageIdx = -1;

            int selectedIndex = TabPages.IndexOf(SelectedTab);
            Rectangle selectedRect = GetTabRect(selectedIndex);

            // Find the tab page that the mouse is over
            int index = 0;
            foreach (TabPage scanTabPage in TabPages)
            {
                Rectangle rect = GetTabRect(index);

                if (selectedRect.Width < rect.Width)
                {
                    // Lessen the strange 'over shifting' effect of moving a small tab over
                    // a larger one

                    int newWidth = (selectedRect.Width + rect.Width) / 2;
                    // Real hot spot width is average of two tab sizes

                    if (rect.X > selectedRect.X) // moving right on the tab display
                    {
                        rect.X += rect.Width - newWidth;
                    }
                    rect.Width = newWidth;
                }

                if (rect.Contains(PointToClient(MousePosition)))
                {
                    overTabPage = scanTabPage;
                    overTabPageIdx = index;
                    break;
                }
                index++;
            }

            if (overTabPage == lastDraggedTabPage)
                return;

            if (overTabPage == null)
                return; // not over a tab page

            if (SelectedTab == overTabPage)
                return; // still over original tab page .. nothing to do

            SuspendLayout();
            
            // Revised method from section commented out below
            TabPages[overTabPageIdx] = SelectedTab;
            TabPages[selectedIndex] = overTabPage;
            SelectedIndex = overTabPageIdx;
            
            // Simply swap the tab pages (this works because they are adjacent)
            //TabPages.Remove(overTabPage);
            //TabPages.Insert(selectedIndex, overTabPage);

            ResumeLayout();
        }

        /// <summary>
        /// The user has lifted the button - stop dragging
        /// </summary>
        private void ReorderableTabControl_MouseUp(object sender, MouseEventArgs e)
        {
            dragging = false;
        }
    }
}