How to make TabPages draggable?

Question

I'd like to enable user to rearrange TabPages order by dragging and dropping. Moreover it'd be cool to enable user to drag TabPages from one TabControl to another. Both the way like in Firefox and Total Commander. How to achieve this?

Answer 1

reordering TabPages with drag and drop - by Ludwig B.
inspired by http://dotnetrix.co.uk/tabcontrol.htm#tip7

        private void tc_MouseDown(object sender, MouseEventArgs e)
        {
            // store clicked tab
            TabControl tc = (TabControl)sender;
            int hover_index = this.getHoverTabIndex(tc);
            if (hover_index >= 0) { tc.Tag = tc.TabPages[hover_index]; }
        }
        private void tc_MouseUp(object sender, MouseEventArgs e)
        {
            // clear stored tab
            TabControl tc = (TabControl)sender;
            tc.Tag = null;
        }
        private void tc_MouseMove(object sender, MouseEventArgs e)
        {           
            // mouse button down? tab was clicked?
            TabControl tc = (TabControl)sender;
            if ((e.Button != MouseButtons.Left) || (tc.Tag == null)) return;
            TabPage clickedTab = (TabPage)tc.Tag;
            int clicked_index = tc.TabPages.IndexOf(clickedTab);

            // start drag n drop
            tc.DoDragDrop(clickedTab, DragDropEffects.All);
        }
        private void tc_DragOver(object sender, DragEventArgs e)
        {
            TabControl tc = (TabControl)sender;

            // a tab is draged?
            if (e.Data.GetData(typeof(TabPage)) == null) return;
            TabPage dragTab = (TabPage)e.Data.GetData(typeof(TabPage));
            int dragTab_index = tc.TabPages.IndexOf(dragTab);

            // hover over a tab?
            int hoverTab_index = this.getHoverTabIndex(tc);
            if (hoverTab_index < 0) { e.Effect = DragDropEffects.None; return; }
            TabPage hoverTab = tc.TabPages[hoverTab_index];
            e.Effect = DragDropEffects.Move;

            // start of drag?
            if (dragTab == hoverTab) return;

            // swap dragTab & hoverTab - avoids toggeling
            Rectangle dragTabRect = tc.GetTabRect(dragTab_index);
            Rectangle hoverTabRect = tc.GetTabRect(hoverTab_index);

            if (dragTabRect.Width < hoverTabRect.Width)
            {
                Point tcLocation = tc.PointToScreen(tc.Location);

                if (dragTab_index < hoverTab_index)
                {
                    if ((e.X - tcLocation.X) > ((hoverTabRect.X + hoverTabRect.Width) - dragTabRect.Width))
                        this.swapTabPages(tc, dragTab, hoverTab);
                }
                else if (dragTab_index > hoverTab_index)
                {
                    if ((e.X - tcLocation.X) < (hoverTabRect.X + dragTabRect.Width))
                        this.swapTabPages(tc, dragTab, hoverTab);
                }
            }
            else this.swapTabPages(tc, dragTab, hoverTab);

            // select new pos of dragTab
            tc.SelectedIndex = tc.TabPages.IndexOf(dragTab);
        }

        private int getHoverTabIndex(TabControl tc)
        {
            for (int i = 0; i < tc.TabPages.Count; i++)
            {
                if (tc.GetTabRect(i).Contains(tc.PointToClient(Cursor.Position)))
                    return i;
            }

            return -1;
        }

        private void swapTabPages(TabControl tc, TabPage src, TabPage dst)
        {
            int index_src = tc.TabPages.IndexOf(src);
            int index_dst = tc.TabPages.IndexOf(dst);
            tc.TabPages[index_dst] = src;
            tc.TabPages[index_src] = dst;
            tc.Refresh();
        }

Answer 2

Based on onx23's answer.

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

namespace Utilities.Windows.Forms
{
    public class DraggableTabControl : TabControl
    {
        private TabPage predraggedTab;

        public DraggableTabControl() {
            this.AllowDrop = true;
        }

        protected override void OnMouseDown(MouseEventArgs e) {
            predraggedTab = getPointedTab();

            base.OnMouseDown(e);
        }

        protected override void OnMouseUp(MouseEventArgs e) {
            predraggedTab = null;

            base.OnMouseUp(e);
        }

        protected override void OnMouseMove(MouseEventArgs e) {
            if(e.Button == MouseButtons.Left && predraggedTab != null)
                this.DoDragDrop(predraggedTab, DragDropEffects.Move);

            base.OnMouseMove(e);
        }

        protected override void OnDragOver(DragEventArgs drgevent) {
            TabPage draggedTab = (TabPage) drgevent.Data.GetData(typeof(TabPage));
            TabPage pointedTab = getPointedTab();

            if(draggedTab == predraggedTab && pointedTab != null) {
                drgevent.Effect = DragDropEffects.Move;

                if(pointedTab != draggedTab)
                    swapTabPages(draggedTab, pointedTab);
            }

            base.OnDragOver(drgevent);
        }

        private TabPage getPointedTab() {
            for(int i=0; i<this.TabPages.Count; i++)
                if(this.GetTabRect(i).Contains(this.PointToClient(Cursor.Position)))
                    return this.TabPages[i];

            return null;
        }

        private void swapTabPages(TabPage src, TabPage dst) {
            int srci = this.TabPages.IndexOf(src);
            int dsti = this.TabPages.IndexOf(dst);

            this.TabPages[dsti] = src;
            this.TabPages[srci] = dst;

            if(this.SelectedIndex == srci)
                this.SelectedIndex = dsti;
            else if(this.SelectedIndex == dsti)
                this.SelectedIndex = srci;

            this.Refresh();
        }
    }
}

(Forgive me for necro-posting.)

UPDATE

I've written an implementation that allows both dragging and closing tabs (configurable), it's available on Bitbucket here.

Answer 3

Here is a way to also enable dragging between different TAB controls. This also works when the second control has no tabs yet (though overriding Wndproc). Based on the answer of bruce965, and info found here. Hope this is helpful for anyone looking for draggable tabs!

namespace Utilities.Windows.Forms
{
    public class DraggableTabControl : TabControl
    {
        private TabPage predraggedTab;

        private const int WM_NCHITTEST = 0x84;
        private const int HTTRANSPARENT = -1;
        private const int HTCLIENT = 1;

        public DraggableTabControl()
        {
            this.AllowDrop = true;
        }

        protected override void WndProc(ref Message m)
        {
            base.WndProc(ref m);
            if (m.Msg == WM_NCHITTEST)
            {
                if (m.Result.ToInt32() == HTTRANSPARENT)
                    m.Result = new IntPtr(HTCLIENT);
            }
        }

        protected override void OnMouseDown(MouseEventArgs e)
        {

            predraggedTab = getPointedTab();

            base.OnMouseDown(e);
        }

        protected override void OnMouseUp(MouseEventArgs e)
        {
            base.OnMouseUp(e);
        }

        protected override void OnMouseMove(MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left && predraggedTab != null)
                this.DoDragDrop(predraggedTab, DragDropEffects.Move);

            base.OnMouseMove(e);
        }

        protected override void OnDragDrop(DragEventArgs drgevent)
        {
            TabPage draggedTab = (TabPage)drgevent.Data.GetData(typeof(TabPage));

            if (draggedTab.Parent != this)
            {
                draggedTab.Parent = this;
                this.SelectedTab = draggedTab;
            }

            predraggedTab = null;

            base.OnDragDrop(drgevent);
        }

        protected override void OnDragOver(DragEventArgs drgevent)
        {
            TabPage draggedTab = (TabPage)drgevent.Data.GetData(typeof(TabPage));
            TabPage pointedTab = getPointedTab();

            if (draggedTab == predraggedTab && pointedTab != null)
            {
                drgevent.Effect = DragDropEffects.Move;

                if (pointedTab != draggedTab)
                    swapTabPages(draggedTab, pointedTab);
            }
            else if (draggedTab != null && draggedTab.Parent != this)
            {
                drgevent.Effect = DragDropEffects.Move;
            }

            base.OnDragOver(drgevent);
        }

        private TabPage getPointedTab()
        {
            for (int i = 0; i < this.TabPages.Count; i++)
                if (this.GetTabRect(i).Contains(this.PointToClient(Cursor.Position)))
                    return this.TabPages[i];
            return null;
        }

        private void swapTabPages(TabPage src, TabPage dst)
        {
            int srci = this.TabPages.IndexOf(src);
            int dsti = this.TabPages.IndexOf(dst);

            this.TabPages[dsti] = src;
            this.TabPages[srci] = dst;

            if (this.SelectedIndex == srci)
                this.SelectedIndex = dsti;
            else if (this.SelectedIndex == dsti)
                this.SelectedIndex = srci;

            this.Refresh();
        }
    }
}