How to draw custom button in Window Titlebar with Windows Forms?

Question

How do you draw a custom button next to the minimize, maximize and close buttons within the Titlebar of the Form?

I know you need to use Win32 API calls and override

Answer 1

I know it's been long since the last answer but this really helped me recently and I like to update the code provided by Chris with my comments and modifications. The version runs perfectly on Win XP and Win 2003. On Win 2008 ot has a small bug that I was not able to identify, when resizing windows. Works on Vista too (no-Aero) but note that the title bar buttons are not square and button dimensions should take that into account.

 switch (m.Msg)
            {
                // WM_NCPAINT / WM_PAINT        
                case 0x85:
                case 0x0A:
                    //Call base method
                    base.WndProc(ref m);
                    //we have 3 buttons in the corner of the window. So first's new button left coord is offseted by 4 widths
                    int crt = 4;
                    //navigate trough all titlebar buttons on the form
                    foreach (TitleBarImageButton crtBtn in titleBarButtons.Values)
                    {
                        //Calculate button coordinates
                        p.X = (Bounds.Width - crt * crtBtn.Size.Width);
                        p.Y = (Bounds.Height - ClientRectangle.Height - crtBtn.Size.Height) / 2;
                        //Initialize button and draw
                        crtBtn.Location = p;
                        crtBtn.ButtonState = ImageButtonState.NORMAL;
                        crtBtn.DrawButton(m.HWnd);
                        //increment button left coord location offset
                        crt++;
                    }
                    m.Result = IntPtr.Zero;
                    break;
                // WM_ACTIVATE      
                case 0x86:
                    //Call base method
                    base.WndProc(ref m);
                    //Draw each button
                    foreach (TitleBarImageButton crtBtn in titleBarButtons.Values)
                    {
                        crtBtn.ButtonState = ImageButtonState.NORMAL;
                        crtBtn.DrawButton(m.HWnd);
                    }
                    break;
                // WM_NCMOUSEMOVE        
                case 0xA0:
                    //Get current mouse position
                    p.X = ((int)m.LParam << 16) >> 16;// Extract the least significant 16 bits            
                    p.Y = (int)m.LParam >> 16;        // Extract the most significant 16 bits          
                    p.X -= windowRect.Left;
                    p.Y -= windowRect.Top;

                    //Call base method
                    base.WndProc(ref m);

                    ImageButtonState newButtonState;
                    foreach (TitleBarImageButton crtBtn in titleBarButtons.Values)
                    {
                        if (crtBtn.HitTest(p))
                        {//mouse is over the current button
                            if (crtBtn.MouseButtonState == MouseButtonState.PRESSED)
                                //button is pressed - set pressed state
                                newButtonState = ImageButtonState.PRESSED;
                            else
                                //button not pressed - set hoover state
                                newButtonState = ImageButtonState.HOOVER;
                        }
                        else
                        {
                            //mouse not over the current button - set normal state
                            newButtonState = ImageButtonState.NORMAL;
                        }

                        //if button state not modified, do not repaint it.
                        if (newButtonState != crtBtn.ButtonState)
                        {
                            crtBtn.ButtonState = newButtonState;
                            crtBtn.DrawButton(m.HWnd);
                        }
                    }
                    break;
                // WM_NCLBUTTONDOWN     
                case 0xA1:
                    //Get current mouse position
                    p.X = ((int)m.LParam << 16) >> 16;// Extract the least significant 16 bits
                    p.Y = (int)m.LParam >> 16;        // Extract the most significant 16 bits      
                    p.X -= windowRect.Left;
                    p.Y -= windowRect.Top;

                    //Call base method
                    base.WndProc(ref m);

                    foreach (TitleBarImageButton crtBtn in titleBarButtons.Values)
                    {
                        if (crtBtn.HitTest(p))
                        {
                            crtBtn.MouseButtonState = MouseButtonState.PRESSED;
                            crtBtn.ButtonState = ImageButtonState.PRESSED;
                            crtBtn.DrawButton(m.HWnd);
                        }
                    }
                    break;
                // WM_NCLBUTTONUP   
                case 0xA2:
                case 0x202:
                    //Get current mouse position
                    p.X = ((int)m.LParam << 16) >> 16;// Extract the least significant 16 bits   
                    p.Y = (int)m.LParam >> 16;        // Extract the most significant 16 bits 
                    p.X -= windowRect.Left;
                    p.Y -= windowRect.Top;

                    //Call base method
                    base.WndProc(ref m);
                    foreach (TitleBarImageButton crtBtn in titleBarButtons.Values)
                    {
                        //if button is press
                        if (crtBtn.ButtonState == ImageButtonState.PRESSED)
                        {
                            //Rasie button's click event
                            crtBtn.OnClick(EventArgs.Empty);

                            if (crtBtn.HitTest(p))
                                crtBtn.ButtonState = ImageButtonState.HOOVER;
                            else
                                crtBtn.ButtonState = ImageButtonState.NORMAL;
                        }

                        crtBtn.MouseButtonState = MouseButtonState.NOTPESSED;
                        crtBtn.DrawButton(m.HWnd);
                    }
                    break;
                // WM_NCHITTEST    
                case 0x84:
                    //Get current mouse position
                    p.X = ((int)m.LParam << 16) >> 16;// Extract the least significant 16 bits
                    p.Y = (int)m.LParam >> 16;        // Extract the most significant 16 bits
                    p.X -= windowRect.Left;
                    p.Y -= windowRect.Top;

                    bool isAnyButtonHit = false;
                    foreach (TitleBarImageButton crtBtn in titleBarButtons.Values)
                    {
                        //if mouse is over the button, or mouse is pressed 
                        //(do not process messages when mouse was pressed on a button)
                        if (crtBtn.HitTest(p) || crtBtn.MouseButtonState == MouseButtonState.PRESSED)
                        {
                            //return 18 (do not process further)
                            m.Result = (IntPtr)18;
                            //we have a hit
                            isAnyButtonHit = true;
                            //return 
                            break;
                        }
                        else
                        {//mouse is not pressed and not over the button, redraw button if needed  
                            if (crtBtn.ButtonState != ImageButtonState.NORMAL)
                            {
                                crtBtn.ButtonState = ImageButtonState.NORMAL;
                                crtBtn.DrawButton(m.HWnd);
                            }
                        }
                    }
                    //if we have a hit, do not process further
                    if (!isAnyButtonHit)
                        //Call base method
                        base.WndProc(ref m);
                    break;
                default:
                    //Call base method
                    base.WndProc(ref m);
                    //Console.WriteLine(m.Msg + "(0x" + m.Msg.ToString("x") + ")");
                    break;
            }

The code demonstrates the messages that heve to be treated and how to treat them. The code uses a collection of custom TitleBarButton objets. That class is too big to be included here but I can provide it if needed along with an example.