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 the WndProc procedure, but I haven’t been able to figure out a solution that works right.

Does anyone know how to do this? More specifically, does anyone know a way to do this that works in Vista?

Answer 1

The following will work in XP, I have no Vista machine handy to test it, but I think your issues are steming from an incorrect hWnd somehow. Anyway, on with the poorly commented code.

// The state of our little button ButtonState _buttState = ButtonState.Normal; Rectangle _buttPosition = new Rectangle();  [DllImport('user32.dll')] private static extern IntPtr GetWindowDC(IntPtr hWnd); [DllImport('user32.dll')] private static extern int GetWindowRect(IntPtr hWnd,                                          ref Rectangle lpRect); [DllImport('user32.dll')] private static extern int ReleaseDC(IntPtr hWnd, IntPtr hDC); protected override void WndProc(ref Message m) {     int x, y;     Rectangle windowRect = new Rectangle();     GetWindowRect(m.HWnd, ref windowRect);      switch (m.Msg)     {         // WM_NCPAINT         case 0x85:         // WM_PAINT         case 0x0A:             base.WndProc(ref m);              DrawButton(m.HWnd);              m.Result = IntPtr.Zero;              break;          // WM_ACTIVATE         case 0x86:             base.WndProc(ref m);             DrawButton(m.HWnd);              break;          // WM_NCMOUSEMOVE         case 0xA0:             // Extract the least significant 16 bits             x = ((int)m.LParam << 16) >> 16;             // Extract the most significant 16 bits             y = (int)m.LParam >> 16;              x -= windowRect.Left;             y -= windowRect.Top;              base.WndProc(ref m);              if (!_buttPosition.Contains(new Point(x, y)) &&                  _buttState == ButtonState.Pushed)             {                 _buttState = ButtonState.Normal;                 DrawButton(m.HWnd);             }              break;          // WM_NCLBUTTONDOWN         case 0xA1:             // Extract the least significant 16 bits             x = ((int)m.LParam << 16) >> 16;             // Extract the most significant 16 bits             y = (int)m.LParam >> 16;              x -= windowRect.Left;             y -= windowRect.Top;              if (_buttPosition.Contains(new Point(x, y)))             {                 _buttState = ButtonState.Pushed;                 DrawButton(m.HWnd);             }             else                 base.WndProc(ref m);              break;          // WM_NCLBUTTONUP         case 0xA2:             // Extract the least significant 16 bits             x = ((int)m.LParam << 16) >> 16;             // Extract the most significant 16 bits             y = (int)m.LParam >> 16;              x -= windowRect.Left;             y -= windowRect.Top;              if (_buttPosition.Contains(new Point(x, y)) &&                 _buttState == ButtonState.Pushed)             {                 _buttState = ButtonState.Normal;                 // [[TODO]]: Fire a click event for your button                  //           however you want to do it.                 DrawButton(m.HWnd);             }             else                 base.WndProc(ref m);              break;          // WM_NCHITTEST         case 0x84:             // Extract the least significant 16 bits             x = ((int)m.LParam << 16) >> 16;             // Extract the most significant 16 bits             y = (int)m.LParam >> 16;              x -= windowRect.Left;             y -= windowRect.Top;              if (_buttPosition.Contains(new Point(x, y)))                 m.Result = (IntPtr)18; // HTBORDER             else                 base.WndProc(ref m);              break;          default:             base.WndProc(ref m);             break;     } }  private void DrawButton(IntPtr hwnd) {     IntPtr hDC = GetWindowDC(hwnd);     int x, y;      using (Graphics g = Graphics.FromHdc(hDC))     {         // Work out size and positioning         int CaptionHeight = Bounds.Height - ClientRectangle.Height;         Size ButtonSize = SystemInformation.CaptionButtonSize;         x = Bounds.Width - 4 * ButtonSize.Width;         y = (CaptionHeight - ButtonSize.Height) / 2;         _buttPosition.Location = new Point(x, y);          // Work out color         Brush color;         if (_buttState == ButtonState.Pushed)             color = Brushes.LightGreen;         else             color = Brushes.Red;          // Draw our 'button'         g.FillRectangle(color, x, y, ButtonSize.Width, ButtonSize.Height);     }      ReleaseDC(hwnd, hDC); }  private void Form1_Load(object sender, EventArgs e) {     _buttPosition.Size = SystemInformation.CaptionButtonSize; }