Comment dessiner bouton personnalisé dans la barre de titre de la Fenêtre avec Windows Forms?

Je sais, ça fait longtemps depuis la dernière réponse, mais cela m'a vraiment aidé récemment et je voudrais mettre à jour le code fourni par Chris avec mes commentaires et modifications.
La version fonctionne parfaitement sur Win XP et Win 2003. Sur Win 2008 ot a un petit bug que je n'étais pas en mesure d'identifier, lorsque le redimensionnement des fenêtres. Fonctionne sur Vista trop (pas-Aero), mais notez que la barre de titre, les boutons ne sont pas carrés, et un bouton de dimensions à prendre en compte.

 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;
}

Le code montre les messages qui réveillon à traiter et la manière de les traiter.
Le code utilise une collection de custom TitleBarButton objets. Cette classe est trop gros pour être inclus ici, mais je peux fournir si nécessaire avec un exemple.