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Hi, I'm trying to create a new component deriving from TComboBox...the only thing I want it does is:
1) the control background color must become yellow when it receives focus
2) the control background color must become white when it receives focus

This is my actual code:

static inline void ValidCtrCheck(TPComboBox *)
{
new TPComboBox(NULL);
}

//========== COSTRUTTORI ===================
__fastcall TPComboBox::TPComboBox(TComponent* Owner)
: TComboBox(Owner)
{
InitClassVariables();
// Intercetto i messaggi Windows nel metodo SubClassWndProc
WindowProc = SubClassWndProc;
}

//========== DISTRUTTORE ===================
__fastcall TPComboBox::~TPComboBox(void)
{

}

//=============== FUNZIONI PRIVATE ====================
void __fastcall TPComboBox::SubClassWndProc(Messages::TMessage &Message)
{
switch (Message.Msg)
{
case WM_SETFOCUS:
HandlerMessage_WM_SETFOCUS(Message);
break;

case WM_KILLFOCUS:
HandlerMessage_WM_KILLFOCUS(Message);
break;

case WM_CHAR:
HandlerMessage_WM_CHAR(Message);
break;
default:
inherited::WndProc(Message);
break;
}
}

void __fastcall TPComboBox::HandlerMessage_WM_SETFOCUS(TMessage &Message)
{
assert(Message.Msg == WM_SETFOCUS);

if (Message.Msg != WM_SETFOCUS) return;

inherited::WndProc(Message);
this->Color = this->m_SetFocusColor;
}

void __fastcall TPComboBox::HandlerMessage_WM_KILLFOCUS(TMessage &Message)
{
assert(Message.Msg == WM_KILLFOCUS);

if (Message.Msg != WM_KILLFOCUS) return;

inherited::WndProc(Message);
this->Color = this->m_KillFocusColor;
}

void __fastcall TPComboBox::HandlerMessage_WM_CHAR(TMessage &Message)
{
assert(Message.Msg == WM_CHAR);

if (Message.Msg != WM_CHAR) return;

if ((this->Style == csDropDownList) && (this->m_AutoComplete))
{
char cChar = Message.WParam;
int iItemIndex = CB_ERR;
this->m_sPartialStringToSearch += AnsiString(cChar);
iItemIndex = SendMessage(this->Handle,
CB_FINDSTRING,
-1,
(LPARAM)this->m_sPartialStringToSearch.c_str());
if (iItemIndex == CB_ERR)
{
this->m_sPartialStringToSearch = AnsiString(cChar);
iItemIndex = SendMessage(this->Handle,
CB_FINDSTRING,
-1,
(LPARAM)this->m_sPartialStringToSearch.c_str());
}
if (iItemIndex != CB_ERR)
{
int iCurrentItemIndex = this->ItemIndex;
this->ItemIndex = iItemIndex;
// Devo scatenare l'evento DOPO che l'item e' cambiato
// (comportamento STANDARD delle ComboBox)
if (iCurrentItemIndex != iItemIndex)
{
DoChange();
}
}
}
else
{
this->m_sPartialStringToSearch = "";
// Comportamento Standard
inherited::WndProc(Message);
}
}

//=============== ALTRE FUNZIONI ====================
void __fastcall TPComboBox::InitClassVariables(void)
{
this->m_SetFocusColor = clYellow;
this->m_KillFocusColor = clWindow;
}

void __fastcall TPComboBox::SetAutoComplete(bool Value)
{
this->m_AutoComplete = Value;
if (!this->m_AutoComplete)
{
this->m_sPartialStringToSearch = "";
}
else
{
}
}

//=============== FUNZIONI PROTETTE ====================
void __fastcall TPComboBox::DoChange(void)
{
if (this->OnChange) this->OnChange(this);
}

I've got a problem when the combo receives the focus: both the messages WM_SETFOCUS and WM_KILLFOCUS are sent to the component.
If I set the style of the Combo as DropDownList the behaviour is right (yellow when it gets focus, window when it losts it).
Any advice???
TIA.