BCB窗体透明控件

头文件：//---------------------------------------------------------------------------#ifndef TransparentFormH
#define TransparentFormH
//---------------------------------------------------------------------------
#include <SysUtils.hpp>
#include <Controls.hpp>
#include <Classes.hpp>
#include <Forms.hpp>
//---------------------------------------------------------------------------
class PACKAGE TTransparentForm : public TComponent
{
private:
protected:
    int m_nAlphaValue;
    HWND m_hParentFormHandle;
    void __fastcall SetAlphaValue(int nAlpha);
    void __fastcall UpdateDisplay();
public:
    __fastcall TTransparentForm(TComponent* Owner);
__published:
    __property int AlphaValue = {read = m_nAlphaValue, write = SetAlphaValue, default = 0};
};
//---------------------------------------------------------------------------
#endif
////////////////////////////////////////////////////////////////////////////////////////////////cpp文件： //---------------------------------------------------------------------------#include <vcl.h>
#pragma hdrstop#include \"TransparentForm.h\"
#pragma package(smart_init)
//---------------------------------------------------------------------------
// ValidCtrCheck is used to assure that the components created do not have
// any pure virtual functions.
// 
static inline void ValidCtrCheck(TTransparentForm *)
{
    new TTransparentForm(NULL);
}
//---------------------------------------------------------------------------
__fastcall TTransparentForm::TTransparentForm(TComponent* Owner)
    : TComponent(Owner)
{
    if (ComponentState.Contains(csDesigning))
        return;
    m_nAlphaValue = 255 ;
    m_hParentFormHandle = ((TForm *)(Owner))->Handle ;
    SetWindowLong(m_hParentFormHandle, GWL_EXSTYLE, GetWindowLong(m_hParentFormHandle, GWL_EXSTYLE) | WS_EX_LAYERED);
}
//---------------------------------------------------------------------------
namespace Transparentform
{
    void __fastcall PACKAGE Register()
    {
         TComponentClass classes[1] = {__classid(TTransparentForm)};
         RegisterComponents(\"Easysoft\", classes, 0);
    }
}
//---------------------------------------------------------------------------
void __fastcall TTransparentForm::SetAlphaValue(int nAlpha)
{
    if (nAlpha >= 0 && nAlpha < 256)
    {
        m_nAlphaValue = nAlpha;
        UpdateDisplay();
    }
}void __fastcall TTransparentForm::UpdateDisplay()
{
    if (ComponentState.Contains(csDesigning))
        return;
    SetLayeredWindowAttributes(m_hParentFormHandle, 0, m_nAlphaValue, 2);
}