BCB 窗体透明控件

////////////////////////////////////////////////////////////////////////////////////////////////

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);
}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////

//wei@shijun.com
//http://www.shijun.com
//5/19/2001