MFC乱七八糟笔记

1.CBitmap-------------------------------------------------------------------------------------

1、类层次
CObject
    CGdiObject
        CBitmap
BOOL CGdiObject::~CGdiObject()
{
    if (m_hObject == NULL)
  return FALSE;
 return ::DeleteObject(Detach());
}
从CGdiObject的析构函数中,可以看出有先Detach再Delete

2、BOOL CBitmap::LoadBitmap(LPCTSTR lpszResourceName);
   BOOL CBitmap::LoadBitmap(UINT nIDResource);
对应Win32 SDK中的LoadBitmap
HBITMAP LoadBitmap(
  HINSTANCE hInstance,  // handle to application instance
  LPCTSTR lpBitmapName  // name of bitmap resource
);
注意:由LoadBitmap

2.CDC-----------------------------------------------------------------------------------------------

class CDC : public CObject
{
public:
 static CDC* PASCAL FromHandle(HDC hDC);
 
 // Attach与Detach函数
 BOOL Attach(HDC hDC);
 HDC Detach();
 
 // 构造与析构函数
 CDC();
 virtual ~CDC();
}

1、CDC的构造函数和析构函数
CDC::CDC()
{
 m_hDC = NULL;
}
CDC::~CDC()
{
 if (m_hDC != NULL)
  ::DeleteDC(Detach());
}
从析构函数中可以看出,释放了关联的HDC
并且在Delete之前还Detach了

2、Attach用于将CDC的对象和HDC的句柄关联在一起
   Detach则相反
BOOL CDC::Attach(HDC hDC)
{
 if (hDC == NULL)
 {
  return FALSE;
 }

 m_hDC = hDC;
 CHandleMap* pMap = afxMapHDC(TRUE); // create map if not exist
 pMap->SetPermanent(m_hDC, this);

 return TRUE;
}
HDC CDC::Detach()
{
 HDC hDC = m_hDC;
 if (hDC != NULL)
 {
  CHandleMap* pMap = afxMapHDC(); // don't create if not exist
  if (pMap != NULL)
   pMap->RemoveHandle(m_hDC);
 }
 m_hDC = NULL;
 
 return hDC;
}

3、FromHandle从映射表中查找有无hDC对应的CDC
   有则返回其指针;没有则先new一个临时的CDC的对象,将其和hDC关联再返回其指针
   注意:这个临时的CDC对象不用由用户delete,系统的空闲线程会处理
CDC* PASCAL CDC::FromHandle(HDC hDC)
{
 CHandleMap* pMap = afxMapHDC(TRUE);       //create map if not exist
 CDC* pDC = (CDC*)pMap->FromHandle(hDC);   // 如果pMap中不存在hDC关联的CDC对象,则new一CDC对象并和hDC关联
 return pDC;
}

3.CDialog----------------------------------------------------------------------------------

1、CDialog析构时销毁了与之关联的窗口
CDialog::~CDialog()
{
 if (m_hWnd != NULL)
 {
  DestroyWindow();
 }
}

4.CWnd---------------------------------------------------------------------------------------

1、CWnd析构时销毁了与之关联的窗口
CWnd::~CWnd()
{
 if (m_hWnd != NULL)
 {
  DestroyWindow();
 }
}

2、获取桌面窗口句柄
static CWnd* PASCAL CWnd::GetDesktopWindow();
对应Win32 SDK中的为
HWND GetDesktopWindow(VOID);