WTL for MFC Programmers(5)

snaill

Defining a Window Implementation

定义一个窗体实现

Any non-dialog window you create will derive from CWindowImpl. Your new class needs to contain three things:

你所产生的任何非对话框的窗体都将从CWindowImpl派生，你需要为你的新类做下面的3件事：

1. A window class definition

2. A message map

3. The default styles to use for the window, called the window traits

1．一个窗体类的定义

2．一个消息映射

3．调用窗体特征为窗体使用缺省的风格。

The window class definition is done using the DECLARE_WND_CLASS or DECLARE_WND_CLASS_EX macro. Both of these define an ATL struct CWndClassInfo that wraps the WNDCLASSEX struct. DECLARE_WND_CLASS lets you specify the new window class name and uses default values for the other members, while DECLARE_WND_CLASS_EX lets you also specify a class style and window background color. You can also use NULL for the class name, and ATL will generate a name for you.

窗体类的定义需要使用DECLARE_WND_CLASS或DECLARE_WND_CLASS_EX宏。这两个宏都将定义一个封装了WNDCLASSEX结构的ATL结构CWndClassInfo。DECLARE_WND_CLASS允许你提供一个新的窗体名并对其他的窗体参数赋缺省值，DECLARE_WND_CLASS_EX允许你提供一个类的风格和窗体的背景色。你可以将类名赋空值，ATL将自动为你生成一个类名。

Let´s start out a new class definition, and I´ll keep adding to it as we go through this section.

让我们开始一个新的类定义，我将在本章中不断地为它加入新的内容。

class CMyWindow : public CWindowImpl<CMyWindow>

{

public:

DECLARE_WND_CLASS(_T("My Window Class"))

};

Next comes the message map. ATL message maps are much simpler than MFC maps. An ATL map expands into a big switch statement; the switch looks for the right handler and calls the corresponding function. The macros for the message map are BEGIN_MSG_MAP and END_MSG_MAP. Let´s add an empty map to our window.

下面开始消息映射。ATL的消息映射比MFC简单的多。它就像一个大的switch语句，通过switch找到正确的句柄并执行相应的函数。消息映射宏是BEGIN_MSG_MAP和END_MSG_MAP。下面让我们添加一个空的消息映射到我们的窗体。

class CMyWindow : public CWindowImpl<CMyWindow>

{

public:

DECLARE_WND_CLASS(_T("My Window Class"))

BEGIN_MSG_MAP(CMyWindow)

END_MSG_MAP()

};

I´ll cover how to add handlers to the map in the next section. Finally, we need to define the window traits for our class. Window traits are a combination of window styles and extended window styles that are used when creating the window. The styles are specified as template parameters so the caller doesn´t have to be bothered with getting the styles right when it creates our window. Here´s a sample traits definition using the ATL class CWinTraits:

我将在下一节讲述如何添加一个句柄到映射中。最后，我们需要为我们的类定义窗体特征。窗体特征是产生窗体时使用的窗体风格和扩展窗体风格的合并。它像模板参数一样提供，使得调用程序不必再为产生窗体时如何取到正确的风格而烦恼。下面是一个使用ATL类CWinTraits定义特征的简单例子：

typedef CWinTraits<WS_OVERLAPPEDWINDOW | WS_CLIPCHILDREN,

WS_EX_APPWINDOW> CMyWindowTraits;

class CMyWindow : public CWindowImpl<CMyWindow, CWindow, CMyWindowTraits>

{

public:

DECLARE_WND_CLASS(_T("My Window Class"))

BEGIN_MSG_MAP(CMyWindow)

END_MSG_MAP()

};

The caller can override the styles in the CMyWindowTraits definition, but generally this is not necessary. ATL also has a few predefined CWinTraits specializations, one of which is perfect for top-level windows like ours, CFrameWinTraits:

调用程序能够在CMyWindowTraits定义时重载风格，但这并不是很必要的。ATL也提供一些预定义的CWinTraits的特殊形式，如为顶级窗体使用的CFrameWinTraits:

typedef CWinTraits<WS_OVERLAPPEDWINDOW | WS_CLIPCHILDREN |

WS_CLIPSIBLINGS,

WS_EX_APPWINDOW | WS_EX_WINDOWEDGE>

CFrameWinTraits;