atl under the hood - part 5.mht

大家知道wtl是window UI库

        <SPAN class=3Dcpp-keyword>return</SPAN> ::DefWindowProc(hWnd, =
uMsg, wParam, lParam);
    }
};

<SPAN class=3Dcpp-keyword>int</SPAN> WINAPI WinMain(HINSTANCE hInstance, =
HINSTANCE hPrevInstance,=20
                   LPSTR lpCmdLine,   <SPAN =
class=3Dcpp-keyword>int</SPAN> nCmdShow)
{
    <SPAN class=3Dcpp-keyword>char</SPAN> szAppName[] =3D <SPAN =
class=3Dcpp-string>"Hello world"</SPAN>;
    MSG msg;
    WNDCLASS wnd;
    ZWindow zwnd;
   =20
    wnd.cbClsExtra    =3D NULL;
    wnd.cbWndExtra    =3D NULL;
    wnd.hbrBackground    =3D (HBRUSH)GetStockObject(WHITE_BRUSH);
    wnd.hCursor    =3D LoadCursor(NULL, IDC_ARROW);
    wnd.hIcon        =3D LoadIcon(NULL, IDI_APPLICATION);
    wnd.hInstance    =3D hInstance;
    wnd.lpfnWndProc    =3D zwnd.WndProc;
    wnd.lpszClassName    =3D szAppName;
    wnd.lpszMenuName    =3D NULL;
    wnd.style        =3D CS_HREDRAW | CS_VREDRAW;
   =20
    <SPAN class=3Dcpp-keyword>if</SPAN> (!RegisterClass(&amp;wnd))
    {
        MessageBox(NULL, <SPAN class=3Dcpp-string>"Can not register =
window class"</SPAN>, <SPAN class=3Dcpp-string>"Error"</SPAN>,=20
                   MB_OK | MB_ICONINFORMATION);
        <SPAN class=3Dcpp-keyword>return</SPAN> -<SPAN =
class=3Dcpp-literal>1</SPAN>;
    }

    g_pWnd =3D &amp;zwnd;
    zwnd.Create(szAppName, <SPAN class=3Dcpp-string>"Hell world"</SPAN>, =
hInstance);
    zwnd.ShowWindow(nCmdShow);
    zwnd.UpdateWindow();

    <SPAN class=3Dcpp-keyword>while</SPAN> (GetMessage(&amp;msg, NULL, =
<SPAN class=3Dcpp-literal>0</SPAN>, <SPAN class=3Dcpp-literal>0</SPAN>))
    {
        DispatchMessage(&amp;msg);
    }
   =20
    <SPAN class=3Dcpp-keyword>return</SPAN> msg.wParam;
}
</PRE>
      <P>So we finally we have working program. Now let's take the =
advantage of=20
      Object Oriented programming. If we call function on each message =
and made=20
      that function virtual then we can call those functions when we =
inherit=20
      class from ZWindow. So we can customize the default behavior of =
ZWindow.=20
      Now the <CODE>WndProc</CODE> is something like this </P><PRE><SPAN =
class=3Dcpp-keyword>static</SPAN> LRESULT CALLBACK WndProc(HWND hWnd, =
UINT uMsg, WPARAM wParam,=20
                                LPARAM lParam)
{
    ZWindow* pThis =3D g_pWnd;

    <SPAN class=3Dcpp-keyword>switch</SPAN> (uMsg)
    {
    <SPAN class=3Dcpp-keyword>case</SPAN> WM_CREATE:
        pThis-&gt;OnCreate(wParam, lParam);
        <SPAN class=3Dcpp-keyword>break</SPAN>;

    <SPAN class=3Dcpp-keyword>case</SPAN> WM_PAINT:
        pThis-&gt;OnPaint(wParam, lParam);
        <SPAN class=3Dcpp-keyword>break</SPAN>;

    <SPAN class=3Dcpp-keyword>case</SPAN> WM_DESTROY:
        ::PostQuitMessage(<SPAN class=3Dcpp-literal>0</SPAN>);
        <SPAN class=3Dcpp-keyword>break</SPAN>;
    }

    <SPAN class=3Dcpp-keyword>return</SPAN> ::DefWindowProc(hWnd, uMsg, =
wParam, lParam);
}
</PRE>
      <P>Here <CODE>OnCreate</CODE> and <CODE>OnPaint</CODE> are virtual =

      function. And when we inherit the class from ZWindow then we can =
override=20
      all those function which we want to customize. Here is a complete =
program=20
      which shows the usage of <CODE>WM_PAINT</CODE> message in the =
drive class.=20
      </P><B>Program 70</B> <PRE><SPAN class=3Dcpp-preprocessor>#include =
&lt;windows.h&gt;</SPAN>

<SPAN class=3Dcpp-keyword>class</SPAN> ZWindow;

ZWindow* g_pWnd =3D NULL;

<SPAN class=3Dcpp-keyword>class</SPAN> ZWindow
{
<SPAN class=3Dcpp-keyword>public</SPAN>:
    HWND m_hWnd;

    ZWindow(HWND hWnd =3D <SPAN class=3Dcpp-literal>0</SPAN>) : =
m_hWnd(hWnd) { }

    <SPAN class=3Dcpp-keyword>inline</SPAN> <SPAN =
class=3Dcpp-keyword>void</SPAN> Attach(HWND hWnd)
    { m_hWnd =3D hWnd; }

    <SPAN class=3Dcpp-keyword>inline</SPAN> BOOL ShowWindow(<SPAN =
class=3Dcpp-keyword>int</SPAN> nCmdShow)
    { <SPAN class=3Dcpp-keyword>return</SPAN> ::ShowWindow(m_hWnd, =
nCmdShow); }

    <SPAN class=3Dcpp-keyword>inline</SPAN> BOOL UpdateWindow()
    {  <SPAN class=3Dcpp-keyword>return</SPAN> ::UpdateWindow(m_hWnd); }

    <SPAN class=3Dcpp-keyword>inline</SPAN> HDC BeginPaint(LPPAINTSTRUCT =
ps)
    {  <SPAN class=3Dcpp-keyword>return</SPAN> ::BeginPaint(m_hWnd, ps); =
}

    <SPAN class=3Dcpp-keyword>inline</SPAN> BOOL EndPaint(LPPAINTSTRUCT =
ps)
    {  <SPAN class=3Dcpp-keyword>return</SPAN> ::EndPaint(m_hWnd, ps); }

    <SPAN class=3Dcpp-keyword>inline</SPAN> BOOL GetClientRect(LPRECT =
rect)
    {  <SPAN class=3Dcpp-keyword>return</SPAN> ::GetClientRect(m_hWnd, =
rect); }

    BOOL Create(LPCTSTR szClassName, LPCTSTR szTitle, HINSTANCE =
hInstance,=20
                HWND hWndParent =3D <SPAN class=3Dcpp-literal>0</SPAN>, =
DWORD dwStyle =3D WS_OVERLAPPEDWINDOW,=20
                DWORD dwExStyle =3D <SPAN class=3Dcpp-literal>0</SPAN>, =
HMENU hMenu =3D <SPAN class=3Dcpp-literal>0</SPAN>)
    {
        m_hWnd =3D ::CreateWindowEx(dwExStyle, szClassName, szTitle, =
dwStyle,=20
                                  CW_USEDEFAULT,CW_USEDEFAULT, =
CW_USEDEFAULT,=20
                                  CW_USEDEFAULT, hWndParent, hMenu, =
hInstance, NULL);
        <SPAN class=3Dcpp-keyword>return</SPAN> m_hWnd !=3D NULL;
    }

    <SPAN class=3Dcpp-keyword>virtual</SPAN> LRESULT OnPaint(WPARAM =
wParam, LPARAM lParam)
    {
        HDC hDC;
        PAINTSTRUCT ps;
        RECT rect;

        hDC =3D BeginPaint(&amp;ps);
        GetClientRect(&amp;rect);
        ::DrawText(hDC, <SPAN class=3Dcpp-string>"Hello world"</SPAN>, =
-<SPAN class=3Dcpp-literal>1</SPAN>, &amp;rect,=20
                   DT_CENTER | DT_VCENTER | DT_SINGLELINE);
        EndPaint(&amp;ps);
        <SPAN class=3Dcpp-keyword>return</SPAN> <SPAN =
class=3Dcpp-literal>0</SPAN>;
    }

    <SPAN class=3Dcpp-keyword>virtual</SPAN> LRESULT OnCreate(WPARAM =
wParam, LPARAM lParam)
    {
        <SPAN class=3Dcpp-keyword>return</SPAN> <SPAN =
class=3Dcpp-literal>0</SPAN>;
    }

    <SPAN class=3Dcpp-keyword>static</SPAN> LRESULT CALLBACK =
WndProc(HWND hWnd, UINT uMsg, WPARAM wParam,=20
                                    LPARAM lParam)
    {
        ZWindow* pThis =3D g_pWnd;

        <SPAN class=3Dcpp-keyword>switch</SPAN> (uMsg)
        {
        <SPAN class=3Dcpp-keyword>case</SPAN> WM_CREATE:
            pThis-&gt;OnCreate(wParam, lParam);
            <SPAN class=3Dcpp-keyword>break</SPAN>;

        <SPAN class=3Dcpp-keyword>case</SPAN> WM_PAINT:
            pThis-&gt;OnPaint(wParam, lParam);
            <SPAN class=3Dcpp-keyword>break</SPAN>;

        <SPAN class=3Dcpp-keyword>case</SPAN> WM_DESTROY:
            ::PostQuitMessage(<SPAN class=3Dcpp-literal>0</SPAN>);
            <SPAN class=3Dcpp-keyword>break</SPAN>;
        }

        <SPAN class=3Dcpp-keyword>return</SPAN> ::DefWindowProc(hWnd, =
uMsg, wParam, lParam);
    }
};

<SPAN class=3Dcpp-keyword>class</SPAN> ZDriveWindow : <SPAN =
class=3Dcpp-keyword>public</SPAN> ZWindow
{
<SPAN class=3Dcpp-keyword>public</SPAN>:
    LRESULT OnPaint(WPARAM wParam, LPARAM lParam)
    {
        HDC hDC;
        PAINTSTRUCT ps;
        RECT rect;

        hDC =3D BeginPaint(&amp;ps);
        GetClientRect(&amp;rect);
        SetBkMode(hDC, TRANSPARENT);
        DrawText(hDC, <SPAN class=3Dcpp-string>"Hello world From =
Drive"</SPAN>, -<SPAN class=3Dcpp-literal>1</SPAN>, &amp;rect,=20
                 DT_CENTER | DT_VCENTER | DT_SINGLELINE);
        EndPaint(&amp;ps);

        <SPAN class=3Dcpp-keyword>return</SPAN> <SPAN =
class=3Dcpp-literal>0</SPAN>;
    }
};
</PRE>
      <P>The output of this program is a message "Hello world from =
Drive" in a=20
      window. Everything works fine until we work on one drive class. =
The=20
      problem started when we drive more than one class from ZWindow. =
Then all=20
      the message goes to the last drive class of ZWindow. Let's take a =
look at=20
      the following program. </P><B>Program 71</B> <PRE><SPAN =
class=3Dcpp-preprocessor>#include &lt;windows.h&gt;</SPAN>

<SPAN class=3Dcpp-keyword>class</SPAN> ZWindow;

ZWindow* g_pWnd =3D NULL;

<SPAN class=3Dcpp-keyword>class</SPAN> ZWindow
{
<SPAN class=3Dcpp-keyword>public</SPAN>:
    HWND m_hWnd;

    ZWindow(HWND hWnd =3D <SPAN class=3Dcpp-literal>0</SPAN>) : =
m_hWnd(hWnd) { }

    <SPAN class=3Dcpp-keyword>inline</SPAN> <SPAN =
class=3Dcpp-keyword>void</SPAN> Attach(HWND hWnd)
    { m_hWnd =3D hWnd; }

    <SPAN class=3Dcpp-keyword>inline</SPAN> BOOL ShowWindow(<SPAN =
class=3Dcpp-keyword>int</SPAN> nCmdShow)
    { <SPAN class=3Dcpp-keyword>return</SPAN> ::ShowWindow(m_hWnd, =
nCmdShow); }

    <SPAN class=3Dcpp-keyword>inline</SPAN> BOOL UpdateWindow()
    {  <SPAN class=3Dcpp-keyword>return</SPAN> ::UpdateWindow(m_hWnd); }

    <SPAN class=3Dcpp-keyword>inline</SPAN> HDC BeginPaint(LPPAINTSTRUCT =
ps)
    {  <SPAN class=3Dcpp-keyword>return</SPAN> ::BeginPaint(m_hWnd, ps); =
}

    <SPAN class=3Dcpp-keyword>inline</SPAN> BOOL EndPaint(LPPAINTSTRUCT =
ps)
    {  <SPAN class=3Dcpp-keyword>return</SPAN> ::EndPaint(m_hWnd, ps); }

    <SPAN class=3Dcpp-keyword>inline</SPAN> BOOL GetClientRect(LPRECT =
rect)
    {  <SPAN class=3Dcpp-keyword>return</SPAN> ::GetClientRect(m_hWnd, =
rect); }

    BOOL Create(LPCTSTR szClassName, LPCTSTR szTitle, HINSTANCE =
hInstance,=20
                HWND hWndParent =3D <SPAN class=3Dcpp-literal>0</SPAN>, =
DWORD dwStyle =3D WS_OVERLAPPEDWINDOW,=20
                DWORD dwExStyle =3D <SPAN class=3Dcpp-literal>0</SPAN>, =
HMENU hMenu =3D <SPAN class=3Dcpp-literal>0</SPAN>, <SPAN =
class=3Dcpp-keyword>int</SPAN> x =3D CW_USEDEFAULT,=20
                <SPAN class=3Dcpp-keyword>int</SPAN> y =3D =
CW_USEDEFAULT, <SPAN class=3Dcpp-keyword>int</SPAN> nWidth =3D =
CW_USEDEFAULT,=20
                <SPAN class=3Dcpp-keyword>int</SPAN> nHeight =3D =
CW_USEDEFAULT)
    {
        m_hWnd =3D ::CreateWindowEx(dwExStyle, szClassName, szTitle, =
dwStyle,=20
                                   x, y, nWidth, nHeight, hWndParent, =
hMenu,=20
                                   hInstance, NULL);
        <SPAN class=3Dcpp-keyword>return</SPAN> m_hWnd !=3D NULL;
    }

    <SPAN class=3Dcpp-keyword>virtual</SPAN> LRESULT OnPaint(WPARAM =
wParam, LPARAM lParam)
    {
        HDC hDC;
        PAINTSTRUCT ps;
        RECT rect;

        hDC =3D BeginPaint(&amp;ps);
        GetClientRect(&amp;rect);
        ::DrawText(hDC, <SPAN class=3Dcpp-string>"Hello world"</SPAN>, =
-<SPAN class=3Dcpp-literal>1</SPAN>, &amp;rect,=20
                   DT_CENTER | DT_VCENTER | DT_SINGLELINE);
        EndPaint(&amp;ps);
        <SPAN class=3Dcpp-keyword>return</SPAN> <SPAN =
class=3Dcpp-literal>0</SPAN>;
    }

    <SPAN class=3Dcpp-keyword>virtual</SPAN> LRESULT =
OnLButtonDown(WPARAM wParam, LPARAM lParam)
    {
        <SPAN class=3Dcpp-keyword>return</SPAN> <SPAN =
class=3Dcpp-literal>0</SPAN>;
    }

    <SPAN class=3Dcpp-keyword>virtual</SPAN> LRESULT OnCreate(WPARAM =
wParam, LPARAM lParam)
    {
        <SPAN class=3Dcpp-keyword>return</SPAN> <SPAN =
class=3Dcpp-literal>0</SPAN>;
    }

    <SPAN class=3Dcpp-keyword>virtual</SPAN> LRESULT OnKeyDown(WPARAM =
wParam, LPARAM lParam)
    {
        <SPAN class=3Dcpp-keyword>return</SPAN> <SPAN =
class=3Dcpp-literal>0</SPAN>;
    }

    <SPAN class=3Dcpp-keyword>static</SPAN> LRESULT CALLBACK =
StartWndProc(HWND hWnd, UINT uMsg,=20
                                          WPARAM wParam, LPARAM lParam)
    {
        ZWindow* pThis =3D g_pWnd;

        <SPAN class=3Dcpp-keyword>if</SPAN> (uMsg =3D=3D WM_NCDESTROY)
            ::PostQuitMessage(<SPAN class=3Dcpp-literal>0</SPAN>);

        <SPAN class=3Dcpp-keyword>switch</SPAN> (uMsg)
        {