<b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .endif</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; invoke 
  CallWindowProc,OldWndProc,hEdit,uMsg,eax,lParam</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ret</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .endif</b> <br>
  <b>&nbsp;&nbsp;&nbsp; .elseif uMsg==WM_KEYDOWN</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; mov eax,wParam</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .if al==VK_RETURN</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; invoke 
  MessageBox,hEdit,addr Message,addr AppName,MB_OK+MB_ICONINFORMATION</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; invoke 
  SetFocus,hEdit</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .elseif al==VK_TAB</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; invoke 
  GetKeyState,VK_SHIFT</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; test eax,80000000</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .if ZERO?</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke GetWindow,hEdit,GW_HWNDNEXT</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  .if eax==NULL</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke GetWindow,hEdit,GW_HWNDFIRST</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  .endif</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .else</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke GetWindow,hEdit,GW_HWNDPREV</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  .if eax==NULL</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke GetWindow,hEdit,GW_HWNDLAST</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  .endif</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .endif</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; invoke 
  SetFocus,eax</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; xor eax,eax</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ret</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .else</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; invoke 
  CallWindowProc,OldWndProc,hEdit,uMsg,wParam,lParam</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ret</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .endif</b> <br>
  <b>&nbsp;&nbsp;&nbsp; .else</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; invoke CallWindowProc,OldWndProc,hEdit,uMsg,wParam,lParam</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ret</b> <br>
  <b>&nbsp;&nbsp;&nbsp; .endif</b> <br>
  <b>&nbsp;&nbsp;&nbsp; xor eax,eax</b> <br>
  <b>&nbsp;&nbsp;&nbsp; ret</b> <br>
  <b>EditWndProc endp</b> <br>
  <b>end start</b> <br>
  &nbsp; 
<h3> Analysis:</h3>
The program will create a simple window with 6 "modified" edit controls in its 
client area. The edit controls will accept only hex digits. Actually, I modified 
the subclassing example to do superclassing. The program starts normally and the 
interesting part is when the main window is created: 
<p><b>&nbsp;&nbsp;&nbsp; .if uMsg==WM_CREATE</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; mov wc.cbSize,sizeof WNDCLASSEX</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; invoke GetClassInfoEx,NULL,addr 
  EditClass,addr wc</b> 
<p>We must first fill the WNDCLASSEX structure with the data from the class which 
  we want to superclass, in this case, it's EDIT class. Remember that you must 
  set the cbSize member of the WNDCLASSEX structure before you call GetClassInfoEx 
  else the WNDCLASSEX structure will not be filled properly. After GetClassInfoEx 
  returns, wc is filled with all information we need to create a new window class. 
<p><b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; push wc.lpfnWndProc</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; pop OldWndProc</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; mov wc.lpfnWndProc, OFFSET EditWndProc</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; push hInstance</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; pop wc.hInstance</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; mov wc.lpszClassName,OFFSET OurClass</b> 
<p>Now we must modify some members of wc. The first one is the pointer to the 
  window procedure. Since we need to chain our own window procedure with the original 
  one, we have to save it into a variable so we can call it with CallWindowProc. 
  This technique is identical to subclassing except that you modify the WNDCLASSEX 
  structure directly without having to call SetWindowLong. The next two members 
  must be changed else you will not be able to register your new window class, 
  hInstance and lpsClassName. You must replace original hInstance value with hInstance 
  of your own program. And you must choose a new name for the new class. 
<p><b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; invoke RegisterClassEx, addr 
  wc</b> 
<p>When all is ready, register the new class. You will get a new class with some 
  characteristics of the old class. 
<p><b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; xor ebx,ebx</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; mov edi,20</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .while ebx&lt;6</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; invoke 
  CreateWindowEx,WS_EX_CLIENTEDGE,ADDR OurClass,NULL,\</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  WS_CHILD+WS_VISIBLE+WS_BORDER,20,\</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  edi,300,25,hWnd,ebx,\</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  hInstance,NULL</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; mov dword 
  ptr [hwndEdit+4*ebx],eax</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; add edi,25</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; inc ebx</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .endw</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; invoke SetFocus,hwndEdit</b> 
<p>Now that we registered the class, we can create windows based on it. In the 
  above snippet, I use ebx as the counter of the number of windows created. edi 
  is used as the y coordinate of the left upper corner of the window. When a window 
  is created, its handle is stored in the array of dwords. When all windows are 
  created, set input focus to the first window. <br>
  At this point, you got 6 edit controls which accept only hex digits. The substituted 
  window proc handles the filter. Actually, it's identical to the window proc 
  in subclassing example. As you can see, you don't have to do extra work of subclassing 
  them. 
<p>I throw in a code snippet to handle control navigation with tabs to make this 
  example more juicy. Normally, if you put controls on a dialog box, the dialog 
  box manager handles the navigation keys for you so you can tab to go to the 
  next control or shift-tab to go back to the previous control. Alas, such feature 
  is not available if you put your controls on a simple window. You have to subclass 
  them so you can handle the Tab keys yourself. In our example, we need not subclass 
  the controls one by one because we already superclassed them, so we can provide 
  a "central control navigation manager" for them. <br>
  &nbsp; 
<p><b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .elseif al==VK_TAB</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; invoke 
  GetKeyState,VK_SHIFT</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; test eax,80000000</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .if ZERO?</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke GetWindow,hEdit,GW_HWNDNEXT</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  .if eax==NULL</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke GetWindow,hEdit,GW_HWNDFIRST</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  .endif</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .else</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke GetWindow,hEdit,GW_HWNDPREV</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  .if eax==NULL</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke GetWindow,hEdit,GW_HWNDLAST</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  .endif</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .endif</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; invoke 
  SetFocus,eax</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; xor eax,eax</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ret</b> 
<p>The above code snippet is from EditWndClass procedure. It checks if the user 
  press Tab key, if so, it call GetKeyState to check if&nbsp; the SHIFT key is 
  also pressed. GetKeyState returns a value in eax that determines whether the 
  specified key is pressed or not. If the key is pressed, the high bit of eax 
  is set. If not, the high bit is clear. So we test the return value against 80000000h. 
  If the high bit is set, it means the user pressed shift+tab which we must handle 
  separately. <br>
  If the user press Tab key alone, we call GetWindow to retrieve the handle of 
  the next control. We use GW_HWNDNEXT flag to tell GetWindow to obtain the handle 
  to the window that is next in line to the current hEdit. If this function returns 
  NULL, we interpret it as no more handle to obtain so the current hEdit is the 
  last control in the line. We will "wrap around" to the first control by calling 
  GetWindow with GW_HWNDFIRST flag. Similar to the Tab case, shift-tab just works 
  in reverse. 
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