windows/class.c

/*
 * Window classes functions
 *
 * Copyright 1993, 1996 Alexandre Julliard
 *           1998 Juergen Schmied (jsch)
 *
 * FIXME: In win32 all classes are local. They are registered at 
 *	  program start. Processes CANNOT share classes. (Source: some
 *	  win31->NT migration book)
 *
 * FIXME: There seems to be a general problem with hInstance in WINE
 *   classes are getting registred with wrong hInstance.
 */

#include <stdlib.h>
#include <string.h>
#include "wine/winbase16.h"
#include "winerror.h"
#include "windef.h"
#include "wingdi.h"
#include "wine/winuser16.h"
#include "wine/unicode.h"
#include "class.h"
#include "heap.h"
#include "win.h"
#include "dce.h"
#include "ldt.h"
#include "toolhelp.h"
#include "winproc.h"
#include "debugtools.h"

DEFAULT_DEBUG_CHANNEL(class);


static CLASS *firstClass = NULL;


/***********************************************************************
 *           CLASS_DumpClass
 *
 * Dump the content of a class structure to stderr.
 */
void CLASS_DumpClass( CLASS *ptr )
{
    char className[MAX_CLASSNAME+1];
    int i;

    if (ptr->magic != CLASS_MAGIC)
    {
        DPRINTF("%p is not a class\n", ptr );
        return;
    }

    GlobalGetAtomNameA( ptr->atomName, className, sizeof(className) );

    DPRINTF( "Class %p:\n", ptr );
    DPRINTF( "next=%p  name=%04x '%s'  style=%08x  wndProc=%08x\n"
             "inst=%04x  dce=%08x  icon=%04x  cursor=%04x  bkgnd=%04x\n"
             "clsExtra=%d  winExtra=%d  #windows=%d\n",
             ptr->next, ptr->atomName, className, ptr->style,
             (UINT)ptr->winproc, ptr->hInstance, (UINT)ptr->dce,
             ptr->hIcon, ptr->hCursor, ptr->hbrBackground,
             ptr->cbClsExtra, ptr->cbWndExtra, ptr->cWindows );
    if (ptr->cbClsExtra)
    {
        DPRINTF( "extra bytes:" );
        for (i = 0; i < ptr->cbClsExtra; i++)
            DPRINTF( " %02x", *((BYTE *)ptr->wExtra+i) );
        DPRINTF( "\n" );
    }
    DPRINTF( "\n" );
}


/***********************************************************************
 *           CLASS_WalkClasses
 *
 * Walk the class list and print each class on stderr.
 */
void CLASS_WalkClasses(void)
{
    CLASS *ptr;
    char className[MAX_CLASSNAME+1];

    DPRINTF( " Class   Name                  Style   WndProc\n" );
    for (ptr = firstClass; ptr; ptr = ptr->next)
    {
        GlobalGetAtomNameA( ptr->atomName, className, sizeof(className) );
        DPRINTF( "%08x %-20.20s %08x %08x\n", (UINT)ptr, className,
                 ptr->style, (UINT)ptr->winproc );
    }
    DPRINTF( "\n" );
}


/***********************************************************************
 *           CLASS_GetMenuNameA
 *
 * Get the menu name as a ASCII string.
 */
static LPSTR CLASS_GetMenuNameA( CLASS *classPtr )
{
    if (!classPtr->menuNameA && classPtr->menuNameW)
    {
        /* We need to copy the Unicode string */
        classPtr->menuNameA = SEGPTR_STRDUP_WtoA( classPtr->menuNameW );
    }
    return classPtr->menuNameA;
}


/***********************************************************************
 *           CLASS_GetMenuNameW
 *
 * Get the menu name as a Unicode string.
 */
static LPWSTR CLASS_GetMenuNameW( CLASS *classPtr )
{
    if (!classPtr->menuNameW && classPtr->menuNameA)
    {
        if (!HIWORD(classPtr->menuNameA))
            return (LPWSTR)classPtr->menuNameA;
        /* Now we need to copy the ASCII string */
        classPtr->menuNameW = HEAP_strdupAtoW( SystemHeap, 0,
                                               classPtr->menuNameA );
    }
    return classPtr->menuNameW;
}


/***********************************************************************
 *           CLASS_SetMenuNameA
 *
 * Set the menu name in a class structure by copying the string.
 */
static void CLASS_SetMenuNameA( CLASS *classPtr, LPCSTR name )
{
    if (HIWORD(classPtr->menuNameA)) SEGPTR_FREE( classPtr->menuNameA );
    if (classPtr->menuNameW) HeapFree( SystemHeap, 0, classPtr->menuNameW );
    classPtr->menuNameA = SEGPTR_STRDUP( name );
    classPtr->menuNameW = 0;
}


/***********************************************************************
 *           CLASS_SetMenuNameW
 *
 * Set the menu name in a class structure by copying the string.
 */
static void CLASS_SetMenuNameW( CLASS *classPtr, LPCWSTR name )
{
    if (!HIWORD(name))
    {
        CLASS_SetMenuNameA( classPtr, (LPCSTR)name );
        return;
    }
    if (HIWORD(classPtr->menuNameA)) SEGPTR_FREE( classPtr->menuNameA );
    if (classPtr->menuNameW) HeapFree( SystemHeap, 0, classPtr->menuNameW );
    if ((classPtr->menuNameW = HeapAlloc( SystemHeap, 0,
                                         (strlenW(name)+1)*sizeof(WCHAR) )))
        strcpyW( classPtr->menuNameW, name );
    classPtr->menuNameA = 0;
}


/***********************************************************************
 *           CLASS_GetClassNameA
 *
 * Get the clas name as a ASCII string.
 */
static LPSTR CLASS_GetClassNameA( CLASS *classPtr )
{
    if (!classPtr->classNameA && classPtr->classNameW)
    {
        /* We need to copy the Unicode string */
        classPtr->classNameA = SEGPTR_STRDUP_WtoA( classPtr->classNameW );
    }
    return classPtr->classNameA;
}


/***********************************************************************
 *           CLASS_GetClassNameW
 *
 * Get the class name as a Unicode string.
 */
static LPWSTR CLASS_GetClassNameW( CLASS *classPtr )
{
    if (!classPtr->classNameW && classPtr->classNameA)
    {
        if (!HIWORD(classPtr->classNameA))
            return (LPWSTR)classPtr->classNameA;
        /* Now we need to copy the ASCII string */
        classPtr->classNameW = HEAP_strdupAtoW( SystemHeap, 0,
                                               classPtr->classNameA );
    }
    return classPtr->classNameW;
}

/***********************************************************************
 *           CLASS_SetClassNameA
 *
 * Set the class name in a class structure by copying the string.
 */
static void CLASS_SetClassNameA( CLASS *classPtr, LPCSTR name )
{
    if (HIWORD(classPtr->classNameA)) SEGPTR_FREE( classPtr->classNameA );
    if (classPtr->classNameW) HeapFree( SystemHeap, 0, classPtr->classNameW );
    classPtr->classNameA = SEGPTR_STRDUP( name );
    classPtr->classNameW = 0;
}


/***********************************************************************
 *           CLASS_SetClassNameW
 *
 * Set the class name in a class structure by copying the string.
 */
static void CLASS_SetClassNameW( CLASS *classPtr, LPCWSTR name )
{
    if (!HIWORD(name))
    {
        CLASS_SetClassNameA( classPtr, (LPCSTR)name );
        return;
    }
    if (HIWORD(classPtr->classNameA)) SEGPTR_FREE( classPtr->classNameA );
    if (classPtr->classNameW) HeapFree( SystemHeap, 0, classPtr->classNameW );
    if ((classPtr->classNameW = HeapAlloc( SystemHeap, 0,
                                         (strlenW(name)+1)*sizeof(WCHAR) )))
        strcpyW( classPtr->classNameW, name );
    classPtr->classNameA = 0;
}


/***********************************************************************
 *           CLASS_FreeClass
 *
 * Free a class structure.
 */
static BOOL CLASS_FreeClass( CLASS *classPtr )
{
    CLASS **ppClass;
    TRACE("%p\n", classPtr);  

    /* Check if we can remove this class */

    if (classPtr->cWindows > 0) return FALSE;

    /* Remove the class from the linked list */

    for (ppClass = &firstClass; *ppClass; ppClass = &(*ppClass)->next)
        if (*ppClass == classPtr) break;
    if (!*ppClass)
    {
        ERR("Class list corrupted\n" );
        return FALSE;
    }
    *ppClass = classPtr->next;

    /* Delete the class */

    if (classPtr->dce) DCE_FreeDCE( classPtr->dce );
    if (classPtr->hbrBackground > (HBRUSH)(COLOR_GRADIENTINACTIVECAPTION + 1))
        DeleteObject( classPtr->hbrBackground );
    GlobalDeleteAtom( classPtr->atomName );
    CLASS_SetMenuNameA( classPtr, NULL );
    CLASS_SetClassNameA( classPtr, NULL );
    WINPROC_FreeProc( classPtr->winproc, WIN_PROC_CLASS );
    HeapFree( SystemHeap, 0, classPtr );
    return TRUE;
}


/***********************************************************************
 *           CLASS_FreeModuleClasses
 */
void CLASS_FreeModuleClasses( HMODULE16 hModule )
{
    CLASS *ptr, *next;
  
    TRACE("0x%08x\n", hModule); 

    for (ptr = firstClass; ptr; ptr = next)
    {
        next = ptr->next;
	if (ptr->hInstance == hModule) CLASS_FreeClass( ptr );
    }
}


/***********************************************************************
 *           CLASS_FindClassByAtom
 *
 * Return a pointer to the class.
 * hinstance has been normalized by the caller.
 *
 * NOTES
 *  980805 a local class will be found now if registred with hInst=0
 *  and looed up with a hInst!=0. msmoney does it (jsch)
 */
CLASS *CLASS_FindClassByAtom( ATOM atom, HINSTANCE hinstance )
{   CLASS * class, *tclass=0;

    TRACE("0x%08x 0x%08x\n", atom, hinstance);

    /* First search task-specific classes */

    for (class = firstClass; (class); class = class->next)
    {
        if (class->style & CS_GLOBALCLASS) continue;
        if (class->atomName == atom)
        {
            if (hinstance==class->hInstance || hinstance==0xffff )
            {
                TRACE("-- found local %p\n", class);
                return class;
            }
            if (class->hInstance==0) tclass = class;
        }
    }
    
      /* Then search global classes */

    for (class = firstClass; (class); class = class->next)
    {
        if (!(class->style & CS_GLOBALCLASS)) continue;
        if (class->atomName == atom)
        {
            TRACE("-- found global %p\n", class);
            return class;
        }
    }

    /* Then check if there was a local class with hInst=0*/
    if ( tclass )
    {
        WARN("-- found local Class registred with hInst=0\n");
        return tclass;
    }
    
    TRACE("-- not found\n");
    return 0;
}


/***********************************************************************
 *           CLASS_RegisterClass
 *
 * The real RegisterClass() functionality.
 */
static CLASS *CLASS_RegisterClass( ATOM atom, HINSTANCE hInstance,
                                   DWORD style, INT classExtra,
                                   INT winExtra, WNDPROC16 wndProc,
                                   WINDOWPROCTYPE wndProcType )
{
    CLASS *classPtr;

    TRACE("atom=0x%x hinst=0x%x style=0x%lx clExtr=0x%x winExtr=0x%x wndProc=0x%p ProcType=0x%x\n",
     atom, hInstance, style, classExtra, winExtra, wndProc, wndProcType);

   /* Check if a class with this name already exists */
    classPtr = CLASS_FindClassByAtom( atom, hInstance );
    if (classPtr)
    {
        /* Class can be created only if it is local and */
        /* if the class with the same name is global.   */

	if (style & CS_GLOBALCLASS) return NULL;
        if (!(classPtr->style & CS_GLOBALCLASS)) return NULL;
    }

    /* Fix the extra bytes value */

    if (classExtra < 0) classExtra = 0;
    else if (classExtra > 40)  /* Extra bytes are limited to 40 in Win32 */
        WARN("Class extra bytes %d is > 40\n", classExtra);
    if (winExtra < 0) winExtra = 0;
    else if (winExtra > 40)    /* Extra bytes are limited to 40 in Win32 */
        WARN("Win extra bytes %d is > 40\n", winExtra );

    /* Create the class */

    classPtr = (CLASS *)HeapAlloc( SystemHeap, 0, sizeof(CLASS) +
                                       classExtra - sizeof(classPtr->wExtra) );
    if (!classPtr) return NULL;
    classPtr->next        = firstClass;
    classPtr->magic       = CLASS_MAGIC;
    classPtr->cWindows    = 0;  
    classPtr->style       = style;
    classPtr->winproc     = (HWINDOWPROC)0;
    classPtr->cbWndExtra  = winExtra;
    classPtr->cbClsExtra  = classExtra;
    classPtr->hInstance   = hInstance;
    classPtr->atomName    = atom;
    classPtr->menuNameA   = 0;
    classPtr->menuNameW   = 0;
    classPtr->classNameA  = 0;
    classPtr->classNameW  = 0;
    classPtr->dce         = (style & CS_CLASSDC) ?
                                 DCE_AllocDCE( 0, DCE_CLASS_DC ) : NULL;

    WINPROC_SetProc( &classPtr->winproc, wndProc, wndProcType, WIN_PROC_CLASS);    

    /* Other values must be set by caller */

    if (classExtra) memset( classPtr->wExtra, 0, classExtra );
    firstClass = classPtr;
    return classPtr;
}


/***********************************************************************
 *           RegisterClass16    (USER.57)
 */
ATOM WINAPI RegisterClass16( const WNDCLASS16 *wc )
{
    ATOM atom;
    CLASS *classPtr;
    int iSmIconWidth, iSmIconHeight;
    HINSTANCE16 hInstance=GetExePtr(wc->hInstance);

    if (!(atom = GlobalAddAtomA( PTR_SEG_TO_LIN(wc->lpszClassName) ))) return 0;
    if (!(classPtr = CLASS_RegisterClass( atom, hInstance, wc->style,
                                          wc->cbClsExtra, wc->cbWndExtra,
                                          wc->lpfnWndProc, WIN_PROC_16 )))
    {
        GlobalDeleteAtom( atom );
        return 0;
    }

    TRACE("atom=%04x wndproc=%08lx hinst=%04x "
                 "bg=%04x style=%08x clsExt=%d winExt=%d class=%p name='%s'\n",
                   atom, (DWORD)wc->lpfnWndProc, hInstance,
                   wc->hbrBackground, wc->style, wc->cbClsExtra,
                   wc->cbWndExtra, classPtr,
		   HIWORD(wc->lpszClassName) ?
                       (char *)PTR_SEG_TO_LIN(wc->lpszClassName) : "" );

    iSmIconWidth  = GetSystemMetrics(SM_CXSMICON);
    iSmIconHeight = GetSystemMetrics(SM_CYSMICON);

    classPtr->hIcon         = wc->hIcon;
    classPtr->hIconSm       = CopyImage(wc->hIcon, IMAGE_ICON,
					iSmIconWidth, iSmIconHeight,
					LR_COPYFROMRESOURCE);
    classPtr->hCursor       = wc->hCursor;
    classPtr->hbrBackground = wc->hbrBackground;

    CLASS_SetMenuNameA( classPtr, HIWORD(wc->lpszMenuName) ?
                 PTR_SEG_TO_LIN(wc->lpszMenuName) : (LPCSTR)wc->lpszMenuName );
    CLASS_SetClassNameA( classPtr, HIWORD(wc->lpszClassName) ?
                 PTR_SEG_TO_LIN(wc->lpszClassName) : (LPCSTR)wc->lpszClassName );

    return atom;
}


/***********************************************************************
 *           RegisterClassA      (USER32.427)
 * RETURNS
 *	>0: Unique identifier
 *	0: Failure
 */
ATOM WINAPI RegisterClassA( const WNDCLASSA* wc ) /* Address of structure with class data */
{
    ATOM atom;
    int iSmIconWidth, iSmIconHeight;
    CLASS *classPtr;

    if (!(atom = GlobalAddAtomA( wc->lpszClassName ))) return 0;

    if (!(classPtr = CLASS_RegisterClass( atom, wc->hInstance, wc->style,
                                          wc->cbClsExtra, wc->cbWndExtra,
                                          (WNDPROC16)wc->lpfnWndProc,
                                          WIN_PROC_32A )))
    {   GlobalDeleteAtom( atom );
        SetLastError(ERROR_CLASS_ALREADY_EXISTS);
        return FALSE;
    }

    TRACE("atom=%04x wndproc=%08lx hinst=%04x bg=%04x style=%08x clsExt=%d winExt=%d class=%p name='%s'\n",
                   atom, (DWORD)wc->lpfnWndProc, wc->hInstance,
                   wc->hbrBackground, wc->style, wc->cbClsExtra,
                   wc->cbWndExtra, classPtr,
                   HIWORD(wc->lpszClassName) ? wc->lpszClassName : "" );
    
    iSmIconWidth  = GetSystemMetrics(SM_CXSMICON);
    iSmIconHeight = GetSystemMetrics(SM_CYSMICON);
    
    classPtr->hIcon         = wc->hIcon;
    classPtr->hIconSm       = CopyImage(wc->hIcon, IMAGE_ICON,
					iSmIconWidth, iSmIconHeight,
					LR_COPYFROMRESOURCE);
    classPtr->hCursor       = (HCURSOR16)wc->hCursor;
    classPtr->hbrBackground = (HBRUSH16)wc->hbrBackground;
    
    CLASS_SetMenuNameA( classPtr, wc->lpszMenuName );
    CLASS_SetClassNameA( classPtr, wc->lpszClassName );
    return atom;
}


/***********************************************************************
 *           RegisterClassW      (USER32.430)
 */
ATOM WINAPI RegisterClassW( const WNDCLASSW* wc )
{
    ATOM atom;
    int iSmIconWidth, iSmIconHeight;
    CLASS *classPtr;

    if (!(atom = GlobalAddAtomW( wc->lpszClassName ))) return 0;

    if (!(classPtr = CLASS_RegisterClass( atom, wc->hInstance, wc->style,
                                          wc->cbClsExtra, wc->cbWndExtra,
                                          (WNDPROC16)wc->lpfnWndProc,
                                          WIN_PROC_32W )))
    {
        SetLastError(ERROR_CLASS_ALREADY_EXISTS);
        GlobalDeleteAtom( atom );
        return 0;
    }

    TRACE("atom=%04x wndproc=%08lx hinst=%04x bg=%04x style=%08x clsExt=%d winExt=%d class=%p\n",
                   atom, (DWORD)wc->lpfnWndProc, wc->hInstance,
                   wc->hbrBackground, wc->style, wc->cbClsExtra,
                   wc->cbWndExtra, classPtr );
    
    iSmIconWidth  = GetSystemMetrics(SM_CXSMICON);
    iSmIconHeight = GetSystemMetrics(SM_CYSMICON);

    classPtr->hIcon         = wc->hIcon;
    classPtr->hIconSm       = CopyImage(wc->hIcon, IMAGE_ICON,
					iSmIconWidth, iSmIconHeight,
					LR_COPYFROMRESOURCE);
    classPtr->hCursor       = (HCURSOR16)wc->hCursor;
    classPtr->hbrBackground = (HBRUSH16)wc->hbrBackground;
    
    CLASS_SetMenuNameW( classPtr, wc->lpszMenuName );
    CLASS_SetClassNameW( classPtr, wc->lpszClassName );
    return atom;
}


/***********************************************************************
 *           RegisterClassEx16    (USER.397)
 */
ATOM WINAPI RegisterClassEx16( const WNDCLASSEX16 *wc )
{
    ATOM atom;
    CLASS *classPtr;
    HINSTANCE16 hInstance = GetExePtr( wc->hInstance );

    if (!(atom = GlobalAddAtomA( PTR_SEG_TO_LIN(wc->lpszClassName) ))) return 0;
    if (!(classPtr = CLASS_RegisterClass( atom, hInstance, wc->style,
                                          wc->cbClsExtra, wc->cbWndExtra,
                                          wc->lpfnWndProc, WIN_PROC_16 )))
    {
        GlobalDeleteAtom( atom );
        return 0;
    }

    TRACE("atom=%04x wndproc=%08lx hinst=%04x bg=%04x style=%08x clsExt=%d winExt=%d class=%p\n",
                   atom, (DWORD)wc->lpfnWndProc, hInstance,
                   wc->hbrBackground, wc->style, wc->cbClsExtra,
                   wc->cbWndExtra, classPtr );
    
    classPtr->hIcon         = wc->hIcon;
    classPtr->hIconSm       = wc->hIconSm;
    classPtr->hCursor       = wc->hCursor;
    classPtr->hbrBackground = wc->hbrBackground;

    CLASS_SetMenuNameA( classPtr, HIWORD(wc->lpszMenuName) ?
                 PTR_SEG_TO_LIN(wc->lpszMenuName) : (LPCSTR)wc->lpszMenuName );
    CLASS_SetClassNameA( classPtr, HIWORD(wc->lpszClassName) ?
                 PTR_SEG_TO_LIN(wc->lpszClassName) : (LPCSTR)wc->lpszClassName );
    return atom;
}


/***********************************************************************
 *           RegisterClassExA      (USER32.428)
 */
ATOM WINAPI RegisterClassExA( const WNDCLASSEXA* wc )
{
    ATOM atom;
    CLASS *classPtr;

    if (!(atom = GlobalAddAtomA( wc->lpszClassName ))) return 0;

    if (!(classPtr = CLASS_RegisterClass( atom, wc->hInstance, wc->style,
                                          wc->cbClsExtra, wc->cbWndExtra,
                                          (WNDPROC16)wc->lpfnWndProc,
                                          WIN_PROC_32A )))
    {
        SetLastError(ERROR_CLASS_ALREADY_EXISTS);
        GlobalDeleteAtom( atom );
        return FALSE;
    }

    TRACE("atom=%04x wndproc=%08lx hinst=%04x bg=%04x style=%08x clsExt=%d winExt=%d class=%p\n",
                   atom, (DWORD)wc->lpfnWndProc, wc->hInstance,
                   wc->hbrBackground, wc->style, wc->cbClsExtra,
                   wc->cbWndExtra, classPtr );
    
    classPtr->hIcon         = (HICON16)wc->hIcon;
    classPtr->hIconSm       = (HICON16)wc->hIconSm;
    classPtr->hCursor       = (HCURSOR16)wc->hCursor;
    classPtr->hbrBackground = (HBRUSH16)wc->hbrBackground;
    CLASS_SetMenuNameA( classPtr, wc->lpszMenuName );
    CLASS_SetClassNameA( classPtr, wc->lpszClassName );
    return atom;
}


/***********************************************************************
 *           RegisterClassExW      (USER32.429)
 */
ATOM WINAPI RegisterClassExW( const WNDCLASSEXW* wc )
{
    ATOM atom;
    CLASS *classPtr;

    if (!(atom = GlobalAddAtomW( wc->lpszClassName ))) return 0;

    if (!(classPtr = CLASS_RegisterClass( atom, wc->hInstance, wc->style,
                                          wc->cbClsExtra, wc->cbWndExtra,
                                          (WNDPROC16)wc->lpfnWndProc,
                                          WIN_PROC_32W )))
    {
        SetLastError(ERROR_CLASS_ALREADY_EXISTS);
        GlobalDeleteAtom( atom );
        return 0;
    }

    TRACE("atom=%04x wndproc=%08lx hinst=%04x bg=%04x style=%08x clsExt=%d winExt=%d class=%p\n",
                   atom, (DWORD)wc->lpfnWndProc, wc->hInstance,
                   wc->hbrBackground, wc->style, wc->cbClsExtra,
                   wc->cbWndExtra, classPtr );
    
    classPtr->hIcon         = (HICON16)wc->hIcon;
    classPtr->hIconSm       = (HICON16)wc->hIconSm;
    classPtr->hCursor       = (HCURSOR16)wc->hCursor;
    classPtr->hbrBackground = (HBRUSH16)wc->hbrBackground;
    CLASS_SetMenuNameW( classPtr, wc->lpszMenuName );
    CLASS_SetClassNameW( classPtr, wc->lpszClassName );
    return atom;
}


/***********************************************************************
 *           UnregisterClass16    (USER.403)
 */
BOOL16 WINAPI UnregisterClass16( LPCSTR className, HINSTANCE16 hInstance )
{
    return UnregisterClassA( className, GetExePtr( hInstance ) );
}


/***********************************************************************
 *           UnregisterClassA    (USER32.563)
 *
 */
BOOL WINAPI UnregisterClassA( LPCSTR className, HINSTANCE hInstance )
{   CLASS *classPtr;
    ATOM atom;
    BOOL ret;

    TRACE("%s %x\n",debugres_a(className), hInstance);

    if (!(atom = GlobalFindAtomA( className )))
    {
        SetLastError(ERROR_CLASS_DOES_NOT_EXIST);
        return FALSE;
    }
    if (!(classPtr = CLASS_FindClassByAtom( atom, hInstance )) ||
        (classPtr->hInstance != hInstance))
    {
        SetLastError(ERROR_CLASS_DOES_NOT_EXIST);
        return FALSE;
    }
    if (!(ret = CLASS_FreeClass( classPtr )))
        SetLastError(ERROR_CLASS_HAS_WINDOWS);
    return ret;
}

/***********************************************************************
 *           UnregisterClassW    (USER32.564)
 */
BOOL WINAPI UnregisterClassW( LPCWSTR className, HINSTANCE hInstance )
{   CLASS *classPtr;
    ATOM atom;
    BOOL ret;

    TRACE("%s %x\n",debugres_w(className), hInstance);

    if (!(atom = GlobalFindAtomW( className )))
    {
        SetLastError(ERROR_CLASS_DOES_NOT_EXIST);
        return FALSE;
    }
    if (!(classPtr = CLASS_FindClassByAtom( atom, hInstance )) ||
        (classPtr->hInstance != hInstance))
    {
        SetLastError(ERROR_CLASS_DOES_NOT_EXIST);
        return FALSE;
    }
    if (!(ret = CLASS_FreeClass( classPtr )))
        SetLastError(ERROR_CLASS_HAS_WINDOWS);
    return ret;
}

/***********************************************************************
 *           GetClassWord16    (USER.129)
 */
WORD WINAPI GetClassWord16( HWND16 hwnd, INT16 offset )
{
    return GetClassWord( hwnd, offset );
}


/***********************************************************************
 *           GetClassWord    (USER32.219)
 */
WORD WINAPI GetClassWord( HWND hwnd, INT offset )
{
    WND * wndPtr;
    WORD retvalue = 0;
    
    TRACE("%x %x\n",hwnd, offset);
    
    if (!(wndPtr = WIN_FindWndPtr( hwnd ))) return 0;
    if (offset >= 0)
    {
        if (offset <= wndPtr->class->cbClsExtra - sizeof(WORD))
        {
            retvalue = GET_WORD(((char *)wndPtr->class->wExtra) + offset);
            goto END;
        }
    }
    else switch(offset)
    {
        case GCW_HBRBACKGROUND: retvalue =  wndPtr->class->hbrBackground;
                                goto END;
        case GCW_HCURSOR:       retvalue =  wndPtr->class->hCursor;
                                goto END;
        case GCW_HICON:         retvalue = wndPtr->class->hIcon;
                                goto END;
        case GCW_HICONSM:       retvalue = wndPtr->class->hIconSm;
                                goto END;
        case GCW_ATOM:          retvalue =  wndPtr->class->atomName;
                                goto END;
        case GCW_STYLE:
        case GCW_CBWNDEXTRA:
        case GCW_CBCLSEXTRA:
        case GCW_HMODULE:
            retvalue = (WORD)GetClassLongA( hwnd, offset );
            goto END;
    }

    WARN("Invalid offset %d\n", offset);
 END:
    WIN_ReleaseWndPtr(wndPtr);
    return retvalue;
}


/***********************************************************************
 *           GetClassLong16    (USER.131)
 */
LONG WINAPI GetClassLong16( HWND16 hwnd, INT16 offset )
{
    WND *wndPtr;
    LONG ret;

    TRACE("%x %x\n",hwnd, offset);

    switch( offset )
    {
    case GCL_WNDPROC:
        if (!(wndPtr = WIN_FindWndPtr( hwnd ))) return 0;
        ret = (LONG)WINPROC_GetProc( wndPtr->class->winproc, WIN_PROC_16 );
        WIN_ReleaseWndPtr(wndPtr);
        return ret;
    case GCL_MENUNAME:
        ret = GetClassLongA( hwnd, offset );
        return (LONG)SEGPTR_GET( (void *)ret );
    default:
        return GetClassLongA( hwnd, offset );
    }
}


/***********************************************************************
 *           GetClassLongA    (USER32.215)
 */
LONG WINAPI GetClassLongA( HWND hwnd, INT offset )
{
    WND * wndPtr;
    LONG retvalue;
    
    TRACE("%x %x\n",hwnd, offset);
    
    if (!(wndPtr = WIN_FindWndPtr( hwnd ))) return 0;
    if (offset >= 0)
    {
        if (offset <= wndPtr->class->cbClsExtra - sizeof(LONG))
        {
            retvalue = GET_DWORD(((char *)wndPtr->class->wExtra) + offset);
            goto END;
        }
    }
        
    switch(offset)
    {
        case GCL_STYLE:      retvalue = (LONG)wndPtr->class->style;
                             goto END;
        case GCL_CBWNDEXTRA: retvalue = (LONG)wndPtr->class->cbWndExtra;
                             goto END;
        case GCL_CBCLSEXTRA: retvalue = (LONG)wndPtr->class->cbClsExtra;
                             goto END;
        case GCL_HMODULE:    retvalue = (LONG)wndPtr->class->hInstance;
                             goto END;
        case GCL_WNDPROC:
            retvalue = (LONG)WINPROC_GetProc(wndPtr->class->winproc, WIN_PROC_32A);
            goto END;
        case GCL_MENUNAME:
            retvalue = (LONG)CLASS_GetMenuNameA( wndPtr->class );
            goto END;
        case GCW_ATOM:
        case GCL_HBRBACKGROUND:
        case GCL_HCURSOR:
        case GCL_HICON:
        case GCL_HICONSM:
            retvalue = GetClassWord( hwnd, offset );
            goto END;
    }
    WARN("Invalid offset %d\n", offset);
    retvalue = 0;
END:
    WIN_ReleaseWndPtr(wndPtr);
    return retvalue;
}


/***********************************************************************
 *           GetClassLongW    (USER32.216)
 */
LONG WINAPI GetClassLongW( HWND hwnd, INT offset )
{
    WND * wndPtr;
    LONG retvalue;

    TRACE("%x %x\n",hwnd, offset);

    switch(offset)
    {
    case GCL_WNDPROC:
        if (!(wndPtr = WIN_FindWndPtr( hwnd ))) return 0;
        retvalue = (LONG)WINPROC_GetProc( wndPtr->class->winproc, WIN_PROC_32W );
        WIN_ReleaseWndPtr(wndPtr);
        return retvalue;
    case GCL_MENUNAME:
        if (!(wndPtr = WIN_FindWndPtr( hwnd ))) return 0;
        retvalue = (LONG)CLASS_GetMenuNameW( wndPtr->class );
        WIN_ReleaseWndPtr(wndPtr);
        return retvalue;
    default:
        return GetClassLongA( hwnd, offset );
    }
}


/***********************************************************************
 *           SetClassWord16    (USER.130)
 */
WORD WINAPI SetClassWord16( HWND16 hwnd, INT16 offset, WORD newval )
{
    return SetClassWord( hwnd, offset, newval );
}


/***********************************************************************
 *           SetClassWord    (USER32.469)
 */
WORD WINAPI SetClassWord( HWND hwnd, INT offset, WORD newval )
{
    WND * wndPtr;
    WORD retval = 0;
    void *ptr;
    
    TRACE("%x %x %x\n",hwnd, offset, newval);
    
    if (!(wndPtr = WIN_FindWndPtr( hwnd ))) return 0;
    if (offset >= 0)
    {
        if (offset + sizeof(WORD) <= wndPtr->class->cbClsExtra)
            ptr = ((char *)wndPtr->class->wExtra) + offset;
        else
        {
            WARN("Invalid offset %d\n", offset );
            WIN_ReleaseWndPtr(wndPtr);
            return 0;
        }
    }
    else switch(offset)
    {
        case GCW_STYLE:
        case GCW_CBWNDEXTRA:
        case GCW_CBCLSEXTRA:
        case GCW_HMODULE:
            WIN_ReleaseWndPtr(wndPtr);
            return (WORD)SetClassLongA( hwnd, offset, (LONG)newval );
        case GCW_HBRBACKGROUND: ptr = &wndPtr->class->hbrBackground; break;
        case GCW_HCURSOR:       ptr = &wndPtr->class->hCursor; break;
        case GCW_HICON:         ptr = &wndPtr->class->hIcon; break;
        case GCW_HICONSM:       ptr = &wndPtr->class->hIconSm; break;
        case GCW_ATOM:          ptr = &wndPtr->class->atomName; break;
        default:
            WARN("Invalid offset %d\n", offset);
            WIN_ReleaseWndPtr(wndPtr);
            return 0;
    }
    retval = GET_WORD(ptr);
    PUT_WORD( ptr, newval );
    
    /* Note: If the GCW_ATOM was changed, this means that the WNDCLASS className fields
    need to be updated as well.  Problem is that we can't tell whether the atom is 
    using wide or narrow characters.  For now, we'll just NULL out the className 
    fields, and emit a FIXME. */
    if (offset == GCW_ATOM)
    {
        CLASS_SetClassNameA( wndPtr->class, NULL );
        FIXME("GCW_ATOM changed for a class.  Not updating className, so GetClassInfoEx may not return correct className!\n");
    }
    WIN_ReleaseWndPtr(wndPtr);
    return retval;
}


/***********************************************************************
 *           SetClassLong16    (USER.132)
 */
LONG WINAPI SetClassLong16( HWND16 hwnd, INT16 offset, LONG newval )
{
    WND *wndPtr;
    LONG retval;

    TRACE("%x %x %lx\n",hwnd, offset, newval);

    switch(offset)
    {
    case GCL_WNDPROC:
        if (!(wndPtr = WIN_FindWndPtr(hwnd))) return 0;
        retval = (LONG)WINPROC_GetProc( wndPtr->class->winproc, WIN_PROC_16 );
        WINPROC_SetProc( &wndPtr->class->winproc, (WNDPROC16)newval,
                         WIN_PROC_16, WIN_PROC_CLASS );
        WIN_ReleaseWndPtr(wndPtr);
        return retval;
    case GCL_MENUNAME:
        return SetClassLongA( hwnd, offset, (LONG)PTR_SEG_TO_LIN(newval) );
    default:
        return SetClassLongA( hwnd, offset, newval );
    }
}


/***********************************************************************
 *           SetClassLongA    (USER32.467)
 */
LONG WINAPI SetClassLongA( HWND hwnd, INT offset, LONG newval )
{
    WND * wndPtr;
    LONG retval = 0;
    void *ptr;
    
    TRACE("%x %x %lx\n",hwnd, offset, newval);
        
    if (!(wndPtr = WIN_FindWndPtr( hwnd ))) return 0;
    if (offset >= 0)
    {
        if (offset + sizeof(LONG) <= wndPtr->class->cbClsExtra)
            ptr = ((char *)wndPtr->class->wExtra) + offset;
        else
        {
            WARN("Invalid offset %d\n", offset );
            retval = 0;
            goto END;
        }
    }
    else switch(offset)
    {
        case GCL_MENUNAME:
            CLASS_SetMenuNameA( wndPtr->class, (LPCSTR)newval );
            retval = 0;  /* Old value is now meaningless anyway */
            goto END;
        case GCL_WNDPROC:
            retval = (LONG)WINPROC_GetProc( wndPtr->class->winproc,
                                            WIN_PROC_32A );
            WINPROC_SetProc( &wndPtr->class->winproc, (WNDPROC16)newval,
                             WIN_PROC_32A, WIN_PROC_CLASS );
            goto END;
        case GCL_HBRBACKGROUND:
        case GCL_HCURSOR:
        case GCL_HICON:
        case GCL_HICONSM:
            retval = SetClassWord( hwnd, offset, (WORD)newval );
            goto END;
        case GCL_STYLE:      ptr = &wndPtr->class->style; break;
        case GCL_CBWNDEXTRA: ptr = &wndPtr->class->cbWndExtra; break;
        case GCL_CBCLSEXTRA: ptr = &wndPtr->class->cbClsExtra; break;
        case GCL_HMODULE:    ptr = &wndPtr->class->hInstance; break;
        default:
            WARN("Invalid offset %d\n", offset );
            retval = 0;
            goto END;
    }
    retval = GET_DWORD(ptr);
    PUT_DWORD( ptr, newval );
END:
    WIN_ReleaseWndPtr(wndPtr);
    return retval;
}


/***********************************************************************
 *           SetClassLongW    (USER32.468)
 */
LONG WINAPI SetClassLongW( HWND hwnd, INT offset, LONG newval )
{
    WND *wndPtr;
    LONG retval;

    TRACE("%x %x %lx\n",hwnd, offset, newval);
    
    switch(offset)
    {
    case GCL_WNDPROC:
        if (!(wndPtr = WIN_FindWndPtr(hwnd))) return 0;
        retval = (LONG)WINPROC_GetProc( wndPtr->class->winproc, WIN_PROC_32W );
        WINPROC_SetProc( &wndPtr->class->winproc, (WNDPROC16)newval,
                         WIN_PROC_32W, WIN_PROC_CLASS );
        WIN_ReleaseWndPtr(wndPtr);
        return retval;
    case GCL_MENUNAME:
        if (!(wndPtr = WIN_FindWndPtr(hwnd))) return 0;
        CLASS_SetMenuNameW( wndPtr->class, (LPCWSTR)newval );
        WIN_ReleaseWndPtr(wndPtr);
        return 0;  /* Old value is now meaningless anyway */
    default:
        return SetClassLongA( hwnd, offset, newval );
    }
}


/***********************************************************************
 *           GetClassName16      (USER.58)
 */
INT16 WINAPI GetClassName16( HWND16 hwnd, LPSTR buffer, INT16 count )
{
    return GetClassNameA( hwnd, buffer, count );
}


/***********************************************************************
 *           GetClassNameA      (USER32.217)
 */
INT WINAPI GetClassNameA( HWND hwnd, LPSTR buffer, INT count )
{   INT ret;
    WND *wndPtr;
            
    if (!(wndPtr = WIN_FindWndPtr(hwnd))) return 0;
    ret = GlobalGetAtomNameA( wndPtr->class->atomName, buffer, count );

    WIN_ReleaseWndPtr(wndPtr);
    TRACE("%x %s %x\n",hwnd, buffer, count);
    return ret;
}


/***********************************************************************
 *           GetClassNameW      (USER32.218)
 */
INT WINAPI GetClassNameW( HWND hwnd, LPWSTR buffer, INT count )
{   INT ret;
    WND *wndPtr;

    if (!(wndPtr = WIN_FindWndPtr(hwnd))) return 0;
    ret = GlobalGetAtomNameW( wndPtr->class->atomName, buffer, count );
    WIN_ReleaseWndPtr(wndPtr);
    TRACE("%x %s %x\n",hwnd, debugstr_w(buffer), count);
    
    return ret;
}


/***********************************************************************
 *           GetClassInfo16      (USER.404)
 */
BOOL16 WINAPI GetClassInfo16( HINSTANCE16 hInstance, LPCSTR name, WNDCLASS16 *wc )
{
    ATOM atom;
    CLASS *classPtr;

    TRACE("%x %s %p\n",hInstance, debugres_a(name), wc);
    
    hInstance = GetExePtr( hInstance );
    if (!(atom = GlobalFindAtomA( name )) ||
        !(classPtr = CLASS_FindClassByAtom( atom, hInstance )))
        return FALSE;
    if ((hInstance != classPtr->hInstance) &&
        !(classPtr->style & CS_GLOBALCLASS)) /*BWCC likes to pass hInstance=0*/
        return FALSE;
    wc->style         = (UINT16)classPtr->style;
    wc->lpfnWndProc   = WINPROC_GetProc( classPtr->winproc, WIN_PROC_16 );
    wc->cbClsExtra    = (INT16)classPtr->cbClsExtra;
    wc->cbWndExtra    = (INT16)classPtr->cbWndExtra;
    wc->hInstance     = (HINSTANCE16)classPtr->hInstance;
    wc->hIcon         = classPtr->hIcon;
    wc->hCursor       = classPtr->hCursor;
    wc->hbrBackground = classPtr->hbrBackground;
    wc->lpszClassName = (SEGPTR)CLASS_GetClassNameA( classPtr );;
    if (HIWORD(wc->lpszClassName))  /* Make it a SEGPTR */
        wc->lpszClassName = SEGPTR_GET( (LPSTR)wc->lpszClassName );
    wc->lpszMenuName  = (SEGPTR)CLASS_GetMenuNameA( classPtr );
    if (HIWORD(wc->lpszMenuName))  /* Make it a SEGPTR */
        wc->lpszMenuName = SEGPTR_GET( (LPSTR)wc->lpszMenuName );
    return TRUE;
}


/***********************************************************************
 *           GetClassInfoA      (USER32.211)
 */
BOOL WINAPI GetClassInfoA( HINSTANCE hInstance, LPCSTR name,
                               WNDCLASSA *wc )
{
    ATOM atom;
    CLASS *classPtr;

    TRACE("%x %p %p\n",hInstance, name, wc);

    /* workaround: if hInstance=NULL you expect to get the system classes
    but this classes (as example from comctl32.dll SysListView) won't be
    registered with hInstance=NULL in WINE because of the late loading
    of this dll. fixes file dialogs in WinWord95 (jsch)*/

    if (!(atom=GlobalFindAtomA(name)) || !(classPtr=CLASS_FindClassByAtom(atom,hInstance)))
        return FALSE;

    if (!(classPtr->style & CS_GLOBALCLASS) &&
        classPtr->hInstance &&
        (hInstance != classPtr->hInstance))
    {
        if (hInstance) return FALSE;
        WARN("systemclass %s (hInst=0) demanded but only class with hInst!=0 found\n",name);
    }

    wc->style         = classPtr->style;
    wc->lpfnWndProc   = (WNDPROC)WINPROC_GetProc( classPtr->winproc,
                                                    WIN_PROC_32A );
    wc->cbClsExtra    = classPtr->cbClsExtra;
    wc->cbWndExtra    = classPtr->cbWndExtra;
    wc->hInstance     = hInstance;
    wc->hIcon         = (HICON)classPtr->hIcon;
    wc->hCursor       = (HCURSOR)classPtr->hCursor;
    wc->hbrBackground = (HBRUSH)classPtr->hbrBackground;
    wc->lpszMenuName  = CLASS_GetMenuNameA( classPtr );
    wc->lpszClassName = CLASS_GetClassNameA( classPtr );
    return TRUE;
}


/***********************************************************************
 *           GetClassInfoW      (USER32.214)
 */
BOOL WINAPI GetClassInfoW( HINSTANCE hInstance, LPCWSTR name,
                               WNDCLASSW *wc )
{
    ATOM atom;
    CLASS *classPtr;

    TRACE("%x %p %p\n",hInstance, name, wc);

    if (	!(atom=GlobalFindAtomW(name)) ||
		!(classPtr=CLASS_FindClassByAtom(atom,hInstance))
    )
        return FALSE;

    if (!(classPtr->style & CS_GLOBALCLASS) &&
        classPtr->hInstance &&
        (hInstance != classPtr->hInstance))
    {
        if (hInstance) return FALSE;
        WARN("systemclass %s (hInst=0) demanded but only class with hInst!=0 found\n",debugstr_w(name));
    }
    wc->style         = classPtr->style;
    wc->lpfnWndProc   = (WNDPROC)WINPROC_GetProc( classPtr->winproc,
                                                    WIN_PROC_32W );
    wc->cbClsExtra    = classPtr->cbClsExtra;
    wc->cbWndExtra    = classPtr->cbWndExtra;
    wc->hInstance     = hInstance;
    wc->hIcon         = (HICON)classPtr->hIcon;
    wc->hCursor       = (HCURSOR)classPtr->hCursor;
    wc->hbrBackground = (HBRUSH)classPtr->hbrBackground;
    wc->lpszMenuName  = CLASS_GetMenuNameW( classPtr );
    wc->lpszClassName = CLASS_GetClassNameW( classPtr );
    return TRUE;
}


/***********************************************************************
 *           GetClassInfoEx16      (USER.398)
 *
 * FIXME: this is just a guess, I have no idea if GetClassInfoEx() is the
 * same in Win16 as in Win32. --AJ
 */
BOOL16 WINAPI GetClassInfoEx16( HINSTANCE16 hInstance, LPCSTR name, WNDCLASSEX16 *wc )
{
    ATOM atom;
    CLASS *classPtr;

    TRACE("%x %s %p\n",hInstance,debugres_a( name ), wc);
    
    hInstance = GetExePtr( hInstance );
    if (!(atom = GlobalFindAtomA( name )) ||
        !(classPtr = CLASS_FindClassByAtom( atom, hInstance )) ||
        (hInstance != classPtr->hInstance)) return FALSE;
    wc->style         = classPtr->style;
    wc->lpfnWndProc   = WINPROC_GetProc( classPtr->winproc, WIN_PROC_16 );
    wc->cbClsExtra    = (INT16)classPtr->cbClsExtra;
    wc->cbWndExtra    = (INT16)classPtr->cbWndExtra;
    wc->hInstance     = (HINSTANCE16)classPtr->hInstance;
    wc->hIcon         = classPtr->hIcon;
    wc->hIconSm       = classPtr->hIconSm;
    wc->hCursor       = classPtr->hCursor;
    wc->hbrBackground = classPtr->hbrBackground;
    wc->lpszClassName = (SEGPTR)0;
    wc->lpszMenuName  = (SEGPTR)CLASS_GetMenuNameA( classPtr );
    if (HIWORD(wc->lpszMenuName))  /* Make it a SEGPTR */
        wc->lpszMenuName = SEGPTR_GET( (LPSTR)wc->lpszMenuName );
    wc->lpszClassName  = (SEGPTR)CLASS_GetClassNameA( classPtr );
    if (HIWORD(wc->lpszClassName))  /* Make it a SEGPTR */
        wc->lpszClassName = SEGPTR_GET( (LPSTR)wc->lpszClassName );

    /* We must return the atom of the class here instead of just TRUE. */
    return atom;
}


/***********************************************************************
 *           GetClassInfoExA      (USER32.212)
 */
BOOL WINAPI GetClassInfoExA( HINSTANCE hInstance, LPCSTR name,
                                 WNDCLASSEXA *wc )
{
    ATOM atom;
    CLASS *classPtr;

    TRACE("%x %p %p\n",hInstance, name, wc);
    
    if (!(atom = GlobalFindAtomA( name )) ||
        !(classPtr = CLASS_FindClassByAtom( atom, hInstance )) 
	/*|| (hInstance != classPtr->hInstance) */ ) return FALSE;
    wc->style         = classPtr->style;
    wc->lpfnWndProc   = (WNDPROC)WINPROC_GetProc( classPtr->winproc,
                                                    WIN_PROC_32A );
    wc->cbClsExtra    = classPtr->cbClsExtra;
    wc->cbWndExtra    = classPtr->cbWndExtra;
    wc->hInstance     = classPtr->hInstance;
    wc->hIcon         = (HICON)classPtr->hIcon;
    wc->hIconSm       = (HICON)classPtr->hIconSm;
    wc->hCursor       = (HCURSOR)classPtr->hCursor;
    wc->hbrBackground = (HBRUSH)classPtr->hbrBackground;
    wc->lpszMenuName  = CLASS_GetMenuNameA( classPtr );
    wc->lpszClassName  = CLASS_GetClassNameA( classPtr );
    
    /* We must return the atom of the class here instead of just TRUE. */
    return atom;
}


/***********************************************************************
 *           GetClassInfoExW      (USER32.213)
 */
BOOL WINAPI GetClassInfoExW( HINSTANCE hInstance, LPCWSTR name,
                                 WNDCLASSEXW *wc )
{
    ATOM atom;
    CLASS *classPtr;

    TRACE("%x %p %p\n",hInstance, name, wc);
    
    if (!(atom = GlobalFindAtomW( name )) ||
        !(classPtr = CLASS_FindClassByAtom( atom, hInstance )) ||
        (hInstance != classPtr->hInstance)) return FALSE;
    wc->style         = classPtr->style;
    wc->lpfnWndProc   = (WNDPROC)WINPROC_GetProc( classPtr->winproc,
                                                    WIN_PROC_32W );
    wc->cbClsExtra    = classPtr->cbClsExtra;
    wc->cbWndExtra    = classPtr->cbWndExtra;
    wc->hInstance     = classPtr->hInstance;
    wc->hIcon         = (HICON)classPtr->hIcon;
    wc->hIconSm       = (HICON)classPtr->hIconSm;
    wc->hCursor       = (HCURSOR)classPtr->hCursor;
    wc->hbrBackground = (HBRUSH)classPtr->hbrBackground;
    wc->lpszMenuName  = CLASS_GetMenuNameW( classPtr );
    wc->lpszClassName = CLASS_GetClassNameW( classPtr );;
    
    /* We must return the atom of the class here instead of just TRUE. */
    return atom;
}


/***********************************************************************
 *           ClassFirst      (TOOLHELP.69)
 */
BOOL16 WINAPI ClassFirst16( CLASSENTRY *pClassEntry )
{
    TRACE("%p\n",pClassEntry);
    pClassEntry->wNext = 1;
    return ClassNext16( pClassEntry );
}


/***********************************************************************
 *           ClassNext      (TOOLHELP.70)
 */
BOOL16 WINAPI ClassNext16( CLASSENTRY *pClassEntry )
{
    int i;
    CLASS *class = firstClass;

    TRACE("%p\n",pClassEntry);
   
    if (!pClassEntry->wNext) return FALSE;
    for (i = 1; (i < pClassEntry->wNext) && class; i++) class = class->next;
    if (!class)
    {
        pClassEntry->wNext = 0;
        return FALSE;
    }
    pClassEntry->hInst = class->hInstance;
    pClassEntry->wNext++;
    GlobalGetAtomNameA( class->atomName, pClassEntry->szClassName,
                          sizeof(pClassEntry->szClassName) );
    return TRUE;
}