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WDJSUB.C
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WDJSUB.C
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/*
* wdjsub.c:
*
* Definitions of subclassing functions declared in wdjsub.h.
*
* See http://www.wdj.com/articles/2000/0003/0003toc.htm for details,
*
* This code was written by Petter Hesselberg and published as part
* of the User Interface Programming column in Windows Developer's
* Journal. There are no restrictions on the use of this code,
* nor are there any guarantees for fitness of purpose or anything
* else. Smile and carry your own risk :-)
*
* Changelog:
*
* Jul 2001 Specified calling convention (APIENTRY) for external interface.
* Nov 2000 Added reference counting; see comments in wdjSubclass()
* and internal_unhook(), another new function. It replaces
* wdjUnhook() and has been somewhat restructured in the
* process.
* Added wdjIsSubclassed().
* Aug 2000 Added wdjSetData().
*/
#include "stdafx.h"
#include <windowsx.h>
#include <assert.h>
#include <stdarg.h>
#include "wdjsub.h"
#ifdef _DEBUG
#define verify assert
static void __cdecl tracef( LPCTSTR pszFmt, ... ) {
TCHAR szTraceLine[ 1000 ] = { 0 };
va_list vl;
va_start( vl, pszFmt );
wvsprintf( szTraceLine, pszFmt, vl );
va_end( vl );
OutputDebugString( szTraceLine );
OutputDebugString( _T( "\r\n" ) );
}
#else
#define verify( X ) ( X )
#define tracef (void)
#endif
typedef struct SUBCLASSING {
WNDPROC wndProc;
WNDPROC wndProcSaved;
void *pData;
struct SUBCLASSING *pNext;
int ref_count;
} SUBCLASSING;
#define getWndProc( hwnd ) \
( (WNDPROC) GetWindowLong( hwnd, GWL_WNDPROC ) )
#define getHead( hwnd ) \
( (SUBCLASSING *) GetProp( hwnd, getPropertyName() ) )
static ATOM s_prop = 0;
#define PROP_NAME MAKEINTRESOURCE( s_prop )
static LPCTSTR INLINE getPropertyName( void ) {
return PROP_NAME;
}
static BOOL INLINE allocPropertyName( void ) {
s_prop = GlobalAddAtom( _T( "wdj_sub_root" ) );
return 0 != s_prop;
}
static void INLINE releasePropertyName( void ) {
verify( 0 == GlobalDeleteAtom( s_prop ) );
}
static SUBCLASSING *find( WNDPROC wndProc, HWND hwnd ) {
SUBCLASSING *p = getHead( hwnd );
while ( 0 != p && wndProc != p->wndProc ) {
p = p->pNext;
}
return p;
}
static BOOL setHead( HWND hwnd, const SUBCLASSING *pHead ) {
if( 0 != GetProp( hwnd, getPropertyName() ) ) {
RemoveProp( hwnd, getPropertyName() );
}
if ( 0 != pHead ) {
SetProp( hwnd, getPropertyName(), (HANDLE) pHead );
}
return (HANDLE) pHead == GetProp( hwnd, getPropertyName() );
}
static BOOL initNode( HWND hwnd, SUBCLASSING *p,
WNDPROC wndProc, void *pData, SUBCLASSING *pNext )
{
p->wndProc = wndProc;
p->pData = pData;
p->pNext = pNext;
p->wndProcSaved = SubclassWindow( hwnd, wndProc );
p->ref_count = 1;
return 0 != p->wndProcSaved;
}
BOOL APIENTRY wdjSubclass( WNDPROC wndProc, HWND hwnd, void *pData ) {
SUBCLASSING *pHead = getHead( hwnd );
SUBCLASSING *pThis = find( wndProc, hwnd );
WNDPROC curr = getWndProc( hwnd );
// If this subclassing has been applied before, just increase
// the reference count and smile. It won't be called twice in
// the chain, it won't be moved to the front of the chain,
// and it won't be unhooked until wdjUnhook() has been called
// the same number of times that wdjSubclass() was called.
if ( 0 != pThis ) {
assert( pData == pThis->pData );
++pThis->ref_count;
tracef( _T( "wdjSubclass: Increasing ref_count for " )
_T( "%#x (hwnd=%#x) to %d" ),
pThis->wndProc, hwnd, pThis->ref_count );
return TRUE; //*** FUNCTION EXIT POINT
}
// Applying the current window function as a subclassing is
// almost certainly an error, so don't. (If the new and current
// window function are the same because of previous subclassing,
// it's OK, and caught by the previous test for 0 != pThis.
if ( curr == wndProc ) {
tracef( _T( "wdjSubclass: Attempting to apply current wndproc " )
_T( "%#x to %#x refused" ), pThis->wndProc, hwnd );
DebugBreak();
return FALSE; //*** FUNCTION EXIT POINT
}
// We have a spankin' new subclassing for this window:
if ( allocPropertyName() ) {
if ( 0 != (pThis = malloc( sizeof( *pThis ) ) ) ) {
if ( initNode( hwnd, pThis, wndProc, pData, pHead ) ) {
if ( setHead( hwnd, pThis ) ) {
tracef( _T( "wdjSubclass: Adding new wndproc %#x " )
_T( "to window %#x" ), pThis->wndProc, hwnd );
return TRUE; //*** FUNCTION EXIT POINT
}
SubclassWindow( hwnd, pThis->wndProcSaved );
}
free( pThis );
}
releasePropertyName();
}
return FALSE; //*** FUNCTION EXIT POINT
}
/**
* pThis is guaranteed to be on the list headed by pHead.
*/
static SUBCLASSING *findPrev( SUBCLASSING *pHead, SUBCLASSING *pThis ) {
SUBCLASSING *pPrev = pHead;
while ( pPrev->pNext != pThis ) {
pPrev = pPrev->pNext;
assert( 0 != pPrev );
}
return pPrev;
}
/**
* disregardRefCount is TRUE when called from wdjCallOldProc, that is to
* say, when we're auto-unhooking. In that case, unhook no matter
* what the ref_count is.
*/
static BOOL internal_unhook( WNDPROC id, HWND hwnd, BOOL disregardRefCount ) {
SUBCLASSING *pHead = getHead( hwnd );
SUBCLASSING *pThis = find( id, hwnd );
WNDPROC expected = 0;
SUBCLASSING *pPrev = 0;
if ( 0 == pThis ) {
tracef( _T( "wdjUnhook: Subclassing %#x not found for hwnd %#x" ),
id, hwnd );
DebugBreak();
return FALSE; //*** FUNCTION EXIT POINT
}
if ( !disregardRefCount && 0 < --pThis->ref_count ) {
tracef( _T( "wdjUnhook: " )
_T( "Decreasing ref_count for %#x (hwnd=%#x) to %d" ),
pThis->wndProc, hwnd, pThis->ref_count );
return TRUE; //*** FUNCTION EXIT POINT
}
// Figure out what we're expecting as the saved proc
if ( pHead == pThis ) {
expected = getWndProc( hwnd );
} else {
pPrev = findPrev( pHead, pThis );
expected = pPrev->wndProcSaved;
}
// Are we blocked?
if ( expected != id ) {
tracef( _T( "wdjUnhook: Subclassing %#x for %#x blocked by %#x" ), id, hwnd, expected );
return FALSE; //*** FUNCTION EXIT POINT
}
// OK, unlink
if ( pHead == pThis ) {
assert( 0 == pPrev );
tracef( _T( "wdjUnhook: Removing head of list wndproc %#x from window %#x" ), pThis->wndProcSaved, hwnd );
SubclassWindow( hwnd, pThis->wndProcSaved );
setHead( hwnd, pThis->pNext );
} else {
assert( 0 != pPrev );
tracef( _T( "wdjUnhook: Unlinking wndproc %#x from window %#x" ),
pThis->wndProcSaved, hwnd );
pPrev->pNext = pThis->pNext;
pPrev->wndProcSaved = pThis->wndProcSaved;
}
free( pThis );
releasePropertyName();
return TRUE; //*** FUNCTION EXIT POINT
}
BOOL APIENTRY wdjUnhook( WNDPROC id, HWND hwnd ) {
return internal_unhook( id, hwnd, FALSE );
}
LRESULT APIENTRY wdjCallOldProc(
WNDPROC id, HWND hwnd, UINT msg, WPARAM w, LPARAM l )
{
LRESULT lResult = 0;
const SUBCLASSING *pThis = find( id, hwnd );
if ( 0 != pThis ) {
const WNDPROC oldProc = pThis->wndProcSaved;
assert( 0 != oldProc );
if ( WM_DESTROY == msg || WM_NCDESTROY == msg ) {
tracef( _T( "wdjCallOldProc: Auto unhook wndproc %#x from window %#x on %s" ),
pThis->wndProcSaved, hwnd,
WM_DESTROY == msg ? _T( "WM_DESTROY" ) : _T( "WM_NCDESTROY" ) );
internal_unhook( id, hwnd, TRUE );
}
if ( 0 != oldProc ) {
lResult = CallWindowProc( oldProc, hwnd, msg, w, l );
}
}
return lResult;
}
void * APIENTRY wdjGetData( WNDPROC id, HWND hwnd ) {
const SUBCLASSING *pThis = find( id, hwnd );
return 0 != pThis ? pThis->pData : 0;
}
BOOL APIENTRY wdjSetData( WNDPROC id, HWND hwnd, void *pData ) {
SUBCLASSING *pThis = find( id, hwnd );
if ( 0 != pThis ) {
assert( 1 == pThis->ref_count || pData == pThis->pData );
pThis->pData = pData;
return TRUE; //*** FUNCTION EXIT POINT
}
tracef( _T( "wdjSetData: Subclassing %#x not found for window %#x" ),
id, hwnd );
return FALSE; //*** FUNCTION EXIT POINT
}
/**
* @return <code>TRUE</code> if the specified subclassing has been applied to
* the specified window; otherwise <code>FALSE</code>.
* @param id The identity of the subclassing to chack for
* @param hwnd The window handle that may or may not be subclassed with <code>id</code>.
*/
BOOL APIENTRY wdjIsSubclassed( WNDPROC id, HWND hwnd ) {
return 0 != find( id, hwnd );
}
// end of file