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Posted 17 Mar 2009

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C++ Header Guard

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3.83/5 (9 votes)
17 Mar 2009CPOL2 min read
Create unique preprocessor macros to prevent multiple header inclusion.


This article is a rework of the idea from an existing article but with the focus on usability and ease of use.

This utility creates unique preprocessor macros to prevent multiple header inclusion. If a filename is specified as a command line argument or a file is dropped onto the dialog, it's name is also included in the macro.

The dialog stays "always on top," accepts dropped shortcuts, snaps to screen edges and can be dragged by its surface. Upon entering a key/OK button, the displayed macro is copied to the clipboard, and the program exits.


The program is designed to be used from inside VC 2005/2008 IDE to generate a unique macro for the currently opened file:



The Code

A unique macro is generated from GUID:

CString CIncludeGen::CreateGuid()
	TCHAR fmtGuid[] = _T("%08lx_%04x_%04x_%02x%02x_%02x%02x%02x%02x%02x%02x");
	GUID guid;

	CString str;
	str.Format(fmtGuid, guid.Data1,guid.Data2,guid.Data3,
			guid.Data4[0], guid.Data4[1], guid.Data4[2], guid.Data4[3],
			guid.Data4[4], guid.Data4[5], guid.Data4[6], guid.Data4[7]);
	return str;

When sending the text to a clipboard, it is necessary to use the HWND of the dialog in OpenClipboard, as stated in MSDN:

"If an application calls OpenClipboard with hwnd set to NULL, EmptyClipboard sets the clipboard owner to NULL; this causes SetClipboardData to fail."

bool CIncludeGen::copy2clipboard(HWND clipbrdowner)
	if (m_text.IsEmpty()) return false;
	bool retVal=true;
		LPTSTR lptstrCopy;
		LPCTSTR txt=m_text;
		HGLOBAL hglbCopy;
		hglbCopy = GlobalAlloc(GMEM_MOVEABLE,
                      (m_text.GetLength() + 1) * sizeof(TCHAR));
		if (hglbCopy != NULL)
			lptstrCopy = (LPTSTR)GlobalLock(hglbCopy);
			memcpy(lptstrCopy, txt, 
                               (m_text.GetLength() * sizeof(TCHAR))); 
			lptstrCopy[m_text.GetLength()] = (TCHAR) 0; // null character 
		if (NULL==::SetClipboardData(CF_UNICODETEXT,
                     hglbCopy)) MessageBeep(-1);
		else retVal=false;
	else retVal=false;
return retVal;

The font for the edit control is created by retrieving the info about current default font and modifying its properties. The edit control is read-only, so the default background color (white) is restored by handling the WM_CTLCOLORSTATIC message:

bool CMainDlg::createEditCtlFont()
	if (m_editCtlFont.IsNull()) return false;
	LOGFONT lfont={0};
	if (0==GetObject(m_editCtlFont,sizeof(LOGFONT), &lfont)) return false;
	if (IsClearTypeEnabled()) lfont.lfQuality=CLEARTYPE_QUALITY;

	lfont.lfPitchAndFamily=FIXED_PITCH | FF_MODERN;
	WCHAR fn[32]=L"Courier New";
	lfont.lfHeight=(LONG)(lfont.lfHeight*1.15);//increase size a bit

	memcpy(lfont.lfFaceName, fn, _countof(fn));
	if (NULL==m_editCtlFont.CreateFontIndirect(&lfont)) return false;
return true;


LRESULT CMainDlg::OnCtlColor(UINT uMsg, WPARAM wParam, LPARAM lParam, BOOL& bHandled)
	if (((HWND)lParam)==GetDlgItem( IDC_EDIT1 )) return (LRESULT)GetStockObject(
             WHITE_BRUSH );
return ::DefWindowProc(m_hWnd, wParam, lParam, bHandled);

The dialog background color is changed by handling WM_CTLCOLORDLG and returning previously created brush of desired color:

#define INCLHG_DLG_BKGCOLOR RGB(198,209,223)
LRESULT CMainDlg::OnMainDialogColor(UINT uMsg, WPARAM wParam, LPARAM lParam,
    BOOL& bHandled)
return (LRESULT)m_dialogbrush.m_hBrush;

The focus in the dialog form has the OK button, set by calling GotoDlgCtrl(GetDlgItem(IDOK)) and returning FALSE in CMainDlg::OnInitDialog.

Dropped shortcuts are resolved using the function assembled by Igor Vigdorchik. I will leave other features in the code as a readers' exercise.

The project is built with VC 2008 Express, Windows SDK 6.1, WTL 8.0 and ATL 3.0 from Platform SDK R2.


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


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Comments and Discussions

GeneralVery nice idea Pin
John R. Shaw23-Mar-09 15:21
MemberJohn R. Shaw23-Mar-09 15:21 
GeneralJust what I was looking for... Pin
Loreia18-Mar-09 5:30
MemberLoreia18-Mar-09 5:30 
GeneralMy vote of 2 Pin
RChin17-Mar-09 14:31
MemberRChin17-Mar-09 14:31 
GeneralMy vote of 1 Pin
wanft17-Mar-09 11:22
Memberwanft17-Mar-09 11:22 
GeneralRe: My vote of 1 [modified] Pin
Emilio Garavaglia17-Mar-09 22:02
MemberEmilio Garavaglia17-Mar-09 22:02 
AnswerRe: My vote of 1 Pin
T800G18-Mar-09 5:35
MemberT800G18-Mar-09 5:35 
GeneralRe: My vote of 1 Pin
Rick York18-Mar-09 8:24
mveRick York18-Mar-09 8:24 
GeneralRe: My vote of 1 Pin
Emilio Garavaglia18-Mar-09 23:30
MemberEmilio Garavaglia18-Mar-09 23:30 
GeneralRe: My vote of 1 Pin
Rick York19-Mar-09 7:33
mveRick York19-Mar-09 7:33 
GeneralRe: My vote of 1 Pin
Goran Mitrovic18-Mar-09 9:53
MemberGoran Mitrovic18-Mar-09 9:53 
Don't forget that #pragma once is an important compiling speed optimization because the file doesn't have to be preprocessed on second usage. This becomes important feature on large projects...

- Goran.

Question#pragma once? Pin
Steve Maier17-Mar-09 11:08
professionalSteve Maier17-Mar-09 11:08 
AnswerRe: #pragma once? Pin
xliqz17-Mar-09 13:22
Memberxliqz17-Mar-09 13:22 
GeneralRe: #pragma once? Pin
snapshot_a17-Mar-09 13:40
Membersnapshot_a17-Mar-09 13:40 
GeneralRe: #pragma once? Pin
kenneth nielsen17-Mar-09 13:57
Memberkenneth nielsen17-Mar-09 13:57 
GeneralRe: #pragma once? Pin
jonnybgood217-Mar-09 14:32
Memberjonnybgood217-Mar-09 14:32 
GeneralRe: #pragma once? Pin
T800G18-Mar-09 5:41
MemberT800G18-Mar-09 5:41 

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