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Posted 9 Mar 2004

Controls-in-controls: An edit box with an icon

, 16 Jun 2004
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Adding controls to a CEdit, an edit box with an icon

Sample Image - editwithicon.gif

Introduction

While adding controls to other controls might be a commonly desired task, and edit box with an icon is perhaps not the most exciting or useful class. It presents a few enjoyable challenges, however, and usefulness is certainly not the only criteria for diving into control subclassing in MFC.

CIconEdit is a small CEdit-derived class with an attached small icon, where the multi line edit box edit rectangle is exploited, instead of the normal handling of non-client areas.

Using the code

Include the cpp- and h-file to the project. CIconEdit can be instantiated either dynamically, by a call to Create, or from a dialog template. In the latter case, a control variable can be created and bound to the control with the class wizard, or SubclassDlgItem can be used. Call SetIcon with either a HICON or a resource id to set the icon to display.

CIconEdit uses the edit rectangle of multi line edit boxes. Basically, it modifies the edit rectangle to add a left margin wide enough to accommodate a small icon. An instance of CIconWnd - a CStatic-derived class - is used to paint the icon. Icons can be set by calling CIconEdit::SetIcon with either a HICON handle to the desired icon, or a UINT resource id. If a resource id is used, the icon is destroyed by CIconEdit, otherwise the caller will have to destroy it.

The class overrides PreSubclassWindow. This call checks the edit box style. If ES_MULTILINE is not set, SetRect will not work, so the function ASSERTs. Sadly, it is not possible to add this style after the control is created - and it is too early to destroy and recreate the it. Then the edit rectangle is established. The width of a small icon is retrieved by a call to GetSystemMetrics, and the current edit rectangle is fetched, updated and set back to the control.

As soon as an icon is set by a call to either of the two SetIcon:s, the icon window is created.

CIconWnd is a very simple CStatic-derived class, handling WM_PAINT and there drawing the icon with a call to ::DrawIconEx. The icon will be scaled to the system small icon size if necessary.

Points of interest

Instantiating this control, doing a few common operations on CEdits, displayed an understandable but annoying quirk - the edit rectangle is reset. As the rectangle is absolute for a CEdit (RTF-controls can use an offset), WM_SIZE will have to be handled anyway. More surprising was that WM_SETFONT also killed the edit rectangle. For this reason, CIconEdit handles WM_SIZE and WM_SETFONT. As SetFont is not virtual, the message itself will have to be handled.

In this case, using a separate control for the icon might seem a bit byzantine, why not just draw it in the non-client area paint handling? Well, now I got myself a small-icon control if I should ever need one (which I doubt), and the edit control and icon is thoroughly separated codewise.

But the more exciting implication is the possibility to use the edit rectangle to put other controls and/or visuals in the edit box, buddy-buttons, line-numbers etc. And as the editing rectangle is not only used by the plain vanilla edit box - the RTF-control also has one - there is the possibility to add rulers etc. this way.

History

15/6 2004

In an explosion of activity, this article is finally updated thanks to the feedback from David Pritchard . I'm getting the system background color using GetSysColor(COLOR_WINDOW) when clearing the background behind the icon, and SetIcon with the HICON parameter will now also create the icon control... *blushing with embarrassment*

License

This article, along with any associated source code and files, is licensed under A Public Domain dedication

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About the Author

Johan Rosengren
Software Developer (Senior) Abstrakt Mekanik AB
Sweden Sweden
45 years old, married, three kids.

Started with computers more than 20 years ago on a CBM-64.

Read Theoretical Philosophy at the University of Lund.

Working as a C++ consultant developer.

Science-fiction freak. Enjoy vintage punkrock.

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Comments and Discussions

 
Questionsource code for Buddy Button "404 - File or directory not found" in http://www.gipsysoft.com/articles/BuddyButton Pin
APache_hema_317-Mar-14 14:05
memberAPache_hema_317-Mar-14 14:05 
AnswerRe: source code for Buddy Button "404 - File or directory not found" in http://www.gipsysoft.com/articles/BuddyButton Pin
Flaviu214-Jan-15 23:07
memberFlaviu214-Jan-15 23:07 
QuestionScrolling ? Pin
Mattthe cooldude9-Mar-05 14:58
memberMattthe cooldude9-Mar-05 14:58 
AnswerRe: Scrolling ? Pin
Johan Rosengren10-Mar-05 6:31
memberJohan Rosengren10-Mar-05 6:31 
GeneralProblem with mouse clicks Pin
David Pritchard20-Oct-04 0:01
memberDavid Pritchard20-Oct-04 0:01 
GeneralFalse alarm? Plus non-client implementation of IconEdit Pin
David Pritchard20-Oct-04 4:47
memberDavid Pritchard20-Oct-04 4:47 
OK, folks, first I need to apologise because I think the bug I saw was caused by something else. What happened was that repainting in my edit control stopped working properly. All my fix did was stop the insertion point from changing when the icon is clicked, which you may (or may not) feel is a worthwhile modification. The bug itself remains unexplained. It's happened to other users of my app before, but in my case it vanished after I restarted Windows (but not the application). I don't have any good theories and I haven't found any references to the problem, so for now I'm going to ignore it. Incidentally, the problem still occurs if I change the CIconEdits to normal CEdits, so CIconEdit is innocent in this respect.

Nevertheless, all this spurred me to try another approach to the icon-in-edit problem, using the buddy button code from GipsySoft. At least this has the merit of being usable in password edit controls. Here's the code. It's Johan's code, but with a few modifications and bits stripped out. The end result is quite a bit simpler than the original CIconEdit. It uses the GipsySoft EnableBuddyButton function from http://www.gipsysoft.com/articles/BuddyButton/[^], which I haven't included. It's just a question of dropping in the header file.

There's not much to comment on. First, I found that, in the same function, I needed to do a quick calculation to centre the icon vertically. Second, the icon must be created as a child of the edit's parent in order for the buddy button code to work in unaltered form. Otherwise you need to fiddle with the latter, which I didn't want to do.

My modifications are marked with "DP" throughout.

I hope somebody finds this useful!

Header:
<br />
class CIconWnd : public CStatic<br />
{<br />
// Construction/destruction<br />
public:<br />
	CIconWnd();<br />
	virtual ~CIconWnd();<br />
<br />
// Operations<br />
public:<br />
	void SetIcon( HICON icon );<br />
<br />
protected:<br />
	afx_msg void OnPaint();<br />
	afx_msg BOOL OnEraseBkgnd(CDC* pDC);<br />
	DECLARE_MESSAGE_MAP()<br />
<br />
private:<br />
// Attributes<br />
	HICON	m_icon;<br />
};<br />
<br />
/////////////////////////////////////////////////////////////////////////////<br />
// CIconEdit window<br />
<br />
class CIconEdit : public CEdit<br />
{<br />
// Construction/destruction<br />
public:<br />
	CIconEdit();<br />
	virtual ~CIconEdit();<br />
<br />
// Operations<br />
public:<br />
	void SetIcon(HICON icon);<br />
	void SetIcon(UINT iconres);<br />
<br />
protected:<br />
<br />
	DECLARE_MESSAGE_MAP()<br />
<br />
private:<br />
	// DP: 27/05/2004 Placed create icon window code in separate function, called from both SetIcon functions<br />
	void		CreateIconWindow();<br />
<br />
// Attributes<br />
	CIconWnd	m_icon;<br />
	HICON		m_internalIcon;<br />
};<br />


Body:
<br />
CIconEdit::CIconEdit()<br />
/*============================================================<br />
	Function :		CIconEdit::CIconEdit<br />
<br />
	Description :	constructor<br />
<br />
	Return :		void<br />
	Parameters :	none<br />
<br />
	Usage :			<br />
  ============================================================*/<br />
{<br />
<br />
	m_internalIcon = NULL;<br />
	m_icon.m_hWnd = NULL;<br />
<br />
}<br />
<br />
CIconEdit::~CIconEdit()<br />
/*============================================================<br />
	Function :		CIconEdit::~CIconEdit<br />
<br />
	Description :	<br />
	Return :		destructor	-	<br />
	Parameters :<br />
	Usage :			<br />
  ============================================================*/<br />
{<br />
<br />
	// Clean up<br />
	if( m_internalIcon )<br />
		::DestroyIcon( m_internalIcon );<br />
<br />
}<br />
<br />
BEGIN_MESSAGE_MAP(CIconEdit, CEdit)<br />
END_MESSAGE_MAP()<br />
<br />
<br />
/////////////////////////////////////////////////////////////////////////////<br />
// CIconEdit implementation<br />
<br />
void CIconEdit::SetIcon( HICON icon ) <br />
/*============================================================<br />
	Function :		CIconEdit::SetIcon<br />
<br />
	Description :	Sets a new icon and updates the control<br />
					<br />
	Return :		void	<br />
	Parameters :	HICON icon	-	Handle to the icon<br />
<br />
	Usage :			The caller must destroy the icon<br />
<br />
  ============================================================*/<br />
{<br />
	// DP: 27/05/2004 Placed create icon window code in separate function, called from both SetIcon functions<br />
	CreateIconWindow();<br />
<br />
	// Update the icon control<br />
	m_icon.SetIcon( icon );<br />
<br />
}<br />
<br />
void CIconEdit::SetIcon( UINT iconres ) <br />
/*============================================================<br />
	Function :		CIconEdit::SetIcon<br />
<br />
	Description :	Sets a new icon and updates the control<br />
					<br />
	Return :		void<br />
	Parameters :	UINT iconres	-	Resource id of the icon<br />
<br />
	Usage :			The class will load and destroy the icon.<br />
<br />
  ============================================================*/<br />
{<br />
	// DP: 27/05/2004 Placed create icon window code in separate function, called from both SetIcon functions<br />
	CreateIconWindow();<br />
<br />
	// If we already have an icon, we destroy it<br />
	if( m_internalIcon )<br />
		::DestroyIcon( m_internalIcon );<br />
<br />
	// Loading the new icon<br />
	m_internalIcon = ( HICON ) ::LoadImage( AfxGetResourceHandle(),<br />
								MAKEINTRESOURCE( iconres ),<br />
								IMAGE_ICON,<br />
								16,<br />
								16,<br />
								LR_DEFAULTCOLOR );<br />
<br />
	ASSERT( m_internalIcon != NULL );<br />
<br />
	// Update the icon control<br />
	m_icon.SetIcon( m_internalIcon );<br />
<br />
}<br />
<br />
// DP: 27/05/2004 Placed create icon window code in separate function, called from both SetIcon functions<br />
void CIconEdit::CreateIconWindow()<br />
{<br />
	if( !m_icon.m_hWnd )<br />
	{<br />
		CRect rectWindow;<br />
		GetWindowRect(&rectWindow);<br />
		<br />
		// If the icon window doesn't exist,<br />
		// we create it<br />
		CRect iconRect( 0, 0, GetSystemMetrics( SM_CXSMICON ), rectWindow.Height() );<br />
		if(m_icon.m_hWnd==NULL)<br />
			// DP: 03/06/2004 Make string Unicode-compatible<br />
			// DP: 20/10/2004 Must create as child of parent, otherwise buddy code fails<br />
			m_icon.Create(_T(""), WS_CHILD | WS_VISIBLE, iconRect, GetParent(), 1 );<br />
<br />
		// Make buddy window<br />
		if (m_icon.m_hWnd)<br />
		{<br />
			EnableBuddyButton(GetSafeHwnd(), m_icon.m_hWnd, BBS_LEFT);<br />
		}<br />
	}<br />
}<br />
<br />
<br />
/////////////////////////////////////////////////////////////////////////////<br />
// CIconEdit implementation<br />
<br />
/////////////////////////////////////////////////////////////////////////////<br />
// CIconWnd<br />
<br />
<br />
CIconWnd::CIconWnd()<br />
/*============================================================<br />
	Function :		CIconWnd::CIconWnd<br />
<br />
	Description :	constructor<br />
					<br />
	Return :		void<br />
	Parameters :	<br />
<br />
	Usage :			<br />
<br />
  ============================================================*/<br />
{<br />
<br />
	m_icon = NULL;<br />
<br />
}<br />
<br />
CIconWnd::~CIconWnd()<br />
/*============================================================<br />
	Function :		CIconWnd::~CIconWnd<br />
<br />
	Description :	destructor<br />
					<br />
	Return :		void<br />
	Parameters :	none<br />
<br />
	Usage :			<br />
<br />
  ============================================================*/<br />
{<br />
}<br />
<br />
BEGIN_MESSAGE_MAP(CIconWnd, CStatic)<br />
	ON_WM_PAINT()<br />
	ON_WM_ERASEBKGND()<br />
<br />
//	// DP: 10/06/2004 Added to set background colour of icon properly<br />
//	ON_WM_CTLCOLOR()<br />
END_MESSAGE_MAP()<br />
<br />
/////////////////////////////////////////////////////////////////////////////<br />
// CIconWnd message handlers<br />
<br />
void CIconWnd::OnPaint() <br />
/*============================================================<br />
	Function :		CIconWnd::OnPaint<br />
<br />
	Description :	Mapped to WM_PAINT. Draws the icon with the<br />
					small icon size (regardless of original)<br />
					<br />
	Return :		void<br />
	Parameters :	none<br />
<br />
	Usage :			Called from Windows<br />
<br />
  ============================================================*/<br />
{<br />
<br />
	CPaintDC dc( this );<br />
	if( m_icon )<br />
	{<br />
		CRect rect;<br />
		GetClientRect( &rect );<br />
<br />
		// Clearing the background<br />
//			dc.FillSolidRect( rect, dc.GetBkColor() );<br />
<br />
		// DP: 10/06/2004 Fixed background colour of icon<br />
		dc.FillSolidRect( rect, GetSysColor(COLOR_WINDOW) );<br />
<br />
		// Drawing the icon<br />
		int width = GetSystemMetrics( SM_CXSMICON );<br />
		int height = GetSystemMetrics( SM_CYSMICON );<br />
<br />
		// DP: 20/10/2004 Calculate Y-Pos<br />
		int nYPos = (rect.Height() - height) / 2;<br />
<br />
//		::DrawIconEx( dc.m_hDC, 1, 1, m_icon, width, height, 0, NULL, DI_NORMAL );<br />
		::DrawIconEx( dc.m_hDC, 1, nYPos, m_icon, width, height, 0, NULL, DI_NORMAL );<br />
	}<br />
}<br />
<br />
BOOL CIconWnd::OnEraseBkgnd( CDC* pDC) <br />
/*============================================================<br />
	Function :		CIconWnd::OnEraseBkgnd<br />
<br />
	Description :	Mapped to the WM_ERASEBKGND<br />
					<br />
	Return :		BOOL		-	Always TRUE<br />
	Parameters :	CDC*		-	From Windows<br />
				<br />
	Usage :			Called from Windows<br />
<br />
  ============================================================*/<br />
{<br />
	return TRUE;<br />
}<br />
<br />
/////////////////////////////////////////////////////////////////////////////<br />
// CIconWnd implementation<br />
<br />
void CIconWnd::SetIcon( HICON icon )<br />
/*============================================================<br />
	Function :		CIconWnd::SetIcon<br />
<br />
	Description :	Called to set/change the icon<br />
					<br />
	Return :		void<br />
	Parameters :	HICON icon	-	icon to use<br />
				<br />
	Usage :			The function is called from the CEditIcon <br />
					class<br />
<br />
  ============================================================*/<br />
{<br />
	m_icon = icon;<br />
	if( ::IsWindow( m_hWnd ) )<br />
		RedrawWindow();<br />
}<br />
<br />


(Incidentally, I'm sure this has been asked a million times, but is there no way to post properly formatted code, i.e. with tabs/spaces preserved, in these messages? I spent ten or fifteen minutes looking for the answer but couldn't find it.)
GeneralRe: False alarm? Plus non-client implementation of IconEdit Pin
Johan Rosengren20-Oct-04 7:17
memberJohan Rosengren20-Oct-04 7:17 
GeneralRe: False alarm? Plus non-client implementation of IconEdit Pin
David Pritchard20-Oct-04 10:38
memberDavid Pritchard20-Oct-04 10:38 
GeneralRe: False alarm? Plus non-client implementation of IconEdit Pin
Johan Rosengren21-Oct-04 9:17
memberJohan Rosengren21-Oct-04 9:17 
GeneralControls-in-controls: An edit box with an icon Pin
Larsson23-Sep-04 23:49
memberLarsson23-Sep-04 23:49 
GeneralRe: Controls-in-controls: An edit box with an icon Pin
Johan Rosengren24-Sep-04 0:20
memberJohan Rosengren24-Sep-04 0:20 
Generalfor an in depth discussion see also... Pin
Amun-Ra19-Jun-04 4:13
memberAmun-Ra19-Jun-04 4:13 
GeneralRe: for an in depth discussion see also... Pin
Johan Rosengren19-Jun-04 4:19
memberJohan Rosengren19-Jun-04 4:19 
GeneralA tiny, tiny painting correction Pin
David Pritchard10-Jun-04 11:12
memberDavid Pritchard10-Jun-04 11:12 
GeneralRe: A tiny, tiny painting correction Pin
Johan Rosengren10-Jun-04 11:16
memberJohan Rosengren10-Jun-04 11:16 
GeneralBug! SetIcon(HICON) Pin
David Pritchard27-May-04 4:15
memberDavid Pritchard27-May-04 4:15 
GeneralRe: Bug! SetIcon(HICON) Pin
Johan Rosengren27-May-04 4:55
memberJohan Rosengren27-May-04 4:55 
GeneralRe: Bug! SetIcon(HICON) Pin
David Pritchard27-May-04 11:44
memberDavid Pritchard27-May-04 11:44 
GeneralRe: Bug! SetIcon(HICON) Pin
Johan Rosengren27-May-04 20:09
memberJohan Rosengren27-May-04 20:09 
GeneralRe: Bug! SetIcon(HICON) Pin
David Pritchard28-May-04 13:02
memberDavid Pritchard28-May-04 13:02 
GeneralRe: Bug! SetIcon(HICON) Pin
Johan Rosengren28-May-04 22:38
memberJohan Rosengren28-May-04 22:38 
GeneralRe: Bug! SetIcon(HICON) Pin
David Pritchard29-May-04 5:01
memberDavid Pritchard29-May-04 5:01 
GeneralRe: Bug! SetIcon(HICON) Pin
Johan Rosengren29-May-04 5:27
memberJohan Rosengren29-May-04 5:27 
GeneralRe: Some comments Pin
Johan Rosengren10-Mar-04 9:23
memberJohan Rosengren10-Mar-04 9:23 
Generalthe ES_MULTILINE issue Pin
.dan.g.10-Mar-04 0:47
member.dan.g.10-Mar-04 0:47 
GeneralRe: the ES_MULTILINE issue Pin
Johan Rosengren10-Mar-04 1:02
memberJohan Rosengren10-Mar-04 1:02 
GeneralRe: the ES_MULTILINE issue Pin
.dan.g.10-Mar-04 1:35
member.dan.g.10-Mar-04 1:35 
GeneralRe: the ES_MULTILINE issue Pin
Johan Rosengren10-Mar-04 9:28
memberJohan Rosengren10-Mar-04 9:28 
Generalinteresting Pin
.dan.g.10-Mar-04 0:43
member.dan.g.10-Mar-04 0:43 
GeneralRe: interesting Pin
grigri18-Mar-04 12:32
membergrigri18-Mar-04 12:32 

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