CodeProject: Changing the background color of a read-only edit control. Free source code and programming help

This is my first article. So bear with me. I know it is a simple control but I spent quite a lot of time figuring this out. I hope someone can read this and figure it out quicker.

The Problem

I needed a read-only text box. I created one using the CEdit control. Problem was that, it had a grey background. There is no option or function to change it directly.

The Solution

I derived a class from CEdit called CReadOnlyEdit. I intercepted the background ON_WM_CTLCOLOR_REFLECT() message. This message's function looks like this:

To change the background color of the EditBox, instead of returning NULL for the function above, I returned a brush with the color I wanted for the background. Also if you notice in the function, above one of the parameters is a pointer to the Device Context (pDC) of the control. I used the pDC->SetTextColor(COLORREF rgb) function to change the text color. I then ran into a slight problem. The background changed to the correct color and the text did as well but the background of the text stayed white. This was a simple fix. I simply set the background color of the text using pDC->SetBkColor(COLORREF rgb) function. This is my modified function:

As you can see my control has three variables: COLORREF m_crText, COLORREF m_crBackGnd, and CBrush m_brBackGnd. I added two functions to my control, one to change the background color (and update the brush) and one to change the text color. Those two functions look like this:

The reason I have a COLORREF background variable is because to change the background color of the device context I need a COLORREF. A problem I ran into was, the entire edit control was not being colored right away, this is why I added the Invalidate(TRUE) call to repaint the control.

That's all there was to it. By the way, my control doesn't set a background or text color by default. This can easily be done in the constructor.

Using the code

Dialog Based:

Create a CEdit control. Control double-click it. The Add Member Variable dialog appears. Choose Control for the Category and CEdit for the variable type. Set the variable name to something like m_wndEdit. When modifying the control, remember m_wndEdit is the control not a string containing the window text. To access the text you will have to use the proper functions for the control (ie. CEdit::SetWindowText()).

Programmatically:

The simplest way I can think of to use this is just change all the CEdit controls you want to be read-only to CReadOnlyEdit.

Changing the colors:

To change the background and text color of the control using the SetBack Color(COLORREF rgb) and SetTextColor(COLORREF rgb) functions. In the demo I use a CColorDialog to get a color. The following is code from my demo. It is located in the Change Back Color button's click function:

Note: My control doesn't set the read-only flag, you have to do this yourself in the CReadOnlyEdit::Create function or in the dialog control properties. Also, this can be done with the CEdit::SetReadOnly(BOOL) function.

History

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Readonly Textbox inside the GroupBox Control

razhia

17:34 11 Nov '09

Backcolor of the readonly textbox is changed only for the textbox in the window. But i want to change the color for the readonly textbox inside the Groupbox or some other container control in the window.
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Mandou ver!

L4U80Y

9:11 9 Nov '09

Valeu mesmo mano! Thanks a lot Bro!
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haha

caolvchong

19:14 17 Dec '08

你好！good good study,day day up!
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Much easier and quicker method

mr. bleh

10:45 30 Oct '07

As another commenter already noted about two years ago...

A much better way of doing this is simply to handle the WM_CTLCOLORSTATIC message and either return the current default window background:

return GetSysColorBrush(COLOR_WINDOW);

or if for some reason you wish to enforce a specific colour, create the brush and return that instead:

HBRUSH hbrBackground = CreateSolidBrush(RGB(...));

Here's the relevant msdn entry:

http://msdn2.microsoft.com/en-us/library/bb787524.aspx

2.00/5

Thank you

miniiiii

19:40 29 Jul '07

^^
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Thank you

compex

11:11 8 Jan '07

That's all i need. Add the colorname.h (http://www.codeproject.com/gdi/colornames.asp) to your cpp's which calls the color-setter and you easily can modify your colors inside an editcontrol.
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How to implement this in WTL

CodeFundu

0:46 18 Mar '06

Any idea how to implement this in WTL?
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textColor stays grayed when Ctrl is disabled

FriendOfAsherah

23:22 11 Mar '06

Thanks a lot for this description of the EditCtrl it works fine but:
When I disable the ctrl the TextColor gets it default gray !
I found out the following:

HBRUSH CColorEditCtrl::CtlColor( CDC* pDC, UINT nCtlColor )
{
	pDC->SetTextColor(COLOR_EDITABLE); // when ctrl is enabled
	pDC->SetBkColor(IsWindowEnabled() ? COLOR_EDITABLE_BKGND : COLOR_DEFAULT_BKGND); // The Bkg Color UNDER THE TEXT !
	return IsWindowEnabled() ? m_EnabledBrush : m_Brush; 
        // The Bkng Color right of the text
}

And I added for the multiline EditCtrl:

BOOL CColorEditCtrl::OnEraseBkgnd(CDC* pDC) 
{
  CRect rect;
  GetClientRect(rect);
  CBrush brush0( IsWindowEnabled() ? COLOR_EDITABLE_BKGND : COLOR_DEFAULT_BKGND );
  pDC->FillRect(&rect,&brush0);
  brush0.DeleteObject();
  return FALSE;
}

which fills the unused part opf the control with the correct Background.
But I cannot change the Textcolor of a disabled EditCtrl !

Chaning the font in ReadOnlyEdit

bcamp

12:50 3 Mar '06

I likewise found it easy to use this class as described in the article. Nice job. However, I ran into a problem when I tried to extend it by allowing the user to specify the font. The problem is that the text gets clipped on the right side of the box. In CReadOnlyEdit::CtlColor, I created the font and set it as follows.

LOGFONT lf;
memset(&lf, 0, sizeof(LOGFONT));
lf.lfHeight = 14;
lf.lfWeight = FW_BOLD;
//lf.lfPitchAndFamily = FF_SWISS;
lstrcpy(lf.lfFaceName,_T("Arial"));
m_font.CreateFontIndirect(&lf);

pDC->SelectObject(&m_font);

Why doesn't it have problems with the System font but larger fonts it can't figure out? With a smaller font it still breaks the line after "read only" even though there is more room to continue with "but still". Nothing in the code seems to tell the system where to break the line. With a really big font, not only does the text get clipped on the right but also on the bottom.

Is there a way to set something in the pDC to tell it the width and height of the font being used?

2.00/5

How does it work.

CastleIsle

9:05 17 Feb '06

I found this article after spending two full days getting nowhere trying to change background colors of a CEdit control. It worked right away and I rated the article 5, but I do not yet know enough to understand how the program works.

Things must happen in a thread. Since I do not know how to set up a breakpoint in a thread, I can't step through the program to discover how things are working.

My best guess is the SetBkColor and SetTextColor functions generate the WM_CTLCOLOR message somehow, which causes the CtlColor function to run, but I do not know where the return value is going--maybe ON_WM_CTLCOLOR_REFLECT()?

I would like to know; it would help me change the font of my control as well.

I noted the compiler did not let me change the names of the CReadOnlyEdit functions SetBkColor or SetTextColor

2.00/5

How to make CReadOnlyEdit in MFC ClassWizard ?

krya

0:43 2 Feb '06

Hi How to make CReadOnlyEdit in MFC ClassWizard ? I can receive in "Add Member Variable" only 1)Category: Value Variable type: CString,int ... or 2)Category: Control Variable type: CEdit and not CReadOnlyEdit ?
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Re: How to make CReadOnlyEdit in MFC ClassWizard ?

CastleIsle

8:29 17 Feb '06

I am new to this, but I believe you need to create the CReadOnlyEdit class before you do the "Add Member Variable" thing in the class wizard. With the CReadOnlyEdit having a base class of CEdit, the class wizard should then give you the option of CEdit or CReadOnlyEdit.
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merci

quicksoft

20:45 15 Dec '05

I am chinese I like your article very much
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All this for what? Here is one liner to accomplish the same.

the_gurudev

19:07 29 Nov '05

Do not use white brush unless you absolutely want white background for your read only control.

What happens if the user changes the desktop color scheme and the text background color is now yellow. Your white background will be out of sync with the windows color scheme.

To use the standard windows color and to make things easy use the following code in the you CtlColor notification handler.


    return GetSysColorBrush(COLOR_WINDOW);

Thats it. So the entire functions looks like


HBRUSH CSomeWindow::CtlColor(CDC* pDC, UINT nCtlColor)
{
    // Return a system standard color
    return GetSysColorBrush(COLOR_WINDOW);
}

Peace...

Re: All this for what? Here is one liner to accomplish the same.

chiona

14:41 18 Dec '07

You actually need a bit more than a one-liner. If you want an arbitrary color for the background, create a CBrush of the appropriate color, and a color for your text. Here's code for a derived dialog with a CEdit control called m_edtMyEdit:

HBRUSH CMyDlg::OnCtlColor(
CDC *pDC,
CWnd *pWnd,
UINT nCtlColor
)
{
HWND hWnd = pWnd->GetSafeHwnd();
if ( hWnd == m_edtMyEdit.GetSafeHwnd() )
{
pDC->SetBkColor( m_clrBackground );
pDC->SetTextColor( m_clrText );
return (HBRUSH)m_brBackground;
}
else
return CDialog::OnCtlColor(pDC, pWnd, nCtlColor);
}

initializing background- and textcolor without control variable

mekanoo

14:35 9 Sep '05

what a fight!!!!!!!

to get the colors activated without using the controlvariable,
just using it as a winform control:
i had to rearrange the "DoPropExchange"..

void CCS_TBoxCtrl::DoPropExchange(CPropExchange* pPX)
{
PX_Color( pPX, _T("BackColor"), m_crBackGrnd );//Force permanent storing
PX_Color( pPX, _T("ForeColor"), m_crForeColor );
OnBackColorChanged();// kick it in
ExchangeVersion(pPX, MAKELONG(_wVerMinor, _wVerMajor));
COleControl::DoPropExchange(pPX);
}
void CCS_TBoxCtrl::OnBackColorChanged(void)
{
AFX_MANAGE_STATE(AfxGetStaticModuleState());
SetBackColor(m_crBackGrnd); //the Demo "SetBackColor" routine

SetModif Roll eyes

iedFlag();
InvalidateControl();
}

thanks a lot for that codepiece!

Text Background

Brian (BH)

1:37 28 Jan '05

Instead of setting the text backgound colour to match the brush using SetBkColor() why not just set the text backgound mode to transparent using SetBkMode( TRANSPARENT ), that way you don't need to store the text background colour and you can even use brush types other than solid.

I have tried this with your demo project and even changed the brush to a hatched type and it works fine. You should even be able to create a bitmap brush if you like, that way you can have any kind of pattern as the background.

2.00/5

Re: Text Background

bob16972

9:04 8 Nov '05

This might work for the control when it's style is read only and single line but this will cause residual droppings of text if you decide to use this control in the general sense and extend it's color capabilities such as when it's focused and when it's disabled.

If it's multiline, and you type some text and place the caret midstream in the text and start typing you will see what I mean. I would recommend using the authors technique of storing the brush and current color and ensuring the background is opaque.

SetBkMode(OPAQUE);

To be fair, I tried the Transparent solution a couple of years back but I quickly found during informal debugging that the potential for refresh issues exists when the control is used outside of the intended context.

3.50/5

Great first article!

Hans Dietrich

15:05 19 Jan '05

Thank you for posting this article. Anyone who is willing to share handy classes & techniques should be applauded, and so I voted 5 for this article.

I encourage you to get in the habit of reading your code - and other's code - to try to learn and improve. I would like to offer the following suggestions for things to think about for your next update:

With GDI objects, get in the habit of freeing them. In the dtor, you could write

CReadOnlyEdit::~CReadOnlyEdit()
{
    if (m_brBackGnd.GetSafeHandle())
        m_brBackGnd.DeleteObject();
}

After creating a class like this, ask yourself, What is first thing someone will want to change? Well, to me, first thing I wanted to know was, how to change background color? You could easily implement a SetBackgroundColor(COLORREF rgb) function, which might look like:
```
CReadOnlyEdit::SetBackgroundColor(COLORREF rgb)
{
    if (m_brBackGnd.GetSafeHandle())
        m_brBackGnd.DeleteObject();
    m_brBackGnd.CreateSolidBrush(rgb);
}
```

The m_brBackGnd member variable should probably be protected.

Best wishes,
Hans

How to do it in c#

nagarsoft

11:08 19 Jan '05

Have you got any idea on how I can do the same thing in C#? Thanks a lot. Andrea
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Re: How to do it in c#

W. Kleinschmit

23:05 19 Jan '05

Good question.
Unfortunately there ist (at least to my knowledge) no such thing like message reflection in the .NET Framework.
So, the only place to handle WM_CTLCOLOR (or better WM_CTLCOLOREDIT) seems to be the parent form.

Do something like this:

"C#">
const int WM_CTLCOLOREDIT = 0x0133;
const int WM_CTLCOLORSTATIC = 0x0138;

[DllImport("gdi32.dll")]
internal static extern IntPtr CreateSolidBrush(int color);
 
[DllImport("gdi32.dll")]
internal static extern int SetBkColor(IntPtr hdc, int color);

protected override void WndProc(ref Message m) {
    base.WndProc (ref m);

    if (m.Msg == WM_CTLCOLOREDIT) { // For Read-Write Controls
        SetBkColor(m.WParam, 0x8080FF);
        IntPtr brush = CreateSolidBrush(0x8080FF);
        m.Result = brush;
    }

    if (m.Msg == WM_CTLCOLORSTATIC) { // For Read-Write Controls
        SetBkColor(m.WParam, 0x80FFFF);
        IntPtr brush = CreateSolidBrush(0x80FFFF);
        m.Result = brush;
    }
}

Re: How to do it in c#

Anonymous

5:42 2 Aug '05

Just check the edit box properties in C#.
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Last Visit: 7:12 23 Nov '09 Last Update: 7:12 23 Nov '09

Introduction

The Problem

The Solution

Using the code

Dialog Based:

Programmatically:

Changing the colors:

History