Changing the Background Color of a Read-only Edit Control

• Download demo project - 11.5 KB
• Download source code - 2.1 KB

Introduction

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. The 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:

HBRUSH CReadOnlyEdit::CtlColor(CDC* pDC, UINT nCtlColor) 
{
	// TODO: Return a non-NULL brush if the parent's 
	//handler should not be called
	return NULL;
}

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:

HBRUSH CReadOnlyEdit::CtlColor(CDC* pDC, UINT nCtlColor) 
{
	// TODO: Return a non-NULL brush if the parent's 
	//handler should not be called

	//set text color
	pDC->SetTextColor(m_crText);

	//set the text's background color
	pDC->SetBkColor(m_crBackGnd);

  //return the brush used for background this sets control background
  return m_brBackGnd;
}

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:

void CReadOnlyEdit::SetBackColor(COLORREF rgb)
{
	//set background color ref (used for text's background)
	m_crBackGnd = rgb;
	
	//free brush
	if (m_brBackGnd.GetSafeHandle())
       m_brBackGnd.DeleteObject();
	//set brush to new color
	m_brBackGnd.CreateSolidBrush(rgb);
	
	//redraw
	Invalidate(TRUE);
}
void CReadOnlyEdit::SetTextColor(COLORREF rgb)
{
  //set text color ref
  m_crText = rgb;

  //redraw
  Invalidate(TRUE);
}

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

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:

void CReadOnlyDlg::OnBack() 
{	
	// call color dialog and change background color
	CColorDialog dlg;
	if (dlg.DoModal() == IDOK)
		m_wndReadOnly.SetBackColor(dlg.GetColor());	
}

Where m_wndReadOnly is the CReadOnlyEdit control.

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

• Jan 21, 2005 - Update
  • Fixed bugs
  • Added SetBackColor and SetTextColor functions
• Jan 18, 2005 - Posted
  • Basic control, changed background color to white

License

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