Read Only ComboBox

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Introduction

This is a very quick fix to displaying a disabled combo box as read only. If you have a form with lots of read only edit boxes, the normal disabled combo box looks a bit funny. Read only edit boxes have black text with grey backgrounds. While disabled combo boxes have dark grey text with grey backgrounds. Hard to explain to users.

This code only works for drop down style combo boxes. This is because I am setting the child edit box as enabled and read only when the parent combo box is disabled.

When the combo box gets a WM_ENABLE message, check the bEnable flag and call EnableWindow and SetReadOnly for the edit box. A pointer to the edit box is retrieved by just getting the first child window of the combo box, GetWindow(GW_CHILD).

BEGIN_MESSAGE_MAP(CReadOnlyComboBox, CComboBox)
	...
	ON_WM_ENABLE()
	...
END_MESSAGE_MAP() 

void  CReadOnlyComboBox::OnEnable(BOOL bEnable)
{
	CComboBox::OnEnable(bEnable); 

	// Get edit control which happens to be the first child window
	CEdit* pEdit = (CEdit*)GetWindow(GW_CHILD);
	
	// Always have the edit box enabled
	pEdit->EnableWindow(TRUE);
	
	// Set read only is combo box is disabled
	pEdit->SetReadOnly(!bEnable);
} 

The only down side to this approach is the text can't be selected with the mouse like a read only edit box.