Advanced MFC Programming

Chapter 1. Tool Bar and Dialog Bar
The function has two parameters, the second parameter dwMode indicates what kind of size is being
retrieved. It can be the combination of many flags, in this section, we need to know only two of them:
Flag
LM_HORZDOCK
LM_VERTDOCK
Meanings
The horizontal dock dimension is being retrieved
The vertical dock dimension is being retrieved
What we need to do in the overridden function is examining the LM_HORZDOCK bit and LM_VERTDOCK bit
of dwMode parameter and setting the button information correspondingly.
To override the member function of CToolBar, we must first derive a new class from it, then
implement a new version of this function in the newly created class. Sample 1.7\Bar demonstrates how to
change the button’s style dynamically, it is based on sample 1.6\Bar.
First, we need to declare the new class, in the sample, this class is named CColorBar:
class CColorBar : public CToolBar
{
public:
CColorBar();
BOOL AddComboBox();
BOOL ShowComboBox();
BOOL HideComboBox();
virtual ~CColorBar();
virtual CSize CalcDynamicLayout(int , DWORD);
//{{AFX_VIRTUAL(CColorBar)
//}}AFX_VIRTUAL
protected:
CComboBox m_wndComboBox;
};
//{{AFX_MSG(CColorBar)
//}}AFX_MSG
DECLARE_MESSAGE_MAP()
Instead of declaring a CComboBox type variable in class CMainFrame, here we implement the declaration
in the derived class. This is a better implementation because the combo box should be made the child
window of the tool bar. By embedding the variable here, we can make it a protected variable so that it is not
accessible from outside the class.
Three functions are added to change the tool bar’s style. Function CColorBar::AddComboBox()
changes the blue button to a separator and creates the combo box window:
BOOL CColorBar::AddComboBox()
{
CRect rect;
}
GetItemRect(2, rect);
rect.bottom=rect.top+150;
if
(
!m_wndComboBox.Create
(
WS_CHILD | CBS_DROPDOWN | CBS_AUTOHSCROLL | WS_VSCROLL | CBS_HASSTRINGS,
rect,
this,
ID_BUTTON_BLUE
)
)return FALSE;
else return TRUE;
This is the same with what we did in function CMainFrame::OnCreate(…) in the previous section. The
only difference is that when creating the combo box within the member function of CMainFrame, the combo
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