Advanced MFC Programming

Chapter 1. Tool Bar and Dialog Bar
One thing to mention here is that CCmdUI has a public member variable m_nID, which stores the ID of
the control that is about to be updated. We can compare it with variable CBarDoc::m_uCurrentBtn and set
the appropriate state of the control.
With the above implementation, the red button will be checked from the beginning. We need to change
the value of variable m_uCurrentBtn in order to check another button. This should happen when the user
clicks on any of the four buttons, which will cause the application to receive a WM_COMMAND message. In the
sample, this will cause the message handlers CBarDoc::OnButtonRed(), CBarDoc::OnButtonBlue()… to be
called. Within these member functions, we can change the value of m_uCurrentBtn to the coresponding
command ID in order to check that button:
void CBarDoc::OnButtonBlue()
{
m_uCurrentBtn=ID_BUTTON_BLUE;
}
void CBarDoc::OnButtonGreen()
{
m_uCurrentBtn=ID_BUTTON_GREEN;
}
void CBarDoc::OnButtonRed()
{
m_uCurrentBtn=ID_BUTTON_RED;
}
void CBarDoc::OnButtonYellow()
{
m_uCurrentBtn=ID_BUTTON_YELLOW;
}
The message box implementation is removed here. By executing the sample application and clicking
on any of the four color buttons, we will see that at any time, one and only one button will be in the
checked state.
1.3. Check Box Implementation
Using Boolean Type Variables
Using the method discussed in section 1.2, it is very easy to implement check-box-like buttons. We can
declare Boolean type variables for each control, and toggle their values between FALSE and TRUE in the
WM_COMMAND message handlers. Within UPDATE_COMMAND_UI message handlers, we can set check for any
button according to the corresponding value of the Boolean type variable.
Sample 1.3-1\Bar is implemented in this way. In this sample, first variable m_uCurrentBtn is removed,
then WM_COMMAND and UPDATE_COMMAND_UI message handlers are made empty. Four new Boolean type
variables are declared in class CBarDoc:
……
……
class CBarDoc : public CDocument
{
protected:
BOOL m_bBtnRed;
BOOL m_bBtnGreen;
BOOL m_bBtnBlue;
BOOL m_bBtnYellow;
}
Their values are initialized in the constructor:
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