Advanced MFC Programming

Chapter 1. Tool Bar and Dialog Bar
……
}
m_wndComboBox.ShowWindow(SW_SHOW);
Function CToolBar::GetItemRect(…) is called in the second statement of above code to retrieve the
size and position of the separator. After calling this function, the information is stored in variable rect,
which is declared using class CRect.
A drop down combo box contains two controls: an edit box and a list box. Normally the list box is not
shown. When the user clicks on the drop down button of the combo box, the list box will be shown.
Because the size of the combo box represents its total size when the list box is dropped down (Figure 1-8),
we need to extend the vertical dimension of the separator before using it to set the size of the combo box.
The third statement of above code sets the rectangle’s vertical size to 150. So when our combo box is
dropped down, its width and the height will be roughly the same.
The fourth statement of above code creates the combo box. Here a lot of styles are specified, whose
meanings are listed below:
Style Flag
WS_CHILD
CBS_DROPDOWN
CBS_AUTOHSCROLL
WS_VSCROLL
CBS_HASSTRINGS
Meanings
Indicates that the window (combo box) being created is a child window. We must
specify this flag in order to embed the combo box in another window
The combo box has a list control that can be dropped down by clicking its drop down
button
When the user types text into the edit control, the text will be automatically scrolled
to the left if it is too long to be fully displayed
If too many items are added to the list controls and not all of them can be displayed at
the same time, a vertical scroll bar will be added to the list control
The items in the list control contains strings
The above styles are the most commonly used ones for a combo box. For details about this control,
please refer to chapter 5.
x
y
Figure 1-8. The size of a combo box is the
total size when the list box is dropped down
Because the blue button will not be pressed to execute command anymore, we use ID_BUTTON_BLUE as
the ID of the combo box. Actually, we can specify any other number so long as it is not used by other
controls.
Finally, we must call function CWnd::ShowWindow(…) and pass SW_SHOW flag to it to show any window
created dynamically.
By compiling and executing the sample at this point, we will see that the blue button has been changed
to a combo box.
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