Working with GUI APIs - Essentials of Interactive Computer Graphics - page 52

GUI Element GUI ID Control Variable

IDC _ V _ SLIDER _ BAR m _ VSliderBar

Slider Bars

IDC _ H _ SLIDER _ BAR m _ HSliderBar

Slider Bar Labels Vertical Bar −

Horizontal Bar −

IDC _ V _ SLIDER _ ECHO m _ VSliderEcho

Slider Bar Echo Areas

IDC _ H _ SLIDER _ ECHO m _ HSliderEcho

Table 2.3. The elements of Tutorial 2.3.

• Slider bar echo control variables (A). We see declaration of the variables
at label A1. Note that m _ HSliderEcho is simply another variable until the
DDX _ Text macro call at label A2. After this macro call, m _ HSliderEcho
becomes the control variable for IDC _ H _ SLIDER _ ECHO GUI element. These
control variables are initialized at label A3.

• Slider bar control variables (B). We see the declaration of the variables
at label B1. These will be the control variables for the slider bars. Notice
the CSliderCtrl data type. MFC predefines data types to support every
type of GUI element (e.g., CButton for button GUI elements, CComboBox
for combo-box GUI elements). At label B2, these variables are bound
to the corresponding slider bar GUI elements. At label B3, during the
initialization OnInitDialog() function call, we initialize the max, min,
and initial position of the slider bar knobs. After the initialization func-
tion calls, the values of the control variables (e.g., m _ VSliderBar )be-
come out-of-sync with the state of the corresponding GUI element (e.g.,
IDC _ V _ SLIDER _ BAR ). The false parameter to the UpdateData() function
call at label B4 flushes the control variables' values onto their correspond-
ing GUI elements.

class CTutorialDlg : public CDialog {

Source file.
TutorialDlg.h/cpp file in
the Source and Header
files folders of the
MFC _ SliderControls
project.

. // removed content similar to that from
// Listing 2.6 (Tutorial 2.2) .
A1: CString m _ HSliderEcho, m _ VSliderEcho;
B1: CSliderCtrl m _ VSliderBar, m _ HSliderBar;
C1: afx _ msg void OnHScroll(UINT nSBCode, UINT nPos, CScrollBar * pScrollBar);
afx _ msg void OnVScroll(UINT nSBCode, UINT nPos, CScrollBar * pScrollBar);

};

Listing 2.7. CTutorialDlg class (Tutorial 2.3).