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Chapter 15: Fundamental Controls Visual C++ and MFC Fundamentals

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GetClientRect() function is called to get the dimensions of the view’s client area of a

frame -based application and use the resulting rectangle to paint that area:

void CCView1View::OnPaint()

{

CPaintDC dc(this); // device context for painting

// TODO: Add your message handler code here

CRect Recto;

CBrush SelectedBrush(SelectedColor);

CPen SelectedBlue(PS_SOLID, 1, SelectedColor);

GetClientRect(&Recto);

CBrush *pOldBrush = dc.SelectObject(&SelectedBrush);

CPen *pOldPen = dc.SelectObject(&SelectedBlue);

dc.Rectangle(Recto);

dc.SelectObje ct(pOldBrush);

// Do not call CView::OnPaint() for painting messages

}

Once the control is already positioned on the client area, to get its location and

dimensions, you can call the CWnd::GetWindowRect() method. Here is an example:

void CTabDlg::OnBtnInfo()

{

// TODO: Add your control notification handler code here

CRect Recto;

char LocDim[80];

m_Panel.GetWindowRect(&Recto);

sprintf(LocDim, " - Panel Information -\nLeft: %d,"

"\nTop: %d,\nWidth: %d,\nHeight: %d",

Recto.left, Recto.top, Recto.Width(), Recto.Height());

MessageBox(LocDim);

}

Practical Learning: Using the Client Area

1. Open the Geometry application you were working on earlier

2. Open the Quadrilateral.cpp source file and change its OnPaint() event as follows:

Visual C++ and MFC Fundamentals Chapter 15: Fundamental Controls

© FunctionX, Inc. 427

void CQuadrilateral::OnPaint()

{

CPaintDC dc(this); // device context for painting

CRect Recto;

// Create a light green brush

CBrush BrushLightGreen(RGB(212, 235, 235));

// Create a navy pen

CPen PenNavy(PS_SOLID, 1, RGB(0, 0, 128));

// Create a green brush

CBrush BrushGreen(RGB(100, 175, 180));

// Create a dark green pen

CPen PenGreen(PS_SOLID, 2, RGB(0, 115, 115));

// Get the location and dimensions of the client rectangle

GetClientRect(&Recto);

// Select the light green brush

CBrush *pOldBrush = dc.SelectObject(&BrushLightGreen);

// Select the navy pen

CPen *pOldPen = dc.SelectObject(&PenNavy);

// Draw a rectangular shape on the left side of the property page

dc.Rectangle(0, 0, 162, Recto.Height());

// Select the green brush

pOldBrush = dc.SelectObject(&BrushGreen);

// Select the dark green pen

pOldPen = dc.SelectObject(&PenGreen);

// Draw the square

dc.Rectangle(40, 40, 120, 100);

// Draw the rectangle

dc.Rectangle(20, 170, 140, 240);

// Set the back mode to transparent for the text

dc.SetBkMode(TRANSPARENT);

// Display indicative labels

dc.TextOut(60, 105, "Square");

dc.TextOut(45, 250, "Rectangle");

// Restore the old GDI tools

dc.SelectObject(pOldPen);

dc.SelectObject(pOldBrush);

if (IsIconic())

{

SendMessage(WM_ICONERASEBKGND,

reinterpret_cast<WPARAM>(dc.GetSafeHdc()), 0);

// Center icon in client rectangle

int cxIcon = GetSystemMetrics(SM_CXICON);

int cyIcon = GetSystemMetrics(SM_CYICON);

CRect rect;

GetClientRect(&rect);

int x = (rect.Width() - cxIcon + 1) / 2;

int y = (rect.Height() - cyIcon + 1) / 2;

Chapter 15: Fundamental Controls Visual C++ and MFC Fundamentals

428 © FunctionX, Inc.

// Draw the icon

dc.DrawIcon(x, y, m_hIcon);

}

else

{

CPropertyPage::OnPaint();

}

}

3. Test the application:

4. Close the application and return to MSVC

14.2.3 The Screen and Client Coordinates

When calling either the GetClientRect() or the GetWindowRect() methods to get the

location and the dimensions of a control or another object, it is important to know the

origin of the produced rectangle. By default, the rectangle returned by the

GetWindowRect() method called by a control has its origin on the top left corner of the

monitor and not on the top-left corner of the parent window. Consider the following

event. It gets the location and dimensions of a control and stores them in a CRect

variable. Then it paints a rectangle (it is supposed to paint the control) located on, and

equal to the dimensions of, the control:

void CTabDlg::OnBtnInfo()

{

// TODO: Add your control notification handler code here

CRect Recto;

m_Panel.GetWindowRect(&Recto);

CClientDC dc(this);

CBrush BlueBrush(RGB(0, 128, 192));

CBrush *pOldBrush = dc.SelectObject(&BlueBrush);

dc.Rectangle(Recto);

Visual C++ and MFC Fundamentals Chapter 15: Fundamental Controls

© FunctionX, Inc. 429

dc.SelectObject(pOldBrush);

}

After executing the program and moving the dialog box somewhere to the middle center

of the screen and clicking the button, the result is as follows:

After moving the dialog box close to the top-left section of the screen and clicking the

button again, the result is the following:

This demonstrates that, although the control is a child of the dialog box, the rectangle

returned by the GetWindowRect() method is based on the screen and not the client

coordinates of the parent window. This is not an anomaly. It is purposely done so you can

specify what origin you want to consider.

As seen in previous lessons, the origin of the screen is positioned on the top-left corner of

the monitor. This is referred to as, or is said that the location uses, screen coordinates.

The origin of a client area is placed on its top-left corner. This is referred to as, or is said

that the location uses, client coordinates. For example, the origin used by the above

GetWindowRect() method is based on the screen. If you want the rectangle resulting

from a call to either the GetClientRect() or the GetWindowRect() methods to be based

on the client area (on client coordinates) of the control that called it, you can transfer the

origin from the screen to the client. This is conveniently done with a call to the

CWnd::ClientToScreen() method. It is overloaded as follows:

void ClientToScreen(LPPOINT lpPoint) const;

void ClientToScreen(LPRECT lpRect) const;

If the location you had requested is a point, pass its POINT or its CPoint variable to the

ClientToScreen() method. If the value you requested is a rectangle, pass its RECT or its

CRect variable. Here is an example:

void CTabDlg::OnBtnInfo()

{

// TODO: Add your control notification handler code here

Chapter 15: Fundamental Controls Visual C++ and MFC Fundamentals

430 © FunctionX, Inc.

CRect Recto;

m_Panel.GetWindowRect(&Recto);

CClientDC dc(this);

CBrush BlueBrush(RGB(0, 128, 192));

CBrush *pOldBrush = dc.SelectObject(&BlueBrush);

ScreenToClient(Recto);

dc.Rectangle(Recto);

dc.SelectObject(pOldBrush);

}

This time, even if the dialog box moves, the GetWindowRect() method returns the same

rectangle.

If the location and/or dimension are given in client coordinates, to convert them to screen

coordinates, call the ScreenToClient() method. It is overloaded as follows:

void ScreenToClient(LPPOINT lpPoint) const;

void ScreenToClient(LPRECT lpRect) const;

This method follows the opposite logic of the ClientToScreen() method.

Practical Learning: Using Client and Screen Coordinates

1. The Geometry application should still be opened.

From the Resource View tab open the IDD_CIRCULAR dialog box

2. On the Controls toolbox, click the Picture control and draw a rectangular shape

on the left side of the dialog box

Visual C++ and MFC Fundamentals Chapter 15: Fundamental Controls

© FunctionX, Inc. 431

3. Change the ID of the new control to IDC_SHP_CIRCULAR and Add a Control

Variable for it named m_ShapeCircular

4. Access the OnPaint event of the CCircular class and implement it as follows:

void CCircular::OnPaint()

{

CPaintDC dc(this); // device context for painting

// TODO: Add your message handler code here

// Do not call CPropertyPage::OnPaint() for painting messages

// The location and dimension variable for the control

CRect ShapeRect;

// Create a cream color brush

CBrush BrushCream(RGB(255, 230, 205));

// Create an orange brush

CBrush BrushOrange(RGB(255, 128, 64));

// Create a brown pen

CPen PenBrown(PS_SOLID, 2, RGB(128, 0, 0));

// Get the location and dimension of the control

m_ShapeCirc.GetWindowRect(&ShapeRect);

// Convert the location and dimensions to client coordinates

ScreenToClient(&ShapeRect);

// Select the cream brush to use

CBrush *pOldBrush = dc.SelectObject(&BrushCream);

// Paint the control's background to light blue

dc.Rectangle(ShapeRect);

// Select the brown pen to paint

CPen *pOldPen = dc.SelectObject(&PenBrown);

// Select an orange brush

pOldBrush = dc.SelectObject(&BrushOrange);

// Draw the circle

dc.Ellipse(40, 30, 120, 110);

Chapter 15: Fundamental Controls Visual C++ and MFC Fundamentals

432 © FunctionX, Inc.

// Draw the ellipse

dc.Ellipse(20, 170, 140, 240);

// Set the back mode to transparent for the text

dc.SetBkMode(TRANSPARENT);

// Display indicative labels

dc.TextOut(60, 115, "Circle");

dc.TextOut(55, 250, "Ellipse");

// Dismiss the GDI objects and restore the originals

dc.SelectObject(pOldBrush);

dc.SelectObject(pOldPen);

}

5. Test the application

6. Close it and return to MSVC

14.2.4 The Window: Its Location and Dimensions

We have reviewed various ways of specifying a control’s location and its dimensions,

eitther at design or run time. Once a window or a control has been positioned on the

screen or in its confined client area, it keeps these attributes until specified otherwise.

When dealing with a main window, such as the frame of an application, a dialog box, a

property sheet, or a wizard, the user can move it around the screen as necessary and if

possible. This is usually done by dragging the title bar.

When the user grabs the title bar of a window and starts dragging to move it, the window

sends the WM_MOVING message as we saw in Lesson 4. The WM_MOVING event

fires the OnMoving() event. This event is usually left alone as it allows the user to use an

application as regularly as possible. The syntax of the OnMoving() event is:

afx_msg void OnMoving(UINT nSide, LPRECT lpRect);

The OnMoving() event fires while the window is being moved. The nSide argument

specifies the side of window that is moving. As the window is moving, this event returns

its location and dimensions as the values of the lpRect member variables.