VIEW WINDOW

DRAWING INSIDE THE VIEW WINDOW

OnDraw member function:

Ø Is a virtual member function of the CView class that the application framework calls every time the view window needs to be repainted.

Windows device context:

Ø Windows doesn’t allow direct access to the display hardware but communicates through an abstraction called a “device context” that is associated with the window.

Ø In the MFC library, the device context is a C++ object of class CDC that is passed as a parameter to OnDraw function.

Steps to build the application:

1.Run AppWizard to generate SDI application source code.

Ø Choose New from visual C++ File menu & then click Projects tab in the resulting New dialog box.

Ø Make sure that MFC AppWizard (exe) is selected and specify the path in the Location textbox finally specify Project Name and click OK.

Ø In the sequence of AppWizard screens select the following:

v Single Document Interface.

v Accept the default in the next four screens.

v In the last screen check the project name, class name and click Finish.

v It displays the New Project Information dialog box, click OK button.

Ø The AppWizard starts to create application’s subdirectory and a series of files in that subdirectory.

FILE	DESCRIPTION
Filename.dsp	A project file that allows Visual C++ to build the application.
Filename.dsw	A workspace file that contains a single entry for the .dsp file.
Filename.rc	An ASCII resource script file.
filenameView.cpp	A view class implementation file that contains class member functions.
filenameView.h	A view class header file that contains the class declaration.
Filename.opt	A binary file that tells Visual C++ which files are open for this project and how the windows are arranged. (not created until project is saved.
Readme.txt	A text file that explains the purpose of generated files.
Resource.h	A header file that contains #define constant declaration.

2. Edit the OnDraw function in the filenameView.cpp:

Ø Find the AppWizard generated OnDraw function in View.cpp and add the following code.

void CfilenameView::OnDraw(CDC* pDC)

{

CfilenameDoc* pDoc = GetDocument();

ASSERT_VALID(pDoc);

pDC->TextOut(0,0,”Hello World!”); // prints in default font & //size, top left corner.

pDC->SelectStockObject(GRAY_BRUSH); // selects a brush for //the circle interior.

pDC->Ellipse(CRect(0,20,100,120)); // draws a gray circle 100 //units in diameter.

}

3. Compile & test the file.