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Course 2D_MFC: 2D-Computer Graphics with C++/MFC
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 An Empty Window TextOut: Hallo World Print Window Size with SetTextColor Left, Right, Top, Bottom MoveTo, LineTo, Rectangle, Ellipse Draw a Star with Random Rays and Random Colors Draw a Polygon Animate it Exercises |
Start Microsoft Visual Studio.
1) Main Menu of Visual Studio: File → New → Project... →
Name: intro1 → Location: C:\temp →
2) The MFC Application Wizard - intro1 appears.
Application Type → Single document →
Database support: None → Next>
Main frame styles: → Thick frame →
Advanced features: → uncheck all advanced features → Next>
Generated classes: Cintro1App, CMainFrame, CChildView → Finish>
Click Debug in the main menu of Visual Studio. A submenu opens.
The rudimentary program now automatically compiles, links and starts. Please observe the Error List-window of Visual Studio below our program.
The program starts automatically as stand-alone window containing four parts:
1. main window = MainFrame with a blue title row,
2. three buttons on the right of the title bar: Minimize, Maximize, Close,
3. a main menu File, Edit, Help,
4. a narrow frame with 4 movable borders and 4 movable edges. Enlarge the window by dragging its borders and edges.
Minimize VisualStudio, to realize that intro1.exe is a stand-alone Windows program.
Start the Explorer. Branch to C:\temp\intro1\bin\debug.
Double click intro1.exe. You can start an arbitrary number of instances of intro1.exe. (You must carefully kill all of them before writing new versions.) Minimize the Explorer.
Make sure that all instances of intro1.exe have been finished.
Important: Always finish all instances of intro1 before writing new code and starting it !
Start the Task Manager with Ctrl+Alt+Del and check if an intro1.exe-process is still to be killed.
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If the Solution Eyplorer - intro1 isnīt already visible, open it via the Visual Studio main menu: View →
The automatically generated source code of
void CChildView::OnPaint()
{
CPaintDC dc(this); // device context for painting
// TODO: Add your message handler code here
// Do not call CWnd::OnPaint() for painting messages
}
Delete the comments and write a new line of code until it looks like this:
void CChildView::OnPaint()
{ CPaintDC dc(this);
dc.TextOut( 10, 10, "Hello world, here is intro1 !" );
}
Click Debug in the main menu of Visual Studio. A submenu opens.
Visual Studio compiles, links and starts the program.
Experiment: Change the first parameter of TextOut( 10, ...) to TextOut( 200, ...) and observe how the output is shifted to the right. Try the same with the second parameter.
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Version 2: Finish all instances of intro1.
Write seven additional lines into void CChildView::OnPaint() until it looks like this:
void CChildView::OnPaint()
{ CPaintDC dc(this); // device context for painting
dc.TextOut(10, 10, "Hello world, here is intro1 !");
CRect r; //a rectangle r of type CRect
CString sometext; //a string sometext of type CString
GetClientRect( r ); //Ask the operating system to report the size of our window
sometext.Format( "width=%d, height=%d", r.right, r.bottom ); //prepare output
dc.TextOut( 10, 30, sometext ); //output a line below the last one
dc.SetTextColor(RGB(255,0,0)); //red text
dc.TextOut(10,50, "Change the size of your window !" );
}
Click Debug in the main menu of Visual Studio →
Important: If there are typing errors, Visual Studio compiles nothing but displays a Message Box: There were build errors. Would you like to continue and run the last successful build ?. Quit this message box with No.
Below the source code CChildView.cpp an Error List-window will appear. Scroll the list upwards until you see the first error. If there is not an error but a warning ignore the warning and scroll downwards until you find the first error. Double click the line reporting the first error. The cursor will automatically jump into your code to the line, where the error has been detected. Correct the typing error. Ignore all further errors (Mostly they are the consequence of the first one.) and start again and repeat this procedure until the program succeeds.
Caution: The error can occur in a command line above the cursor. Perhaps you forgot a semicolon or a bracket there.
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Version 3: Finish all instances of intro1.
Write eight new lines below the already existing lines of void CChildView::OnPaint():
CPoint p; //a point p of type CPoint p.x = r.right / 2; // mid x p.y = r.bottom / 2; // mid y dc.SetTextColor( RGB( 0, 0, 255 ) ); //blue writing dc.TextOut( 0 , p.y , "left" ); dc.TextOut( r.right-50, p.y , "right" ); dc.TextOut( p.x , 0 , "top" ); dc.TextOut( p.x , r.bottom-20, "bottom" );
Click Debug in the main menu of Visual Studio →
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Version 4: Finish all instances of intro1.
Write another eight new lines below the already existing lines of void CChildView::OnPaint():
dc.MoveTo( 0 , 0 ); dc.LineTo( r.right, r. bottom ); dc.MoveTo( r.right, 0 ); dc.LineTo( 0 , r. bottom ); int w5 = r.right / 5; // 20% of the width int h5 = r.bottom / 5; // 20% of the height dc.Rectangle( w5, h5, 4*w5, 4*h5 ); dc.Ellipse ( w5, h5, 4*w5, 4*h5 );
Click Debug in the main menu of Visual Studio →
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Version 5: Finish all instances of intro1.
Below the three #include command lines on top of CChildView.cpp write another line starting immediately at the left margin of the text:
#include "math.h" //in order to find sin() and cos()
Write a line starting immediately at the left margin of the text directly above the
#define nn 120
Write the following lines below the already existing lines of void CChildView::OnPaint():
int i;
CPen pen; //a pen of type CPen
CPoint splash[ nn ]; //an array named splash of length nn containing x/y-coordinates
double arcus = 2. * 3.14159 / nn; // a small segment of the unit circle
double radius_x = 1.5 * w5; // horizontal radius of the ellipse
double radius_y = 1.5 * h5; // vertical radius of the ellipse
for ( i = 0; i < nn; i++ )
{ COLORREF multicolor = RGB ( rand()%255, rand()%255, rand()%255 );
pen.CreatePen( PS_SOLID, 20, multicolor ); //20 = thickness of the random-color pen
dc.SelectObject( pen ); //take the pen in your hand
double factor = (double)rand() / (double)RAND_MAX; //something between 0.0 and 1.0
if ( factor < 0.25 ) factor = 0.25; //but not less than 1/4
double cosinus = radius_x * factor * cos( i * arcus );
double sinus = radius_y * factor * sin( i * arcus );
dc.MoveTo( p ); //mid of ellipse
dc.LineTo( p.x + (int)cosinus, p.y + (int)sinus );//ending point
pen.DeleteObject(); //dispose the pen
splash[i].x = p.x + int( cosinus * 0.8 ); //store the x-coordinate
splash[i].y = p.y + int( sinus * 0.8 );//store the y-coordinate
}
Click Debug in the main menu of Visual Studio →
Drag the borders and/or the edges of our program intro1.
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Version 6: Finish all instances of intro1.
Write the following lines below the already existing lines of void CChildView::OnPaint():
dc.SelectStockObject( WHITE_PEN ); //an existing pen of thickness 1 named WHITE_PEN CBrush brush; //a brush of type CBrush brush.CreateSolidBrush( RGB( 255,0,0 ) ); //dip it into red color dc.SelectObject( brush ); //take the brush in your hand dc.Polygon( splash, nn ); //draw a polygon with nn vertices brush.DeleteObject(); //dispose the brush dc.SetTextColor( RGB( 0,0,255 ) ); //blue writing dc.TextOut( p.x-30, p.y-8, "Splash !" );
Click Debug in the main menu of Visual Studio →
Drag the borders and/or the edges of our program intro1.
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Version 6: Finish all instances of intro1.
Write the following lines below the already existing lines of void CChildView::OnPaint():
Sleep( 100 ); //slow down to 10 per second Invalidate(); //call void CChildView::OnPaint() again
Click Debug in the main menu of Visual Studio →
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Read the explanations of the command lines in Code Comments.
Click Help in the main menu of Visual Studio. Click the submenu Index.
Choose Visual C++ in the text box Filtered by:. Type the following key words into Look for:
#define, CPoint, rand, Polygon, Ellipse, Rectangle etc. With each key word you obtain a list. Click the most interesting key word of the list. If there are complicated alternatives, an additional pop up window appears on the lower border of Visual Studio. Read the help texts.
Finish Visual Studio, start the Explorer, delete the complete directory C:\temp\intro1.
Start Visual Studio again and rewrite intro1 until you can write it by heart.
Increase your writing speed by extensive use of Drag&Drop.
Invent and try new versions of the program in form of new projects intro2, intro3 etc.
Ideas: parallel horizontal color bars, parallel vertical color bars, colorful rectangles and ellipses at random positions.
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