MFC-如何在矩形内绘制像素波

Question

I am new to MFC trying to learn from the scratch.

I am trying to create a small dialog based application in VS2012 - MFC.

On the dialog window i have drawn a rectangle (in OnPaint event) like this.

CPaintDC dc(this);
CRect background1(10,10,208,92);
dc.Rectangle(10,10,208,92);

Then i filled the bacground with some color. Like this.

   CBrush brush1;
   brush1.CreateSolidBrush(RGB(2,3,4));
   dc.FillRect(background1,&brush1);

Now i wanted to draw waves in form of pixels continuously inside the rectangle.

As of now what i have done is,

bool top = false;
    for(i=10,j=92;i<200 && j>10;)
    {
        pDC->SetPixel(i,j,NewColor);
        Sleep(10);

        if(!top)
            j-=1;
        else
            j+=1;
        if(j%4==0)
        {
            i+=1;

        }
        if(j==12)
            top=true;
        if(j==90)
            top = false;

    }

I am just drawing the pixels straightaway on the window, but within the dimensions where the rectangle lies. And the waves stop as it reaches the right dimension of the rect. But i feel thats not the right way to do it.

I want to draw the waves inside the rectangle and also continuosly, like when it reacahes the right end it should move left and it should be continuous.

Is there any proper way in MFC to draw something inside a rectangle (technically inside another object)?

Please help me out.

Answer 1

I tried your code and just added some condition, so that if it reaches right side it should start moving toward left.

void CMyDlg::OnBnClickedOk()
{
    CWnd *cWnd = FromHandle(m_hWnd);
    CDC *pDC = cWnd->GetDC();
    bool top = false;
    bool right = false;
    int i,j;
    for(i=10,j=92;i<=200 && j>10;)
    {
        pDC->SetPixel(i,j,RGB(255,255,255));
        Sleep(10);

        if(!top)
            j-=1;
        else
            j+=1;
        if(j%4==0)
        {
            if(!right)
                i++;  // if reaches right side i--;
            else{
                i--;
            }
        }
        if(j==12)
            top=true;
        else if(j==90)
            top = false;
        if(i == 200)// make right = true if reaches right side
            right = true;
        else if(i == 10)// make false it reaches left side
            right = false;
    }
}

I am getting output something like this

NOTE: this will cause infinite loop, you need to check condition where you have to stop printing pixels.

Answer 2

You are NOT looping with Sleep(10) in your WM_PAINT handler, are you?

MFC or not, you should separate your data processing from presentation. It appears you are trying to do an animation; the simplest way to do it is to have an off-screen (memory) DC and drawing your pixels on it. At certain times (frame rate?), you would call parent's InvalidateRect()/UpdateWindow() pair. Then in ON_PAINT, you would BitBlt() your prepared DC onto your preferred location in the dialog.

Answer 3

The ScrollWindow function can be used to scroll the existing graph to the left. Then you draw the new data to the right of the scrolled area. The drawing will be much faster if you use the Polyline function instead of DrawPixel: Polyline draws an array of pixels.