使用graphics.h的C ++图形

Question

I am using graphics.h for a small program, written for educational purpose. It has a moon orbiting around earth. the issue is, after a few iteration, whole screen went blank(white). I have tried many alternatives but could not able to find the problem. Please review below code and see if you can find out the issue?

#include <stdio.h>
#include <conio.h>
#include <graphics.h>
#include <math.h>

int main()
{
int gd,gm;

detectgraph(&gd,&gm);
initgraph(&gd,&gm,"c:\\tc\\bgi");

int Earth_x,Earth_y;
Earth_x=10+390/2;
Earth_y=60+340/2;

int Moon_x,Moon_y;
Moon_x=Earth_x+100;         //Moon initial coordinates
Moon_y=Earth_y;
float t = 0;

int new_page, old_page; // declare integer variables representing two graphics pages

while(1)
        {  
            old_page = getvisualpage( ); // set old_page to the number of the visual page
            new_page = abs(old_page-0); // set new_page to the visual page number-1
            setactivepage(new_page); // set the active page to the value of the new page
            cleardevice( ); // erase the active page

            //rectangle(x1,y1,x2,y2);
            rectangle(10,60,400,400);

            //code for drawing and filing Earth.
            setcolor(GREEN);
            setfillstyle(1,GREEN);
            circle(Earth_x,Earth_y,30);
            floodfill(Earth_x,Earth_y,GREEN);
            setcolor(WHITE);
            outtextxy(Earth_x, Earth_y, "Earth");

            //code for drawing and filling Moon.
            setfillstyle(1,WHITE);
            circle(Moon_x,Moon_y,10);
            floodfill(Moon_x,Moon_y,WHITE);

            //****We can add delay to slow down the moon*** 
            //delay(1);    

             setvisualpage(new_page); // move the activepage to the visual page

            //Code for modification of Moon coordinates
             Moon_x=Earth_x+100*cos(t*3.1415/180.0);
             Moon_y=Earth_y+100*sin(t*3.1415/180.0);
             t=t+1;
        }

getch();
closegraph();
}

Thank you for your help!

Answer 1

I am not familiar with the library you are using so I cannot find the error, but there are a few things that don't look all right.

int Moon_x,Moon_y; // they should be floats (since you assign the result of a trigonometric function)

new_page = abs(old_page-0); // -> should this be -1 ???

As a general debugging tip, I would recommend try removing things from the scene (eg remove the moon, then the earth, and so on) and see if you get the same results. This way you can detect what causes the problem.

Answer 2

There doesn't seem to be any error with the code. I think you're not compiling the code the right way. If you're using Code::Blocks, you'll need to first include graphics.h header file in your compiler library. This tutorial should help!