C program with g2 graphic library

Hey,
I had to create a graphic with g2 graphic library, but the program doesn't draw anything, not even the line. Also, I can't change the font size. I'm using gcc with -Wall -ansi -pedantic -lgd -lX11 -lm and -lg2. I have ubuntu running in virtualbox.
Could you give me some help?
Here's the code:

Code:

#include<stdio.h>
#include<stdlib.h>
#include<g2.h>
#include<g2_X11.h>
#include<math.h>


void funcao1(janela){

    const double pi = 4.*atan(1.);

    int x;
    float y1;

    while(x!=600){


    y1=sin(2*pi*0.01*x)+300;
    
    g2_pen(janela,2);

    g2_plot(janela,x,y1);
    x=x+1;
    

    }

    return (1);
    }




int main(){
    int janela;

    janela = g2_open_X11(800,600);

    g2_line(janela,1,300,1,300);

    funcao1(janela);
    
    


    



    getchar();
    g2_close(janela);
    exit(0);
}

Also, could someone explain to me why I couldn't put zero in the return? As far as I know, the function won't return anything or will it?

you probably need a g2_flush in there after your drawing commands

edit: btw I never heard of g2. all I did was google 'g2 graphics library example' and got this link http://www.tp.umu.se/modsim/linux-guide/g2.html

What is the value of x in funcao1 before the loop starts? It's probably not 0.

Why are you drawing a line between (1,300) and (1,300)? That would be a single point (or no point at all if the line drawing routine does not draw the last pixel of the line).

Also, you cannot return any value from a function declared as returning void. You can use a return statement without a return value (you also don't need parentheses; return is not a function call). On the other hand, if it's at the end of a void function a return statement is not needed. You should also return 0 from main (though exit(0) has the same effect in practice).

X is supposed to be the beginning of my graphic, as in y=sen(2*pi*1.0*x). What i mean is, I want to start drawing the graph from x=0.
That's what I tought, but gcc was warning me that the function returns a value.
Thanks for the help.