I am trying to make a program which draws polygons. depending on the amount of sides I set, all polygons must keep the same perimiter and no vertex of the polygon can be less than 100 pixels from the nearest window edge.

I know I must use turtle graphics to draw regular N sided polygons. But i do not know how to keep the same perimiter and to keep the vertices of the polygon 100 pixels away from the window edge.
This is what i have doen so far
int N = 4;
int l = 100;
void setup ()
{
 size(513,513);
 background(255);
 strokeWeight(2);
 smooth();

//ellipse(256,256,313,313);
}
void translateDrawPolygon(int x, int y , int N,int l)
 {
 translate (x,y);
 drawPolygon(N,l);
 }
void drawPolygon(int N, int l)
{
for(int i=0;i<N;i++)
{
line(0,0,l,0);
translate(l,0);
rotate(TWO_PI/N);
}
}
void draw ()
{
translateDrawPolygon(145,145,N,l);
}

Please Help

beginShape is the right way to start and as you want draw an regular polygon its very simple to check the distance. All your vertices must lie on a circle with a given radius, so you have to check if the middle point of your polygon is fulfilling the following rules:

Code:

x>radius+100 && x<width-radius-100 && y>radius+100 && y<height-radius-100 
 

And so you can calculated the vertices:
Code:

for(int i=0; i<vertexCount; i++){
 float vertexX=x+cos(i*TWO_PI/vertexCount)*radius;
 float vertexY=y+sin(i*TWO_PI/vertexCount)*radius;
}