Function lwDrawSquare

app/redis-6.2.6/src/lolwut.c:167–188

Draw a square centered at the specified x,y coordinates, with the specified * rotation angle and size. In order to write a rotated square, we use the * trivial fact that the parametric equation: * * x = sin(k) * y = cos(k) * * Describes a circle for values going from 0 to 2*PI. So basically if we start * at 45 degrees, that is k = PI/4, with the first point, and then we find * the other

 * performing the rotation/translation transformation, so for LOLWUT it's
 * a good approach. */
void lwDrawSquare(lwCanvas *canvas, int x, int y, float size, float angle, int color) {
    int px[4], py[4];

    /* Adjust the desired size according to the fact that the square inscribed
     * into a circle of radius 1 has the side of length SQRT(2). This way
     * size becomes a simple multiplication factor we can use with our
     * coordinates to magnify them. */
    size /= 1.4142135623;
    size = round(size);

    /* Compute the four points. */
    float k = M_PI/4 + angle;
    for (int j = 0; j < 4; j++) {
        px[j] = round(sin(k) * size + x);
        py[j] = round(cos(k) * size + y);
        k += M_PI/2;
    }

    /* Draw the square. */
    for (int j = 0; j < 4; j++)
        lwDrawLine(canvas,px[j],py[j],px[(j+1)%4],py[(j+1)%4],color);
}