PShape.translate does not seem to update vertex position. Bug?

In the code below I am making translations to a line and printing the line's x coordinate.  The value that is printed never changes even though the line is clearly moving on the screen.  Is this a bug?

PShape shape;

boolean left = false;

int count = 0;

void setup() {

  size(1280, 720, P2D);

  shape = createShape();

  shape.beginShape();

  shape.stroke(0);

  shape.strokeWeight(10);

  shape.vertex(0, 0);

  shape.vertex(0, height);

  shape.endShape();

}

void draw() {

  background(255);

  if (left)

    shape.translate(-1, 0);

  else

    shape.translate(1, 0);

  count++;

  if (count == width) {

    left = !left;

    count = 0;

  }

  shape(shape);

  println(shape.getVertexX(0));

}