import megamu.shapetween.*;

BezierShaper bezier;

void setup(){
  bezier = new BezierShaper();
  bezier.setInHandle( 0.7, 0.3 );
  bezier.setOutHandle( 0.7, 0.7 );
}

void draw(){
  background(255);
  
  beginShape();
  for( float i=0; i<=1; i+= 0.05 )
    vertex( i*width, bezier.shape( i )*height );
  endShape();
}

void mouseMoved(){
  float x = norm( mouseX, 0, width );
  float y = norm( mouseY, 0, height );
  bezier.setOutHandle( x,y );
}

x

The handle point in the x dimension

y

The handle point in the f(x) dimension