title: Updating a canvas diagram based on user input
body: <p>I want to be able to create diagrams and drawings on the fly, using input from the user.</p>
  
  <p>If I have 2 text boxes for width and height, i want to be able to draw a rectangle based on user entered values, if they change the value in the input fields i want the drawing to change.</p>
  
  <p>is canvas capable of this? does it need to work along with javascript?</p>
  
  <p>thanks</p>