title: Get position on canvas AFTER rotating/translating and restoring
body: <p>Okay, this is getting complicated...</p>
  
  <p>Given situation:<br>
  I have a canvas with the dimensions of 800x600.<br>
  My mouse is at canvas position 100x200 (for example).</p>
  
  <p>I save my canvas state.<br>
  Now I rotate and translate the canvas, I draw a square.<br>
  I restore my canvas state.   </p>
  
  <p>Is there any way to determine if my mouse is over the square?<br>
  I think I would have to translate/rotate my mouse position as well - in the opposite direction, but how would I do this?</p>