CSC 418/2504 Fall 2001 Assignment 1: Frequently asked questions

1. Question 1.
2. Question 2.
3. Question 3.
4. Question 4.
5. Question 5.
6. Question 6.
7. Question 7.

• Q: The code doesn't compile!
  Sorry. CDF improved the compiler. Download it again. It should compile now.
• Q: How can I run CDF programs on MY machine?
  A: There's a mini-faq that tells you how to upload your programs to CDF when you're done.
  A2: There are also brief instructions on how to run a program on CDF and have the graphics appear on your screen.
• Q: What parts of the text deal with this stuff?
  A: Section 2.4 (pages 63-67) of the text may help.
• Q: What does onHandle do?
  A: It tells you if the mouse pointer is on a particular handle. I've updated the documentation as follows:

        // Inputs:
  //    x,y   - mouse coordinates (they are passed in to handleMouseAction
  //            or handleMouseMotion
  //    hx,hy - coordinates of the CENTRE of the handle.
  //
  // Returns:
  //    true - the mouse x,y lies within the square centred on
  //           the handle's hx,hy (ie, if the mouse is on the handle).
  //
  // NOTE:
  //    You will have to call this function nine (9) times, to
  //    identify which handle the user clicked on.
  

• Q: I still don't get it. What are handleMouseAction and handleMouseMotion used for?
  A: They are called when the user does something with the mouse.
  • If the user clicks (or releases) a mouse button, handleMouseAction is called, with info about which button, where the mouse pointer was, wether it was a click or a release. This is when you have to figure out which handle (if any), the user clicked on.
  • If the user drags the mouse with a button held down, handleMouseMotion is called, with the mouse pointer's current location.
  Whenever the user does something, you should update the current rectangle, and re-draw it. Your mission (you must decide to accept it if you want marks) is to build a finite state machine, with states such as "Idle" or "dragging top left", and transitions such as "left button down" or "mouse dragged".