COMP 310 Spring 2017	HW04: Fishworld

Assignment Instructions and Point Values

The assignment is to replicate the command-dispatching Fishworld demo.   You must complete the following features:

1. The architecture must satisfy HW03 requirements, e.g. must be a Model-View-Controller design with apprpriately created interfaces and adapters and appropriate methods on each interface/adapter.   (10 pts)
2. Painting should be performed as a strategy that the user can select.  (70 pts total)
   • The GUI should be updated to enable different painting strategies to be selected. (10 pts)
   • At least 6 different painting strategies should be available, with at least one choice from each of the 4 types below:  (60 pts)  
     • Non-affine transform-based paint strategy, i.e. directly implements IPaintStrategy
     • Affine transform-based paint strategy:
       • Simple geometric shape and/or polygon
       • Composite shape that stays upright
       • Image
3. Implement command-based updating
   • The updating of the balls must be done by sending a command whose purpose is to update the ball  (5 pts)
   • The ball must be able to accept and execute any command sent to it.  (5 pts)
   • You are not required to use the generic dispatcher but it highly recommended.   Get your HW04 fully operational before switching over to the generic dispatcher!  Use of the generic dispatcher will be required for the next assignment!
4. Full Documentation
   • All classes and methods except for those auto-generated from WindowBuilder.   (5 pts)
   • Tooltips on all GUI components ( 5 pts)

Development Process

In this assignment, it is important to be very clear about exactly what you are doing and the role of each method you write.   On the last assignment, many of the errors and confusions stemmed for not carefully reading the lecture, lab and resource materials and following the directions that were outlined there.   An important skill that Comp310 emphasizes is to be able to assemble information spread across multiple sources and locations into a coherent solution to a problem.   Do not expect that the solution to this assignment can be found in a single lecture page.   Look in the lectures, look in the labs, look in the resource pages, look at your class lecture notes, look at the demos and their documentation, even....look at this page.

A very common mistake to make in this assignment is to attempt to program the entire painting process.  Everything that happens in an object-oriented program is the combination of invariant and variant pieces.  Remember that the superclasses provide the invariant pieces and the subclasses provide the variant pieces.   In an inheritance hierarchy, as one moves down the inheritance tree, each subsequent class adds more and more invariant behavior that its subclasses can use.  By the time you are at the bottom of the inheritance tree, the class is just adding some small piece to a much larger process, a piece that may in fact be in the middle of that larger process, so it looks like it isn't accomplishing anything.   Most of the code you will need is already printed on the web pages.   Most subclasses add very little code, perhaps even just supplying parameters to a superclass constructor.   

When writing your own custom paint strategy, first consider where in the paint strategy hierarchy it should be located.   In general, put it as low on the hierarchy as possible to take advantage of invariant behavior defined by its superclasses.   This minimizes the amount of code in your class to just its variant part.  In fact, your specific code may reduce to just a very few lines.

So, here are some things to remember:

• IPaintStrategy: The top-level interface that the Ball uses.   It defines two methods that the Ball must deal with:
  • paint -  This is the replacement for the paint method in the Ball.   Any concrete class that directly implments IPaintStrategy should have code here that is essentiatlly exactly what would have gone in the Ball's paint method.
  • init -- This method is used to initialize the paint strategy, if needed.   If no specialized initialization is needed this method should simply do nothing.   The method should be run by the Ball whenever (make sure you find all the possibilities!) the Ball gets a new strategy.
• APaintStrategy:  This second-level abstract class implements an affine transform-based painting process that uses a Template Method pattern of code for its paint method.   This paint method is now invariant for all its subclasses, i.e. the subclasses don't have to implement the paint method anymore, just the supporting methods for that painting process.
The affine transform-based painting process is essentially what was done in lab.   APaintStrategy defines an invariant paint method that all its subclasse will inherit and thus not have to implement.  So, in addition to the init method, 2 other methods are defined that sub-classes need to implement if desired:
•  paintCfg - Defined by a subclass if additional processing, e.g. staying upright, is required before the actual painting takes place in paintXfrm.  This method is part of the invariant painting process defined by the paint method.    Because subclasses may or may not do this aditional processing, APaintStrategy provides default no-op processing for it.
• paintXfrm -  This is where the actual painting takes place and thus must abstract in APaintStrategy.   Since this method takes the affine transform as an input parameter, do not use the internal affine transform to perform the transformation of the prototype image.   Because this method is independent of the internal affine transform, it contains only the variant parts of the painting process, ie. the actual painting of the image using the Graphics object.
• ShapePaintStrategy:  This class build upon and specializes the services provided by APaintStrategy to better support the painting of Shape objects.  In particular, the paintXfrm method is invariant for any Shape.    Subclasses thus do not have to implement paintXfrm.
• IShapeFactory:   Shape factories encapsulate and hide the construction details of the Shape prototypes used by ShapePaintStrategy.   Input parameters are used to customize the shape.   ShapeFactories can be used in many places as a quick and easy way to produce Shape objects.
• MultiPaintStrategy - This class adds the invariant behaviors specific to a composite of APaintStrategies.    Besides providing the storage of the references for the strategies in the composition, it provides the dispatching of paintXfrm to all the composees (why paintXfrm and not paint?).  Thus, any subclass of MultiPaintStrategy need not implement paintXfrm.
• ImagePaintStrategy:  This APaintStrategy subclass adds specialized init and paintXfrm methods to load the image and calculate a secondary affine transform that is used to help create the the required additional scaling needed convert the image file into a prototype.  This secondary affine transform is then combined with the supplied affine transform in paintXfrm to create a net transform that will enable the image to be painted onto the screen at the correct location, orientation and size.  It is recommended that you go find your own images to use on the Internet.   GIFs, JPGs, and PNGs will all work.   Here are some images to test with:  images.zip. 
  • Check your scaling calculations using the FIFA_Soccer_Ball.png image, which has a 0.33 fill factor.   This fill factor should cause the ball to appear to bounce off of its edge just like a normal ball.    The Earth.png, Jupiter.png, Mars.png and Venus.png all have fill factors of 1.0 so they can be used as secondary checks.   (Why are they not useful as primary checks?)
  • Be sure to put your "images" folder directly below the folder where ImagePaintStrategy is located as all file location references will be relative to the folder that contains ImagePaintStrategy.   Thus you can access the files by writing something like  "images\myImage.png" 

© 2017 by Stephen Wong