Documentation for the graphics library
svn: r2013
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Kathy Gray
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collects/htdch/graphics/doc.txt
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278
collects/htdch/graphics/doc.txt
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This graphics package provides libraries for creating images and modeling in a visual world.
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The package includes the following classes, each to be discussed in their own section:
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Posn
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Image
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PictureFactory
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Color
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View
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Command
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CommandSequence
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World
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GameWorld
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---------------------------
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class Posn:
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+----------+
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| Posn |
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+----------+
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| int x |
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| int y |
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+----------+
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new Posn(3,4).equals(new Posn(3,4)) == true
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-------------------------
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class Image:
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+---------------------------------------------+
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| Image |
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+---------------------------------------------+
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+---------------------------------------------+
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| Posn getPinhole() |
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| Image movePinhole(Posn) |
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| Image putPinhole(Posn) |
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| Image overlay(Image) |
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| Image overlayXY(Image, Posn) |
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| Image addLine( Posn start, Posn end, Color) |
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| boolean inside( Image ) |
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| Posn find(Image) |
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| int width() |
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| int height() |
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+---------------------------------------------+
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An Image is created either by inserting a Special Image into DrScheme or by building an Image using the PictureFactory.
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Headers & Purposes:
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//Return the pinhole for this Image, typically its center point
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Posn getPinhole()
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//Create an Image like this Image, with its pinhole offset by p from this pinhole
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Image movePinhole( Posn p )
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//Create an Image like this Image, with its pinhole at p
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Image putPinhole( Posn p )
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//Create an Image by placing i over this Image at the pinholes
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Image overlay( Image i )
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//Create an Image by placing i over this Image, centering i's pinhole at p
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Image overlayXY( Image i, Posn p)
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//Create an Image by adding a line to this Image
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Image addLine(Posn start, Posn end, Color c)
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//Determine whether the Image isInside is inside this Image
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boolean inside( Image isInside )
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//Report the position at which inside is in this Image
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Posn find( Image inside )
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//Report the width of this Image
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int width()
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//Report the height of this Image
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int height()
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------------------------
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class PictureFactory :
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+-----------------------------------------------+
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| PictureFactory |
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+-----------------------------------------------+
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+-----------------------------------------------+
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| Image makeCircle(int, String, Color) |
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| Image makeRectangle( int, int, String, Color) |
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| Image makeEllipse( int, int, String, Color) |
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| Image makeTriangle( int, String, Color) |
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| Image makeLine( Posn, Color) |
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| Image makeText( String, int, Color) |
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+-----------------------------------------------+
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A PictureFactory is created by calling new PictureFactory(boolean).
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If the boolean is true, then the pinhole of created images will be in the center, otherwise the top left.
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Possible values for mode, "solid" "outline"
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Headers & Purposes:
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//Create a circle with radius r, color c, in the style of the mode
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Image makeCircle( int r, String mode, Color c)
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//Create a rectangle with width, and height, of color c, in the style of mode
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Image makeRectangle( int width, int height, String mode, Color c)
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//Create an Ellipse with width and height and color c, in the style of mode
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Image makeEllipse( int width, int height, String mode, Color c)
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//Create an equalateral triangle with edge length edge and color c, in the style of mode
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Image makeTriangle( int edge, String mode, Color c)
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//Create a line with end position to (start is 0,0) and color c
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Image makeLine( Posn to, Color c)
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//Create a text Image with the given text, of height ptSize and color c
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Image makeText( String text, int ptSize, Color c)
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Note: PictureWorld at present ignores the boolean argument and always assumes its true.
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-----------------------
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abstract class Color:
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+-------+
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| Color |
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+-------+
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+-------+
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/ \
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---
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----------------------------------------------------------------------------------------------------------------------
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| | | | | | | | | |
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+-------+ +------+ +-------+ +-------+ +--------+ +--------+ +--------+ +-----+ +-------+ +--------+
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| Black | | Blue | | Brown | | Green | | Purple | | Orange | | Purple | | Red | | White | | Yellow |
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+-------+ +------+ +-------+ +-------+ +--------+ +--------+ +--------+ +-----+ +-------+ +--------+
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+-------+ +------+ +-------+ +-------+ +--------+ +--------+ +--------+ +-----+ +-------+ +--------+
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Each variant of Color is a color within the drawing system. Additional colors can be addded by subclassing Color.
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The toString method of a subclass of Color should return a string in all lower-case of color to be depicted:
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new Brown.toString().equals("brown")
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(Note: Color aught to be an interface)
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------------------------
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class View:
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+---------------------------------------+
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| View |
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+---------------------------------------+
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+---------------------------------------+
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| View display(int, int) |
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| View hide() |
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| View show() |
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| Image draw( Command ) |
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| Image drawSequence( CommandSequence ) |
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+---------------------------------------+
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Headers and Purposes:
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//Produces a View with a visible canvas of size x and y
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View display( int x, int y)
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//Produces a View without a visible canvas
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View hide()
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//Produce a View with a visible canvas (display must have been called)
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View show()
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//Issue the drawing command, produce an Image that reflects what the canvas displays.
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Image draw( Command c)
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//Issue the drawing commands in the seqence, produce an Image that reflects what the canvas displays after all commands
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Image drawSequence( CommandSequence commands )
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--------------------------
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class Command:
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+---------+
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| Command |
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+---------+
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+---------+
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/ \
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---
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--------------------------------------------
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| | |
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+-------------+ +-----------------+ +---------------+
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| DrawLine | | DrawImage | | DrawRectangle |
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+-------------+ +-----------------+ +---------------+
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| Color color | | Image i | | Posn corner |
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| Posn start | | Posn leftCorner | | int width |
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| Posn end | +-----------------+ | int height |
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| int width | | Color c |
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+-------------+ | String style |
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+---------------+
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-------------------------
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class CommandSequence:
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+-----------------+
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| CommandSequence |<--------------+
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+-----------------+ |
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+-----------------+ |
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/ \ |
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--- |
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| |
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----------------------- |
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| | |
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+----------+ +----------------------+ |
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| EmptySeq | | LargerSeq | |
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+----------+ +----------------------+ |
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+----------+ | Command first | |
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| CommandSequence rest |----+
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+----------------------+
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------------------------
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abstract class World, abstract class GameWorld extends World
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+---------------------+
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| World |<----------+
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+---------------------+ |
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| View display | |
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+---------------------+ |
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| World onKey(String) | |
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| World onTick() | |
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| Image draw() | |
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| Image erase() | |
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+---------------------+ |
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/ \ |
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--- |
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- |
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+------------------------------+ |
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| GameWorld | |
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+------------------------------+ |
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+------------------------------+ |
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| World transition( World) |----+
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| boolean animate(int,int,int) |
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+------------------------------+
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To create games, you should subclass GameWorld, othewise you should await more classes.
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Subclasses of GameWorld do not need to set the World's display.
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Headers & Purposes (from subclassing GameWorld):
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//Produce a World with the effects of receiving the given key press
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abstract World onKey( String key );
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//Produce a World with the effects of one clock tick passing
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abstract World onTick();
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//Issue the commands that represent this world to the display
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abstract Image draw();
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//Issue the commands that will erase portions of the world that should no longer be visible to the display
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abstract Image erase();
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//Produces a World that will animate with a clock tick of rate, in a display of size width x height
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boolean animate( int width, int height, int rate )
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//Produces a world where animation has stopped
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World endOfWorld();
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//Produces a World with the same display but potentially different representations
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World transition( World w);
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Things to know when making a Game:
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animate will call the onTick method every rate miliseconds.
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Prior to calling onTick, animate will call erase.
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After calling onTick, animate will call draw on the resulting world.
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