Class: DisplayItem

Environment: Siren
Superclass: DependentPart
Category: MusicUI-DisplayLists
Instance variables: offset color

Instances of the subclasses of the abstract class DisplayItem are used as the items in display lists. They can generally display themselves on graphics contexts.
These are done this way because I don't think wrappers are right for use in display lists.

Instance Variables:
offset the object's offset relative to its container (display list)
color the object's display color (or nil)

The subclasses add special display-related state and behavior such as an extent point and display method, or a visual item such as a string or image to display.
They generally implement displayOn: aGraphicsContext and bounds accessing methods.

This implementation is MODE 1.1, STEIM, Amsterdam, May/June 1990; updated at the Lagoon in Palo Alto, July, 1991-May, 1992.

The entirety of this software is Copyright (c) 1990, Stephen Travis Pope, Nomad Object Design/Nomad Computer Music Research.
All Rights Reserved.

transforming

asVisualComponent
Answer an encapsulated version of the receiver which understands
VisualComponent protocol.

scaleBy: aPoint
Translate the receiver's offset by the argument.

scaledBy: aPoint
Translate the receiver's offset by the argument.

translateBy: aPoint
Translate the receiver's offset by the argument.

printing

printCompleteOn: aStream depth: depth
Print the receiver in the given Stream.

printOn: aStream
Print the receiver in the given Stream.

accessing

color
Answer the receiver's display color.

color: aVal
Set the receiver's display color to the argument.

extent
Answer the extent of the receiver (dummy in this class).

extent: aPoint
Ignored

offset
Answer the receiver's offset.

offset: aPoint
Set the receiver's offset to the argument.

testing

isDisplayItem
Answer whether the receiver is a kind of DisplayItem

initialize-release

initialize
Initialize the instance variables of the receiver.

displaying

displayOn: aGraphicsContext
Display the receiver on the argument.

displayPostScriptOn: aPostScriptContext
Display the receiver on the argument in PostScript.

copying

copy
Answer a shallow copy of the receiver.

bounds accessing

computePreferredBounds
Answer the receiver's bounds--hack.

MetaClass: DisplayItem class

instance creation

model: aM offset: aPt
Answer an instance of DisplayItem with the given instance variables.

offset: aPt
Answer an instance of DisplayItem with the given instance variables.