Artwork.tioga
Picture making systems
    Illustrator:  related to drawing; making shapes
    Compostion:  related to formating;  combining shapes to make pages
Artwork operations
TiogaArtwork
    Tioga artwork is a tree structure of nodes.  Each level in the tree has a transformation associated with it.  The leaves of the 
    tree are: paths, images and arbitrary JaM programs.  Each node has a format which encodes the style.  The style properties for 
    paths are:
        filled, outlined or both
        linewidth
        line color
        area color
    Text is represented as a regular Tioga node.  However, the style properties for text have been extended to include:
        centered, left-flush, right-flush with respect to a point
        top-aligned, base-line-aligned, or bottom-aligned
        rotated
    You can change the style, change the nesting, or edit the text.  You can include arbitrary pictures through the JaM program 
    facility.  (Note that JaM programs can call Cedar programs. ie. the parametric mapping stuff). 
Graphical Style
    I want to use the Tioga mechanism, so Artwork nodes will have format names.
    Besides the existing line parameters we could consider:
        arrowheads
        dash patterns
        Interpress end conditions
        general mapped patterns
        ...
    Besides the existing area parameters we could consider:
        shaded colors
        computed textures
        sampled textures
        ...
    The existing text styles barely work.  Besides making them more robust we could consider:
        condensed
        expanded
        backslant
        oblique
        circular? curves?
        ...
    There are currently no image styles.  We could consider:
        screens
        tints (duotones)
    Miscellaneous
        drop shadows
        offset shadows
Composition
    Composition operations are Move, Copy, Delete, Crop, Scale.  These simple names hide a number of more complicated issues.
    Delete: Selection, objects and instances.
    Move and Copy:  Positioning, coordinate systems, semantics such as "center, left edge, etc."
    Crop:  Clipping region.  Rectangles only?  How big is the graphics "frame".  If you change the frame size, what moves?
    Scale:  Optical or geometric (ie, do the line width scale).  What moves?
Artwork structure
Tioga Nodes and Items
    A place in a document where pictures occure is called a graphics frame.  The first node in the frame is a box item node with a 
    $Graphics ItemClass.  Such and item node has the following structure:
        item.next  --Ref to next node at this level.  Probably the following paragraph
        item.date  --frame related data 
        item.contents  --Ref to objects in the frame.  Usually basic nodes.  May be items or branches. 
Item Data
    The data for a graphics frame includes: frame size, clipping region (if other than frame size).  Other global information. 
Contents
    The contents field of a graphics frame points to a tree of nodes.  Basic nodes are graphics objects such as paths, images, and 
    clipping regions.   Basic nodes may be nested.  Basic nodes have the following structure:
        basic.next  --Ref to next node at this level.  Another object in the frame
        basic.contents  --Ref to "children" of this basic node, if any
        basic.data  --actual representation for the graphics
    The basic.data for all objects includes a bounding box and a transformation.  All objects are defined relative to their bounding 
    box.
    I can think of the following basic classes.  This will undoubtedly expand as I work on this project
        Simple objects: paths, images, and clipping regions.  Data is primitive types, contents is NIL.
        Symbols: nested objects.  Data is list of instances, contents is objects in the symbol
        Symbol instances:  Contents is NIL.  Data is a ref to a symbol
    The contents of a graphics frame may include text items.  I assume that text may include branches, so I should deal with that as 
    well.
Artwork representation
    To solve the problem of laying out arbitrary graphics in a tioga document, an interpreted text representation is probably the way 
    to go.  JaMGraphics is one such representation, and I'm inclined to start with it.  It has all the advantages mentioned above 
    in the TiogaArtwork section.
    I would use GraphicsLists as accelerators for the display of interpreted objects.  A GraphicsList is a list of encoded calls to 
    Graphics.  It is optimised for fast refresh.  It is now easy to generate a GraphicsList from JaMGraphics.
    Interpress is another interpreted representation.  It can be either text or encoded.  An Interpress master is a sequence of bodies. 
     A body is a list of operators.  All the style properties are bound.  Since there are operators for linear transformations in 
    Interpress, it would be possible to use the Artwork structure to provide an interactive "InterpressEdit" facility.  There is no 
    clipping defined in the current version of Interpress, so cropping is a problem.   It may be possible to break out the common 
    operators, such as MASKSTROKE, MASKFILL and SHOW, as objects so it would be possible to manipulate pieces of the picture.  
    Interpress also has a symbol facility. 
Illustrators
Path editor
SIL
Star Graphics
Griffin