Cedar Graphics Overview

Principles and Concepts

Interfaces and Implementation

Status and Plans



Principles

Low level display facilities

powerful but primitive

primary client is Documents

Wide variety of raster display devices

displays, printers

different resolutions

bitmap, gray, color

Display-independent interface

geometric abstractions

world coordinate system

color specification

display-independent implementation

Floating point representation

wide range

device resolution

user coordinates

high precision

performance



Concepts

The Pipeline

Map, Reduce, Clip, Render

transducer: doesn’t retain objects

Display Context

virtual display

state

display procedures

Drawing things

lines, areas, paths

text, fonts

current position

Mapping

world => device

user => world => device

user => device

Clipping, Boxing



Interfaces

Client (most stable)

Graphics

AltoDevice, PressDevice, etc.

Device implementor

simple shapes

fill color / image

Internal (most volatile)

Mapper, Reducer, Clipper

useful to other graphics software



Implementation

The pipeline

Client

Mapper

Path / Reducer

Clipper

Patches

Edges

Device

Object style

Pipe interface

advantages

uniform interface

plug-compatible modules

disadvantages

allocation expense

superclassing is difficult

LOOPHOLEs (use REF ANY?)



Status

Why is it so slow?

Clipper

Devices: Alto, Press

Text: well... still messy

Images: AIS, bitmaps

Plans

Use REFs; safe interface

Moving to Pilot: REALs, BitBlt, font files

Unify path specification for lines and areas

Color vs. PaintingFunction/Texture

Persistent pipelines

Simpler device interface

Integration of images

Move text outside