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Modifications to RFC 177 (RFC0181) Disclosure Number: IPCOM000004066D
Original Publication Date: 1971-Jul-21
Included in the Prior Art Database: 2000-Sep-13
Document File: 2 page(s) / 5K

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Internet Society Requests For Comment (RFCs)

Related People

J. McConnell: AUTHOR


JUNE 27, 1971

This text was extracted from a ASCII Text document.
This is the abbreviated version, containing approximately 64% of the total text.



NIC #7124

JUNE 27, 1971






RFC's Obsoleted none

RFC's Updated 177


This RFC is intended to modifiy the proposal for a device

independent graphical display description discussed in RFC #177. Thanks

are due to Stan Mantiply of Ames for his ideas. The main changes are in

the defini- tion of coordinate areas to avoid one problem encountered

with the old definition and to provide more flexibility. Terms used are

those defined in RFC #177.

The problem encountered in the previous proposal was that the areas

of the NGS (network standard graphics screen), which were supposed to be

absolute boundaries, could be crossed when a list was executed within

that space. Scaling of lists was also awkwardly done with specific

commands in the network standard graphic display list (NGDL).

Coordinates will still be defined with 16 bit unsigned normalized

fractions. This will leave the resolution of the picture up to the de-

vice which eventually receives the NGDL. The values will not now be

tied to the NGS or an area of the screen, but will be fractional

displace- ments from the lower left corner of the screen, an area, or an

image space.

Areas will still be rectangular and will be allowed to overlap, but

not contain another area completely. The attributes of an area are: its

16 bit integer name, by which it may be manipulated, two (x,y) pairs

which will define its lower left and upper right corners with respect to

the NGS. No list executed in an area may cross its boundaries. Within

an area may be any number of image spaces which are dynamically defined

with the execution of a list and define its relationship to the contain-

ing area.

The list item types 7 and 8 shall be changed from EXECUTE LIST

(Name,x,y) and COPY LIST (Name,x,y) to EXECUTE LIST

(Name,(Xl,Yl),(Xr,Yr)) and COPY LIST (Name,(Xl,Yl),(Xr,Yr))

respectively. The coordinate pairs (Xl,Yl) and (Xr,Yr) define the image

area of that list as displacements from the lower left corner of the

containing area. If the list executes other lists within it, their

image areas are defined as displacements from the image area of the list

containing the execute command. Thus each list can be scaled

differently each time it is executed and may even be distorted if the

image area defined has different ratios of X and Y lengths. Lists

executed within other lists will have the same relationship to their

containing lists regardless of that lists's rela- tionship to the NGS

area. Since the initial image area is defined rela- tive to the NGSD

area, no overlaps can occur.

If a table (item type = 9) is executed, the coordinate pairs it

contains are rel...