Proposal for a Network Standard Format for a Data Stream to Control Graphics Display (RFC0086)

Network Working Group                                           S. Crocker Request for Comments #86                                        January 5, 1971 NIC 5631                                                        UCLA

                 Proposal for a Network Standard Format              for a Data Stream to Control Graphics Display

 A typical arrangement of facilities is to have a console attached to a

computer at the user's site, and to be using the computational facilities

of a remote site.  Information entered by the user is transmitted to the

remote Host, and output from the remote Host is transmitted back to the

local user.  In this proposal I am concerned with specifying the form of

the output stream for the case that the output portion of the console is a

typical refresh display with point, vector and character drawing capability.

Devices in this class include the DEC 338, DEC 340, IBM 2250, and IMLAC

PDS-1.

It must be understood that this proposal is illustrative only, and knowingly

avoids important issues.  Its main purpose is to provide a basis for dis-

cussion and development.

In order to specify the semantices of the network standard graphics data

stream (NGDS), I will postulate

   1.   a network standard display list (NGDL)

   2.   a network standard stream interpreter (NGSI)

   3.   a network standard list interpreter (NGLI), also called the         display controller, and

   4.   a network standard screen (NGS)

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 The NGDS is accepted into the local Host and interpreted by the NGSI.  The

NGSI is a process which modifies the NGDL according to inputs in the NGDS.

The NGDL is the display list for the NGLI; the NGLI executes the NGDL and

controls the beam which writes on the NGS.

The NGS is square, has horizontal and vertical sides, and positions on it

are specified by an ordered pair of unsigned 16 bit fractions.  The first

fraction specifies the horizontal distance from the left hand edge, and

the second specifies the vertical distance from the bottom edge.  The

resolution of the screen is unspecified.

The lack of specification of the resolution of the NGS is intentional;

programs designers should not interpret this to mean that they may impose

a particular requirement on the using system.  Thus the quality of the

displayed picture should degrade gradually with decreasing resolution.

The NGLI has primitives for moving the beam to a particular point, intensify-

ing a point, drawing a vector, or drawing a character.  Characters are

assumed to be not more than .015 screen width wide, and not more than .025

screen height high.  When the beam is moved to a screen position before

drawing characters, tha...