Modifications to RFC 177 (RFC0181)
Original Publication Date: 1971-Jul-01
Included in the Prior Art Database: 2019-Feb-10
Internet Society Requests For Comment (RFCs)
NETWORK WORKING GROUP
REQUEST FOR COMMENTS 181
JUNE 27, 1971
JOHN Mc CONNELL
AMES RESEARCH CENTER
MOFFET FIELD, CALIFORNIA
MODIFICATIONS TO RFC #177
CATEGORY D.6 RFC’s Obsoleted none RFC’s Updated 177
MODIFICATIONS TO RFC #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 exe...