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Defect Report Number: 8632-1/051

 

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Submitter: Henderson

 

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Addressed to: JTC1/SC 24/WG 6 Rapporteur Group on ISO/IEC 8632, CGM

 

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WG secretariat: NNI

 

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Date Circulated by WG secretariat: 1 January 1995

 

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Deadline on response from editor: : 1 April 1995

 

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Defect Report concerning IS 8632:1992 Computer Graphics: Metafile for the storage and transfer of picture description information (CGM) Part 1, Functional

specification.

 

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Qualifier (e.g. error, omission, clarification required): Correction

 

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References in document (e.g. page, clause, figure and/or table numbers):

Clauses 5.5.7, 5.5.8, 5.5.9, the clipping mode elements, clauses 4.6.1.5 and 4.6.2.3, and clause 6.

 

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Nature of defect (complete, concise explanation of the perceived problem):

 

First: For Version 1 metafiles, the marker clipping behavior is described as either locus, or locus-then-shape. There is no description of the behavior for line clipping behavior, Version 1. What is intended — is it "unrestricted"?

 

Second: For Version 2 and 3, the default is ‘locus’. Therefore if one took a valid version 1 metafile and changed only the METAFILE VERSION element to "2", the required behavior of the interpreter would change. Another way to look at this is that it is not possible to have a Version 2 or 3 metafile with "unspecified" or "interpreter dependent" for the default clipping behavior. This is a consequence of the manner in which these CGI elements were adopted into CGM. For many Version 3 elements, e.g., LINE JOIN, which explicitly address drawing aspects which might be of concern to Version 1 interpreters as well, there is a parameter value "unspecified", and this is the default. It would be too disruptive to add such values to the standard now. The least disruptive solution, if any solution is pursued, would be to change the defaults to "interpreter dependent".

 

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Solution proposed by the submitter (optional):

None.

 

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Editor's response (any material proposed for processing as a technical corrigendum to, an amendment to, or a commentary on the International Standard or DIS final text is attached separately to this completed report):

In clause 6, p228, for LINE CLIPPING MODE, MARKER CLIPPING MODE, EDGE CLIPPING MODE replace "locus" with "interpreter dependent".