ISSUE(S): Style Attributes

[Lofton Henderson <lofton@rockynet.com>]

Hi,

While working on test cases and other stuff, I have come upon some problems 
around Style Attributes.  Although I don't have a review assignment per se, 
I have written them up here.

References:  The stuff on Style Attributes is found in 5.4, and at 5.7.5 
"SetStyleAttr".

-- At 5.7.5, following the table, it says "Note Descriptions of all style 
attributes have to be provide. [...]".  The basic descriptions do indeed 
follow, so the 1st sentence of the note should be deleted.  However, the 
rest of that paragraph provides information that should be in the 
descriptions, but is not.  For example, that stroke-weight affects 
line-weight and edge-weight (or in CGM parlance, "line width" and "edge 
width".

-- 5.7.5 "SetStyleAttr".  The description of text-font is "TODO".  What is 
this going to be?  A font name (presumably), or a CGM text font index 
(awkward)?  Is the font constrained to be amongst those in the CGM Font List?

-- 5.4 Style Attributes.  This starts right off talking about style 
attributes without a clue as to what they are.  Either the table should be 
right here, or there should be an intro paragraph that points to the table 
in 5.7.5 setStyleAttr.

5.4.1.1, #1, "If the style attribute is assigned a value, use 
it".  Assigned a value where?  Not in the CGM, as these are not CGM 
attribute elements.  So it could only be via SetStyleAttr, and that should 
be mentioned (and linked) here.    (One exception:  visibility is settable 
via XCF also.)

5.4.1.1, #3, "The initial value of each property is indicated in the style 
attribute's definition."  Oops.  We didn't do this.  Neither the table in 
5.7.5 nor the following style attributes' descriptions give initial 
value.  Problem:  what should they be?  If you look at the table and 
descriptions, it is clear that "100%" is appropriate for all except 
text-font and visibility.  What should 'text-font' be?  (I think we want 
"as-in-CGM", as it is well defined there -- this is sort of the text-font 
equivalent of "100%".)  What should 'visibility' be?  3.2.2.9 says "Initial 
value: on".

5.4.1.1, #3, s/property/style attribute/.  Actually, maybe we ought to 
change the terminology to something like "style property"?  That would help 
to distance it from the CGM element class, "Attribute elements", which is 
usually just shortened to "attributes".

5.4.1.2, "Specified values are resolved to computed values after the 
document tree is create[d]; for example relative units ('%') are computed to
absolute values (i.e., RGB color or NVDC)."  There is a conceptual problem 
here.  Stroke-weight illustrates it.  Suppose "initial stroke-weight" is 
100%.  Suppose the CGM's line-width is 5 and edge width 10 in a given 
APS.  What is the NVDC Computed Value for stroke-weight for that APS?  I 
don't know the answer.  I suspect, because we don't have a 1-to-1 
relationship between style properties and affected CGM attributes, that 
we're going to have some problems with Computed Values.

5.4.1.2, 2nd pgph, "When the specified value is not 'inherit', the computed 
value of a style attribute is determined as specified by the Computed Value 
line in the definition of the property."  Oops.  We didn't do this.  This 
is not specified in 5.7.5, neither in the table nor the following 
descriptions.  I don't know what it should be.  We need a proposal.

5.4.2, "Each style attribute defines whether it is inherited or 
not."   Oops.  We didn't do this.  Neither the table in 5.7.5 nor the 
following style attributes' descriptions give inheritance rules.  We need a 
proposal (I don't have time right now to work one up.)  (Exception: we know 
about 'visibility' from 3.2.2.9.)

Some small editorials:
-----
5.4.1.3, "...for example:  todo".  We need an example here.

5.4.1, 2nd sentence, s/attributes/attribute/

5.4.1.1, 1st sentence, s/attributes/attribute/

5.4.1.1, #3, s/attributes's/attribute's/

5.4.1.2, s/create/created/

5.4.2.1, s/Chapter on inheritance to be done.//  (Presumably, that is 5.4.2 
plus 5.4.2.1).

All for now,
-Lofton.