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Subject: Re: [cgmo-webcgm] ISSUE(S): Style Attributes
Friday, May 6, 2005, 3:10:44 PM, Lofton wrote: LH> Hi, LH> While working on test cases and other stuff, I have come upon some problems LH> around Style Attributes. Although I don't have a review assignment per se, LH> I have written them up here. LH> References: The stuff on Style Attributes is found in 5.4, and at 5.7.5 LH> "SetStyleAttr". LH> -- At 5.7.5, following the table, it says "Note Descriptions of all style LH> attributes have to be provide. [...]". The basic descriptions do indeed LH> follow, so the 1st sentence of the note should be deleted. I agree. LH> However, the rest of that paragraph provides information that LH> should be in the descriptions, but is not. For example, that LH> stroke-weight affects line-weight and edge-weight (or in CGM LH> parlance, "line width" and "edge width". Ok, what do we do about it? We need a proposal. LH> -- 5.7.5 "SetStyleAttr". The description of text-font is "TODO". What is LH> this going to be? A font name (presumably), or a CGM text font index LH> (awkward)? Is the font constrained to be amongst those in the CGM Font List? Is there much use for this? Why would someone bother changing the actual font of a 'para' or 'subpara'? Could we take this out? LH> -- 5.4 Style Attributes. This starts right off talking about style LH> attributes without a clue as to what they are. Either the table should be LH> right here, or there should be an intro paragraph that points to the table LH> in 5.7.5 setStyleAttr. This section is the CSS2 inheritance model. I agree that it needs some wording, and a proposal. LH> 5.4.1.1, #1, "If the style attribute is assigned a value, use LH> it". Assigned a value where? Assigned a value onto the APS. (where else?). We should review the words 'style attribute'... this is not the CSS 'style' attribute we are talking about. LH> Not in the CGM, as these are not CGM attribute elements. It could be. 'visibility' and 'interactivity' are (now) cgm attributes. The problem is the title of section 5.4 "Style attributes", it needs to be rename. LH> So it could only be via SetStyleAttr, and that should be mentioned LH> (and linked) here. I don't agree. LH> (One exception: visibility is settable via XCF also.) I think what's confusing is the fact that an introduction is missing. LH> 5.4.1.1, #3, "The initial value of each property is indicated in the style LH> attribute's definition." Oops. We didn't do this. We don't need to. #3 will never be reached for the exception of 'visibility' and 'interactivity'. All these style attributes have an implicit value within the CGM document. The problem with the spec is that this section doesn't make the distinction between 'visibility' and 'interactivity' and these other style attributes. LH> Neither the table in 5.7.5 nor the following style attributes' LH> descriptions give initial value. Problem: what should they be? LH> If you look at the table and descriptions, it is clear that LH> "100%" is appropriate for all except text-font and visibility. LH> What should 'text-font' be? (I think we want "as-in-CGM", as it LH> is well defined there -- this is sort of the text-font equivalent LH> of "100%".) What should 'visibility' be? 3.2.2.9 says "Initial LH> value: on". BTW, 'visibility' should be removed from this table. LH> 5.4.1.1, #3, s/property/style attribute/. Actually, maybe we ought to LH> change the terminology to something like "style property"? That would help LH> to distance it from the CGM element class, "Attribute elements", which is LH> usually just shortened to "attributes". I agree we need to improve the terminology, "style property" work for me. I'm starting to think we may need two inheritance models. One for 'visibility' and 'interactivity' using the 3 current bullets founds in the spec. And a second one for the other style properties using only the first two bullets. LH> 5.4.1.2, "Specified values are resolved to computed values after the LH> document tree is create[d]; for example relative units ('%') are computed to LH> absolute values (i.e., RGB color or NVDC)." There is a conceptual problem LH> here. Stroke-weight illustrates it. Suppose "initial stroke-weight" is LH> 100%. Suppose the CGM's line-width is 5 and edge width 10 in a given LH> APS. What is the NVDC Computed Value for stroke-weight for that APS? I LH> don't know the answer. We could require the implementations to behave 'as if' two values where inherited (line-width and edge-width)... But to be honest, I don't even know what's the difference between the two values? LH> I suspect, because we don't have a 1-to-1 relationship between LH> style properties and affected CGM attributes, that we're going to LH> have some problems with Computed Values. LH> 5.4.1.2, 2nd pgph, "When the specified value is not 'inherit', the computed LH> value of a style attribute is determined as specified by the Computed Value LH> line in the definition of the property." Oops. We didn't do this. This LH> is not specified in 5.7.5, neither in the table nor the following LH> descriptions. I don't know what it should be. We need a proposal. Dieter proposed that we add 'inherit' as a possible value for 'visibility' and 'interactivity'. I don't think it was proposed for the other style properties. So again, the problem here, is that we fail to make the distinction between CGM attributes and style properties. LH> 5.4.2, "Each style attribute defines whether it is inherited or LH> not." Oops. We didn't do this. Neither the table in 5.7.5 nor the LH> following style attributes' descriptions give inheritance rules. We need a LH> proposal (I don't have time right now to work one up.) (Exception: we know LH> about 'visibility' from 3.2.2.9.) Same comment than above. LH> Some small editorials: LH> ----- LH> 5.4.1.3, "...for example: todo". We need an example here. LH> 5.4.1, 2nd sentence, s/attributes/attribute/ LH> 5.4.1.1, 1st sentence, s/attributes/attribute/ LH> 5.4.1.1, #3, s/attributes's/attribute's/ LH> 5.4.1.2, s/create/created/ LH> 5.4.2.1, s/Chapter on inheritance to be done.// (Presumably, that is 5.4.2 LH> plus 5.4.2.1). LH> All for now, LH> -Lofton. -- Benoit mailto:benoit@itedo.com
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