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Subject: Re[2]: [cgmo-webcgm] SV, CV and CSS2-like inheritance [was: Re[2]: [cgmo-webcgm] Style properties]
Got it. So for stroke-weight, the easiest would be to inherit the specified value and not the computed value. -- Benoit mailto:benoit@itedo.com Wednesday, May 18, 2005, 11:46:28 AM, Lofton wrote: LH> At 10:27 AM 5/18/2005 -0400, Benoit Bezaire wrote: >>[...] >>LH> [Stroke-weight is a property of an APS. If convert-to-absolute for >>LH> stroke-weight means that you must convert % to NVDC, this cannot be >>done at >>LH> the APS level. >>Why can't this be done at the APS level? LH> Example: LH> BegAps obj1; LH> BegApsBody; LH> linewidth 10; LH> line 0 0 1000 1000 LH> edgewidth 15; LH> intstyle empty; LH> rect 100 100 900 900; LH> EndAps; LH> First, stroke-weight that is already nvdc is no problem. E.g., if DOM LH> applied a stroke-weight style property of 25 to 'obj1' ... no issues there. LH> Suppose stroke-weight is 100%. What is the nvdc equivalent of that, at the LH> BegAps element? What it means inside the APS, at the level of individual LH> line and fill primitives, is lw 10 and ew 15. What can you say is the LH> equivalent inheritable (single) nvdc value of CV of stroke-weight at the LH> BegAps element? (To make that last question more interesting, consider LH> sub-trees of nested APSs within 'obj1'.) LH> Suppose DOM sets stroke-width to 50% on obj1. What is the nvdc equivalent LH> of that, at the BegAps element? Etc... LH> -Lofton. >>LH> So the CV of stroke-weight is ill-defined at the APS level, >>LH> if the CV requires convert-to-absolute.] >> >>LH> B.) CSS2 says that Computed Values are inherited. (CSS3 allows each >>LH> property to define which type of value is inherited.) >> >>LH> Condition A and condition B taken together makes it problematic to apply >>LH> the CSS2 inheritance model exactly to our style properties inheritance. >>Why is it problematic? LH> You cannot have both condition A, plus condition B, plus keep close LH> alignment with the 3 steps (or 4, or 2) of the CSS2 inheritance model. LH> -Lofton. >> >>LH> If we relax condition B, i.e., if we say that SV is inherited down APS >>LH> branches (for style properties) instead of CV, as allowed by CSS3, then >>LH> that inheritance model works. (But it leaves CV pretty much unused in the >>LH> model, and doesn't solve the problem of uncomputable CV at the APS level.) >> >>LH> If we relax condition A -- i.e., convert-to-absolute happens after CV, >>LH> e.g., at the Used Value stage -- then CV is the same as SV (except for >>LH> resolution of the values 'inherit', which we don't allow anyway for style >>LH> properties.) And inheritance down APS branches works, CSS2-like. >> >>LH> -Lofton.
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