Re: On the connectors examples - is this intended in the 'use with symbols' example?

On Sat, Nov 8, 2014 at 12:12 AM, Juergen Roethig
<roethig@dhbw-karlsruhe.de> wrote:
> Juergen Roethig wrote:
>> Smailus, Thomas O wrote:
>>> Circles mean something in logic gate diagrams – negating the signal.  So
>>> an AND gate may or may not have a negated input and/or output.
>>>
>>> How would this work in a logic diagram where we have an AND gate where we
>>> specify a gate (do we need to have the combinatorial explosion of gates
>>> defined when using circle or non-circle terminators)?
>>
>> If you are interested in the practical usecase of "combinational and
>> sequential circuits" as an example for connectors in SVG, you might have a
>> look at my "SVG connector proposal" page. I just had a few minutes time to
>> provide two simple circuits as examples, using a real and working "SVG
>> reference point implementation". Just have a look at
>> http://jroethig.de/geolog/connector.html#l2demcircuits
>>
>> [...]
>>
>> Referring to your specific question: The "circles" (or negations) are done
>> via marker-start and marker-end for the "connectors", although this might
>> also be achieved by a special symbol positioned at the start or end of that
>> connector, instead (basically just a case of personal taste). But the
>> negations would most probably not be achieved as a part of the symbol for
>> the specific gate.
>
> As I just remembered, I would like to add that this is another perfect
> example for the sillyness of the precedence of CSS properties over
> presentation attribute values. If you now carefully realize all the
> negations at the inputs and outputs of the gates via markers at the start or
> end of the respective connectors (lines, polylines, paths, whatever) given
> by presentation attributes "marker-start" and/or "marker-end", one simple
> CSS rule
> * { marker-start: none; marker-end: none }
> (even when given in the user style sheet (!) of someones browser) will
> override all those nice negations given in the SVG source code ... you might
> try it by yourself! But this is another topic, the battle "breakage of
> useful content by bad design" vs. "breakage of silly content by removing
> silly rules" - so far, the latter seems to be a more important issue which
> needs to be avoided in any case.

No, if that rule shows up in the user stylesheet, the attribute wins;
presentational attributes are placed in the "author" origin, which
auto-wins against "user".

SVG attributes being classes as "presentational attributes" is just
for consistency with HTML, though the two serve different purposes -
the placement of HTML presentational attributes in the cascade is
purposeful, as they're a legacy feature that shouldn't be used, which
isn't true of SVG's presentational attributes, but consistency was
deemed more important than coming up with something slightly more
sensible; you can always use the style attribute to specify styles at
a higher point in the cascade than author rules.

~TJ

Received on Wednesday, 12 November 2014 00:08:59 UTC