On 23-1-2010 14:32, Hans van der Meer wrote:
Further experimentation has shown that it is not impossible to color
\vrule's, thus \blackrule is not specifically needed. Let me first
mention that I put the colored rules away with \setbox\B=\hbox{} and
then later call \B up. It is a pity until now I am not able to concoct a
minimal example showing consistently the behaviour.
However I have made the following observations:
define: \definecolor[mycolor][r=myR,g=myG,b=myB]
(1) \color[mycolor]{rule} typesets a black rule
(2) \color[red]{something}\color[mycolor]{rule} typesets a mycolor rule
(3) \definecolor[green][r=myR,g=myG,b=myB]\color[mycolor]{rule} typesets
a mycolor rule
(4) changing the values of myR,myG,myB between runs keeps typesetting
the old mycolor
(5) it seems there is a memory effect on defined colors, something with
a cache that keeps me from changing things.
It is mainly the seemingly erratic behaviour of the color changes that
puzzles me. I seem not being able to pinpoint a culprit.
it's not that erratic at all, just do the same experiment with fonts ...
In traditional tex color is implemented using specials and code is
injected. Compare this with fonts: you choose a font, which sets a state
and that state carries with the following glyphs till set otherwise (or
restored). Boxing and unboxing keeps that state.
In mkiv we use attributes for color (btw, the mk.pdf documents mentions
al those things). And attributes are kept with objects and as a result
are retained, which in my opinion is as it shoul dbe.
So, in traditional tex you have:
box == somerule
[somecolor][thatbox]
which effectively is
[somecolor]somerule
so the rule gets somecolor
but if you have
box == [somecolor]somerule
[anothercolor][thatbox]
you have
[anothercolor][somecolor]somerule
and te box will stay somecolor
in mkiv nocolor is really nocolor so in the first example your rule will
be black (as it has no attribute set and will not gte one set either as
a box has frozen states
When I wrote the backend code for colors I added an inheritance model
but it's not yet perfect (and might even disappear or change).
\starttext
x\definecolor[mycolor][green]\color[mycolor]{\vrule width 10cm}x
\setbox0\hbox{x\color[mycolor]{\vrule width 10cm}x}
x\definecolor[mycolor][red]\color[mycolor]{\vrule width 10cm}x
\color[mycolor]{\copy0}
\enableattributeinheritance
\color[mycolor]{\attributedcopy0}
\stoptext
Your bad luck is that inheritance does not play well with rules currently.
On the other hand, the fact that you could this in mkii is no proof that
it's the right way to do it. Most attribute driven features behave like
fonts have been doing in mkii for ages.
Hans
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Hans Hagen | PRAGMA ADE
Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
tel: 038 477 53 69 | fax: 038 477 53 74 | www.pragma-ade.com
| www.pragma-pod.nl
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