On 19.03.07, Michael J Gruber wrote:
> Michael SCHINDLER venit, vidit, dixit 2007-03-19 10:42:
> > On 19.03.07, Joerg Lehmann wrote:
> ...
> > No. The scaling is intended. When a user scales everything -- why not also 
> > the
> > tangent?
> > 
> >> I agree, this was one of the reasons, I didn't like the patch. The
> >> scaling problem could be solved by using true cms. But the question is
> >> whether one should really introduce a more or less arbitrary length
> >> scale here?
> > 
> > I do not see the problem. As I introduced the default value as a
> > simple number and not a pyx.length, I will be scaled as many other
> > default lengths in pyx.
> 
> Do you scale like a ``true'', ``user'', ``visual'', ``width'', or
> ``TEX'' length?

The unit is evaluated by normpath.normpath.tangent in the following
way:

  unit.topt(length)

Thus, it is only the unit module which defines the scaling here. It is
therefore always the default scaling that the user has set with all
his unit.set(...) commands. If the user does not change anything, this
is

  user cm

The user can change the "cm", but not the "user". I really like to
stress that this type of scaling is used in PyX _everywhere_. Just
consider the simple example

  p = path.circle(0, 0, 1)

or check all the unit.topt() calls in normpath.py. Here, all the
numbers are scaled in exactly the same way as the length above. The
only difference is that there are no default arguments for
path.circle.


> Sorry I couldn't resist ;)

BTW: I really find this discussion a bit boring. If there are severe
objections against the default behaviour of the method tangent (which
I find _completely_ _unnecessary_, besides that it has a wrong name,
as it does not provide a tangent but a "line parallel to the tangent
vector" (sic!)), then please make a suggestion, be it to remove the
default behaviour -- or the complete method, which would be my
favourite!

Michael.

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