Re: [PyX-devel] [PATCH 2/2] arrow: make pos relative to the full arclength

[André W. <wo...@us...>]

Hi,

Am 22.05.2012 um 09:18 schrieb Joerg Lehmann:
>> We do try to position the arrow head based on the "inward tip"
>> (constriction center) since r3151, which can be considered the "middle
>> of the head". 
> 
> I am not sure if I understand you correctly, but I would say no.

Jörg is right. We definitely don't do that. pos defines the position of the tip of the arrow. Originally before your patches. We really should stick at this simple rule.

>> It's the result of this principle:
>> We calculate/restrict "admissible positions" so that 0 and 1 mean begin
>> and end arrow, where an end arrow head has its tip lined up the end of
>> the path, and a begin arrow has its constriction center lined up with
>> the start of the path. That's why (1-0) has to mean
>> (arclen-constrictionlen) which creates the other problems.
> 
> Yes.

Really, I don't see where this creates any problem. It's simple and it's the right thing to do.

>> Basically, I would love (1-0) to mean arclen (patch 2/2), i.e.
>> everything relative to full arclen, then a beginhead would have pos=0,
>> and an endhead would be at pos=1-constrictionlen/arclen. Consequently, a
>> head at pos=1 would have its constriction center ("middle") at the end
>> of the path. This would require additional adjustments to the way we cut
>> the path, though. Which is why I did the min/max thingy.

Sorry, IMHO this whole discussion will not result in anything useful. 

> We would need to extend the path, which is rather tricky. But doing the
> min/max thing is not a solution, IMHO.


Don't even think about extending the path. This is an absolute no-go. (I do understand that Michael did try to not do this. But he did so by using some very obscure min/max thing. Absolutely bizarre. No, no, no. Never.)


André

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