[metapost] some question about pens

[Stephan Hennig]

Hi,

the attached code compares six variants of a stroked half circle drawn
with a circled and squared pen (left and right column) and with linecap
set to {rounded, squared, butt} (top to bottom).

(i) I'm only happy with the upper right variant (squared pen, rounded
linecap).

(ii) For all examples in the left-hand column (rounded pen) the end
points of the strokes seems to have a slightly wrong direction, i.e., it
is not exactly "up" or "down".  A bug?

(iii) For the upper and middle example in the right-hand column (squared
pen with rounded/squared linecap) I'd expect exactly the same results.
Or better, what exactly is the effect of linecap on squared pens?  The
manual is not very verbose about that.

(iv) Why are there diagonal end points in the middle and lower example
in the right-hand column (squared pen, squared/butt linecap)?

I'm using MetaPost v1.001.

Best regards,
Stephan Hennig
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