[cairo] line width = 0.0 ?

[Christian Krause]

Hi,

recently I've searched a problem in the poppler library:

Without explaining the whole story, at least the line width was set to
0.0 with cairo_set_line_width(cairo, 0.0). After that, a line was
drawed but it was not visible. If the line width is greater than 0.0
(e.g. 1.0) the line is visible.

To understand the problem I've looked into the API specification of
cairo (http://www.cairographics.org/manual/cairo-cairo-t.html#id2647684),
but unfortunately the explanation was not sufficiant.

So I have 2 questions:

1. What is the meaning of a line width = 0.0? Should the line be visible?

2. How can the following achieved in cairo (as e.g. required in the
pdf specification):
"Draw the thinnest line which can be rendered in the current context"?

Thanks in advance.

Best regards,
Christian