[pstricks] Trouble with \pssin inside clipping path

[Luis Sequeira]

It appeared to me that this was a problem between \pssin and \pscustom, as
I tried just the \pscustom command without the \psclip and it had the same problem.

After looking at it a bit more thoroughly, this seems to be caused by how some commands behave differently inside a pscustom - as there are notions of path and of current point that are specific to it.

Some commands set a current point, and some don’t. When a current point is set, a command like \pscurve or \psline implicitly uses the current point. \pssin(4,4)(8,4) sets the current point as (8,4) and the origin at (4,4) (I believe this to be a bug of \pssin, but I am guessing a bit, there is a lot about this that I don’t know).
This makes the next command \psline(8,4)(8,-4) to in effect trace two lines, starting at (8,4) and *relative* to the “new” origin (4,4): in effective tracing a line from (8,4) to (12,8) and then to (12,0).

You can work around this problem by replacing \psline(8,4)(8,-4) with 

    \psline(4,-8) 

or 
 
     \lineto(4,-8)

(again, this is relative to the “origin” (4,4) and equals (8,-4) in “normal” coordinates).

Luis Sequeira