I suppose it'd be possible to do something like get the MD5 hash of the output and the Pctricks pakage for latex, put it in the aux file, and then on recompile, if the hash of the input or output do not match the stored one, recompute. It is required for PDFTricks to run. The -shell-escape parameter enables shell command calls. Vector graphics markup languages and file formats. As for rectangles, the starred version prints a filled polygon.