On 12-Apr-10 07:06:17, Patrik Schindler wrote: > > Am 12.04.2010 um 04:31 schrieb Doug McIlroy: > >> It it seems like a good idea, I might volunteer to try to do it right. > > > From my point of view, it absolutely makes sense. I also missed polys > from time to time.
The fundamental issue is the small repertoire of fillable, colourable or shadeable objects in pic -- basically box, circle, ellipse. A closely related question came up in 2005, which led to a quite deep discussion. The thread starts with a post from Ole Schoenig on 13 September 2005, and can be found at http://lists.gnu.org/archive/html/groff/2005-09/msg00018.html One idea which came to me in the course of that was that it would be useful to be able to assign a "closed" attribute to an object drawn by pic, which could then embed its PostScript execution in a "newpath ... closepath" with an optional "fill", "coloured" or "shaded" attribute which would then additionaly cause PostScript to apply an appropriate "fill". I gave a hypothetical example: [ arc down rad 1; arc rad 1; line up 0.5 left 0.75; line left 0.5; line left 0.75 down 0.5 ] closed shaded "green" (being the part of a house+garden plan showing the grass lawn). The idea here is that anything within [ ... ] consisting of a series of connected segments, arcs of circles or ellipses, splines, etc. can be made into a closed object with the 'closed' attribute and subsequently shaded (with "shaded" or filled (with "fill"). However, inmplementing this sort of thing would involve modifying pic extensively at a deep level. Another approach (which I have recently been playing with for arbitrary rotations in pic) is to implement PostScript commands as troff strings (e.g. ".ds PSop1 \X'ps: exec ... '") and then you can plant them as "troff text" within pic code. For examples of what can be done on the rotation front have a look at the thread "[Groff] A little Greetings card," which starts on 29 December 2010 near the bottom of http://lists.gnu.org/archive/html/groff/2009-12/threads.html There are follow-ups, implementing the "\X'ps: exec ... '" mechanism more explicitly, at http://lists.gnu.org/archive/html/groff/2010-01/msg00007.html [Groff] Rotating element of a PIC fogure http://lists.gnu.org/archive/html/groff/2010-01/msg00008.html [Groff] More on rotation in PIC I will try to see what can be done along similar lines for implementing arbitrary closed and filled/coloured/shaded objects in pic. Another approach one could consider for shaded polygons is to exploit pic's capabilities as a numerical computing engine. This would basically use pic to compute the troff "\D'P ... '" command for drawing a closed polygon, and combining this with the appropriate commands to set fill level or colour. I will look into this too. I have, indeed, a somewhat intermittent project in hand to implement a fairly general repertoire of such things for pic. The general idea is to get pic to construct something which is then dropped into a constructed PostScript context to be further processed by PostScript when grops gets at it. The "\*[rotate] ... \*[restore]" method implemented in the last two URLs above is a simple instance of the kind of thing I have in mind. Hoping this is helpful! Ted. -------------------------------------------------------------------- E-Mail: (Ted Harding) <ted.hard...@manchester.ac.uk> Fax-to-email: +44 (0)870 094 0861 Date: 12-Apr-10 Time: 09:54:24 ------------------------------ XFMail ------------------------------
