bug in fps 1.0

["Walter C. Pelissero" <pelissero@tiscali.de>]

[ Sorry to send this message to the scsh-bugs mailing list, but
  wandy@mit.edu seems not a valid address any more, and maybe someone
  on the list is able to get things addressed to the right person. ]

It seems to me that bounding-box suffers from a bug that shows up only
in some circumstances.

Here is a sample session to reproduce the bug:

  > ,config ,load fps-package.scm
  fps-package.scm ......
  > ,in fps
  Load structure program (y/n)? y
  [elided stuff]
  > (define l (line (pt 0 0) (pt 3 3)))
  > (bounding-box (translate 0 10 (translate 10 0 l)))
  '#{bbox #{pt 10 10} #{pt 13 13}}
  > (define a (translate 0 10 l))
  > (bounding-box a)
  '#{bbox #{pt 0 10} #{pt 3 13}}
  > (define b (translate 10 0 a))
  > (bounding-box b)
  '#{bbox #{pt 0 10} #{pt 3 13}}

The last result should have been:

  '#{bbox #{pt 10 10} #{pt 13 13}}

Here is a patch that solves the problem:

diff -c fps.ask.scm\~ fps.ask.scm
*** fps.ask.scm~        Thu Oct 31 20:07:18 1996
--- fps.ask.scm Sun Apr 20 00:21:23 2003
***************
*** 37,43 ****
              ((close-path?  obj) (loop (close-path:path obj) TM))
              ((stroke-outline-path? obj) (loop (stroke-outline-path:path obj)
                                                TM))
!             ((instance?    obj) (or (instance:bbox obj)
                                      (let ((box (loop (instance:obj obj)
                                                       (matrix* (instance:TM 
obj)
                                                                TM))))
--- 37,44 ----
              ((close-path?  obj) (loop (close-path:path obj) TM))
              ((stroke-outline-path? obj) (loop (stroke-outline-path:path obj)
                                                TM))
!             ((instance?    obj) (if (instance:bbox obj)
!                                     (transform-bbox TM (instance:bbox obj))
                                      (let ((box (loop (instance:obj obj)
                                                       (matrix* (instance:TM 
obj)
                                                                TM))))
***************
*** 49,55 ****
              ((composite?   obj) (composite-bbox   obj TM))
              ((clipped?     obj) (clipped-bbox     obj TM))
              ((bitmap-pict? obj) (bitmap-pict-bbox obj TM))
!             ((instance?    obj) (or (instance:bbox obj)
                                      (let ((box (loop (instance:obj obj)
                                                       (matrix* (instance:TM 
obj)
                                                                TM))))
--- 50,57 ----
              ((composite?   obj) (composite-bbox   obj TM))
              ((clipped?     obj) (clipped-bbox     obj TM))
              ((bitmap-pict? obj) (bitmap-pict-bbox obj TM))
!             ((instance?    obj) (if (instance:bbox obj)
!                                     (transform-bbox TM (instance:bbox obj))
                                      (let ((box (loop (instance:obj obj)
                                                       (matrix* (instance:TM 
obj)
                                                                TM))))


-- 
walter pelissero
http://members.lycos.co.uk/wpelissero