Hello Racket friends,
I was playing with the plot module (which is very nice, btw) and discovered
that the parameter plot-decorations? is ignored when plotting to a new
window.
The file plot3d.rkt (plot\plot-gui-lib\plot\private\gui) is where
plot-new-window? makes a distinction of the cases and this is where I got
rather confused.
Inside plot3d.rkt, the function plot3d-snip has an internal helper function
make-bm, preceded by curious step that stores the values of the
plot-parameters in a variable that the helper function then uses to recall
them. This is the gist of it:
(define (plot3d-snip renderer-tree ...)
...
(parameterize ([plot-title title]
...)
(define saved-plot-parameters (plot-parameters)) ; <- store parameters
...
(define (make-bm anim? ...)
(parameterize/group ([plot-parameters saved-plot-parameters] ; <-
recall parameters, why?
...)
...))
...)
The function for plotting into a frame did not have such a step but has the
same structure with make-snip as the helper function so I added the
store/recall step, and with it, plot does respect the value of the
parameter.
(define (plot3d-frame renderer-tree ...)
...
(define saved-plot-parameters (plot-parameters)) ; <- store parameters
(define (make-snip width height)
(parameterize/group ([plot-parameters saved-plot-parameters]) ;<-
recall parameters
(plot3d-snip renderer-tree ...))
)
A quick printf also showed that the parameters have a different value
between the outside and the inside of the helper functions.
Now, this behavior is expected, otherwise the solution would not have been
present in the same file; my question is why is it behaving this way? how
is the helper function seeing the value of the parameter from the initial
definition and not the one being set before invoking plot3d?
To add to my confusion, I made this simple test in which I tried to copy
the previous behavior, and it behaves as I expect, but differently to the
plot3d case.
#lang racket
(module m racket
(provide (all-defined-out))
(define test-param (make-parameter #t))
(define (f)
(define (g)
(test-param))
(g)))
(require 'm)
(f)
(test-param #f)
(f)
-----
#t
#f
Thanks for reaching the end of this long question :)
Carlos
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