Incremental changes like this can work, but a good program design is necessary to prevent running into situations that cannot be solved with a few hacks. I cannot suggest a better way without knowing your goals.
By the way, in the email I intended to paste those two lines after the definitions in that function. I doubt they should be in that function anyway; I threw them in there because I (like you) wanted an easy way to see if what you were trying to do was possible. rac On Oct 28, 2010, at 12:02 AM, kty1...@gmail.com wrote: > omg it works!! > thank you! > although I am satisfied with this method, > do you know the better way for it? > > , Richard Cleis <rcl...@mac.com>님이 작성: > > Insert the two lines below to see that what you want is possible, but I > > doubt such a quick hack is the right way to do it. > > > > > > > > rac > > > > > > > > On Oct 27, 2010, at 8:48 PM, kty1...@gmail.com wrote: > > > > > > > > > hello > > > > > I finally circle the bitmap where I point by mouse > > > > > but there are several problem > > > > > 1. the circle filled with white color that I can't see bitmap through the > > > circle > > > > > 2. the drawn circle didn't erased after I point another coordinates > > > > > > > > > > could somebody give me an little advice? > > > > > > > > > > my code looks messy and not neat but > > > > > I paste the code for make it easier to understand > > > > > > > > > > > > > > > #lang scheme > > > > > (require 2htdp/image > > > > > racket/gui) > > > > > (define chipset (make-object bitmap% "town.png" 'png)) > > > > > (define (check dc m) > > > > > > > > > > > > (send dc draw-bitmap chipset 0 0) > > > > (send dc set-brush "blue" 'transparent) > > > > > > > > > > > > > > > > > (define x (send m get-x)) > > > > > (define y (send m get-y)) > > > > > (send dc draw-ellipse (- x (modulo x 16)) (- y (modulo y 16)) 16 16)) > > > > > (define f (new frame% (label "map editor"))) > > > > > (define xymsg (new message% (label "nth so far") (parent f))) > > > > > (define select% > > > > > (class canvas% > > > > > (override on-event on-paint) > > > > > (define on-paint (λ () (send (send this get-dc) draw-bitmap chipset 0 0))) > > > > > (define on-event (λ (m) > > > > > (send xymsg set-label > > > > > (string-append "x:" > > > > > (number->string (send m get-x)) > > > > > " y:" > > > > > (number->string (send m get-y)))) > > > > > (when (send m get-left-down) (check (send this get-dc) m)))) > > > > > > > > > > (super-new ) > > > > > )) > > > > > (new select% (parent f) (min-width (image-width chipset)) (min-height > > > (image-height chipset)) ) > > > > > (send f show #t)_________________________________________________ > > > > > For list-related administrative tasks: > > > > > http://lists.racket-lang.org/listinfo/users > > > > > > > > _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
