I want to make a snip that resizes based on vertical scroll input. I
currently have the following snip code:
#lang racket
(require racket/gui
racket/gui/base)
;; snip-class
(define test-snip-class
(make-object
(class snip-class%
(inherit set-classname)
(super-new)
(set-classname "(lib test-snip)")
;; not sure if necessary
(define/override (read f)
(define w-b (box 0.0))
(define h-b (box 0.0))
(send f get w-b)
(send f get h-b)
(new scroll-snip% [w (unbox w-b)] [h (unbox h-b)]))
)))
(define scroll-step-pixels 12)
;; snip stuff
(define scroll-snip%
(class snip%
(inherit get-admin set-snipclass set-flags)
(init-field [w 250] [h 250])
(super-new)
(set-snipclass test-snip-class)
(send (get-the-snip-class-list) add test-snip-class)
(set-flags (list 'handles-events))
(define/override (get-extent dc x y width height descent space lspace
rspace)
(define (maybe-set-box! b v) (when b (set-box! b v)))
(maybe-set-box! width w)
(maybe-set-box! height h)
(maybe-set-box! descent 1.0)
(maybe-set-box! space 1.0)
(maybe-set-box! lspace 1.0)
(maybe-set-box! rspace 1.0))
(define/override (find-scroll-step y) (inexact->exact (round (/ y
scroll-step-pixels))))
(define/override (get-num-scroll-steps) (quotient h scroll-step-pixels))
(define/override (get-scroll-step-offset step) (* step
scroll-step-pixels))
(define/override (on-char dc x y editorx editory event)
(cond
[(equal? (send event get-key-code) 'down)
(define admin (get-admin))
(set! w (+ w 20))
(set! h (+ h 20))
(when admin
(send admin resized this #t))]
[(equal? (send event get-key-code) 'up)
(define admin (get-admin))
(set! w (- w 20))
(set! h (- h 20))
(when admin
(send admin resized this #t))]
;; NOT WORKING!
[(equal? (send event get-key-code) 'wheel-up)
(print "wheelup")
(define admin (get-admin))
(set! w (+ w 20))
(set! h (+ h 20))
(when admin
(send admin resized this #t))]
[(equal? (send event get-key-code) 'wheel-down)
(print "wheelup")
(define admin (get-admin))
(set! w (- w 20))
(set! h (- h 20))
(when admin
(send admin resized this #t))]
[(equal? (send event get-key-code) 'escape)
(print "wheelup")
(define admin (get-admin))
(set! w 150)
(set! h 150)
(when admin
(send admin resized this #t))]))
(define/override (on-event dc x y editorx editory event)
(cond
[(send event button-down?)
(define admin (get-admin))
(set! w (+ w 20))
(set! h (+ h 20))
(when admin
(send admin resized this #t))]))
(define/override (draw dc x y left top right bottom dx dy draw-caret)
(send dc set-brush "red" 'solid)
(send dc set-pen "black" 3 'solid)
(send dc draw-ellipse (+ x 1.0) (+ y 1.0) (- w 2) (- h 2)))
(define/override (copy)
(new scroll-snip%))
))
I tried implementing this behavior in two different ways:
1. find-scroll-step, get-num-scroll-steps, and get-scroll-step-offset
methods - I doubt this is the purpose these methods, but I couldn't find
any examples online and the documentation wasn't entirely clear on what
they do.
2. Overriding on-char - this seemed more promising because 'wheel-up and
'wheel-down are listed as key codes for a key event, but my snip is still
unresponsive to scrolling.
Worse, I suspect that it may not be possible to scroll within a snip in the
interactions window because currently every time I scroll it just scrolls
the interactions window itself (seems like the interactions window, rather
than the snip, is in focus?).
Please let me know how I can implement scrolling on my snip to resize.
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