Snip responds to scroll input

21 views

Skip to first unread message

Kshitij Sachan

unread,

Jul 10, 2019, 1:07:12 PM7/10/19

to Racket Users

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?).