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add the pixels-per-scroll-step init argument #4

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add the pixels-per-scroll-step init argument #4

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263c9a9
add the `pixels-per-scroll-step` init argument
rfindler Feb 5, 2024
ea0cf96
try 2 as a default, pending others' comments
rfindler Feb 6, 2024
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12 changes: 11 additions & 1 deletion pict-snip-doc/scribblings/pict-snip/pict-snip.scrbl
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@
pict
racket
racket/snip
racket/math
racket/contract))


Expand All @@ -18,9 +19,18 @@
}

@defclass[pict-snip% snip% ()]{
@defconstructor[([pict pict?])]{
@defconstructor[([pict pict?]
[pixels-per-scroll-step (or/c #f natural?) 2])]{
Creates a @racket[pict-snip%] object, using
@racket[pict] to draw.

If @racket[pixels-per-scroll-step] is @racket[#f], then the
snip will have only one scroll step (see
@method[snip% get-num-scroll-steps] for more information).
The default means that the scroll bars will stop every two
pixels.

@history[#:changed "1.1" @list{Added the @racket[pixels-per-scroll-snip] argument}]
}
@defmethod[(get-pict) pict?]{
Returns the pict passed to the constructor.
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2 changes: 2 additions & 0 deletions pict-snip-lib/info.rkt
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Expand Up @@ -16,3 +16,5 @@

(define license
'(Apache-2.0 OR MIT))

(define version "1.1")
29 changes: 28 additions & 1 deletion pict-snip-lib/pict/snip.rkt
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Expand Up @@ -3,6 +3,7 @@
racket/snip
racket/draw
racket/format
racket/math
(prefix-in racket: racket/base)
pict
pict/convert
Expand All @@ -19,7 +20,13 @@

(define pict-snip%
(class* snip% (convert<%>)
(init-field pict)
(init-field pict [pixels-per-scroll-step 2])
(unless (or (natural? pixels-per-scroll-step)
(not pixels-per-scroll-step))
(error 'pict-snip%
"pixels-per-scroll-step init arg wrong\n expected: ~s\n got: ~e"
'(or/c #f natural?)
pixels-per-scroll-step))
(define drawer (make-pict-drawer pict))
(define/override (get-extent dc x y wb hb db sb lb rb)
(set-box/f! wb (pict-width pict))
Expand Down Expand Up @@ -50,6 +57,26 @@
(define bts (get-output-bytes bp))
(send f put (bytes-length bts) bts))

(define/override (get-num-scroll-steps)
(cond
[pixels-per-scroll-step
(define height (pict-height pict))
(exact-ceiling (/ height pixels-per-scroll-step))]
[else (super get-num-scroll-steps)]))

(define/override (get-scroll-step-offset offset)
(cond
[pixels-per-scroll-step
(exact-floor (* offset pixels-per-scroll-step))]
[else
(super get-scroll-step-offset offset)]))

(define/override (find-scroll-step y)
(cond
[pixels-per-scroll-step
(exact-floor (/ y pixels-per-scroll-step))]
[else (super find-scroll-step y)]))

(define/public (get-pict) pict)

(inherit set-snipclass)
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