4288c6c2c7
punctuations outside of the form, as it does with quote punctuations.
So things like this
#, @foo{...}
that required the space to make the @foo read as a scribble form are
now better written as
@#,foo{...}
This changes all such occurrences. (In case you see this change in
your files and are worried that there might be changes: I mechanically
verified that the result of `read'ing the modified files is identical
to the previous version.)
svn: r15111
102 lines
4.1 KiB
Racket
102 lines
4.1 KiB
Racket
#lang scribble/doc
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@(require scribble/manual "shared.ss"
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(for-label scheme
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teachpack/htdp/draw))
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@teachpack["draw"]{Simple Drawing}
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@declare-exporting[teachpack/htdp/draw]
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The teachpack provides two sets of functions: one for drawing into a canvas
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and one for reacting to canvas events.
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@bold{Warning:} @emph{This teachpack is deprecated. Unless you're solving exercises
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taken from @emph{How To Design Programs}, we strongly encourage
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you to use the world teachpack instead; see @secref{world}.}
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@section[#:tag "drawing"]{Drawing on a Canvas}
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@deftech{DrawColor}: @scheme[(and/c symbol? (one-of/c 'white 'yellow 'red 'blue 'green 'black))]
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These six colors are definitely provided. If you want other colors,
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guess! For example, @scheme['orange] works, but @scheme['mauve]
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doesn't. If you apply the function to a symbol that it doesn't recognize as
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a color, it raises an error.
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@defproc[(start [width number?][height number?]) true]{Opens a
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@scheme[width] x @scheme[height] canvas.}
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@defproc[(start/cartesian-plane [width number?][height number?])
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true]{
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Opens a @scheme[width] x @scheme[height] canvas and draws a Cartesian
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plane.}
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@defproc[(stop) true]{Closes the canvas.}
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@defproc[(draw-circle [p posn?] [r number?] [c (unsyntax @tech{DrawColor})])
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true]{
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Draws a @scheme[c] circle at @scheme[p] with radius @scheme[r].}
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@defproc[(draw-solid-disk [p posn?] [r number?] [c (unsyntax @tech{DrawColor})])
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true]{
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Draws a @scheme[c] disk at @scheme[p] with radius @scheme[r].}
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@defproc[(draw-solid-rect [ul posn?] [width number?] [height number?]
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[c (unsyntax @tech{DrawColor})])
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true]{
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Draws a @scheme[width] x @scheme[height], @scheme[c] rectangle with the
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upper-left corner at @scheme[ul].}
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@defproc[(draw-solid-line [strt posn?] [end posn?]
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[c (unsyntax @tech{DrawColor})])
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true]{
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Draws a @scheme[c] line from @scheme[strt] to @scheme[end].}
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@defproc[(draw-solid-string [p posn?] [s string?]) true]{
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Draws @scheme[s] at @scheme[p].}
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@defproc[(sleep-for-a-while [s number?]) true]{
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Suspends evaluation for @scheme[s] seconds.}
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The teachpack also provides @scheme[clear-] operations for each
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@scheme[draw-] operation. The arguments are the same. Note: use
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@scheme[clear-rectangle] instead of @scheme[clear-string] for now.
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The color argument for all @scheme[clear-] functions are optional.
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@;-----------------------------------------------------------------------------
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@section[#:tag "interaction"]{Interactions with Canvas}
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@defproc[(wait-for-mouse-click) posn?]{
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Waits for the user to click on the mouse, within the canvas.}
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@deftech{DrawKeyEvent}: @scheme[(or/c char? symbol?)] A
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@tech{DrawKeyEvent} represents keyboard events:
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@itemize[
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@item{@scheme[char?], if the user pressed an alphanumeric key;}
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@item{@scheme[symbol?], if the user pressed, for example, an arror key:
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@scheme['up] @scheme['down] @scheme['left] @scheme['right]}
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]
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@defproc[(get-key-event) (or/c false (unsyntax @tech{DrawKeyEvent}))]{Checks whether the
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user has pressed a key within the window; @scheme[false] if not.}
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@deftech{DrawWorld}: For proper interactions, using the teachpack
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requires that you provide a data definition for @tech{DrawWorld} . In
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principle, there are no constraints on this data definition. You can even
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keep it implicit, even if this violates the Design Recipe.
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The following functions allow programs to react to events from the canvas.
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@defproc[(big-bang [n number?] [w (unsyntax @tech{DrawWorld})]) true]{Starts the clock, one tick every
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@scheme[n] (fractal) seconds; @scheme[w] becomes the first ``current'' world.}
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@defproc[(on-key-event [change (-> (unsyntax @tech{DrawKeyEvent}) (unsyntax @tech{DrawWorld}) (unsyntax @tech{DrawWorld}))])
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true]{Adds @scheme[change] to the world. The function reacts to keyboard
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events and creates a new @scheme[@#,tech{DrawWorld}].}
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@defproc[(on-tick-event [tock (-> (unsyntax @tech{DrawWorld}) (unsyntax @tech{DrawWorld}))]) true]{Adds @scheme[tock]
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to the world. The function reacts to clock tick events, creating a new
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current world.}
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@defproc[(end-of-time) (unsyntax @tech{DrawWorld})]{Stops the world; returns the current world.}
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