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Danny Yoo 2011-08-29 15:32:27 -04:00
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@ -65,8 +65,123 @@ fermi ~/whalesong/examples $
}|
There are examples in the @link["https://github.com/dyoo/whalesong/tree/master/examples"]{@filepath{whalesong/examples}} and
@section{Examples}
There are examples in the
@link["https://github.com/dyoo/whalesong/tree/master/examples"]{@filepath{whalesong/examples}}
and
@link["https://github.com/dyoo/whalesong/tree/master/web-world/examples"]{@filepath{whalesong/web-world/examples}}.
Let's look at a few of them.
@subsection{Hello world}
Let's try making a simple, standalone executable. At the moment, the
program must be written in the base language of @racket[(planet
dyoo/whalesong)]. This restriction unfortunately prevents arbitrary
@racketmodname[racket/base] programs from compiling at the moment;
the developers (namely, dyoo) will be working to remove this
restriction as quickly as possible.
Write a @filepath{hello.rkt} with the following content
@filebox["hello.rkt"]{
@codeblock{
#lang planet dyoo/whalesong
(display "hello world")
(newline)
}}
This program is a regular Racket program, and can be executed normally,
@verbatim|{
$ racket hello.rkt
hello world
$
}|
However, it can also be packaged with @filepath{whalesong}.
@verbatim|{
$ whalesong build hello.rkt
$ ls -l hello.xhtml
-rw-rw-r-- 1 dyoo nogroup 692213 Jun 7 18:00 hello.xhtml
}|
Running @tt{whalesong build} on a Racket program will produce a self-contained
@filepath{.xhtml} file. If you open this file in your favorite web browser,
you should see a triumphant message show on screen.
@subsection{Tick tock}
Let's do something a little more interesting, and create a ticker that
counts on the screen.
The first thing we can do is mock up a web page with a user interface, like this.
@filebox["index.html"]{
@verbatim|{
<html>
<head><title>My simple program</title></head>
<body>
<p>The current counter is: <span id="counter">fill-me-in</span></p>
</body>
</html>
}|
}
We can even look at this in a standard web browser.
Once we're happy with the statics of our program, we can inject dynamic behavior.
Write a file called @filepath{tick-tock.rkt} with the following content.
@filebox["tick-tock.rkt"]{
@codeblock|{
#lang planet dyoo/whalesong
(require (planet dyoo/whalesong/web-world)
(planet dyoo/whalesong/resource))
(define-resource index.html)
;; draw: world view -> view
(define (draw world dom)
(update-view-text (view-focus dom "#counter") world))
;; tick: world view -> world
(define (tick world dom)
(add1 world))
;; stop?: world view -> boolean
(define (stop? world dom)
(> world 10))
(big-bang 0
(initial-view index.html)
(to-draw draw)
(on-tick tick 1)
(stop-when stop?))
}|
}
Several things are happening here.
@itemize[
@item{We @racket[require] a few libraries to get us some additional
behavior; in particular, @racketmodname/this-package[web-world] to let
us write event-driven web-based programs, and @racketmodname/this-package[resource]
to give us access to external resources.}
@item{We use @racket[define-resource] to refer to external files, like @filepath{index.html} that
we'd like to include in our program.}
@item{We use @racket[big-bang] to start up a computation that
responses to events. In this example, that's clock ticks introduced
by @racket[on-tick], though because we're on the web, we can
bind to many other kinds of web events (by using @racket[view-bind]).}
]
The rest of this document describes the API.
@ -94,12 +209,50 @@ provides additional information about the event that triggered the callback.
Start a big bang computation.
}
@defproc[(initial-view [x any]) big-bang-handler]{
Provide an initial view for the big-bang.}
@defproc[(stop-when [stop? ([w world] [dom view] -> boolean)]) big-bang-handler]{
Tells @racket[big-bang] the predicate for termination.
Provide an initial view for the big-bang. Normally, @racket[x] will be a resource
to a web page.
@codeblock|{
...
(define-resource page1.html)
...
(big-bang ...
(initial-view page1.html))
}|
}
@defproc[(on-tick [tick-f ([w world] [v view] [e event]? -> world)]) big-bang-handler]{
@defproc[(stop-when [stop? ([w world] [dom view] -> boolean)]) big-bang-handler]{
Tells @racket[big-bang] when to stop.
@codeblock|{
...
(define-struct world (given expected))
...
;; stop?: world view -> boolean
(define (stop? world dom)
(string=? (world-given world) (world-expected world)))
(big-bang ...
(stop-when stop?))
}|
}
@defproc*[(((on-tick [tick-f ([w world] [v view] [e event]? -> world)] [delay real]) big-bang-handler)
((on-tick [tick-f ([w world] [v view] [e event]? -> world)]) big-bang-handler))]{
Tells @racket[big-bang] to update the world during clock ticks.
By default, this will send a clock tick 28 times a second, but if
given @racket[delay], it will use that instead.
@codeblock|{
...
;; tick: world dom -> world
(define (tick world view)
(add1 world))
(big-bang ...
(on-tick tick 5)) ;; tick every five seconds
}|
}
@ -112,7 +265,16 @@ events.
The optional @tech{event} argument will contain numbers for
@racket["latitude"] and @racket["longitude"].
@codeblock|{
...
;; move: world view event -> world
(define (move world dom event)
(list (event-ref event "latitude")
(event-ref event "longitude")))
...
(big-bang ...
(on-mock-location-change move))
}|
}
@ -123,13 +285,37 @@ received by the
The optional @tech{event} argument will contain numbers for
@racket["latitude"] and @racket["longitude"].
@codeblock|{
...
;; move: world view event -> world
(define (move world dom event)
(list (event-ref event "latitude")
(event-ref event "longitude")))
...
(big-bang ...
(on-location-change move))
}|
}
@defproc[(to-draw [draw-f ([w world] [v view] -> view)]) big-bang-handler]{
Tells @racket[big-bang] how to update the rendering of the world.
Tells @racket[big-bang] how to update the rendering of the world. The draw
function will be called every time an event occurs.
@codeblock|{
...
(define-struct world (name age))
;; draw: world view -> view
(define (draw world dom)
(update-view-text (view-focus dom "#name-span")
(world-name world)))
...
(big-bang ...
(to-draw draw))
}|
}
@ -216,9 +402,16 @@ Add the dom node @racket[d] as the last child of the focused node.}
@subsection{Events}
An @deftech{event} is a structure that holds name-value pairs.
@defstruct[event ([kvpairs (listof (list symbol value))])]{}
An @deftech{event} is a structure that holds name-value pairs.
Whenever an event occurs in web-world, it may include some auxiliary
information about the event. As a concrete example, location events
from @racket[on-location-change] and @racket[on-mock-location-change]
can send latitude and longitude values, as long as the world callback
can accept the event as an argument.
@defstruct[event ([kvpairs (listof (list symbol (or/c string number)))])]{}
@defproc[(event-ref [evt event?] [name (or/c symbol string)]) value]{
Get an value from the event, given its @racket[name].
@ -231,8 +424,6 @@ Get an list of the event's keys.
@section{Including external resources}
@defmodule/this-package[resource]