643 lines
21 KiB
JavaScript
643 lines
21 KiB
JavaScript
/*
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<br>
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**Parasitical Inheritance**
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*/
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/*
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The following examples illustrate the common design pattern for `OxJS` UI
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widgets: an inheritance model that is neither classical nor prototypal, but
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"parasitical" (a term coined by <a
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href="http://www.crockford.com/javascript/inheritance.html">Douglas
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Crockford</a>). In a nutshell, "instances" are created by augmenting other
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instances, but in addition to private members (`var foo`) and public members
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(`that.bar`), they can have shared private members (`self.baz`). `self` cannot
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be accessed from outside, but since `self` itself is an argument of the
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"constructor", an instance can inherit its parent's `self` by passing its own
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`self`.
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*/
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'use strict';
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/*
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Create our own namespace. Not required, but if we wanted to create a module
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named `My`, this is how we would do it.
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*/
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Ox.My = {};
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/*
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**Box**
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*/
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/*
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First, lets build the most basic Box widget. A widget is a "constructor"
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function that takes two (optional) arguments, `options` and `self`, and returns
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a widget object. It's not a constructor in JavaScript terms though: It doesn't
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have to be called with `new`, and doesn't return an `instanceof` anything. It
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just enhances another widget object and returns it.
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*/
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Ox.My.Box = function(options, self) {
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/*
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This is how every widget "constructor" begins. `self` is the widget's shared
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private object.
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*/
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self = self || {};
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/*
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`that` is the widget itself, its public object, or, in JavaScript terms, its
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`this`. Every widget "inherits" from another widget by simple assignment.
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All public properties of the "super" widget, i.e. all properties of its
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`that`, will be present on our own `that`. In this case, we use Ox.Element,
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the "root" widget at the end of the inheritance chain, and pass an empty
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options object. But we always pass our own `self`, which means that any
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property that Ox.Element (or any other widget in the inheritance chain) adds
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to `self` will be present on our own `self`.
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*/
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var that = Ox.Element({}, self)
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/*
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Then we call the public `defaults`, `options` and `update` methods of
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Ox.Element. `defaults` assigns the defaults object to `self.defaults`
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and copies it to `self.options`, `options` extends `self.options` with
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the options object, and `update` adds one or more callbacks that are
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invoked whenever, by way of calling the `options` method, a property of
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`self.options` is modified or added.
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*/
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.defaults({
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color: [128, 128, 128],
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size: [128, 128]
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})
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.options(options || {})
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.update({
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color: setColor,
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size: setSize
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})
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/*
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`addClass` is a jQuery method. In fact, Ox.Element (and any widget
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derived from it) provides, on its prototype, all methods of a jQuery
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`$('<div>')`. Chaining works too: If you have `var $d = $('<div>'), $e =
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Ox.Element();`, then `$d.appendTo($e)` returns `$d`, and `$e.append($d)`
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returns `$e`. If you type Ox.Element() in the console, you will get
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something like `[<div class="OxElement"></div>]`. Any widget's `0`
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property is an actual DOM element, and in case you ever need the
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jQuery-wrapped element — that's the widget's `$element` property.
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The purpose of the `OxMyBox` class is just to allow us to add CSS
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declarations in an external style sheet. In this case, `.css({float:
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'left'})` would do the same thing.
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*/
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.addClass('OxMyBox');
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/*
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The second part of the "constructor" function can be thought of as the
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"initializer", and contains everything needed to set up the "instance". In
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this case, we just define a minimum and maximum size and then set the
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widget's color and size.
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We could have used `var minSize` and `var maxSize` here, but by using `self`
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for private variables that we want to be accessible across all the widget's
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methods, we can be sure that inside such methods, any local `var` is
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actually local to the method.
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*/
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self.minSize = 1;
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self.maxSize = 256;
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setColor();
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setSize();
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/*
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Third, we declare the widget's private methods. These are just function
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declarations, hoisted to the top of the "constructor".
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*/
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function setColor() {
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that.css({
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backgroundColor: 'rgb(' + self.options.color.join(', ') + ')',
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});
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}
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function setSize() {
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/*
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Before setting the size, we make sure the value is between `minSize` and
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`maxSize`.
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*/
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self.options.size = self.options.size.map(function(value) {
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return Ox.limit(value, self.minSize, self.maxSize);
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});
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that.css({
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width: self.options.size[0] + 'px',
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height: self.options.size[1] + 'px'
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});
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}
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/*
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Next, we define the widgets public methods, as properties of `that`. (Note
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that unlike private methods, they are not hoisted.)
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*/
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that.displayText = function(text) {
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/*
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As there isn't much to do yet, this method just displays some text.
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Here, `.addClass('OxMyText')` is equivalent to `.css({padding: '4px'})`.
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*/
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that.empty();
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text && that.append($('<div>').addClass('OxMyText').html(text));
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/*
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Public methods should return `that`, for chaining.
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*/
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return that;
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};
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/*
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And finally, at the very end of the "constructor", we return `that`. And
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that's it.
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*/
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return that;
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};
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/*
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**InvertibleBox**
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*/
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/*
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Now we can "subclass" our Box. Let's build one that can have its color inverted.
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*/
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Ox.My.InvertibleBox = function(options, self) {
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self = self || {};
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/*
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We no longer inherit from Ox.Element, but from `Ox.My.Box`.
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We could have written
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<pre>
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var that = Ox.My.Box({}, self)
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.defaults({
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color: [128, 128, 128],
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inverted: false,
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size: [128, 128]
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})
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.options(options || ())
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.update({
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...
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})
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</pre>
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— but why repeat the defaults of `Ox.My.Box` if we can simply extend
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them. (Just like `options()` returns all options of a widget, `defaults()`
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returns all its defaults.)
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*/
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var that = Ox.My.Box({}, self);
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that.defaults(Ox.extend(that.defaults(), {
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inverted: false
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}))
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.options(options || {})
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/*
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Again, we add handlers that run when the widget's options are updated.
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The original handlers of `Ox.My.Box` will run next, so we just add the
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ones we need. We leave out `size`, so when the `size` option changes,
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we'll get the original behavior.
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*/
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.update({
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color: setColor,
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inverted: setColor
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})
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/*
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The same as `.css({cursor: 'pointer'})`.
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*/
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.addClass('OxMyInvertibleBox')
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/*
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Ox.Element and its descendants provide a number of public methods
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(`bindEvent`, `bindEventOnce`, `triggerEvent` and `unbindEvent`) that
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allow widgets to communicate via custom events. Here, we add a handler
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for Ox.Element's `doubleclick` event. If we just wanted to handle a
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`click` event, we could also use jQuery here:
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<pre>
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.on({
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click: function() {
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that.invert();
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}
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})
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</pre>
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*/
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.bindEvent({
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doubleclick: function() {
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that.invert();
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}
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});
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/*
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The idea is that our widget's inverted state is separate from its color. If
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the inverted option is set, then the color option stays the same, but has
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the inverse effect. This means that when initializing the widget, we have
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to call our custom `setColor` method if `self.options.inverted` is `true`.
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*/
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self.options.inverted && setColor();
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/*
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When `setColor` is invoked as an update handler, returning `false` signals
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that no other handler should run. Otherwise, the original handler of
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`Ox.My.Box` would run next, and revert any inversion we might have done
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here.
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*/
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function setColor() {
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that.css({backgroundColor: 'rgb(' + (
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self.options.inverted ? self.options.color.map(function(value) {
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return 255 - value;
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}) : self.options.color
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).join(', ') + ')'});
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return false;
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}
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/*
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The public `invert` method is added as a convenience for the users of our
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widget, so that when they want to toggle its inverted state, they don't have
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to write
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<pre>
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$widget.options({
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inverted: !$widget.options('inverted')
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});
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</pre>
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all the time.
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Also, we trigger an `invert` event, that anyone can bind to via
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<pre>
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$widget.bindEvent({
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invert: function() { ... }
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});
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</pre>
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*/
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that.invert = function() {
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that.options({inverted: !self.options.inverted});
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that.triggerEvent('invert');
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return that;
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};
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/*
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And again, we return `that`.
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*/
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return that;
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};
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/*
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**MetaBox**
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*/
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/*
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Now it's time for something more funky: A MetaBox — that is, a box of
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boxes.
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*/
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Ox.My.MetaBox = function(options, self) {
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/*
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This time, we inherit from `Ox.My.InvertibleBox`. The one thing that's
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different though is the `color` option: It is no longer a single value, but
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an array of array of values. That's how the boxes inside out MetaBox are
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specified. The following would create a grid of boxes with two rows and
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three columns:
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<pre>
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Ox.My.MetaBox({
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color: [
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[[255, 0, 0], [255, 255, 0], [0, 255, 0]],
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[[0, 255, 255], [0, 255, 0], [255, 0, 255]]
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]
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});
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</pre>
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*/
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self = self || {};
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var that = Ox.My.InvertibleBox({}, self)
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.options(options || {})
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.update({color: setColor});
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/*
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But we keep the default color of `Ox.My.InvertibleBox` (`[128, 128, 128]`)
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as our own default color, and only here check if the color option is a
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single RGB value. In that case, we convert it to an array of one row and one
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column. This way, whenever someone accidentally passes a single color value,
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our MetaBox can handle it.
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*/
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if (Ox.isNumber(self.options.color[0])) {
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self.options.color = [[self.options.color]];
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}
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/*
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`self.sizes` holds the width of each column and the height of each row.
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`self.options.color.length` is the number of rows,
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`self.options.color[0].length` the number of columns, and Ox.splitInt(a, b)
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"splits" an integer `a` into an array of `b` integers that sum up to `a`.
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(We don't want fractional pixel sizes.)
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*/
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self.sizes = [
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Ox.splitInt(self.options.size[0], self.options.color[0].length),
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Ox.splitInt(self.options.size[1], self.options.color.length)
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];
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/*
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`self.$boxes` are the actual boxes. We use `Ox.My.InvertibleBox`, but remove
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the `doubleclick` handlers, since our MetaBox already has one, being an
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InvertibleBox itself. (`unbindEvent(event)` removes all handlers,
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`unbindEvent(event, handler)` removes a specific one.) Then we simply append
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each box to the meta-box.
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*/
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self.$boxes = self.options.color.map(function(array, y) {
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return array.map(function(color, x) {
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return Ox.My.InvertibleBox({
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color: color,
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size: [self.sizes[0][x], self.sizes[1][y]]
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})
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.unbindEvent('doubleclick')
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.appendTo(that);
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});
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});
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/*
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To set the color of a meta-box means to set the color of each box.
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*/
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function setColor() {
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self.$boxes.forEach(function(array, y) {
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array.forEach(function($box, x) {
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$box.options({color: self.options.color[y][x]});
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});
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});
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}
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/*
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This is the rare case of a shared private method. Its purpose will become
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apparent a bit later. Otherwise, we could just have made a private function,
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or an anonymous function in the loop below.
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*/
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self.invertBox = function($box) {
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$box.invert();
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};
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/*
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Here, we override the public `invert` method of `Ox.My.InvertibleBox`. When
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inverting an `Ox.My.MetaBox`, we have to invert each of its boxes. (If we
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wanted to keep the original method around, we could store it as
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`that.superInvert` before.)
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*/
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that.invert = function() {
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self.$boxes.forEach(function(array) {
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array.forEach(self.invertBox);
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});
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that.triggerEvent('invert');
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return that;
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};
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/*
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And that's all it takes to make a meta-box.
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*/
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return that;
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};
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/*
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**PixelBox**
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*/
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/*
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The next widget is a peculiar type of meta-box. A PixelBox has only one color,
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but this color will be split up into a red box, a green box and a blue box.
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*/
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Ox.My.PixelBox = function(options, self) {
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self = self || {};
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/*
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The challenge here is that we want our PixelBox to be an instance of
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`Ox.My.MetaBox`, but with a `color` option like `Ox.My.Box`. So we have to
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parse the options ourselves, by first extending the defaults of `Ox.My.Box`
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and then transforming the single-value `color` option into a multi-value
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`color` option. Calling<br>
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`Ox.My.PixelBox().options('color')`<br>
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will now return<br>
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`[[[128, 0, 0], [0, 128, 0], [0, 0, 128]]]`.
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*/
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self.options = Ox.extend(Ox.My.Box().defaults(), options || {});
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self.options.color = getColor();
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/*
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Now we can pass `self.options` to `Ox.My.MetaBox`.
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*/
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var that = Ox.My.MetaBox(self.options, self)
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/*
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Again, we add a custom handler for `color` updates.
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*/
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.update({color: setColor});
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/*
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This is how a single RGB value gets split up into a red box, a green box and
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a blue box.
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*/
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function getColor(color) {
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return [[
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[self.options.color[0], 0, 0],
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[0, self.options.color[1], 0],
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[0, 0, self.options.color[2]]
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]];
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}
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/*
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When the `color` option gets updated to a new single value, we update it
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again, this time to multiple values, and return `false` to keep the MetaBox
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handler from running. We have updated `color`, so our handler will get
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called again, but now it does nothing, and the MetaBox handler will get
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invoked.
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*/
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function setColor() {
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if (Ox.isNumber(self.options.color[0])) {
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that.options({color: getColor()});
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return false;
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}
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}
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/*
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Inverting a PixelBox is different from inverting a MetaBox, since we only
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want to invert one color channel per box. This is where the shared private
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`invertBox` method of `Ox.My.MetaBox` comes into play. Since we share the
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same `self`, we can simply override it. (Alternatively, we could have added
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an `invertBox` option to `Ox.My.MetaBox`, but overriding a shared private
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method is much more elegant than cluttering the public API of
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`Ox.My.MetaBox` with such an option.)
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*/
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self.invertBox = function($box, x) {
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$box.options({
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color: $box.options('color').map(function(value, i) {
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return i == x ? 255 - value : value
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})
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});
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};
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/*
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And that's the PixelBox.
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*/
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return that;
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};
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/*
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**ImageBox**
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*/
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/*
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And finally — a meta-meta-box! An ImageBox takes an image and, for each
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pixel, displays a PixelBox.
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*/
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Ox.My.ImageBox = function(options, self) {
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self = self || {};
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/*
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Loading the image is asynchronous, but we want to display a box immediately.
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So we just subclass `Ox.My.Box`. Also, this seems to be a good use case for
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its `displayText` method.
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*/
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var that = Ox.My.Box({}, self).displayText('Loading...');
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/*
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It's not required to define empty defaults — omitting them would
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simply leave them undefined). Still, to add an explicit `null` default is a
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good practice, as it makes it obvious to any reader of our code that
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`Ox.My.ImageBox` expects an `image` option.
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*/
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that.defaults(Ox.extend(that.defaults(), {
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image: null
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}))
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.options(options || {});
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/*
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Ox.Image takes a URI and passes an image object to its callback function.
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*/
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self.options.image && Ox.Image(self.options.image, function(image) {
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var size = image.getSize();
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size = [size.width, size.height];
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/*
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Again, we have to compute the width of each column and the height of
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each row.
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*/
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self.sizes = size.map(function(value, index) {
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return Ox.splitInt(self.options.size[index], value);
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});
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/*
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Remove the 'Loading...' message.
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*/
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that.displayText();
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/*
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For each pixel ...
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*/
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self.$boxes = Ox.range(size[1]).map(function(y) {
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return Ox.range(size[0]).map(function(x) {
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/*
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... create a PixelBox ...
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*/
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return Ox.My.PixelBox({
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/*
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(`image.pixel` returns RGBA, so discard alpha)
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*/
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color: image.pixel(x, y).slice(0, 3),
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size: [self.sizes[0][x], self.sizes[1][y]]
|
|
})
|
|
/*
|
|
... remove its `doubleclick` handler ...
|
|
*/
|
|
.unbindEvent('doubleclick')
|
|
/*
|
|
... and append it to the ImageBox.
|
|
*/
|
|
.appendTo(that);
|
|
});
|
|
});
|
|
});
|
|
|
|
/*
|
|
We've inherited from `Ox.My.Box`, so we don't have an `invert` method yet.
|
|
This is how we can borrow the one from `Ox.My.MetaBox`. We're passing our
|
|
own `self`, so the `self.$boxes` that the `invert` method of `Ox.My.MetaBox`
|
|
operates on will be the PixelBoxes that we are assigning in the asynchronous
|
|
callback above. (This pattern is somewhat analogous to the
|
|
`someOtherObject.method.apply(this, args)` idiom that is common in
|
|
JavaScript.)
|
|
|
|
Note that we have to pass `self.options` too, otherwise our own
|
|
`self.options.size` would get overwritten by the MetaBox default size.
|
|
|
|
Passing `self` to `Ox.My.MetaBox` has another nice effect: the MetaBox will
|
|
add its own event handlers to it. So even though `Ox.My.ImageBox` is just an
|
|
`Ox.My.Box`, it has now inherited `doubleclick` handling from
|
|
`Ox.My.MetaBox`.
|
|
|
|
(Internally, `Ox.Element` stores event handlers in `self`. So what happens
|
|
is this: `self` gets passed all the way down from `Ox.My.ImageBox` to
|
|
`Ox.My.MetaBox` to `Ox.My.InvertibleBox` to `Ox.My.Box` to Ox.Element, and
|
|
when `Ox.My.InvertibleBox` defines its `doubleclick` handler, it ends up on
|
|
`self`. So when the Ox.Element that is actually in the DOM — the
|
|
`Ox.My.Box` that `Ox.My.ImageBox` inherits from, which shares the same
|
|
`self` — receives a `doubleclick`, there is now a handler for it.)
|
|
*/
|
|
that.invert = Ox.My.MetaBox(self.options, self).invert;
|
|
|
|
/*
|
|
And that's it.
|
|
*/
|
|
return that;
|
|
|
|
};
|
|
|
|
/*
|
|
**VideoBox**
|
|
*/
|
|
/*
|
|
This one is left as an exercise to the reader ;)
|
|
*/
|
|
Ox.My.VideoBox = function(options, self) {
|
|
|
|
};
|
|
|
|
/*
|
|
**Demo**
|
|
*/
|
|
/*
|
|
Load the Image and UI modules.
|
|
*/
|
|
Ox.load(['Image', 'UI'], function() {
|
|
/*
|
|
Pick a random color. Ox.rgb will convert HSL to RGB.
|
|
*/
|
|
var h = Ox.random(360), s = 1, l = 0.5;
|
|
/*
|
|
Create a global variable, so that we can play with our widgets in the
|
|
console.
|
|
*/
|
|
window.My = {};
|
|
/*
|
|
Since `Ox.My.Box` is a good multi-purpose container, we create one to
|
|
contain the first four boxes.
|
|
*/
|
|
My.$container = Ox.My.Box({
|
|
size: [256, 256]
|
|
})
|
|
.append(
|
|
My.$box = Ox.My.Box({
|
|
color: Ox.rgb(h, s, l)
|
|
}),
|
|
My.$invertibleBox = Ox.My.InvertibleBox({
|
|
color: Ox.rgb(h + 120, s, l)
|
|
}),
|
|
My.$metaBox = Ox.My.MetaBox({
|
|
color: Ox.range(2).map(function(y) {
|
|
return Ox.range(3).map(function(x) {
|
|
return Ox.rgb(h + x * 60 + y * 180, s, l);
|
|
});
|
|
})
|
|
}),
|
|
My.$pixelBox = Ox.My.PixelBox({
|
|
color: Ox.rgb(h + 120, s, l)
|
|
})
|
|
)
|
|
.appendTo(Ox.$body);
|
|
/*
|
|
The ImageBox is a bit larger.
|
|
*/
|
|
My.$imageBox = Ox.My.ImageBox({
|
|
image: 'png/pandora32.png',
|
|
size: [256, 256]
|
|
})
|
|
.appendTo(Ox.$body);
|
|
/*
|
|
As a last step, we add a handler to the `invert` event of each widgets. It
|
|
will display the widget name inside the `Ox.My.Box`.
|
|
*/
|
|
Ox.forEach(My, function($element, name) {
|
|
$element.bindEvent({
|
|
invert: function() {
|
|
My.$box.displayText(name[1].toUpperCase() + name.slice(2));
|
|
}
|
|
});
|
|
});
|
|
});
|