1 % The MasterKey Widget Set developer's guide
6 Required development tools
7 ==========================
9 If you are building the widget set, as opposed to just using it, you
10 will need the following Debian packages (or their equivalents on your
13 $ sudo apt-get install curl git pandoc yui-compressor libbsd-resource-perl
15 You also need Node.js, but unfortunately the `node-js` package is not
16 available for Debian wheezy. You can either get it from
17 wheezy-backports or download the source from
18 http://nodejs.org/download/ and build it yourself. You need both Node
19 itself and its package manager NPM: `make install` puts them into
22 To compile the default templates you'll need to install the stable
23 version of Handlebars. Currently it's at 2.0.0 and available by npm:
25 $ npm install handlebars@2.0.0 -g
34 Development with MKWS consists primarily of defining new types of
35 widgets. These can interact with the core functionality is several
38 You create a new widget type by calling the `mkws.registerWidgetType`
39 function, passing in the widget name and a function. The name is used
40 to recognise HTML elements as being widgets of this type -- for
41 example, if you register a `Foo` widget, elements like
42 `<div class="mkwsFoo">` will be widgets of this type.
44 The function promotes a bare widget object (passed as `this`) into a
45 widget of the appropriate type. MKWS doesn't use classes or explicit
46 prototypes: it just makes objects that have the necessary
47 behaviours. There are _no_ behaviours that Widgets are obliged to
48 provide: you can make a doesn't-do-anything-at-all widget if you like:
50 mkws.registerWidgetType('Sluggard', function() {});
52 More commonly, widgets will subscribe to one or more events, so that
53 they're notified when something interesting happens. For example, the
54 `Log` widget asks to be notified when a `log` event happens, and
55 appends the logged message to its node, as follows:
57 mkws.registerWidgetType('Log', function() {
60 this.team.queue("log").subscribe(function(teamName, timestamp, message) {
61 $(that.node).append(teamName + ": " + timestamp + message + "<br/>");
65 This simple widget illustrates several important points:
67 * The base widget object (`this`) has several baked-in properties and
68 methods that are available to individual widgets. These include
69 `this.team` (the team that this widget is a part of) and `this.node`
70 (the DOM element of the widget). See below for a full list.
72 * The team object (`this.team`) also has baked-in properties and
73 methods. These include the `queue` function, which takes an event-name
74 as its argument. See below for a full list.
76 * You can add functionality to a widget by subscribing it to an
77 event's queue using `this.team.queue("EVENT").subscribe`. The
78 argument is a function which is called whenever the event is
79 published. The arguments to the function are different for different
82 * As with so much JavaScript programming, the value of the special
83 variable `this` is lost inside the `subscribez` callback function,
84 so it must be saved if it's to be used inside that callback
85 (typically as a local variable named `that`).
88 Widget specialisation (inheritance)
89 -----------------------------------
91 Many widgets are simple specialisations of existing widgets. For
92 example, the `Record` widget is the same as the `Records` widget
93 except that it defaults to displaying a single record. It's defined as
96 mkws.registerWidgetType('Record', function() {
97 mkws.promotionFunction('Records').call(this);
98 if (!this.config.maxrecs) this.config.maxrecs = 1;
101 Remember that when a promotion function is called, it's passed a base
102 widget object that's not specialised for any particular task. To make
103 a specialised widget, you first promote that base widget into the type
104 that you want to specialise from -- in this case, `Records` -- using
105 the promotion function that's been registered for that type.
107 Once this has been done, the specialisations can be introduced. In
108 this case, it's a very simple matter of changing the `maxrecs`
109 configuration setting to 1 unless it's already been given an explicit
110 value. (That would occur if the HTML used an element like `<div
111 class="mkwsRecord" maxrecs="2">`, though it's not obvious why anyone
119 Widget properties and methods
120 -----------------------------
122 The following properties and methods exist in the bare widget object
123 that is passed into `registerWidgetType`'s callback function, and can
124 be used by the derived widget.
126 * `String this.type` --
127 A string containing the type of the widget.
129 * `Team this.team` --
130 The team object to which this widget belongs. The team has
131 several additional important properties and methods, described
134 * `DOMElement this.node` --
135 The DOM element of the widget
137 * `Hash this.config` --
138 A table of configuration values for the widget. This table
139 inherits missing values from the team's configuration, which
140 in turn inherits from the top-level MKWS configuration, which
141 inherits from the default configuration. Instances of widgets
142 in HTML can set configuration items as HTML attributes: for
143 example, the HTML element
144 `<div class="mkwsRecords" maxrecs="10">`.
145 creates a widget for which `this.config.maxrecs` is set to 10.
147 * `String this.toString()` --
148 A function returning a string that briefly names this
149 widget. Can be useful in logging.
151 * `Void this.log(string)` --
152 A function to log a string for debugging purposes. The string
153 is written on the browser console, and also published to any
154 subcribers to the `log` event.
156 * `String this.value()` --
157 A function returning the value of the widget's HTML element.
159 * `VOID autosearch()` --
160 Registers that this kind of widget is one that requires an
161 automatic search to be run for it if an `autosearch` attribute
162 is provided on the HTML element. This is appropriate for
163 widgets such as `Records` and `Facet` that display some part
166 * `VOID hideWhenNarrow()` --
167 Registers that this widget should hide itself when the page
168 becomes "narrow" -- that is, fewer pixels in width that the
169 threshhold value specified by the top-level configuration item
170 `responsive_design_width`. Should be used for "unimportant"
171 widgets that can be omitted from the mobile version of a site.
174 TODO: either document this or remove it from the API.
176 * `subwidget(type, overrides, defaults)` --
177 Returns the HTML of a subwidget of the specified type, which
178 can then be inserted into the widget using the
179 `this.node.html` function. The subwidget is given the same
180 attributes at the parent widget that invokes this function,
181 except where overrides are passed in. If defaults are also
182 provided, then these are used when the parent widget provides
183 no values. Both the `overrides` and `defaults` arguments are
184 hashes: the latter is optional.
186 See for example the `Credo` widget defined in the example
187 area's `mkws-widget-credo.js` file. This uses several
188 invocations of `subwidget` to create a complex compound widget
189 with numerous text, facet and image panes. TODO: rename this
190 widget and everything related to it.
192 In addition to these properties and methods of the bare widget object,
193 some kinds of specific widget add other properties of their own. For
194 example, the `Builder` widget uses a `callback` property as the
195 function that it use to publish the widget definition that it
196 constructs. This defaults to the builtin function `alert`, but can be
197 overridden by derived widgets such as `ConsoleBuilder`.
203 Since the team object is supposed to be opaque to widgets, all access
204 is via the following API methods rather than direct access to
207 * `String team.name()`
208 * `Bool team.submitted()`
209 * `Num team.perpage()`
210 * `Num team.totalRecordCount()`
211 * `Num team.currentPage();`
212 * `String team.currentRecordId()`
213 * `String team.currentRecordData()`
215 These are all simple accessor functions that provide the ability to
216 read properties of the team.
218 * `Array team.filters()` --
219 Another accessor function, providing access to the array of
220 prevailing filters (which narrow the search results by means
221 of Pazpar2 filters and limits). This is really too complicated
222 an object for the widgets to be given access to, but it's
223 convenient to do it this way. If you must insist on using
224 this, see the `Navi` widget, which is the only place it's used.
226 * `Bool team.targetFiltered(targetId)` --
227 Indicates whether the specified target has been filtered by
228 selection as a facet. This is used only by the `Facet` widget,
229 and there is probably no reason for you to use it.
231 * `Hash team.config()` --
232 Access to the team's configuration settings. There is almost
233 certainly no reason to use this: the settings that haven't
234 been overridden are accessible via `this.config`.
236 * `Void team.set_sortOrder(string)`, `Void team.set_perpage(number)` --
237 "Setter" functions for the team's sortOrder and perpage
238 functions. Unlikely to be needed outside of the `Sort` and
241 * `Queue team.queue(eventName)` --
242 Returns the queue associated with the named event: this can be
243 used to subscribe to the event (or more rarely to publish it).
245 * `Void team.newSearch(query, sortOrder, maxrecs, perpage, limit, targets, targetfilter)` --
246 Starts a new search with the specified parameters. All but the
247 query may be omitted, in which case the prevailing defaults
250 * `Void team.reShow()` --
251 Using the existing search, re-shows the result records after a
252 change in sort-order, per-page count, etc.
254 * `String team.recordElementId(recordId)` --
255 Utility function for converting a record identifer (returned
256 from Pazpar2) into a version suitable for use as an HTML
259 * `String team.renderDetails(recordData)` --
260 Utility function returns an HTML rendering of the record
261 represented by the specified data.
263 * `Template team.loadTemplate(templateName)` --
264 Loads (or retrieves from cache) the named Handlebars template,
265 and returns it in a form that can be invoked as a function,
268 Some of these methods either (A) are really too low-level and should
269 not be exposed, or (B) should be widget-level methods. The present
270 infelicities reflect the fact that some code that rightly belongs in
271 widgets is still in the team. When we finish migrating it, the widget
272 API should get simpler.
278 TODO: list of events that can be usefully subscribed to.
283 Copyright (C) 2013-2014 by Index Data ApS, <http://www.indexdata.com>