1 % The MasterKey Widget Set developer's guide
9 This manual is for people who want to build the widget set from
10 source, develop the widget set's core code, or (more likely) create
11 their own widgets as extensions to the main set.
13 Those who want to use existing widgets should read
14 [The MKWS manual: embedded metasearching with the MasterKey Widget
15 Set](mkws-manual.html) instead.
18 Required development tools
19 ==========================
21 If you are building the widget set, you will need the following Debian
22 packages (or their equivalents on your operating system):
24 $ sudo apt-get install curl git make unzip apache2 \
25 pandoc yui-compressor libbsd-resource-perl
27 You also need Node.js, but unfortunately the `node-js` package is not
28 available for Debian wheezy. You can either get it from
29 wheezy-backports or download the source from
30 http://nodejs.org/download/ and build it yourself. You need both Node
31 itself and its package manager NPM: `make install` puts them into
41 The code of the widget set is in four main layers, described here from
44 1. The core code, which manages the set of widget teams, default
45 options, authentication onto the Service Proxy, and the creation of
46 widgets from HTML elements.
47 This code is in `mkws-core.js`
49 2. The team code, which manages teams of widgets. This is responsible
50 for the collections of widgets that make up teams, event queues, and
51 handling search-and-retrieval events
52 This code is in `mkws-team.js`
54 3. The generic widget code, which handles the creation of widget
55 objects, parsing configuration attributes from their HTML elements,
56 and firing off automatic searches.
58 4. The code for individual widgets, which is specific to those
59 widgets. It often involves subscribing to events and responding to
60 them by setting the HTML of the widget element, but need not do
61 so. The code for many of the most important widgets is in
62 `mkws-widget-main.js`, but certain other widgets are defined in other
63 files beginning with the prefix `mkws-widget-`.
65 In addition to this code, there are several source files containing
68 * `mkws-filter.js` contains support routine implementing the
69 filter-set data structure, which contains information about which
70 filters (e.g. by target, or by facet) are in force.
72 * `mkws-handlebars.js` contains Handlebars helpers which can be used
73 by the HTML templates.
75 * `mkws-popup.js` defines a special widget for creating popup
76 windows. These may, but need not, contain other MKWS widgets,
77 forming a popup searching application.
79 The final component of the source code is the set of Handlebars
80 templates, in the `templates` directory, which are used to emit the
81 HTML of the various widgets' contents. These are compiled into the
82 file `mkws-templates.js`.
89 The primary method of communication between components of the widget
90 set -- specifically, between teams and their widgets -- is event
91 passing. Widgets subscribe to named events; when something relevant
92 happens (such as the reception of a message from metasearch
93 middleware), the event is published, along with the relevant data. All
94 widgets that susbcribed to the event are then notified, and can take
97 Different kinds of events have different data associated with
98 them. This data is passed when the event is published, and so is made
99 available to the subscribing code.
101 The possible events, and their associated data, are described
105 Defining new types of widget
106 ----------------------------
108 Development with MKWS consists primarily of defining new types of
109 widgets. This is done using exactly the same API as the the widgets
110 that come as part of the set: they have no privileged access.
112 You create a new widget type by calling the `mkws.registerWidgetType`
113 function, passing in the widget name and a function. The name is used
114 to recognise HTML elements as being widgets of this type -- for
115 example, if you register a `foo` widget, elements like
116 `<div class="mkws-foo">` will become widgets of this type.
118 The function promotes a bare widget object (which is created by the
119 core widget code and passed in as `this`) into a
120 widget of the appropriate type. MKWS doesn't use classes or explicit
121 prototypes: it just makes objects that have the necessary
122 behaviours. There are _no_ behaviours that Widgets are obliged to
123 provide: you can make a doesn't-do-anything-at-all widget if you like:
125 mkws.registerWidgetType('sluggard', function() {});
127 More commonly, widgets will subscribe to one or more events, so that
128 they're notified when something interesting happens. For example, the
129 `log` widget asks to be notified when a `log` event happens, and
130 appends the logged message to its node, as follows:
132 mkws.registerWidgetType('log', function() {
135 this.team.queue("log").subscribe(function(teamName, timestamp, message) {
136 $(that.node).append(teamName + ": " + timestamp + message + "<br/>");
140 This simple widget illustrates several important points:
142 * The base widget object (`this`) has several baked-in properties and
143 methods that are available to individual widgets. These include
144 `this.team` (the team that this widget is a part of) and `this.node`
145 (the DOM element of the widget). See below for a full list.
147 * The team object (`this.team`) also has baked-in properties and
148 methods. These include the `queue` function, which takes an event-name
149 as its argument. See below for a full list.
151 * You can add functionality to a widget by subscribing it to an
152 event's queue using `this.team.queue("EVENT").subscribe`. The
153 argument is a function which is called whenever the event is
154 published. The arguments to the event-callback function are
155 different for different events.
157 * As with so much JavaScript programming, the value of the special
158 variable `this` is lost inside the `subscribe` callback function,
159 so it must be saved if it's to be used inside that callback
160 (typically as a local variable named `that`).
163 Widget specialisation (inheritance)
164 -----------------------------------
166 Many widgets are simple specialisations of existing widgets. For
167 example, the `images` widget is the same as the `records` widget
168 except that it defaults to using the `images` template for displaying
169 its result list. It's defined as follows:
171 mkws.registerWidgetType('images', function() {
172 mkws.promotionFunction('records').call(this);
173 if (!this.config.template) this.config.template = 'images';
176 Remember that when a promotion function is called, it's passed a base
177 widget object that's not specialised for any particular task. To make
178 a specialised widget, you first promote that base widget into the type
179 that you want to specialise from -- in this case, `Records` -- using
180 the promotion function that's been registered for that type.
182 Once this has been done, the specialisations can be introduced. In
183 this case, it's a very simple matter of changing the `template`
184 configuration setting to `'images'` unless it's already been given an
185 explicit value. (That would occur if the HTML used an element like
186 `<div class="mkws-images" template="my-images">` to use a customised
194 Widget properties and methods
195 -----------------------------
197 The following properties and methods exist in the bare widget object
198 that is passed into `registerWidgetType`'s callback function, and can
199 be used by the derived widget.
201 * `String this.type` --
202 A string containing the type of the widget (`search`,
205 * `Team this.team` --
206 The team object to which this widget belongs. The team has
207 several additional important properties and methods, described
210 * `DOMElement this.node` --
211 The DOM element of the widget. Most often used for inserting
212 HTML into the widget element.
214 * `Hash this.config` --
215 A table of configuration values for the widget. This table
216 inherits missing values from the team's configuration, which
217 in turn inherits from the top-level MKWS configuration, which
218 inherits from the default configuration. Instances of widgets
219 in HTML can set configuration items as HTML attributes: for
220 example, the HTML element
221 `<div class="mkwsRecords" maxrecs="10">`
222 creates a widget for which `this.config.maxrecs` is set to 10.
224 * `String this.toString()` --
225 A function returning a string that briefly names this
226 widget. Can be useful in logging.
228 * `Void this.log(string)` --
229 A function to log a string for debugging purposes. The string
230 is written on the browser console, and also published to any
231 subcribers to the `log` event.
233 * `String this.value()` --
234 A function returning the value of the widget's HTML element.
236 * `VOID autosearch()` --
237 Registers that this kind of widget is one that requires an
238 automatic search to be run for it if an `autosearch` attribute
239 is provided on the HTML element. This is appropriate for
240 widgets such as `Records` and `Facet` that display some part
243 * `subwidget(type, overrides, defaults)` --
244 Returns the HTML of a subwidget of the specified type, which
245 can then be inserted into the widget using the
246 `this.node.html` function. The subwidget is given the same
247 attributes at the parent widget that invokes this function,
248 except where overrides are passed in. If defaults are also
249 provided, then these are used when the parent widget provides
250 no values. Both the `overrides` and `defaults` arguments are
251 hashes: the latter is optional. This can be used to assemble
252 compound widgets containing several subwidgets.
254 In addition to these properties and methods of the bare widget object,
255 some kinds of specific widget add other properties of their own. For
256 example, the `builder` widget uses a `callback` property as the
257 function that it use to publish the widget definition that it
258 constructs. This defaults to the builtin function `alert`, but can be
259 overridden by derived widgets such as `console-builder`.
265 Since the team object is supposed to be opaque to widgets, all access
266 is via the following API methods rather than direct access to
269 * `String team.name()`
270 * `Bool team.submitted()`
271 * `Num team.perpage()`
272 * `Num team.totalRecordCount()`
273 * `Num team.currentPage();`
274 * `String team.currentRecordId()`
275 * `String team.currentRecordData()`
277 These are all simple accessor functions that provide the ability to
278 read properties of the team. `submitted` is initially false, then
279 becomes true when the first search is submitted (manually or
282 * `Array team.filters()` --
283 Another accessor function, providing access to the array of
284 prevailing filters (which narrow the search results by means
285 of Pazpar2 filters and limits). This is really too complicated
286 an object for the widgets to be given access to, but it's
287 convenient to do it this way. If you have a reason for using
288 this, see the `Navi` widget, which is the only place it's used.
290 * `Bool team.targetFiltered(targetId)` --
291 Indicates whether the specified target has been filtered by
292 selection as a facet. This is used only by the `Facet` widget,
293 and there is probably no reason for you to use it.
295 * `Hash team.config()` --
296 Access to the team's configuration settings. There is
297 rarely a need to use this: the settings that haven't
298 been overridden are accessible via `this.config`.
300 * `Void team.set_sortOrder(string)`, `Void team.set_perpage(number)` --
301 "Setter" functions for the team's `sortOrder` and `perpage`
302 functions. Unlikely to be needed outside of the `Sort` and
305 * `Queue team.queue(eventName)` --
306 Returns the queue associated with the named event: this can be
307 used to subscribe to the event (or more rarely to publish
308 it). See [the section on events, below](#events).
310 * `Void team.newSearch(query, sortOrder, maxrecs, perpage, limit, targets, targetfilter)` --
311 Starts a new search with the specified parameters. All but the
312 query may be omitted, in which case the prevailing defaults
313 are used. The meanings of the parameters are those of the
314 same-named [configuration
315 settings](mkws-manual.html#configuration-settings) described in
318 * `Void team.reShow()` --
319 Using the existing search, re-shows the result records after a
320 change in sort-order, per-page count, etc.
322 * `String team.recordElementId(recordId)` --
323 Utility function for converting a record identifer (returned
324 from Pazpar2) into a version suitable for use as an HTML
327 * `String team.renderDetails(recordData)` --
328 Utility function returns an HTML rendering of the record
329 represented by the specified data.
331 * `Template team.loadTemplate(templateName)` --
332 Loads (or retrieves from cache) the named Handlebars template,
333 and returns it in a form that can be invoked as a function,
336 Some of these methods are arguably too low-level and should not be
337 exposed; others should probably be widget-level methods. The present
338 infelicities should be fixed in future releases, but backwards
339 compatibility with the present API will be maintained for at least one
340 complete major-release cycle.
346 FIXME: list of events that can be usefully subscribed to.
351 Copyright (C) 2013-2014 Index Data ApS. <http://indexdata.com>