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
156 * As with so much JavaScript programming, the value of the special
157 variable `this` is lost inside the `subscribe` callback function,
158 so it must be saved if it's to be used inside that callback
159 (typically as a local variable named `that`).
162 Widget specialisation (inheritance)
163 -----------------------------------
165 Many widgets are simple specialisations of existing widgets. For
166 example, the `images` widget is the same as the `records` widget
167 except that it defaults to using the `images` template for displaying
168 its result list. It's defined as follows:
170 mkws.registerWidgetType('images', function() {
171 mkws.promotionFunction('records').call(this);
172 if (!this.config.template) this.config.template = 'images';
175 Remember that when a promotion function is called, it's passed a base
176 widget object that's not specialised for any particular task. To make
177 a specialised widget, you first promote that base widget into the type
178 that you want to specialise from -- in this case, `Records` -- using
179 the promotion function that's been registered for that type.
181 Once this has been done, the specialisations can be introduced. In
182 this case, it's a very simple matter of changing the `template`
183 configuration setting to `'images'` unless it's already been given an
184 explicit value. (That would occur if the HTML used an element like
185 `<div class="mkws-images" template="my-images">` to use a customised
193 Widget properties and methods
194 -----------------------------
196 The following properties and methods exist in the bare widget object
197 that is passed into `registerWidgetType`'s callback function, and can
198 be used by the derived widget.
200 * `String this.type` --
201 A string containing the type of the widget (`search`,
204 * `Team this.team` --
205 The team object to which this widget belongs. The team has
206 several additional important properties and methods, described
209 * `DOMElement this.node` --
210 The DOM element of the widget. Most often used for inserting
211 HTML into the widget element.
213 * `Hash this.config` --
214 A table of configuration values for the widget. This table
215 inherits missing values from the team's configuration, which
216 in turn inherits from the top-level MKWS configuration, which
217 inherits from the default configuration. Instances of widgets
218 in HTML can set configuration items as HTML attributes: for
219 example, the HTML element
220 `<div class="mkwsRecords" maxrecs="10">`
221 creates a widget for which `this.config.maxrecs` is set to 10.
223 * `String this.toString()` --
224 A function returning a string that briefly names this
225 widget. Can be useful in logging.
227 * `Void this.log(string)` --
228 A function to log a string for debugging purposes. The string
229 is written on the browser console, and also published to any
230 subcribers to the `log` event.
232 * `String this.value()` --
233 A function returning the value of the widget's HTML element.
235 * `VOID autosearch()` --
236 Registers that this kind of widget is one that requires an
237 automatic search to be run for it if an `autosearch` attribute
238 is provided on the HTML element. This is appropriate for
239 widgets such as `Records` and `Facet` that display some part
242 * `subwidget(type, overrides, defaults)` --
243 Returns the HTML of a subwidget of the specified type, which
244 can then be inserted into the widget using the
245 `this.node.html` function. The subwidget is given the same
246 attributes at the parent widget that invokes this function,
247 except where overrides are passed in. If defaults are also
248 provided, then these are used when the parent widget provides
249 no values. Both the `overrides` and `defaults` arguments are
250 hashes: the latter is optional. This can be used to assemble
251 compound widgets containing several subwidgets.
253 In addition to these properties and methods of the bare widget object,
254 some kinds of specific widget add other properties of their own. For
255 example, the `builder` widget uses a `callback` property as the
256 function that it use to publish the widget definition that it
257 constructs. This defaults to the builtin function `alert`, but can be
258 overridden by derived widgets such as `console-builder`.
264 Since the team object is supposed to be opaque to widgets, all access
265 is via the following API methods rather than direct access to
268 * `String team.name()`
269 * `Bool team.submitted()`
270 * `Num team.perpage()`
271 * `Num team.totalRecordCount()`
272 * `Num team.currentPage();`
273 * `String team.currentRecordId()`
274 * `String team.currentRecordData()`
276 These are all simple accessor functions that provide the ability to
277 read properties of the team. `submitted` is initially false, then
278 becomes true when the first search is submitted (manually or
281 * `Array team.filters()` --
282 Another accessor function, providing access to the array of
283 prevailing filters (which narrow the search results by means
284 of Pazpar2 filters and limits). This is really too complicated
285 an object for the widgets to be given access to, but it's
286 convenient to do it this way. If you have a reason for using
287 this, see the `Navi` widget, which is the only place it's used.
289 * `Bool team.targetFiltered(targetId)` --
290 Indicates whether the specified target has been filtered by
291 selection as a facet. This is used only by the `Facet` widget,
292 and there is probably no reason for you to use it.
294 * `Hash team.config()` --
295 Access to the team's configuration settings. There is
296 rarely a need to use this: the settings that haven't
297 been overridden are accessible via `this.config`.
299 * `Void team.set_sortOrder(string)`, `Void team.set_perpage(number)` --
300 "Setter" functions for the team's `sortOrder` and `perpage`
301 functions. Unlikely to be needed outside of the `Sort` and
304 * `Queue team.queue(eventName)` --
305 Returns the queue associated with the named event: this can be
306 used to subscribe to the event (or more rarely to publish
307 it). See [the section on events, below](#events).
309 * `Void team.newSearch(query, sortOrder, maxrecs, perpage, limit, targets, targetfilter)` --
310 Starts a new search with the specified parameters. All but the
311 query may be omitted, in which case the prevailing defaults
312 are used. The meanings of the parameters are those of the
313 same-named [configuration
314 settings](mkws-manual.html#configuration-settings) described in
317 * `Void team.reShow()` --
318 Using the existing search, re-shows the result records after a
319 change in sort-order, per-page count, etc.
321 * `String team.recordElementId(recordId)` --
322 Utility function for converting a record identifer (returned
323 from Pazpar2) into a version suitable for use as an HTML
326 * `String team.renderDetails(recordData)` --
327 Utility function returns an HTML rendering of the record
328 represented by the specified data.
330 * `Template team.loadTemplate(templateName)` --
331 Loads (or retrieves from cache) the named Handlebars template,
332 and returns it in a form that can be invoked as a function,
335 Some of these methods are arguably too low-level and should not be
336 exposed; others should probably be widget-level methods. The present
337 infelicities should be fixed in future releases, but backwards
338 compatibility with the present API will be maintained for at least one
339 complete major-release cycle.
345 The following events are generated by the widget-set code:
349 authenticated(authName, realm)
351 log(m_teamName, timestamp, s)
354 firstrecords(hitcount)
360 navi -- consult team.filters.
366 Copyright (C) 2013-2014 Index Data ApS. <http://indexdata.com>