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 pandoc
26 You also need Node.js, but unfortunately the `node-js` package is not
27 available for Debian wheezy. You can either get it from
28 wheezy-backports or download the source from
29 http://nodejs.org/download/ and build it yourself. You need both Node
30 itself and its package manager NPM: `make install` puts them into
40 The code of the widget set is in four main layers, described here from
43 1. The core code, which manages the set of widget teams, default
44 options, authentication onto the Service Proxy, and the creation of
45 widgets from HTML elements.
46 This code is in `mkws-core.js`
48 2. The team code, which manages teams of widgets. This is responsible
49 for the collections of widgets that make up teams, event queues, and
50 handling search-and-retrieval events
51 This code is in `mkws-team.js`
53 3. The generic widget code, which handles the creation of widget
54 objects, parsing configuration attributes from their HTML elements,
55 and firing off automatic searches.
57 4. The code for individual widgets, which is specific to those
58 widgets. It often involves subscribing to events and responding to
59 them by setting the HTML of the widget element, but need not do
60 so. The code for many of the most important widgets is in
61 `mkws-widget-main.js`, but certain other widgets are defined in other
62 files beginning with the prefix `mkws-widget-`.
64 In addition to this code, there are several source files containing
67 * `mkws-filter.js` contains support routine implementing the
68 filter-set data structure, which contains information about which
69 filters (e.g. by target, or by facet) are in force.
71 * `mkws-handlebars.js` contains Handlebars helpers which can be used
72 by the HTML templates.
74 * `mkws-popup.js` defines a special widget for creating popup
75 windows. These may, but need not, contain other MKWS widgets,
76 forming a popup searching application.
78 The final component of the source code is the set of Handlebars
79 templates, in the `templates` directory, which are used to emit the
80 HTML of the various widgets' contents. These are compiled into the
81 file `mkws-templates.js`.
88 The primary method of communication between components of the widget
89 set -- specifically, between teams and their widgets -- is event
90 passing. Widgets subscribe to named events; when something relevant
91 happens (such as the reception of a message from metasearch
92 middleware), the event is published, along with the relevant data. All
93 widgets that susbcribed to the event are then notified, and can take
96 Different kinds of events have different data associated with
97 them. This data is passed when the event is published, and so is made
98 available to the subscribing code.
100 The possible events, and their associated data, are described
104 Defining new types of widget
105 ----------------------------
107 Development with MKWS consists primarily of defining new types of
108 widgets. This is done using exactly the same API as the the widgets
109 that come as part of the set: they have no privileged access.
111 You create a new widget type by calling the `mkws.registerWidgetType`
112 function, passing in the widget name and a function. The name is used
113 to recognise HTML elements as being widgets of this type -- for
114 example, if you register a `foo` widget, elements like
115 `<div class="mkws-foo">` will become widgets of this type.
117 The function promotes a bare widget object (which is created by the
118 core widget code and passed in as `this`) into a
119 widget of the appropriate type. MKWS doesn't use classes or explicit
120 prototypes: it just makes objects that have the necessary
121 behaviours. There are _no_ behaviours that Widgets are obliged to
122 provide: you can make a doesn't-do-anything-at-all widget if you like:
124 mkws.registerWidgetType('sluggard', function() {});
126 More commonly, widgets will subscribe to one or more events, so that
127 they're notified when something interesting happens. For example, the
128 `log` widget asks to be notified when a `log` event happens, and
129 appends the logged message to its node, as follows:
131 mkws.registerWidgetType('log', function() {
134 this.team.queue("log").subscribe(function(teamName, timestamp, message) {
135 $(that.node).append(teamName + ": " + timestamp + message + "<br/>");
139 This simple widget illustrates several important points:
141 * The base widget object (`this`) has several baked-in properties and
142 methods that are available to individual widgets. These include
143 `this.team` (the team that this widget is a part of) and `this.node`
144 (the DOM element of the widget). See below for a full list.
146 * The team object (`this.team`) also has baked-in properties and
147 methods. These include the `queue` function, which takes an event-name
148 as its argument. See below for a full list.
150 * You can add functionality to a widget by subscribing it to an
151 event's queue using `this.team.queue("EVENT").subscribe`. The
152 argument is a function which is called whenever the event is
155 * As with so much JavaScript programming, the value of the special
156 variable `this` is lost inside the `subscribe` callback function,
157 so it must be saved if it's to be used inside that callback
158 (typically as a local variable named `that`).
161 Widget specialisation (inheritance)
162 -----------------------------------
164 Many widgets are simple specialisations of existing widgets. For
165 example, the `images` widget is the same as the `records` widget
166 except that it defaults to using the `images` template for displaying
167 its result list. It's defined as follows:
169 mkws.registerWidgetType('images', function() {
170 mkws.promotionFunction('records').call(this);
171 if (!this.config.template) this.config.template = 'images';
174 Remember that when a promotion function is called, it's passed a base
175 widget object that's not specialised for any particular task. To make
176 a specialised widget, you first promote that base widget into the type
177 that you want to specialise from -- in this case, `Records` -- using
178 the promotion function that's been registered for that type.
180 Once this has been done, the specialisations can be introduced. In
181 this case, it's a very simple matter of changing the `template`
182 configuration setting to `'images'` unless it's already been given an
183 explicit value. (That would occur if the HTML used an element like
184 `<div class="mkws-images" template="my-images">` to use a customised
192 Widget properties and methods
193 -----------------------------
195 The following properties and methods exist in the bare widget object
196 that is passed into `registerWidgetType`'s callback function, and can
197 be used by the derived widget.
199 * `String this.type` --
200 A string containing the type of the widget (`search`,
203 * `Team this.team` --
204 The team object to which this widget belongs. The team has
205 several additional important properties and methods, described
208 * `DOMElement this.node` --
209 The DOM element of the widget. Most often used for inserting
210 HTML into the widget element.
212 * `Hash this.config` --
213 A table of configuration values for the widget. This table
214 inherits missing values from the team's configuration, which
215 in turn inherits from the top-level MKWS configuration, which
216 inherits from the default configuration. Instances of widgets
217 in HTML can set configuration items as HTML attributes: for
218 example, the HTML element
219 `<div class="mkwsRecords" maxrecs="10">`
220 creates a widget for which `this.config.maxrecs` is set to 10.
222 * `String this.toString()` --
223 A function returning a string that briefly names this
224 widget. Can be useful in logging.
226 * `Void this.log(string)` --
227 A function to log a string for debugging purposes. The string
228 is written on the browser console, and also published to any
229 subcribers to the `log` event.
231 * `String this.value()` --
232 A function returning the value of the widget's HTML element.
234 * `VOID autosearch()` --
235 Registers that this kind of widget is one that requires an
236 automatic search to be run for it if an `autosearch` attribute
237 is provided on the HTML element. This is appropriate for
238 widgets such as `Records` and `Facet` that display some part
241 * `subwidget(type, overrides, defaults)` --
242 Returns the HTML of a subwidget of the specified type, which
243 can then be inserted into the widget using the
244 `this.node.html` function. The subwidget is given the same
245 attributes at the parent widget that invokes this function,
246 except where overrides are passed in. If defaults are also
247 provided, then these are used when the parent widget provides
248 no values. Both the `overrides` and `defaults` arguments are
249 hashes: the latter is optional. This can be used to assemble
250 compound widgets containing several subwidgets.
252 In addition to these properties and methods of the bare widget object,
253 some kinds of specific widget add other properties of their own. For
254 example, the `builder` widget uses a `callback` property as the
255 function that it use to publish the widget definition that it
256 constructs. This defaults to the builtin function `alert`, but can be
257 overridden by derived widgets such as `console-builder`.
263 Since the team object is supposed to be opaque to widgets, all access
264 is via the following API methods rather than direct access to
267 * `String team.name()`
268 * `Bool team.submitted()`
269 * `Num team.perpage()`
270 * `Num team.totalRecordCount()`
271 * `Num team.currentPage();`
272 * `String team.currentRecordId()`
273 * `String team.currentRecordData()`
275 These are all simple accessor functions that provide the ability to
276 read properties of the team. `submitted` is initially false, then
277 becomes true when the first search is submitted (manually or
280 * `Array team.filters()` --
281 Another accessor function, providing access to the array of
282 prevailing filters (which narrow the search results by means
283 of Pazpar2 filters and limits). This is really too complicated
284 an object for the widgets to be given access to, but it's
285 convenient to do it this way. If you have a reason for using
286 this, see the `Navi` widget, which is the only place it's used.
288 * `Bool team.targetFiltered(targetId)` --
289 Indicates whether the specified target has been filtered by
290 selection as a facet. This is used only by the `Facet` widget,
291 and there is probably no reason for you to use it.
293 * `Hash team.config()` --
294 Access to the team's configuration settings. There is
295 rarely a need to use this: the settings that haven't
296 been overridden are accessible via `this.config`.
298 * `Void team.set_sortOrder(string)`, `Void team.set_perpage(number)` --
299 "Setter" functions for the team's `sortOrder` and `perpage`
300 functions. Unlikely to be needed outside of the `Sort` and
303 * `Queue team.queue(eventName)` --
304 Returns the queue associated with the named event: this can be
305 used to subscribe to the event (or more rarely to publish
306 it). See [the section on events, below](#events).
308 * `Void team.newSearch(widget, query, sortOrder, maxrecs, perpage, limit, targets, targetfilter)` --
309 Starts a new search with the specified parameters, taking
310 settings from the nominated widget's configuration when not
311 specified explicitly. All but the query may be omitted. The
312 meanings of the parameters are those of the same-named
314 settings](mkws-manual.html#configuration-settings) described
315 in the user's manual.
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:
347 * `authenticated` (authName, realm) --
348 When authentication is completed successfully, this event is
349 published to _all_ teams. Two parameters are passed: the
350 human-readable name of the library that has been authenticated
351 onto, and the correponding machine-readable library ID.
354 Published to _all_ teams when they are ready to search. No
355 parameters are passed. This event is used to implement
356 automatic searching, and should probably not be used by
360 Published to a team when a `stat` response is reveived from
361 Pazpar2. The data from the response is passed as a parameter.
363 * `firstrecords` (hitcount) --
364 Published to a team when the first set of records is found by
365 a search. The number of records found (so far) is passed as
368 * `complete` (hitcount) --
369 Published to a team when a search is complete, and no more
370 records will be found (i.e. all targets have either responded
371 or failed with an error). The final number of records found is
372 passed as the parameter.
374 * `targets` (data) --
375 Published to a team when a `bytarget` response is reveived from
376 Pazpar2. The data from the response is passed as a parameter.
379 Published to a team when a `term` response is reveived from
380 Pazpar2. The data from the response is passed as a parameter.
383 Published to a team when a `show` response is reveived from
384 Pazpar2. The data from the response is passed as a
385 parameter. This event is used to update the pager, showing how
386 many records have been found, which page is being displayed,
389 * `records` (data) --
390 Also published to a team when a `show` response is reveived
391 from Pazpar2. The data from the response is passed as a
392 parameter. This event is used to update the displayed records.
395 Published to a team when a `record` response is reveived from
396 Pazpar2 (i.e. the full data for a single record). The data
397 from the response is passed as a parameter.
400 Published to a team when a new search is about to be
401 submitted. This is a signal that the navigation area, showing
402 which filters are in effect, should be updated. No parameter
403 is passed: the event handler should consult `team.filters` to
404 see what the prevailing set is.
406 * `log` (teamName, timestamp, message) --
407 Published to a team when a message is about to be logged to
408 the console for debugging. Three arguments are passed: the
409 name of the team that generated the log message, a timestamp
410 string, and the message itself. Note that this event is _not_
411 published when the widget-set core code generates a log
412 message -- only when a team or a widget does.
416 Copyright (C) 2013-2014 Index Data ApS. <http://indexdata.com>