1 % The MasterKey Widget Set developer's guide
12 Development with MKWS consists primarily of defining new types of
13 widgets. These can interact with the core functionality is several
16 You create a new widget type by calling the `mkws.registerWidgetType`
17 function, passing in the widget name and a function. The name is used
18 to recognise HTML elements as being widgets of this type -- for
19 example, if you register a `Foo` widget, elements like
20 `<div class="mkwsFoo">` will be widgets of this type.
22 The function promotes a bare widget object (passed as `this`) into a
23 widget of the appropriate type. MKWS doesn't use classes or explicit
24 prototypes: it just makes objects that have the necessary
25 behaviours. There are _no_ behaviours that Widgets are obliged to
26 provide: you can make a doesn't-do-anything-at-all widget if you like:
28 mkws.registerWidgetType('Sluggard', function() {});
30 More commonly, widgets will subscribe to one or more events, so that
31 they're notified when something interesting happens. For example, the
32 `Log` widget asks to be notified when a `log` event happens, and
33 appends the logged message to its node, as follows:
35 mkws.registerWidgetType('Log', function() {
38 this.team.queue("log").subscribe(function(teamName, timestamp, message) {
39 $(that.node).append(teamName + ": " + timestamp + message + "<br/>");
43 This simple widget illustrates several important points:
45 * The base widget object (`this`) has several baked-in properties and
46 methods that are available to individual widgets. These include
47 `this.team` (the team that this widget is a part of) and `this.node`
48 (the DOM element of the widget). See below for a full list.
50 * The team object (`this.team`) also has baked-in properties and
51 methods. These include the `queue` function, which takes an event-name
52 as its argument. See below for a full list.
54 * You can add functionality to a widget by subscribing it to an
55 event's queue using `this.team.queue("EVENT").subscribe`. The
56 argument is a function which is called whenever the event is
57 published. The arguments to the function are different for different
60 * As with so much JavaScript programming, the value of the special
61 variable `this` is lost inside the `subscribez` callback function,
62 so it must be saved if it's to be used inside that callback
63 (typically as a local variable named `that`).
66 Widget specialisation (inheritance)
67 -----------------------------------
69 Many widgets are simple specialisations of existing widgets. For
70 example, the `Record` widget is the same as the `Records` widget
71 except that it defaults to displaying a single record. It's defined as
74 mkws.registerWidgetType('Record', function() {
75 mkws.promotionFunction('Records').call(this);
76 if (!this.config.maxrecs) this.config.maxrecs = 1;
79 Remember that when a promotion function is called, it's passed a base
80 widget object that's not specialised for any particular task. To make
81 a specialised widget, you first promote that base widget into the type
82 that you want to specialise from -- in this case, `Records` -- using
83 the promotion function that's been registered for that type.
85 Once this has been done, the specialisations can be introduced. In
86 this case, it's a very simple matter of changing the `maxrecs`
87 configuration setting to 1 unless it's already been given an explicit
88 value. (That would occur if the HTML used an element like `<div
89 class="mkwsRecord" maxrecs="2">`, though it's not obvious why anyone
97 Widget properties and methods
98 -----------------------------
100 The following properties and methods exist in the bare widget object
101 that is passed into `registerWidgetType`'s callback function, and can
102 be used by the derived widget.
104 * `String this.type` --
105 A string containing the type of the widget.
107 * `Team this.team` --
108 The team object to which this widget belongs. The team has
109 several additional important properties and methods, described
112 * `DOMElement this.node` --
113 The DOM element of the widget
115 * `Hash this.config` --
116 A table of configuration values for the widget. This table
117 inherits missing values from the team's configuration, which
118 in turn inherits from the top-level MKWS configuration, which
119 inherits from the default configuration. Instances of widgets
120 in HTML can set configuration items as HTML attributes: for
121 example, the HTML element
122 `<div class="mkwsRecords" maxrecs="10">`.
123 creates a widget for which `this.config.maxrecs` is set to 10.
125 * `String this.toString()` --
126 A function returning a string that briefly names this
127 widget. Can be useful in logging.
129 * `Void this.log(string)` --
130 A function to log a string for debugging purposes. The string
131 is written on the browser console, and also published to any
132 subcribers to the `log` event.
134 * `String this.value()` --
135 A function returning the value of the widget's HTML element.
137 * `VOID autosearch()` --
138 Registers that this kind of widget is one that requires an
139 automatic search to be run for it if an `autosearch` attribute
140 is provided on the HTML element. This is appropriate for
141 widgets such as `Records` and `Facet` that display some part
144 * `VOID hideWhenNarrow()` --
145 Registers that this widget should hide itself when the page
146 becomes "narrow" -- that is, fewer pixels in width that the
147 threshhold value specified by the top-level configuration item
148 `responsive_design_width`. Should be used for "unimportant"
149 widgets that can be omitted from the mobile version of a site.
152 TODO: either document this or remove it from the API.
154 * `subwidget(type, overrides, defaults)` --
155 Returns the HTML of a subwidget of the specified type, which
156 can then be inserted into the widget using the
157 `this.node.html` function. The subwidget is given the same
158 attributes at the parent widget that invokes this function,
159 except where overrides are passed in. If defaults are also
160 provided, then these are used when the parent widget provides
161 no values. Both the `overrides` and `defaults` arguments are
162 hashes: the latter is optional.
164 See for example the `Credo` widget defined in the example
165 area's `mkws-widget-credo.js` file. This uses several
166 invocations of `subwidget` to create a complex compound widget
167 with numerous text, facet and image panes. TODO: rename this
168 widget and everything related to it.
170 In addition to these properties and methods of the bare widget object,
171 some kinds of specific widget add other properties of their own. For
172 example, the `Builder` widget uses a `callback` property as the
173 function that it use to publish the widget definition that it
174 constructs. This defaults to the builtin function `alert`, but can be
175 overridden by derived widgets such as `ConsoleBuilder`.
181 Since the team object is supposed to be opaque to widgets, all access
182 is via the following API methods rather than direct access to
185 * `String team.name()`
186 * `Bool team.submitted()`
187 * `Num team.perpage()`
188 * `Num team.totalRecordCount()`
189 * `Num team.currentPage();`
190 * `String team.currentRecordId()`
191 * `String team.currentRecordData()`
193 These are all simple accessor functions that provide the ability to
194 read properties of the team.
196 * `Array team.filters()` --
197 Another accessor function, providing access to the array of
198 prevailing filters (which narrow the search results by means
199 of Pazpar2 filters and limits). This is really too complicated
200 an object for the widgets to be given access to, but it's
201 convenient to do it this way. If you must insist on using
202 this, see the `Navi` widget, which is the only place it's used.
204 * `Bool team.targetFiltered(targetId)` --
205 Indicates whether the specified target has been filtered by
206 selection as a facet. This is used only by the `Facet` widget,
207 and there is probably no reason for you to use it.
209 * `Hash team.config()` --
210 Access to the team's configuration settings. There is almost
211 certainly no reason to use this: the settings that haven't
212 been overridden are accessible via `this.config`.
214 * `Void team.set_sortOrder(string)`, `Void team.set_perpage(number)` --
215 "Setter" functions for the team's sortOrder and perpage
216 functions. Unlikely to be needed outside of the `Sort` and
219 * `Queue team.queue(eventName)` --
220 Returns the queue associated with the named event: this can be
221 used to subscribe to the event (or more rarely to publish it).
223 * `Void team.newSearch(query, sortOrder, maxrecs, perpage, limit, targets, targetfilter)` --
224 Starts a new search with the specified parameters. All but the
225 query may be omitted, in which case the prevailing defaults
228 * `Void team.reShow()` --
229 Using the existing search, re-shows the result records after a
230 change in sort-order, per-page count, etc.
232 * `String team.recordElementId(recordId)` --
233 Utility function for converting a record identifer (returned
234 from Pazpar2) into a version suitable for use as an HTML
237 * `String team.renderDetails(recordData)` --
238 Utility function returns an HTML rendering of the record
239 represented by the specified data.
241 * `Template team.loadTemplate(templateName)` --
242 Loads (or retrieves from cache) the named Handlebars template,
243 and returns it in a form that can be invoked as a function,
246 Some of these methods either (A) are really too low-level and should
247 not be exposed, or (B) should be widget-level methods. The present
248 infelicities reflect the fact that some code that rightly belongs in
249 widgets is still in the team. When we finish migrating it, the widget
250 API should get simpler.
256 TODO: list of events that can be usefully subscribed to.
261 Copyright (C) 2013-2014 by Index Data ApS, <http://www.indexdata.com>