1 % The MasterKey Widget Set developer's guide
9 Development with MKWS consists primarily of defining new types of
10 widgets. These can interact with the core functionality is several
13 You create a new widget type by calling the mkws.registerWidgetType
14 function, passing in the widget name and a function. The name is used
15 to recognise HTML elements as being widgets of this type -- for
16 example, if you register a "Foo" widget, elements like <div
17 class="mkwsFoo"> will be widgets of this type.
19 The function promotes a bare widget object (passed as `this') into a
20 widget of the appropriate type. MKWS doesn't use classes or explicit
21 prototypes: it just makes objects that have the necessary
22 behaviours. Widgets have *no* behaviours that they have to provide:
23 you can make a doesn't-do-anything-at-all widget if you like:
25 mkws.registerWidgetType('Sluggard', function() {});
27 More commonly, widgets will subscribe to one or more events, so that
28 they're notified when something interesting happens. For example, the
29 "Log" widget asks to be notified when a "log" event happens, and
30 appends the logged message to its node, as follows:
32 mkws.registerWidgetType('Log', function() {
35 this.team.queue("log").subscribe(function(teamName, timestamp, message) {
36 $(that.node).append(teamName + ": " + timestamp + message + "<br/>");
40 This simple widget illustrates several important points:
42 * The base widget object (`this') has several baked-in properties and
43 methods that are available to individual widgets. These include
44 this.team (the team that this widget is a part of) and this.node
45 (the DOM element of the widget).
47 * The team object (`this.team') also has baked-in properties and
48 methods. These include the queue function, which takes an event-name
49 as its argument. It's possible to subscribe to an event's queue
50 using this.team.queue("EVENT").subscribe. The argument is a function
51 which is called whenever the event is published. The arguments to
52 the function are different for different events.
54 * The value of `this' is lost inside the subscribe callback, so it
55 must be saved if it's to be used inside that callback (typically as
56 a local variable named `that').
59 SPECIALISATION (INHERITANCE)
60 ============================
62 Many widgets are simple specialisations of existing widgets. For
63 example, the "Record" widget is the same as the "Records" widget
64 except that it defaults to displaying a single record. It's defined as
67 mkws.registerWidgetType('Record', function() {
68 mkws.promotionFunction('Records').call(this);
69 if (!this.config.maxrecs) this.config.maxrecs = 1;
72 Remember that when a promotion function is called, it's passed a base
73 widget object that's not specialised for any particular task. To make
74 a specialised widget, first promote that base widget into the type
75 that you want to specialise from -- in this case, "Records" -- using
76 the promotion function that's been registered for that type.
78 Once this has been done, the specialisations can be introduced. In
79 this case, it's a very simple matter of changing the "maxrecs"
80 configuration setting to 1 unless it's already been given an explicit
81 value. (That would occur if the HTML used an element like <div
82 class="mkwsRecord" maxrecs="2">, though it's not obvious why anyone
86 WIDGET PROPERTIES AND METHODS
87 =============================
90 A string containing the type of the widget.
93 The team object to which this widget belongs. The team has
94 several additional important properties and methods, described
98 The DOM element of the widget
101 A table of configuration values for the widget. This table
102 inherits missing values from the team's configuration, which
103 in turn inherits from the top-level MKWS configuration, which
104 inherits from the default configuration. Instances of widgets
105 in HTML can set configuration items as HTML attributes, as in
106 <div class="mkwsRecords" maxrecs="2">.
108 String this.toString()
109 A function returning a string that briefly names this
110 widget. Can be useful in logging.
112 Void this.log(string)
113 A function to log a string for debugging purposes. The string
114 is written on the browser console, and also published to any
118 A function returning the value of the widget's HTML element.
124 Since the team object is supposed to be opaque to widgets, all access
125 is via the following API methods rather than direct access to
129 Bool team.submitted()
131 Num team.totalRecordCount()
132 Num team.currentPage();
133 String team.currentRecordId()
134 String team.currentRecordData()
135 Simple accessor functions that provide the ability to read
136 properties of the team.
139 Another accessor function, providing access to the array of
140 prevailing filters (which narrow the search results by means
141 of Pazpar2 filters and limits). This is really too complicated
142 an object for the widgets to be given access to, but it's
143 convenient to do it this way. See the "Navi" widget, which is
144 the only place it's used.
147 Access to the team's configuration settings. There is almost
148 certainly no reason to use this: the settings that haven't
149 been overridden are accessible via this.config.
151 Void team.set_sortOrder(string)
152 Void team.set_perpage(number)
153 "Setter" functions for the team's sortOrder and perpage
154 functions. Unlikely to be needed outside of the "Sort" and
157 Queue team.queue(eventName)
158 Returns the queue associated with the named event: this can be
159 used to subscribe to the event (or more rarely to publish it).
161 Bool team.targetFiltered(targetId)
162 Indicates whether the specified target has been filtered by
163 selection as a facet.
165 Void team.newSearch(query, sortOrder, maxrecs, perpage, limit, targets, targetfilter)
166 Starts a new search with the specified parameters. All but the
167 query may be omitted, in which case the prevailing defaults
171 Using the existing search, re-shows the result records after a
172 change in sort-order, per-page count, etc.
174 String team.recordElementId(recordId)
175 Utility function for converting a record identifer (returned
176 from Pazpar2) into a version suitable for use as an HTML
179 String team.renderDetails(recordData)
180 Utility function returns an HTML rendering of the record
181 represented by the specified data.
183 Template team.loadTemplate(templateName)
184 Loads (or retrieves from cache) the named Handlebars template,
185 and returns it in a form that can be invoked as a function,
188 Some of these methods either (A) are really too low-level and should
189 not be exposed, or (B) should be widget-level methods. The present
190 infelicities reflect the fact that some code that rightly belongs in
191 widgets is still in the team. When we finish migrating it, the widget
192 API should get simpler.