% The MasterKey Widget Set developer's guide
% Mike Taylor
-% 11 August 2014
+% November 2014
Introduction
============
+This manual is for people who want to build the widget set from
+source, develop the widget set's core code, or (more likely) create
+their own widgets as extensions to the main set.
+
+Those who want to use existing widgets should read
+[The MKWS manual: embedded metasearching with the MasterKey Widget
+Set](mkws-manual.html) instead.
+
+
+Required development tools
+==========================
+
+If you are building the widget set, you will need the following Debian
+packages (or their equivalents on your operating system):
+
+ $ sudo apt-get install curl git make unzip apache2 \
+ pandoc libbsd-resource-perl
+
+You also need Node.js, but unfortunately the `node-js` package is not
+available for Debian wheezy. You can either get it from
+wheezy-backports or download the source from
+http://nodejs.org/download/ and build it yourself. You need both Node
+itself and its package manager NPM: `make install` puts them into
+`/usr/local/bin`.
+
+
+Concepts
+========
+
+Code structure
+--------------
+
+The code of the widget set is in four main layers, described here from
+the bottom up:
+
+1. The core code, which manages the set of widget teams, default
+options, authentication onto the Service Proxy, and the creation of
+widgets from HTML elements.
+This code is in `mkws-core.js`
+
+2. The team code, which manages teams of widgets. This is responsible
+for the collections of widgets that make up teams, event queues, and
+handling search-and-retrieval events
+This code is in `mkws-team.js`
+
+3. The generic widget code, which handles the creation of widget
+objects, parsing configuration attributes from their HTML elements,
+and firing off automatic searches.
+
+4. The code for individual widgets, which is specific to those
+widgets. It often involves subscribing to events and responding to
+them by setting the HTML of the widget element, but need not do
+so. The code for many of the most important widgets is in
+`mkws-widget-main.js`, but certain other widgets are defined in other
+files beginning with the prefix `mkws-widget-`.
+
+In addition to this code, there are several source files containing
+support code:
+
+* `mkws-filter.js` contains support routine implementing the
+filter-set data structure, which contains information about which
+filters (e.g. by target, or by facet) are in force.
+
+* `mkws-handlebars.js` contains Handlebars helpers which can be used
+by the HTML templates.
+
+* `mkws-popup.js` defines a special widget for creating popup
+ windows. These may, but need not, contain other MKWS widgets,
+ forming a popup searching application.
+
+The final component of the source code is the set of Handlebars
+templates, in the `templates` directory, which are used to emit the
+HTML of the various widgets' contents. These are compiled into the
+file `mkws-templates.js`.
+
+
+
+Event passing
+-------------
+
+The primary method of communication between components of the widget
+set -- specifically, between teams and their widgets -- is event
+passing. Widgets subscribe to named events; when something relevant
+happens (such as the reception of a message from metasearch
+middleware), the event is published, along with the relevant data. All
+widgets that susbcribed to the event are then notified, and can take
+appropriate action.
+
+Different kinds of events have different data associated with
+them. This data is passed when the event is published, and so is made
+available to the subscribing code.
+
+The possible events, and their associated data, are described
+[below](#events).
+
+
+Defining new types of widget
+----------------------------
+
Development with MKWS consists primarily of defining new types of
-widgets. These can interact with the core functionality is several
-defined ways.
+widgets. This is done using exactly the same API as the the widgets
+that come as part of the set: they have no privileged access.
-You create a new widget type by calling the mkws.registerWidgetType
+You create a new widget type by calling the `mkws.registerWidgetType`
function, passing in the widget name and a function. The name is used
to recognise HTML elements as being widgets of this type -- for
-example, if you register a "Foo" widget, elements like <div
-class="mkwsFoo"> will be widgets of this type.
+example, if you register a `foo` widget, elements like
+`<div class="mkws-foo">` will become widgets of this type.
-The function promotes a bare widget object (passed as `this') into a
+The function promotes a bare widget object (which is created by the
+core widget code and passed in as `this`) into a
widget of the appropriate type. MKWS doesn't use classes or explicit
prototypes: it just makes objects that have the necessary
-behaviours. Widgets have *no* behaviours that they have to provide:
-you can make a doesn't-do-anything-at-all widget if you like:
+behaviours. There are _no_ behaviours that Widgets are obliged to
+provide: you can make a doesn't-do-anything-at-all widget if you like:
- mkws.registerWidgetType('Sluggard', function() {});
+ mkws.registerWidgetType('sluggard', function() {});
More commonly, widgets will subscribe to one or more events, so that
they're notified when something interesting happens. For example, the
-"Log" widget asks to be notified when a "log" event happens, and
+`log` widget asks to be notified when a `log` event happens, and
appends the logged message to its node, as follows:
- mkws.registerWidgetType('Log', function() {
- var that = this;
+ mkws.registerWidgetType('log', function() {
+ var that = this;
- this.team.queue("log").subscribe(function(teamName, timestamp, message) {
- $(that.node).append(teamName + ": " + timestamp + message + "<br/>");
- });
+ this.team.queue("log").subscribe(function(teamName, timestamp, message) {
+ $(that.node).append(teamName + ": " + timestamp + message + "<br/>");
+ });
});
This simple widget illustrates several important points:
-* The base widget object (`this') has several baked-in properties and
+* The base widget object (`this`) has several baked-in properties and
methods that are available to individual widgets. These include
- this.team (the team that this widget is a part of) and this.node
- (the DOM element of the widget).
+ `this.team` (the team that this widget is a part of) and `this.node`
+ (the DOM element of the widget). See below for a full list.
+
+* The team object (`this.team`) also has baked-in properties and
+ methods. These include the `queue` function, which takes an event-name
+ as its argument. See below for a full list.
-* The team object (`this.team') also has baked-in properties and
- methods. These include the queue function, which takes an event-name
- as its argument. It's possible to subscribe to an event's queue
- using this.team.queue("EVENT").subscribe. The argument is a function
- which is called whenever the event is published. The arguments to
- the function are different for different events.
+* You can add functionality to a widget by subscribing it to an
+ event's queue using `this.team.queue("EVENT").subscribe`. The
+ argument is a function which is called whenever the event is
+ published.
-* The value of `this' is lost inside the subscribe callback, so it
- must be saved if it's to be used inside that callback (typically as
- a local variable named `that').
+* As with so much JavaScript programming, the value of the special
+ variable `this` is lost inside the `subscribe` callback function,
+ so it must be saved if it's to be used inside that callback
+ (typically as a local variable named `that`).
-Specialisation (Inheritance)
-============================
+Widget specialisation (inheritance)
+-----------------------------------
Many widgets are simple specialisations of existing widgets. For
-example, the "Record" widget is the same as the "Records" widget
-except that it defaults to displaying a single record. It's defined as
-follows:
+example, the `images` widget is the same as the `records` widget
+except that it defaults to using the `images` template for displaying
+its result list. It's defined as follows:
- mkws.registerWidgetType('Record', function() {
- mkws.promotionFunction('Records').call(this);
- if (!this.config.maxrecs) this.config.maxrecs = 1;
+ mkws.registerWidgetType('images', function() {
+ mkws.promotionFunction('records').call(this);
+ if (!this.config.template) this.config.template = 'images';
});
Remember that when a promotion function is called, it's passed a base
widget object that's not specialised for any particular task. To make
-a specialised widget, first promote that base widget into the type
-that you want to specialise from -- in this case, "Records" -- using
+a specialised widget, you first promote that base widget into the type
+that you want to specialise from -- in this case, `Records` -- using
the promotion function that's been registered for that type.
Once this has been done, the specialisations can be introduced. In
-this case, it's a very simple matter of changing the "maxrecs"
-configuration setting to 1 unless it's already been given an explicit
-value. (That would occur if the HTML used an element like <div
-class="mkwsRecord" maxrecs="2">, though it's not obvious why anyone
-would do that.)
+this case, it's a very simple matter of changing the `template`
+configuration setting to `'images'` unless it's already been given an
+explicit value. (That would occur if the HTML used an element like
+`<div class="mkws-images" template="my-images">` to use a customised
+template.
+
+
+Reference Guide
+===============
-Widget Properties and Methods
-=============================
+Widget properties and methods
+-----------------------------
-String this.type
- A string containing the type of the widget.
+The following properties and methods exist in the bare widget object
+that is passed into `registerWidgetType`'s callback function, and can
+be used by the derived widget.
-Team this.team
+* `String this.type` --
+ A string containing the type of the widget (`search`,
+ `switch`, etc.)
+
+* `Team this.team` --
The team object to which this widget belongs. The team has
several additional important properties and methods, described
below.
-DOMElement this.node
- The DOM element of the widget
+* `DOMElement this.node` --
+ The DOM element of the widget. Most often used for inserting
+ HTML into the widget element.
-Hash this.config
+* `Hash this.config` --
A table of configuration values for the widget. This table
inherits missing values from the team's configuration, which
in turn inherits from the top-level MKWS configuration, which
inherits from the default configuration. Instances of widgets
- in HTML can set configuration items as HTML attributes, as in
- <div class="mkwsRecords" maxrecs="2">.
+ in HTML can set configuration items as HTML attributes: for
+ example, the HTML element
+ `<div class="mkwsRecords" maxrecs="10">`
+ creates a widget for which `this.config.maxrecs` is set to 10.
-String this.toString()
+* `String this.toString()` --
A function returning a string that briefly names this
widget. Can be useful in logging.
-Void this.log(string)
+* `Void this.log(string)` --
A function to log a string for debugging purposes. The string
is written on the browser console, and also published to any
- "log" subcribers.
+ subcribers to the `log` event.
-String this.value()
+* `String this.value()` --
A function returning the value of the widget's HTML element.
+* `VOID autosearch()` --
+ Registers that this kind of widget is one that requires an
+ automatic search to be run for it if an `autosearch` attribute
+ is provided on the HTML element. This is appropriate for
+ widgets such as `Records` and `Facet` that display some part
+ of a search result.
+
+* `subwidget(type, overrides, defaults)` --
+ Returns the HTML of a subwidget of the specified type, which
+ can then be inserted into the widget using the
+ `this.node.html` function. The subwidget is given the same
+ attributes at the parent widget that invokes this function,
+ except where overrides are passed in. If defaults are also
+ provided, then these are used when the parent widget provides
+ no values. Both the `overrides` and `defaults` arguments are
+ hashes: the latter is optional. This can be used to assemble
+ compound widgets containing several subwidgets.
+
+In addition to these properties and methods of the bare widget object,
+some kinds of specific widget add other properties of their own. For
+example, the `builder` widget uses a `callback` property as the
+function that it use to publish the widget definition that it
+constructs. This defaults to the builtin function `alert`, but can be
+overridden by derived widgets such as `console-builder`.
+
Team methods
-============
+------------
Since the team object is supposed to be opaque to widgets, all access
is via the following API methods rather than direct access to
properties.
-String team.name()
-Bool team.submitted()
-Num team.perpage()
-Num team.totalRecordCount()
-Num team.currentPage();
-String team.currentRecordId()
-String team.currentRecordData()
- Simple accessor functions that provide the ability to read
- properties of the team.
-
-Array team.filters()
+* `String team.name()`
+* `Bool team.submitted()`
+* `Num team.perpage()`
+* `Num team.totalRecordCount()`
+* `Num team.currentPage();`
+* `String team.currentRecordId()`
+* `String team.currentRecordData()`
+
+These are all simple accessor functions that provide the ability to
+read properties of the team. `submitted` is initially false, then
+becomes true when the first search is submitted (manually or
+automatically).
+
+* `Array team.filters()` --
Another accessor function, providing access to the array of
prevailing filters (which narrow the search results by means
of Pazpar2 filters and limits). This is really too complicated
an object for the widgets to be given access to, but it's
- convenient to do it this way. See the "Navi" widget, which is
- the only place it's used.
+ convenient to do it this way. If you have a reason for using
+ this, see the `Navi` widget, which is the only place it's used.
-Hash team.config()
- Access to the team's configuration settings. There is almost
- certainly no reason to use this: the settings that haven't
- been overridden are accessible via this.config.
+* `Bool team.targetFiltered(targetId)` --
+ Indicates whether the specified target has been filtered by
+ selection as a facet. This is used only by the `Facet` widget,
+ and there is probably no reason for you to use it.
-Void team.set_sortOrder(string)
-Void team.set_perpage(number)
- "Setter" functions for the team's sortOrder and perpage
- functions. Unlikely to be needed outside of the "Sort" and
- "Perpage" widgets.
+* `Hash team.config()` --
+ Access to the team's configuration settings. There is
+ rarely a need to use this: the settings that haven't
+ been overridden are accessible via `this.config`.
-Queue team.queue(eventName)
- Returns the queue associated with the named event: this can be
- used to subscribe to the event (or more rarely to publish it).
+* `Void team.set_sortOrder(string)`, `Void team.set_perpage(number)` --
+ "Setter" functions for the team's `sortOrder` and `perpage`
+ functions. Unlikely to be needed outside of the `Sort` and
+ `Perpage` widgets.
-Bool team.targetFiltered(targetId)
- Indicates whether the specified target has been filtered by
- selection as a facet.
+* `Queue team.queue(eventName)` --
+ Returns the queue associated with the named event: this can be
+ used to subscribe to the event (or more rarely to publish
+ it). See [the section on events, below](#events).
-Void team.newSearch(query, sortOrder, maxrecs, perpage, limit, targets, targetfilter)
+* `Void team.newSearch(query, sortOrder, maxrecs, perpage, limit, targets, targetfilter)` --
Starts a new search with the specified parameters. All but the
query may be omitted, in which case the prevailing defaults
- are used.
+ are used. The meanings of the parameters are those of the
+ same-named [configuration
+ settings](mkws-manual.html#configuration-settings) described in
+ the user's manual.
-Void team.reShow()
+* `Void team.reShow()` --
Using the existing search, re-shows the result records after a
change in sort-order, per-page count, etc.
-String team.recordElementId(recordId)
+* `String team.recordElementId(recordId)` --
Utility function for converting a record identifer (returned
from Pazpar2) into a version suitable for use as an HTML
element ID.
-String team.renderDetails(recordData)
+* `String team.renderDetails(recordData)` --
Utility function returns an HTML rendering of the record
represented by the specified data.
-Template team.loadTemplate(templateName)
+* `Template team.loadTemplate(templateName)` --
Loads (or retrieves from cache) the named Handlebars template,
and returns it in a form that can be invoked as a function,
passed a data-set.
-Some of these methods either (A) are really too low-level and should
-not be exposed, or (B) should be widget-level methods. The present
-infelicities reflect the fact that some code that rightly belongs in
-widgets is still in the team. When we finish migrating it, the widget
-API should get simpler.
-
+Some of these methods are arguably too low-level and should not be
+exposed; others should probably be widget-level methods. The present
+infelicities should be fixed in future releases, but backwards
+compatibility with the present API will be maintained for at least one
+complete major-release cycle.
+
+
+Events
+------
+
+The following events are generated by the widget-set code:
+
+* `authenticated` (authName, realm) --
+ When authentication is completed successfully, this event is
+ published to _all_ teams. Two parameters are passed: the
+ human-readable name of the library that has been authenticated
+ onto, and the correponding machine-readable library ID.
+
+* `ready` --
+ Published to _all_ teams when they are ready to search. No
+ parameters are passed. This event is used to implement
+ automatic searching, and should probably not be used by
+ application code.
+
+* `stat` (data) --
+ Published to a team when a `stat` response is reveived from
+ Pazpar2. The data from the response is passed as a parameter.
+
+* `firstrecords` (hitcount) --
+ Published to a team when the first set of records is found by
+ a search. The number of records found (so far) is passed as
+ the parameter.
+
+* `complete` (hitcount) --
+ Published to a team when a search is complete, and no more
+ records will be found (i.e. all targets have either responded
+ or failed with an error). The final number of records found is
+ passed as the parameter.
+
+* `targets` (data) --
+ Published to a team when a `bytarget` response is reveived from
+ Pazpar2. The data from the response is passed as a parameter.
+
+* `facets` (data) --
+ Published to a team when a `term` response is reveived from
+ Pazpar2. The data from the response is passed as a parameter.
+
+* `pager` (data) --
+ Published to a team when a `show` response is reveived from
+ Pazpar2. The data from the response is passed as a
+ parameter. This event is used to update the pager, showing how
+ many records have been found, which page is being displayed,
+ etc.
+
+* `records` (data) --
+ Also published to a team when a `show` response is reveived
+ from Pazpar2. The data from the response is passed as a
+ parameter. This event is used to update the displayed records.
+
+* `record` (data) --
+ Published to a team when a `record` response is reveived from
+ Pazpar2 (i.e. the full data for a single record). The data
+ from the response is passed as a parameter.
+
+* `navi` --
+ Published to a team when a new search is about to be
+ submitted. This is a signal that the navigation area, showing
+ which filters are in effect, should be updated. No parameter
+ is passed: the event handler should consult `team.filters` to
+ see what the prevailing set is.
+
+* `log` (teamName, timestamp, message) --
+ Published to a team when a message is about to be logged to
+ the console for debugging. Three arguments are passed: the
+ name of the team that generated the log message, a timestamp
+ string, and the message itself. Note that this event is _not_
+ published when the widget-set core code generates a log
+ message -- only when a team or a widget does.
+
+- - -
+
+Copyright (C) 2013-2014 Index Data ApS. <http://indexdata.com>
projects / mkws-moved-to-github.git / blobdiff