% The MasterKey Widget Set developer's guide
% Mike Taylor
-% 11 August 2014
+% November 2014
-Overview
+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 yui-compressor 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
========
-Core 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`.
+
+
+
+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`
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. 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() {
+ mkws.registerWidgetType('log', function() {
var that = this;
this.team.queue("log").subscribe(function(teamName, timestamp, message) {
* 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 arguments to the function are different for different
- events.
+ published. The arguments to the event-callback function are
+ different for different events.
* As with so much JavaScript programming, the value of the special
- variable `this` is lost inside the `subscribez` callback function,
+ 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`).
-----------------------------------
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
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
be used by the derived widget.
* `String this.type` --
- A string containing the type of the widget.
+ 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
below.
* `DOMElement this.node` --
- The DOM element of the widget
+ The DOM element of the widget. Most often used for inserting
+ HTML into the widget element.
* `Hash this.config` --
A table of configuration values for the widget. This table
inherits from the default configuration. Instances of widgets
in HTML can set configuration items as HTML attributes: for
example, the HTML element
- `<div class="mkwsRecords" maxrecs="10">`.
+ `<div class="mkwsRecords" maxrecs="10">`
creates a widget for which `this.config.maxrecs` is set to 10.
* `String this.toString()` --
widgets such as `Records` and `Facet` that display some part
of a search result.
-* `VOID hideWhenNarrow()` --
- Registers that this widget should hide itself when the page
- becomes "narrow" -- that is, fewer pixels in width that the
- threshhold value specified by the top-level configuration item
- `responsive_design_width`. Should be used for "unimportant"
- widgets that can be omitted from the mobile version of a site.
-
-* `expandValue()` --
- TODO: either document this or remove it from the API.
-
* `subwidget(type, overrides, defaults)` --
Returns the HTML of a subwidget of the specified type, which
can then be inserted into the widget using the
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.
-
- See for example the `Credo` widget defined in the example
- area's `mkws-widget-credo.js` file. This uses several
- invocations of `subwidget` to create a complex compound widget
- with numerous text, facet and image panes. TODO: rename this
- widget and everything related to it.
+ 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
+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 `ConsoleBuilder`.
+overridden by derived widgets such as `console-builder`.
Team methods
Events
------
-TODO: list of events that can be usefully subscribed to.
+FIXME: list of events that can be usefully subscribed to.
- - -
-Copyright (C) 2013-2014 by Index Data ApS, <http://www.indexdata.com>
+Copyright (C) 2013-2014 Index Data ApS. <http://indexdata.com>
projects / mkws-moved-to-github.git / blobdiff