Enketo Core

The engine that powers Enketo Smart Paper and various third party tools including these.

This repo is meant to use as a building block for any enketo-powered application.

Follow the Enketo blog or Enketo on twitter to stay up to date.

Usage as a library

1. Install with npm install enketo-core --save or include as a git submodule.
2. Develop a way to perform an XSL Transformation on OpenRosa-flavoured XForms inside your app. The transformation will output an XML instance and a HTML form. See enketo-transformer for an example.
3. Add themes to your stylesheet build system (2 stylesheets per theme, 1 is for media="print").
4. Override config.json and optionally widgets.js with your app-specific versions.
5. Main methods illustrated in code below:

	
var Form = require('enketo-core');

// The XSL transformation result contains a HTML Form and XML instance.
// These can be obtained dynamically on the client, or at the server/
// In this example we assume the HTML was injected at the server and modelStr 
// was injected as a global variable inside a <script> tag.

// required string of the jquery selector of the HTML Form DOM element
var formSelector = 'form.or:eq(0)';

// required object containing data for the form
var data = {
	// required string of the default instance defined in the XForm
	modelStr: globalXMLInstance,
	// optional string of an existing instance to be edited
	instanceStr: null,
	// optional boolean whether this instance has ever been submitted before
	submitted: false,
	// optional array of external data objects containing: 
	// {id: 'someInstanceId', xmlStr: '<root>external instance content</root>'}
	external: [],
    // optional object of session properties 
    // 'deviceid', 'username', 'email', 'phonenumber', 'simserial', 'subscriberid'
    session: {}
};

// form-specific configuration
var options = {
    clearIrrelevantImmediately: true  // this is the default, it can be omitted
}

// instantiate a form, with 2 parameters
var form = new Form( formSelector, data, options);

// initialize the form and capture any load errors
var loadErrors = form.init();

// submit button handler for validate button
$( '#submit' ).on( 'click', function() {
    // clear irrelevant questions and validate
    form.validate()
    	.then(function (valid){
    		if ( !valid ) {
       			alert( 'Form contains errors. Please see fields marked in red.' );
    		} else {
        		// Record is valid! 
        		var record = form.getDataStr();

        		// reset the form view
        		form.resetView();

        		// reinstantiate a new form with the default model and no options
        		form = new Form( formSelector, { modelStr: modelStr }, {} );

        		// do what you want with the record
    		}
    	});
} );

Browser support

The following browsers are officially supported:

• latest Android webview on latest Android OS
• latest WKWebView on latest iOS
• latest version of Chrome/Chromium on OS X, Linux, Windows, Android and iOS
• latest version of Firefox on OS X, Windows, Linux, Android and iOS
• latest version of Safari on OS X, Windows, and on the latest version of iOS
• latest version of Microsoft Edge

We have to admit we do not test on all of these, but are committed to fixing browser-specific bugs that are reported for these browsers. Naturally, older browsers versions will often work as well - they are just not officially supported. Note that some applications using Enketo Core (e.g. Enketo Express) may have more limited browser support.

Global Configuration

Global configuration (per app) is done in config.json which is meant to be overriden by a config file in your own application (e.g. by using aliasify).

maps

The maps configuration can include an array of Mapbox TileJSON objects (or a subset of these with at least a name, tiles (array) and an attribution property, and optionally maxzoom and minzoom). You can also mix and match Google Maps layers. Below is an example of a mix of two map layers provided by OSM (in TileJSON format) and Google maps.

[ {
        "name": "street",
        "tiles": [ "http://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png" ],
        "attribution": "Map data © <a href=\"http://openstreetmap.org\">OpenStreetMap</a> contributors"
    }, {
        "name": "satellite",
        "tiles": "GOOGLE_SATELLITE"
} ]

For GMaps layers you have the four options as tiles values: "GOOGLE_SATELLITE", "GOOGLE_ROADMAP", "GOOGLE_HYBRID", "GOOGLE_TERRAIN". You can also add other TileJSON properties, such as minZoom, maxZoom, id to all layers.

googleApiKey

The Google API key that is used for geolocation (in the geo widgets' search box). Can be obtained here. Make sure to enable the GeoCoding API service. If you are using Google Maps layers, the same API key is used. Make sure to enable the Google Maps JavaScript API v3 service as well in that case (see next item).

validateContinuously

This setting with the default false value determines whether Enketo should validate questions immediately if a related value changes. E.g. if question A has a constraint that depends on question B, this mode would re-validate question A if the value for question B changes. This mode will slow down form traversal. When set to false that type of validation is only done at the end when the Submit button is clicked or in Pages mode when the user clicks Next.

validatePage

This setting with default true value determines whether the Next button should trigger validation of the current page and block the user from moving to the next page if validation fails.

Form Configuration

Per-form configuration is done by adding an (optional) options object as 3rd parameter when instantiating a form.

Behaviour of skip logic

    new Form(formselector, data, { 
        clearIrrelevantImmediately: false
    });

If clearIrrelevantImmediately is set to true or not set at all, Enketo will clear the value of a question as soon as it becomes irrelevant, after loading (so while the user traverses the form). If it is set to false Enketo will leave the values intact (and just hide the question).

In the second case the irrelevant values will not be cleared until form.validate() is called (usually when the user marks a record as complete).

How to develop Enketo Core

1. install node and grunt-cli
2. install dependencies with npm install
3. build with grunt
4. start built-in auto-reloading development server with grunt develop
5. browse to http://localhost:8005/forms/index.html

How to create or extend widgets

To create new widgets, we recommend using this plugin template. The option {touch: [boolean]}, is added automatically to all widgets to indicate whether the client is using a touchscreen device.

Each widget needs to fulfill following requirements:

• be an CommonJS/AMD-compliant jQuery plugin
• it needs to return an object with its own name and selector-to-instantiate with
• path to stylesheet scss file relative to the widget's own folder to be added in _widgets.scss (this will be automated in the future)
• be responsive up to a minimum window width of 320px
• use JSDoc style documentation for the purpose of passing the Google Closure Compiler without warnings and errors
• if hiding the original input element, it needs to load the default value from that input element into the widget
• if hiding the original input element, it needs to keep it synchronized and trigger a change event on the original whenever it updates
• it is recommended to apply the widget css class to any new elements it adds to the DOM (but not to their children)
• new input/select/textarea elements inside widgets need to get the ignore class
• it requires the following methods (which can be automatically obtained by extending the Widget base class as demonstrated in the plugin template
  • destroy(element) to totally destroy widgets in repeat groups/questions when these groups/questions are cloned This may be an empty function if:
    • a deep $.clone(true, true) of the widget (incl data and eventhandlers) works without problems (problems are likely!)
  • enable() to enable the widget when a disabled ancestor gets enabled. This may be an empty function if that happens automatically.
  • disable() This may be an empty function if the widgets gets disabled automatically cross-browser when its branch becomes irrelevant.
  • update() to update the widget when called after the content used to instantiate it has changed (language or options). In its simplest form this could simply call destroy() and then re-initialize the widget, or be an empty function if language changes are handled automatically and it is not a <select> widget.
• any eventhandlers added to the original input should be namespaced (if extending the Widget base class, the namespace is available as this.namespace)
• if the widget needs tweaks or needs to be disabled for mobile (touchscreen) use, build this in. The option { touch: [boolean] } is passed to the plugin by default. If your widget requires tweaks for mobile, you could create an all-in-one widget using the options.touch check or you could create separate widgets for desktop and mobile (as done with select-desktop and select-mobile widgets)
• allow clearing of the original input (i.e. setting value to '')
• send a fakefocus and fakeblur event to the original input when the widget gets focus or looses it (see select-desktop)
• please write test specs in the widget's /test folder.....(yeah, need to do that for the existing widgets too...)

Notes for All Developers

• build with grunt
• helpful to use grunt develop to automatically compile (sass and js) when a source file changes, serve, and refresh
• adding the querystring touch=true and reducing the window size allows you to simulate mobile touchscreens

Notes for JavaScript Developers

• The JS library uses CommonJS modules, but all the modules are still AMD-compliant. It may be quite a bit of work to get them working properly using requirejs though (AMD-specific issues won't be fixed by us, but AMD-specific patches/PRs are welcome)
• Will be moving back to Google Closure (Advanced Mode) in future (hence JSDoc comments should be maintained)
• Still trying to find a JS Documentation system to use that likes Closure-style JSDoc
• JavaScript style see JsBeautifier config file, the jsbeautifier check is added to the grunt test task. You can also manually run grunt jsbeautifier:fix to fix style issues.
• Testing is done with Jasmine and Karma (all: grunt karma, headless: grunt karma:headless, browsers: grunt karma:browsers)
• When making a pull request, please add tests where relevant

Notes for CSS Developers

The core can be fairly easily extended with alternative themes. See the plain, the grid, and the formhub themes already included in /src/sass. We would be happy to discuss whether your contribution should be a part of the core, the default theme or be turned into a new theme.

For custom themes that go beyond just changing colors and fonts, keep in mind all the different contexts for a theme:

1. non-touchscreen vs touchscreen (add ?touch=true during development)
2. default one-page-mode and multiple-pages-mode
3. right-to-left form language vs left-to-right form language (!) - also the UI-language may have a different directionality
4. screen view vs. print view
5. questions inside a (nested) repeat group have a different background
6. large screen size --> smaller screen size ---> smallest screen size
7. question in valid vs. invalid state

Sponsors

The development of this app and enketo-core was sponsored by:

• Sustainable Engineering Lab at Columbia University
• WHO - HRP project
• Santa Fe Insitute & Slum/Shack Dwellers International
• Enketo LLC
• iMMAP
• KoBo Toolbox (Harvard Humanitarian Initiative)
• Ona
• Medic Mobile
• Enketo LLC

Related Projects

• Enketo Express - The modern node.js Enketo Smart Paper app
• Enketo Legacy - The old PHP Enketo Smart Paper app
• Enketo XpathJS - The XPath evaluator used in the form engine (enketo-core)
• Enketo Transformer - Node.js XSL Transformer module for Enketo.
• Enketo XSLT - The XSLT sheets used to transform OpenRosa XForms into Enketo HTML forms
• Enketo XSLT Transformer PHP - A minimalistic example in PHP of an XSLT transformer
• Enketo Dristhi - used inside an Android app around enketo
• Enketo JSON - XML-JSON instance convertor used inside e.g. Dristhi

Change log

See change log

Performance (live)

See graphs

License

See license document.

In addition, any product that uses enketo-core is required to have a "Powered by Enketo" footer, according to the specifications below, on all screens in which enketo-core or parts thereof, are used, unless explicity exempted from this requirement by Enketo LLC in writing. Partners and sponsors of the Enketo Project, listed on https://enketo.org/#about and on this page are exempted from this requirements and so are contributors listed in package.json.

The aim of this requirement is to force adopters to give something back to the Enketo project, by at least spreading the word and thereby encouraging further adoption.

Specifications:

1. The word "Enketo" is displayed using Enketo's logo.
2. The minimum font-size of "Powered by" is 12 points.
3. The minimum height of the Enketo logo matches the font-size used.
4. The Enketo logo is hyperlinked to https://enketo.org

Example:

Powered by