enketo-core

enketo-core

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

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. For development purposes you may also use the free (and slow, not robust at all) API provided by Enketo LLC at http://xslt-dev.enketo.org/transform (add ?xform=http://myforms.com/myform.xml to use API).
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 been submitted already
	submitted: false,
	// optional array of objects containing {id: 'someInstanceId', xmlStr: '<root>external instance content</root>'}
	external = []
};

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

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

//submit button handler for validate button
$( '#submit' ).on( 'click', function() {
    form.validateForm();
    if ( !form.isValid() ) {
        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 
        form = new Form( 'form.or:eq(0)', { modelStr: modelStr } );

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

How to run to develop on 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 (Note, I had to add "ensure_newline_at_eof_on_save": true to the Sublime Text 3 user settings to make grunt jsbeautifier happy with the style produced by the ST3 JsFormat plugin.)
• 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

Acknowledgements

I would like to acknowledge and thank the indirect contribution by the creators of the following excellent works that were used in the project:

• XPathJS by Andrej Pavlovic
• Bootstrap Datepicker by eternicode
• Bootstrap Timepicker by jdewit

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)
• 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