npm package: @rnacentral/fornac
Description: An RNA secondary structure display component
Latest version: 1.1.10

# FornaContainer

In many situations, the user interaction is superfluous and the desired goal is
to simply display a secondary structure on a web page. This is a common
scenario in, for example, servers that predict a secondary structure. The
output, a dot-bracket string can simply be added to a `FornaContainer` object
to display.

## Trivial Example

Below is an example of a simple web page which uses a `FornaContainer` to show
a simple RNA molecule:

![blah blah](https://raw.githubusercontent.com/pkerpedjiev/fornac/develop/doc/img/forna-container-screenshot.png "An example of the FornaContainer")

The code for creating this web page is rather straightforward. After importing
some necessary javascript files, we create a container using `new
FornaContainer("#rna_ss", {'applyForce': false})`, passing in `#rna_ss` as the
id of the `div` which will hold the container and then populate it with a
structure and sequence using `container.addRNA`:

```html
<!DOCTYPE html>
<meta charset="utf-8">

This is an RNA container.
<div id='rna_ss'> </div>
This after the RNA container.

    <link rel='stylesheet' type='text/css' href='styles/fornac.css' />
    <script type='text/javascript' src='scripts/fornac.js'></script>
    <script type='text/javascript'>
        var container = new FornaContainer("#rna_ss", {'applyForce': false});

        var options = {'structure': '((..((....)).(((....))).))',
                        'sequence': 'CGCUUCAUAUAAUCCUAAUGACCUAU'
        };

        container.addRNA(options.structure, options);
    </script>
```

### Cofolded sequences

Display two cofolded sequences using the format of [RNAcofold](http://rna.tbi.univie.ac.at/cgi-bin/RNAcofold.cgi):

![Cofolded sequences](https://raw.githubusercontent.com/pkerpedjiev/fornac/master/doc/img/cofold_example.png "An example of cofolded sequences displayed using the FornaContainer")

```javascript
    var container = new fornac.FornaContainer("#cofold_ss",
            {'applyForce': false, 'allowPanningAndZooming': true, 'initialSize':[500,300]});
                                                     
    var options = {'structure': '..((((...))))...((...((...((..&............))...))...))..',
        'sequence': 'ACGAUCAGAGAUCAGAGCAUACGACAGCAG&ACGAAAAAAAGAGCAUACGACAGCAG'
    };                                                                                     
    container.addRNA(options.structure, options);
    container.setSize(); 
```

## Options

The `FornaContainer` supports a number of options to allow users to customize how the RNA will be presented.

### applyForce

Indicate whether the force-directed layout will be applied to the displayed
molecule. Enabling this option allows users to change the layout of the
molecule by selecting and dragging the individual nucleotide nodes

### allowPanningAndZooming [default=true]

Allow users to zoom in and pan the display. If this is enabled then pressing
the 'c' key on the keyboard will center the view.

### circularizeExternal [default=true]

This only makes sense in connection with the `applyForce` argument. If it's
true, the external loops will be arranged in a nice circle. If false, they will
be allowed to flop around as the force layout dictates:

<img src="https://github.com/pkerpedjiev/fornac/blob/master/doc/img/uncircularized_exterior.png" width=200 align=center />

### labelInterval [default=10]

Change how often nucleotide numbers are labelled with their number.


## Implementation

Each RNA molecule is represented as a JSON file which encodes all of the
information necessary to display it. The example shows a trivial and slightly
modified example. `nodeType` can be either `nucleotide` or `label` or `middle`,
the latter of which is used only as a placeholder for maintaining an aesthetically
pleasing layout.

The links can be any of `basepair` (representing a basepair between two
nucleotides), `backbone` (backbone bond between adjacent nodes), `pseudoknot`
(pseudoknot, extracted from the specified structure using maximum matching
algorithm), `extra` (extra links specified by the user), `label_link` (links
between nucleotides and their nucleotide number labels), `fake` (invisible
links for maintaining the layout),  and `fake_fake` (invisible links for
maintaining the layout).

This structure is initially created in `rnagraph.js` starting from a sequence
and dotbracket string.

```
{
  "nodes": 
    [ {
      "name": "A",
      "num": 1,
      "radius": 5,
      "rna": null,
      "nodeType": "nucleotide",
      "structName": "empty",
      "elemType": "e",
      "uid": "44edb966-aca9-4058-a6bc-784a34959329",
      "linked": false,
      "prevNode": null,
      "nextNode": null,
      "x": 100,
      "px": 100,
      "y": 100,
      "py": 100
    },
    ...
    ],
  "links": 
    [ {
      "source": null,
      "target": null,
      "linkType": "basepair",
      "value": 1,
      "uid": "6664a569-5af1-4d86-8ada-d1c00da72a899f87a224-52a0-4ede-a29c-04fddc09e4c4"
      },
      ...
    ]
}
```


## Development

First:

```
npm install
bower install
```

To debug:

```
gulp serve
```

To build:

```
gulp build
```

The output will be placed in the `dist` directory. To use `fornac` in a web page, simply include `dist/scripts/fornac.js` in your web page.

## Acknowledgements

Thanks to [Benedikt Rauscher](https://github.com/bene200) for the Javascript
version of the NAView layout and to the creators of
[VARNA](http://varna.lri.fr/) for the java implementation that it's based on.