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https://github.com/bijection/g9

Automatically Interactive Graphics 🖼✨💯
https://github.com/bijection/g9

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Automatically Interactive Graphics 🖼✨💯

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README 

        
# [g9.js](http://omrelli.ug/g9)



g9 is a javascript library for creating **automatically interactive graphics**.



With g9, interactive visualization is as easy as visualization that isn't. Just write a function which draws shapes based on data, and g9 will automatically figure out how to manipulate that data when you drag the shapes around.



For example, the following code:

```javascript

g9({

    x: 0,

    y: 0

}, function(data, ctx){

    ctx.point(data.x, data.y)

    ctx.point(data.y, data.x)

})

.insertInto('#container')

```



draws two dots at (x,y) and (y,x). With no additional effort, it's interactive - dragging either of the dots changes the value of x and y, and moves the other dot: 



![basic demo](basic.gif)



This **automatic interactivity** makes it trivial to manipulable complex visualizations like this fractal:



![dragon demo](dragon.gif)



You can see (and play with!) more examples [on the website](http://omrelli.ug/g9/gallery), or [head to the docs](#docs) for a full treatment of the API.



# Installation

You can use g9 with npm (if your're using webpack or browserify) or with a script tag:



## npm



```

npm install g9

```



```javascript

var g9 = require('g9')

// or 

import g9 from 'g9'

```



## ``



First download a copy of g9 [here](https://raw.githubusercontent.com/bijection/g9/master/dist/g9.js), then



```html



 



    // g9 is now defined 



```



You can also hotlink a copy of g9 from a CDN:

```html



 



	// g9 is now defined 



```



# Docs



* [g9(initialData, render[, onRender]): g9Canvas](#g9initialdata-render-onrender-g9canvas)

  + [initialData](#initialdata)

  + [render(data, ctx: g9Context)](#renderdata-ctx-g9context)

  + [onRender(data, renderedObjects)](#onrenderdata-renderedobjects)

* [g9Canvas](#g9canvas)

  + [g9Canvas.insertInto(selectorOrDOMNode)](#g9canvasinsertintoselectorordomnode)

  + [g9Canvas.align(xAlign, yAlign)](#g9canvasalignxalign-yalign)

  + [g9Canvas.node](#g9canvasnode)

  + [g9Canvas.setData(data)](#g9canvassetdatadata)

  + [g9Canvas.getData()](#g9canvasgetdata)

  + [g9Canvas.isManipulating](#g9canvasismanipulating)

  + [g9Canvas.resize()](#g9canvasresize)

  + [g9Canvas.desire(id, ...desires)](#g9canvasdesireid-desires)

* [g9Context](#g9context)

  + [g9Context.[shape]](#g9contextshape)

    - [The Affects Argument](#the-affects-argument)

    - [g9Context.point(cx, cy[, affects])](#g9contextpointcx-cy-affects)

    - [g9Context.circle(cx, cy, r[, affects])](#g9contextcirclecx-cy-r-affects)

    - [g9Context.line(x1, y1, x2, y2[, affects])](#g9contextlinex1-y1-x2-y2-affects)

    - [g9Context.rect(x, y, width, height[, affects])](#g9contextrectx-y-width-height-affects)

    - [g9Context.text(text, x, y[, affects])](#g9contexttexttext-x-y-affects)

    - [g9Context.image(href, x, y, width, height[, affects])](#g9contextimagehref-x-y-width-height-affects)

  + [g9Context.width](#g9contextwidth)

  + [g9Context.height](#g9contextheight)

  + [g9Context.pure(pureFn)](#g9contextpurepurefn)

* [Adding new shapes to g9Context](#adding-new-shapes-to-g9context)

  + [g9.shapes.myNewShape = shape](#g9shapesmynewshape--shape)



## g9([initialData](#initialdata), [render](#render)[, [onRender](#onrender)]): [g9Canvas](#g9canvas)

This is the main g9 function, which returns a [g9Canvas](#g9Canvas) which you can mount in your page with the `g9Canvas.insertInto(selectorOrDOMNode)` method. For example: 



```javascript

g9({foo: 10}, function(data, ctx){

	ctx.point(data.foo, 17)

})

.insertInto('#container')

```



The g9Canvas API is covered [here](#g9Canvas).



`g9()` takes the following arguments:



### initialData

`initialData` is a flat object with numeric values, which will be used in the first call to `render`. For example:



```javascript

var initialData = {

    foo: 10

}

```



### render(data, ctx: [g9Context](#g9context))



`render(data, ctx)` is a function that receives a `data` object with the same keys as `initialData`, but possibly different values, and a [g9Context](#g9context) `ctx`. The g9Context API is covered [here](#g9context).



`render` is responsible for calling methods on `ctx` to produce a drawing.

For example:



```javascript

function render(data, ctx){

    ctx.point(data.foo, 17)

}

```

creates a point at x-coordinate `data.foo` and y-coordinate 17.



When someone interacts with the graphics, for example by trying to drag an element to a new position, g9 optimizes over the space of possible values for `data` to find a set of values that comes closest to creating the change. In the preceeding example, if `data.foo` is initially 10 and you tried to drag the point to the left, g9 might come up with



```javascript

{

    foo: 8

}

```

After optimization, g9 rerenders the entire scene with the new data, so that everything is consistent.



### onRender(data, renderedObjects)

`onRender(data, renderedObjects)` is an optional argument which, if included, is called after each re-render with the data that determined the render, and the set of rendered objects. Typical uses for `onRender` include debugging compositions and updating other parts of your page.



## g9Canvas

A `g9Canvas` is the object returned by a call to g9(initialData, render, onRender)



### g9Canvas.insertInto(selectorOrDOMNode)

Mounts the graphics' svg node as a child of `selectorOrDOMNode`, which can be either a selector or a DOM node, and returns the graphics object to enable chaining.



For example:



```javascript

g9({foo: 10}, function(data, ctx){

	ctx.point(data.foo, 17)

})

.insertInto('#container')

```



> Note: You can change the size of the mounted svg node with javascript, e.g `g9Canvas.node.style.height = '500px'; g9Canvas.resize()`, or css, e.g. `#g9NodesParentElement > svg {width: 100%; height: 300px}`.



### g9Canvas.align(xAlign, yAlign)

Sets the position of the origin in relation to which graphics are drawn. `xAlign` and `yAlign` are both strings that default to 'center'. Returns the graphics object to enable chaining.



* `xAlign` can be either 'left', 'center', or 'right'.

* `yAlign` can be either 'top', 'center', or 'bottom'.



For example:



```javascript

g9({foo: 10}, function(data, ctx){

	ctx.point(data.foo, 17)

})

.align('bottom', 'left')

.insertInto('#container')

```



### g9Canvas.node

A read-only reference to the `svg` DOM node that holds the g9 graphics.



### g9Canvas.setData(data)

Sets the data currently being visualized by a g9 instance to `data`. This is useful for animations. For example: 



```javascript

var graphics = g9({foo: 10}, function(data, ctx){

	ctx.point(data.foo, 17)

})

.insertInto('#container')



var theta = 0



setInterval(function(){

	graphics.setData( {foo: Math.cos( theta += 0.01 )} )

}, 30)

```



### g9Canvas.getData()

Get the data currently being visualized by a g9Canvas. For example:



```javascript

var graphics = g9({foo: 10}, function(data, ctx){

    ctx.point(data.foo, 17)

})

.insertInto('#container')



alert(JSON.stringify(graphics.getData()))

```



###g9Canvas.isManipulating

A boolean property that's true when a user is manupulating a shape on the g9 canvas.



### g9Canvas.resize()

Invalidates the g9 display. Usually a noop, but should be called after programmatically resizing the g9 DOM node or its container.



### g9Canvas.desire(id, ...desires)

Internal method, genreally safe to ignore, but useful for complex animation. For now, the best way to use this is to read the source.



## g9Context

A new, immutable g9Context object `ctx` is passed as the second argument to `render` each time `render` is called. It has a variety of drawing methods and some read-only properties that the render function uses to create a drawing.



### g9Context.[shape]

When calling a drawing method, you can include any number of ordered arguments, optionally followed by an object that specifies further arguments by name, and / or includes svg properties. For example, all of the following are equivalent: 



```javascript

ctx.point(30, 50, ['a'])



ctx.point(30, 50, {affects: ['a']})



ctx.point(30, {

	y: 50,

	affects: ['a']

})



ctx.point({

	x: 30,

	y: 50,

	affects: ['a']

})

```



#### The Affects Argument



All g9 shapes take an optional argument `affects`, a list of key names. When you drag a shape with an `affects` list, g9 will only change the values of the keys in the `affects` list.



For example, dragging the following point will only change the value of `data.x`, and thus the point will only move horizontally:

```javascript

g9({

    x: 0,

    y: 0

}, function(data, ctx){

    

    ctx.point(data.x, data.y, {affects: ['x']})

    

})

```



Currently, the built-in shapes are



#### g9Context.point(cx, cy[, affects])

  

A point. Useful svg properties are `r` (radius), and `fill`. For example:



```javascript

ctx.point(30, 50, {r: 40, 	fill: 'red'	})

```



#### g9Context.circle(cx, cy, r[, affects])

  

A circle. As opposed to the point, circles can rotate around your mouse as you drag them. Useful svg properties are `stroke` (a color), and `fill`. For example:



```javascript

ctx.circle(30, 50, 40, { stroke: 'blue' })

```



#### g9Context.line(x1, y1, x2, y2[, affects])

  

A line. Useful svg properties are `stroke-width`, `stroke` (stroke color), and `stroke-linecap`. For example:



```javascript

ctx.line(30, 50, 60, 100, {

	'stroke-width': 10,

	'stroke': 'red',

	'stroke-linecap': 'round'

})

```

#### g9Context.rect(x, y, width, height[, affects])

  

A rectangle. A useful svg property is `fill`. For example:



```javascript

ctx.rect(0, 0, 100, 100, {'fill': '#ff6600'})

```



#### g9Context.text(text, x, y[, affects])

  

A text label. Useful svg properties are `font-family`, `font-size`, `fill`, and `text-anchor`. For example:



```javascript

ctx.text('Hello World!', 30, 50, {

	'font-family': 'sans-serif',

	'font-size': '20px',

	'text-anchor': 'middle',

	'fill': '#badd09'

})

```



#### g9Context.image(href, x, y, width, height[, affects])

  

An image. A useful svg property is `preserveAspectRatio`. For example:



```javascript

ctx.image('http://placehold.it/350x150', 0, 0, 350, 150, {

	'preserveAspectRatio': 'xMaxYMax'

})

```



### g9Context.width

Read only. The current width of the svg container, as dertermined by page size and / or css.



### g9Context.height

Read only. The current height of the svg container, as dertermined by page size and / or css.



### g9Context.pure(pureFn)

`ctx.pure(pureFn)` is a decorator that speeds up deterministic, stateless (and usually recursive) functions. Internally, `ctx.pure` tells g9 that it doesn't have to execute certain branches when it is optimizing. For recursive funtions, this can make optimization take `O(log(n))` time, instead of `O(n)` time, where `n` is the number of objects drawn by `pureFn`. For example: 



```javascript

g9({

    deltaAngle:33,

    attenuation:0.7,

    startLength:189

}, function(data, ctx){



    var deltaAngle = data.deltaAngle,

        attenuation = data.attenuation,

        startLength = data.startLength

    

    var drawTree = function (x1, y1, length, angle, n){

        var x2 = x1 + length * Math.cos(angle*Math.PI/180);

        var y2 = y1 + length * Math.sin(angle*Math.PI/180);

     

        ctx.point(x2, y2, {affects:['deltaAngle', 'attenuation']})

        

        ctx.line(x1,y1,x2,y2)



        if(n > 0) {

            drawTree(x2, y2, length*attenuation, angle+deltaAngle, n-1);

            drawTree(x2, y2, length*attenuation, angle-deltaAngle, n-1);

        }



    }

    

    drawTree = ctx.pure(drawTree)



    drawTree(0, ctx.height/2 - 30, startLength, -90, 9)



})

```

A live version of this example is on [the examples page](https://omrelli.ug/g9/gallery).



## Adding new shapes to g9Context



### g9.shapes.myNewShape = shape



    This is an experimental API and may be subject to change. That said, pull requests with particularly good new shapes are encouraged!



g9 allows you to go beyond basic shapes like circles and rectangles by adding your own shapes, which will then be available as drawing methods on g9Context objects. 



You can add a custom shape in the folowing way: 

```javascript

g9.shapes.myNewShape = shape

```



After which it will be available as 

```javascript

g9({

    x: 0,

    y: 0

}, function render(data, ctx){

    ctx.myNewShape(ctx.x, ctx.y, 1, 3, 5, 'asdf')

})

```



A shape is a javascript class with the following properties:

- **argNames**: an array of the names that should be assigned to arguments passed to the shape

- **contructor(get_args, minimize_args)**: a constructor method, which usually saves the two functions it recieves.

    - **get_args()**: A getter that returns a flat set of keys and values that represents that arguments passed to your shape's drawing method on the last render.

    - **minimize_args(cost(potentialArgs) -> Number[, keys: array])**: changes the values of data with the keys `keys`, or all of the values of data if `keys` is not included, to minimize the number returned by `cost`. `cost` is passed an abject `potentialArgs`, a flat set of keys and values that represent the arguments that *would be passed* to your shape's drawing method for some potential new values of your drawing's `data`. After minimization your graphics are rerendered.

- **mount(container)**: a method which recieves the relevant g9Canvas.node svg element as its only argument. Typically you use this method to add an svg object to container, attach event handlers, etc.

- **unmount()**: a method responsible for cleaning up any mutation to the DOM or event listeners created in mount(). 

- **update()**: a method that is called every time the graphics are rendered. `update` usually call `get_args` and uses the result to change the DOM.



For example, you might define an `equilateral_triangle` shape like this:

```javascript

function equilateral_triangle(get_args, minimize_args){

    this.minimize_args = minimize_args

    this.get_args = get_args

}



equilateral_triangle.argNames = ['x', 'y', 'size', 'affects']



equilateral_triangle.prototype.mount = function(container){

    this.container = container

    this.el = document.createElementNS("http://www.w3.org/2000/svg", "polygon")

    this.container.appendChild(this.el)

    this.el.setAttributeNS(null, 'fill', 'red')



    var startex, startey;



    var self = this



    function onmove(e){

        var dx = e.clientX - startex

        var dy = e.clientY - startey



        var current_affects = self.get_args().affects



        self.minimize_args(function(args){

            var ddx = (args.x - start_args.x) - dx

            var ddy = (args.y - start_args.y) - dy



            return ddx*ddx + ddy*ddy

        }, current_affects)

    }



    function onstart(e){



        var start_args = self.get_args()



        e.preventDefault()



        startex = e.clientX

        startey = e.clientY



        var onend = function(e){

            document.removeEventListener('mousemove', onmove)

            document.removeEventListener('mouseup', onend)

        }



        document.addEventListener('mousemove', onmove)

        document.addEventListener('mouseup', onend)

    }



    this.el.addEventListener('mousedown', onstart)

}



equilateral_triangle.prototype.unmount = function() {

    this.container.removeChild(this.el)

}



equilateral_triangle.prototype.update = function() {

    g9.utils.setAttributes(this.el, this.get_args())



    var points = [x+Math.cos(0)*size, y+Math.sin(0)*size,

                  x+Math.cos(2*Math.PI/3)*size, y+Math.sin(2*Math.PI/3)*size,

                  x+Math.cos(2*Math.PI*2/3)*size, y+Math.sin(2*Math.PI*2/3)*size]

    this.el.setAttributeNS(null, 'points', points.join(' '))

}



g9.shapes.equilateral_triangle = equilateral_triangle

```



After which you can use it like so: 

```javascript

g9({

    x: 0,

    y: 0

}, function render(data, ctx){

    ctx.equilateral_triangle(ctx.x, ctx.y, 50)

})

```