bgrapher

1.1.2 • Public • Published

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Bgrapher presents as much information about a graph as possible in a concise format, while removing all unnecessary noise. This lets you focus on the bigger picture, while still allowing you to focus in on the details as needed.

Bgrapher works particularly well for visualizing large, sparse, directed, hierarchical graphs. Anything that you might want to draw with dot, but which doesn't neatly fit into a single image, is a good candidate for Bgrapher.

Getting started

Say you already have a bgraph, and would like to draw yourBgraph inside yourElement = document.createElement('div'), you can do so directly:

<script src="https://unpkg.com/bgrapher/dist/bgrapher.min.js"></script>
<script>
  let yourBgrapher = new bgrapher.Bgrapher(yourBgraph, yourElement);
</script>

Or, if installed via npm:

import { Bgrapher } from 'bgrapher';
let yourBgrapher = new Bgrapher(yourBgraph, yourElement);

If your graph is not in bgraph format yet, you can create it using the format described below.

Bgraph format

Bgraphs are like any other graphs, except optimized for speed and flexibility on the frontend. This means that you may need to do a bit more prep work "offline" before rendering a graph.

Bgraph structure

Bgraphs are formatted in JSON. Comments cannot be used. Nodes are represented with blocks and edges are pairs of edgeEnds. A bgraph must contain a list of each, as well as all required properties:

Property Description
width & height The total dimensions of the bgraph. This should be sufficiently large to contain all of your blocks/edgeEnds.
bgColor Background color of the bgraph.
highlightBgColor & highlightFgColor Highlight colors for highlighting graph interactions. Choosing 2 contrasting colors for these values improves visibility.

For example, this is a 4 by 4 bgraph with a white background (16777215 corresponds to #ffffff), black on white highlights (0 and 16777215), and no blocks or edgeEnds:

{
  "width":  4,
  "height": 4,
  "bgColor": 16777215,
  "highlightFgColor": 0,
  "highlightBgColor": 16777215,
  "blocks": [],
  "edgeEnds": []
}

blocks and edgeEnds are objects that can be added to the two lists in order to define a graph.

Bgraph blocks

Each block consists of, crucially, an (x,y) location and an id, as well as other properties that define how it appears in a bgraph:

Property Description
width & height Dimensions of the rectangle representing the block in the bgraph.
depth How the block is ordered relative to others. Higher depth blocks appear above lower depth blocks.
color A decimal representation of the block's color (e.g., "#123456" ==> 1193046).

A block also holds an edgeEnds list of edgeEnd IDs, which helps provide contextual highlighting when interacting with a block using Bgrapher. Typically, this is a list of edgeEnds that correspond to edges going to and from the given block.

This is an example of a 2 by 1, #000001-colored block, located at the top-left of the bgraph (0,0), which has two edgeEnds (0 and 100) associated with it:

  ...
  "blocks": [
    {
      "id": 0,
      "x": 0, "y": 0,
      "width": 2, "height": 1,
      "depth": 0, "color": 1,
      "edgeEnds": [
        0,
        100
      ]
    }
  ],
  ...

Bgraph edgeEnds

Like blocks, each edgeEnd consists of an (x,y) location and an id, as well as some additional properties:

Property Description
isSource true/false. Whether the edgeEnd represents a start of an edge or the end of an edge.
direction 1/2/3/4, which correspond to up/right/down/left. Influences how a highlighted edge appears when drawn.
color Same format as for blocks.

Like a block, an edgeEnd also holds an edgeEnds list of edgeEnd IDs, representing all the edgeEnds that this edgeEnd is coming from/going to. An edgeEnd usually has at least one other edgeEnd in this list, in order to form a complete edge, with a source edgeEnd and a destination edgeEnd.

Additionally, an edgeEnd can correspond to a particular block, which is represented by the block's ID. It is best to have the block point back to the corresponding edgeEnds that refer to it.

Below is an example of the edgeEnds from the block above. The first is at the bottom-left of the block (0,1), while the other is at the bottom-right (1,1). Both are colored black (#000000). Both are edge ends to one another (as evident from each edgeEnds array), and both correspond to block 0. One is the source ("isSource": true) and is pointing downward ("direction": 3) while the other is a destination ("isSource": false) and is pointing up ("direction": 1).

  ...
  "edgeEnds": [
    {
      "id": 0,
      "x": 0, "y": 1,
      "color": 0,
      "direction": 3,
      "isSource": true,
      "block": 0,
      "edgeEnds": [
        100
      ]
    },
    {
      "id": 100,
      "x": 1, "y": 1,
      "color": 0,
      "direction": 1,
      "isSource": false,
      "block": 0,
      "edgeEnds": [
        0
      ]
    }
  ]
  ...

In total, this example bgraph represents a single node with a loop.

Suggested bgraph style guide

Note that the above is only one of the many ways in which this graph could be represented in bgraph format. The following style guide suggests one possible convention for writing out bgraphs, tailored to directed graphs.

Representing nodes in a directed graph:

  • Have one block for each node in the graph.
  • Increment each block's id by one from the previous block, starting from 0.
  • Use at least 1 for both height and width.
  • Position blocks at least 3 units away from other blocks, unless those other blocks are parent hierarchies.
  • Use the maximum of the number of edgeEnds that correspond to the block and are located to the right or left of the block as the height of the block; use 1 if none are present.
  • Use the maximum of the number of edgeEnds that correspond to the block and are located above or below the block as the width of the block; use 1 if none are present.
  • Place all edgeEnds that correspond to the block either 1 unit below, above, to the left, or to the right of the block.
  • Place edgeEnds that are to the left or to the right within the height of the block; place edgeEnds that are above or below the block within the width of the block.
  • Ensure that edgeEnds that correspond to the block are listed in the edgeEnds list in the block.

Representing edges in a directed graph:

  • Use two edgeEnds to represent an edge: one edgeEnd represents the beginning of the edge, and another edgeEnd represents the end of the edge.
  • Increment each edgeEnd's id by one from the previous edgeEnd, starting from 0.
  • Position edgeEnds that are the start of an edge to the right of the block they correspond to and use direction pointing to the right.
  • Position edgeEnds that are the end of an edge to the left of the block they correspond to and use direction pointing to the right.
  • Position edgeEnds that are the start of an edge that crosses hierarchy below the block that the edgeEnd corresponds to and use direction pointing down.
  • Position edgeEnds that are the end of an edge that crosses hierarchy above the block that the edgeEnd corresponds to and use direction pointing down.
  • Use direction to go right for edges that don't cross hierarchy and down for edges that do.
  • Place edgeEnds next to each other contiguously and not in the same position.
  • Use 0 for block depth when no hierarchies exist in the graph.

Representing hierarchies in a directed graph:

  • Use blocks to represent hierarchies.
  • Use lower depth values for parent hierarchies and higher depth for child hierarchies. Use the highest depth for the blocks that represent the nodes themselves.
  • Make sure that the blocks used to represent hierarchies have width and height that encompass all the contents of the hierarchy, plus 2 units of padding on all sides.
  • For edges from/to the hierarchies themselves (rather than nodes within the hierarchies), follow the same convention as for blocks.

The rest of the info is about the Bgrapher JS object and its various interfaces.

Member variables

A Bgrapher object contains all of the data that you provide to it in the Bgrapher.blocksData and Bgrapher.edgeEndsData member variables, keyed by each block's or edgeEnd's corresponding ID. All of the metadata is also held in the Bgrapher object itself.

For example:

let yourBgrapher = new Bgrapher({
  width:  4,
  height: 4,
  ...
  blocks: [
    ...
    {
      id: 12,
      edgeEnds: [0, 100],
      ...
    },
    ...
  ],
  ...
}, yourElement);

let bgraphWidth  = yourBgrapher.width;  // 4
let bgraphHeight = yourBgrapher.height; // 4
let edgeEndsOf12 = yourBgrapher.blocksData[12].edgeEnds; // [0, 100]

Treat these as read-only to avoid undefined behavior. Instead use Bgrapher methods to make changes to the bgraph data.

Methods

Bgrapher constructor

Bgrapher([yourBgraph [, yourElement [, yourBgraphState]]])

The most convenient form is:

let yourBgrapher = new Bgrapher(yourBgraph, yourElement);

Where you simply specify the input bgraph and where you want the bgraph to be displayed.

Parameters

yourBgraph: Either a javascript object or a JSON string containing the bgraph to be displayed.

yourElement: An HTML element within which the Bgrapher will draw the bgraph.

yourBgraphState: Externally-managed state of the user's interaction with the bgraph, such as the user's zoom and offset.

Bgrapher.activeBlocks & Bgrapher.activeEdgeEnds

activeBlocks()
activeEdgeEnds()

Return value

Returns either the objects of the active blocks or active edgeEnds in the bgraph. "Active" blocks/edgeEnds include any which the user selected or hovered over, and which are thus highlighted in the bgraph.

Bgrapher.activeEdges

activeEdges()

Return value

Returns a pair of active edgeEnd objects. Since edges aren't highlighted directly, these are the result of user interaction with blocks and edgeEnds.

Bgrapher.toggleBlock & Bgrapher.toggleEdgeEnd

toggleBlock(blockID)
toggleEdgeEnd(edgeEndID)

Toggling a block or edgeEnd using these functions is equivalent to a user clicking on them.

Parameters

blockID/edgeEndID: ID of either the block or edgeEnd which you are toggling.

Bgrapher.selectBlock & Bgrapher.selectEdgeEnd

selectBlock(blockID)
selectEdgeEnd(edgeEndID)

Selecting a block or edgeEnd using these functions is equivalent to a user right-clicking on them.

Parameters

blockID/edgeEndID: ID of either the block or edgeEnd which you are toggling.

Bgrapher.hoverBlock & Bgrapher.hoverEdgeEnd

hoverBlock(blockID)
hoverEdgeEnd(edgeEndID)

Hovering a block or edgeEnd using these functions is equivalent to a user hovering over them.

Parameters

blockID/edgeEndID: ID of either the block or edgeEnd which you are toggling.

Callbacks

Bgrapher.onHoverBlock & Bgrapher.onHoverEdgeEnd

onHoverBlock(yourCallback)
onHoverEdgeEnd(yourCallback)

Parameters

yourCallback: The callback to be called when the user hovers over an element in the graph. block or edgeEnd object is passed in to the callback.

Bgrapher.onToggleBlock & Bgrapher.onToggleEdgeEnd

onHoverBlock(yourCallback)
onHoverEdgeEnd(yourCallback)

Parameters

yourCallback: The callback to be called when the user toggles an element in the graph, meaning that they click to highlight a node and its edges. block or edgeEnd object is passed in to the callback.

Bgrapher.onSelectBlock & Bgrapher.onSelectEdgeEnd

onHoverBlock(yourCallback)
onHoverEdgeEnd(yourCallback)

Parameters

yourCallback: The callback to be called when the user selects an element, seeking to extract more information about it, by default via right-click. block or edgeEnd object is passed in to the callback.

Shared BgraphState for multiple Bgraphers

It can be convenient to sync user interaction across multiple bgraphers. This can be achieved by using a shared bgraph state.

To use bgraph state that is shared across bgrapher objects:

  1. Instantiate a new BgraphState() to be used by all of your bgraphers.
  2. Instantiate new Bgrapher()s with yourBgraphState passed in.

For example:

import { Bgrapher, BgraphState } from 'bgrapher';
let yourBgraphState = new BgraphState();

let yourBgrapher1 = new Bgrapher(yourBgraph1, yourElement1, yourBgraphState);
let yourBgrapher2 = new Bgrapher(yourBgraph2, yourElement2, yourBgraphState);

When working with a shared state, ensure that both bgraphs have the same dimensions.

BgraphState

new BgraphState()

The BgraphState object contains the user's location/zoom level within the bgraph, as well as a list of Bgraphers subscribed to be notified of state changes.

BgraphState.update

update()

This is the preferred method to use if you need to force-update all Bgraphers state (e.g., if modifying BgraphState manually). Any Bgraphers that are subscribed to be notified of state changes are notified when yourBgraphState's update method is called.

To ensure that Bgraphers are subscribed, pass in yourBgraphState to the new Bgrapher() constructor, or to the populateElement call.

BgraphState.center

center()

Centers (i.e., places client view in the middle of the bgraph) all bgraphs that are subscribed to the BgraphState.

BgraphState versus React state

Don't let React manage your BgraphState! Bgrapher regenerates only the relevant parts of the graph, while React won't know any better than to refresh the entire HTML element.

In other words, instead of this:

this.state = { myBgraphState: new BgraphState() };

Do this:

this.myBgraphState = new BgraphState();

Other interfaces

Bgrapher.hoveredBlock & Bgrapher.hoveredEdgeEnd

hoveredBlock()
hoveredEdgeEnd()

Return value

Returns only the current hovered block or edgeEnd in the bgraph. Returns null if no block or edgeEnd is currently hovered.

Prefer to use onHoverBlock & onHoverEdgeEnd instead.

Bgrapher.initBgraph

initBgraph(bgraph)

Useful for re-initializing the data used to construct the bgraph.

Parameters

yourBgraph: Either a javascript object or a JSON string containing the bgraph to be displayed.

Bgrapher.populateElement

populateElement(yourElement [, yourBgraphState])

Populates yourElement and optionally registers Bgrapher with an external BgraphState. Useful for moving a bgraph to another element. You must pass the BgraphState explicitly for it to be preserved.

Parameters

yourElement: An HTML element within which the Bgrapher will draw the bgraph.

yourBgraphState: Externally-managed state of the user's interaction with the bgraph, such as the user's zoom and offset.

Bgrapher.draw

draw()

Re-draws the bgrapher using the latest BgraphState.

If using an external BgraphState, prefer to call BgraphState.update() instead.

Bgrapher.centerView

centerView()

Re-draws the bgrapher with client view in the center of the bgraph.

If using an external BgraphState, prefer to call BgraphState.center() instead.

Bgrapher.clientWidth & Bgrapher.clientHeight

clientWidth()
clientHeight()

Return value

Returns the width or height of the Bgrapher element within yourElement, based on the underlying Bgrapher implementation used.

Bgrapher.updateClientSize

updateClientSize()

Changes the size of the bgraph to match the size of yourElement, which contains the bgraph. Useful if the dimensions of the element change.

This is called automatically whenever the window is re-sized.

Bgrapher.curBlock & Bgrapher.curEdgeEnd

curBlock(cur)
curEdgeEnd(cur)

Parameters

cur: Object of the form {x: yourX, y: yourY}, where the x,y coordinate corresponds to a location relative to the bgraph. For example, this can correspond to a mouse cursor location, but it would not correspond to the x,y coordinate of a block or edgeEnd as specified in the input bgraph object.

Return value

Returns the block or edgeEnd object at the specified location.


Development

Run build

npm install
npm run build

Note that jsdom needs canvas, which may need the following:

export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig:/opt/X11/lib/pkgconfig

Run tests

npm run test:cov

Run example

npm run build:dev

Then access at localhost:3000.

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npm i bgrapher

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