A flexible, adaptable, and easy to use tooltip positioning algorithm.

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5.2.06 years ago7 years agoMinified + gzip package size for flowtip-core in KB


FlowTip layout resolver algorithm.


FlowTip has 3 required config values (target, content, and bounds as DOMRect-shaped objects) as input in addition to a number of optional config values. The returned result is a resolved region (top, right, bottom, or left) and a DOMRect-shaped object of the resolved position of the content.
const config = {
  target: {top: 10, left: 100, width: 100, height: 20},
  content: {width: 250, height: 200},
  bounds: {top: 0, left: 0, width: 1200, height: 800},
  // Optional config values.

const {region, rect} = flowtip(config);


target: object

The measured position of the target element as a DOMRect-shaped object.

content: object

The measured width and height of the tooltip content. as a dimensions object.

bounds: object

The measured position of the available layout area for the tooltip content as a DOMRect-shaped object. This defines the outer collision boundaries referenced by the constrain option.
This should be the browser viewport rect in most instances.

region: string

The preferred region in which the tooltip will appear at first relative to its target. Possibly values are: top, bottom, left, and right.
If region is omitted, the algorithm will pick default to the region with the most available space. (handled by the getIdealRegion function)

offset: number

optional, default: 0
The desired distance between the positioned content and the target.
Since the layout algorithm does not factor the size of an indicator triangle element into the calculation, this value should be supplied as the combined length of the indicator plus the desired margin.

overlap: number

optional, default: 0
The minimum overlap along an edge for each region to be considered valid.
If you are rendering an indicator triangle, this should be the minimum linear overlap necessary to fit the indicator triangle along the adjacent edge.
Providing a negative number is a valid option, this would be useful for rendering a "noodle" connection where direct linear overlap is not required.

align: string | number

optional, default: center
Linear alignment between the positioned content and the target. Possible values are a number in the range of 0 to 1, or one of start, center, and end (aliases for 0, 0.5, and 1 respectively).

disabled: object

optional, default: {top: false, left: false, bottom: false, right: false}
Map of boolean values denoting particular regions as disabled.
Use this option to restrict the tooltip to the regions above and below the content:
  disabled: {
    left: true,
    right: true,

constrain: object

optional, default: {top: true, left: true, bottom: true, right: true}
Map of boolean values denoting particular boundary edges should constrain the positioned tooltip.
The tooltip is allowed to occpuy a region beyond the boundary if a particular edge is disabled. This is used to disable the "sticky" behavior of a positioned tooltip when the viewport scrolls beyond the target element.

Rect Interface

While flowtip-core has no dependency on the DOM, it is designed to be directly compatible with DOMRect instances returned from getClientBoundingRect() calls. Any object that satisfies the DOMRect object interface top: number, left: number, bottom: number, right: number, width?: number, height:? number can be used.
The absolute reference frame of the measurements does not have an impact on the calculation - as long as all measurements are relative to the same frame everything will work out.