tldraw/packages/curve

@tldraw/curve

This package contains the curve methods used by tldraw.

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Installation

yarn add @tldraw/curve
# or
npm i @tldraw/curve

Examples

There are two examples in this repository.

The simple example in the example folder shows a minimal use of the library. It does not do much but this should be a good reference for the API without too much else built on top.

The advanced example in the example-advanced folder shows a more realistic use of the library. (Try it here). While the fundamental patterns are the same, this example contains features such as: panning, pinching, and zooming the camera; creating, cloning, resizing, and deleting shapes; keyboard shortcuts, brush-selection; shape-snapping; undo, redo; and more. Much of the code in the advanced example comes from the @tldraw/tldraw codebase.

If you're working on an app that uses this library, I recommend referring back to the advanced example for tips on how you might implement these features for your own project.

Usage

Import the Renderer React component and pass it the required props.

import * as React from "react"
import { Renderer, TLShape, TLShapeUtil, Vec } from '@tldraw/core'
import { BoxShape, BoxUtil } from "./shapes/box"

const shapeUtils = { box: new BoxUtil() }

function App() {
  const [page, setPage] = React.useState({
    id: "page"
    shapes: {
      "box1": {
        id: 'box1',
        type: 'box',
        parentId: 'page',
        childIndex: 0,
        point: [0, 0],
        size: [100, 100],
        rotation: 0,
      }
    },
    bindings: {}
  })

  const [pageState, setPageState] = React.useState({
    id: "page",
    selectedIds: [],
    camera: {
      point: [0,0],
      zoom: 1
    }
  })

  return (<Renderer
    page={page}
    pageState={pageState}
    shapeUtils={shapeUtils}
  />)
}

Documentation

Renderer

To avoid unnecessary renders, be sure to pass "stable" values as props to the Renderer. Either define these values outside of the parent component, or place them in React state, or memoize them with React.useMemo.

Prop	Type	Description
page	TLPage	The current page object.
pageState	TLPageState	The current page's state.
shapeUtils	TLShapeUtils	The shape utilities used to render the shapes.

In addition to these required props, the Renderer accents many other optional props.

Property	Type	Description
containerRef	React.MutableRefObject	A React ref for the container, where CSS variables will be added.
theme	object	An object with overrides for the Renderer's default colors.
hideBounds	boolean	Do not show the bounding box for selected shapes.
hideHandles	boolean	Do not show handles for shapes with handles.
hideBindingHandles	boolean	Do not show binding controls for selected shapes with bindings.
hideResizeHandles	boolean	Do not show resize handles for selected shapes.
hideRotateHandles	boolean	Do not show rotate handles for selected shapes.
snapLines	TLSnapLine[]	An array of "snap" lines.
users	object	A table of TLUsers.
userId	object	The current user's TLUser id.

The theme object accepts valid CSS colors for the following properties:

Property	Description
foreground	The primary (usually "text") color
background	The default page's background color
brushFill	The fill color of the brush selection box
brushStroke	The stroke color of the brush selection box
selectFill	The fill color of the selection bounds
selectStroke	The stroke color of the selection bounds and handles

The Renderer also accepts many (optional) event callbacks.

Prop	Description
onPan	Panned with the mouse wheel
onZoom	Zoomed with the mouse wheel
onPinchStart	Began a two-pointer pinch
onPinch	Moved their pointers during a pinch
onPinchEnd	Stopped a two-pointer pinch
onPointerDown	Started pointing
onPointerMove	Moved their pointer
onPointerUp	Ended a point
onPointCanvas	Pointed the canvas
onDoubleClickCanvas	Double-pointed the canvas
onRightPointCanvas	Right-pointed the canvas
onDragCanvas	Dragged the canvas
onReleaseCanvas	Stopped pointing the canvas
onHoverShape	Moved their pointer onto a shape
onUnhoverShape	Moved their pointer off of a shape
onPointShape	Pointed a shape
onDoubleClickShape	Double-pointed a shape
onRightPointShape	Right-pointed a shape
onDragShape	Dragged a shape
onReleaseShape	Stopped pointing a shape
onHoverHandle	Moved their pointer onto a shape handle
onUnhoverHandle	Moved their pointer off of a shape handle
onPointHandle	Pointed a shape handle
onDoubleClickHandle	Double-pointed a shape handle
onRightPointHandle	Right-pointed a shape handle
onDragHandle	Dragged a shape handle
onReleaseHandle	Stopped pointing shape handle
onHoverBounds	Moved their pointer onto the selection bounds
onUnhoverBounds	Moved their pointer off of the selection bounds
onPointBounds	Pointed the selection bounds
onDoubleClickBounds	Double-pointed the selection bounds
onRightPointBounds	Right-pointed the selection bounds
onDragBounds	Dragged the selection bounds
onReleaseBounds	Stopped the selection bounds
onHoverBoundsHandle	Moved their pointer onto a selection bounds handle
onUnhoverBoundsHandle	Moved their pointer off of a selection bounds handle
onPointBoundsHandle	Pointed a selection bounds handle
onDoubleClickBoundsHandle	Double-pointed a selection bounds handle
onRightPointBoundsHandle	Right-pointed a selection bounds handle
onDragBoundsHandle	Dragged a selection bounds handle
onReleaseBoundsHandle	Stopped a selection bounds handle
onShapeClone	Clicked on a shape's clone handle
onShapeChange	A shape's component prompted a change
onShapeBlur	A shape's component was prompted a blur
onRenderCountChange	The number of rendered shapes changed
onBoundsChange	The Renderer's screen bounding box of the component changed
onError	The Renderer encountered an error

The @tldraw/core library provides types for most of the event handlers:

Type
TLPinchEventHandler
TLPointerEventHandler
TLCanvasEventHandler
TLBoundsEventHandler
TLBoundsHandleEventHandler
TLShapeChangeHandler
TLShapeBlurHandler
TLShapeCloneHandler

TLPage

An object describing the current page. It contains:

Property	Type	Description
id	string	A unique id for the page.
shapes	TLShape{}	A table of shapes.
bindings	TLBinding{}	A table of bindings.
backgroundColor	string	(optional) The page's background fill color. Will also overwrite the theme.

TLPageState

An object describing the current page. It contains:

Property	Type	Description
id	string	The corresponding page's id
selectedIds	string[]	An array of selected shape ids
camera	object	An object describing the camera state
camera.point	number[]	The camera's [x, y] coordinates
camera.zoom	number	The camera's zoom level
pointedId	string	(optional) The currently pointed shape id
hoveredId	string	(optional) The currently hovered shape id
editingId	string	(optional) The currently editing shape id
bindingId	string	(optional) The currently editing binding.
brush	TLBounds	(optional) A Bounds for the current selection box

TLShape

An object that describes a shape on the page. The shapes in your document should extend this interface with other properties. See Shape Type.

Property	Type	Description
id	string	The shape's id.
type	string	The type of the shape, corresponding to the type of a TLShapeUtil
parentId	string	The id of the shape's parent (either the current page or another shape)
childIndex	number	the order of the shape among its parent's children
name	string	the name of the shape
point	number[]	the shape's current [x, y] coordinates on the page
rotation	number	(optiona) The shape's current rotation in radians
children	string[]	(optional) An array containing the ids of this shape's children
handles	{}	(optional) A table of TLHandle objects
isGhost	boolean	(optional) True if the shape is "ghosted", e.g. while deleting
isLocked	boolean	(optional) True if the shape is locked
isHidden	boolean	(optional) True if the shape is hidden
isEditing	boolean	(optional) True if the shape is currently editing
isGenerated	boolean	optional) True if the shape is generated programatically
isAspectRatioLocked	boolean	(optional) True if the shape's aspect ratio is locked

TLHandle

An object that describes a relationship between two shapes on the page.

Property	Type	Description
id	string	An id for the handle
index	number	The handle's order within the shape's handles
point	number[]	The handle's [x, y] coordinates

When a shape with handles is the only selected shape, the Renderer will display its handles. You can respond to interactions with these handles using the `on

TLBinding

An object that describes a relationship between two shapes on the page.

Property	Type	Description
id	string	A unique id for the binding
fromId	string	The id of the shape where the binding begins
toId	string	The id of the shape where the binding begins

TLSnapLine

A snapline is an array of points (formatted as [x, y]) that represent a "snapping" line.

TLShapeUtil

The TLShapeUtil is an abstract class that you can extend to create utilities for your custom shapes. See the Creating Shapes guide to learn more.

TLUser

A TLUser is the presence information for a multiplayer user. The user's pointer location and selections will be shown on the canvas. If the TLUser's id matches the Renderer's userId prop, then the user's cursor and selections will not be shown.

Property	Type	Description
id	string	A unique id for the user
color	string	The user's color, used for indicators
point	number[]	The user's pointer location on the page
selectedIds[]	string[]	The user's selected shape ids

Utils

A general purpose utility class. See source for more.

Guide: Creating Shapes

The Renderer component has no built-in shapes. It's up to you to define every shape that you want to see on the canvas. While these shapes are highly reusable between projects, you'll need to define them using the API described below.

For several example shapes, see the folder /example/src/shapes/.

Shape Type

Your first task is to define an interface for the shape that extends TLShape. It must have a type property.

// BoxShape.ts
import type { TLShape } from '@tldraw/core'

export interface BoxShape extends TLShape {
  type: 'box'
  size: number[]
}

Component

Next, use TLShapeUtil.Component to create a second component for your shape's Component. The Renderer will use this component to display the shape on the canvas.

// BoxComponent.ts

import * as React from 'react'
import { shapeComponent, SVGContainer } from '@tldraw/core'
import type { BoxShape } from './BoxShape'

export const BoxComponent = TLShapeUtil.Component<BoxShape, SVGSVGElement>(
  ({ shape, events, meta }, ref) => {
    const color = meta.isDarkMode ? 'white' : 'black'

    return (
      <SVGContainer ref={ref} {...events}>
        <rect
          width={shape.size[0]}
          height={shape.size[1]}
          stroke={color}
          strokeWidth={2}
          strokeLinejoin="round"
          fill="none"
          pointerEvents="all"
        />
      </SVGContainer>
    )
  }
)

Your component can return HTML elements or SVG elements. If your shape is returning only SVG elements, wrap it in an SVGContainer. If your shape returns HTML elements, wrap it in an HTMLContainer. Not that you must set pointerEvents manually on the shapes you wish to receive pointer events.

The component will receive the following props:

Name	Type	Description
shape	TLShape	The shape from page.shapes that is being rendered
meta	{}	The value provided to the Renderer's meta prop
events	{}	Several pointer events that should be set on the container element
isSelected	boolean	The shape is selected (its id is in pageState.selectedIds)
isHovered	boolean	The shape is hovered (its id is pageState.hoveredId)
isEditing	boolean	The shape is being edited (its id is pageState.editingId)
isGhost	boolean	The shape is ghosted or is the child of a ghosted shape.
isChildOfSelected	boolean	The shape is the child of a selected shape.
onShapeChange	Function	The callback provided to the Renderer's onShapeChange prop
onShapeBlur	Function	The callback provided to the Renderer's onShapeBlur prop

Indicator

Next, use TLShapeUtil.Indicator to create a second component for your shape's Indicator. This component is shown when the shape is hovered or selected. Your Indicator must return SVG elements only.

// BoxIndicator.ts

export const BoxIndicator = TLShapeUtil.Indicator<BoxShape>(({ shape }) => {
  return (
    <rect
      fill="none"
      stroke="dodgerblue"
      strokeWidth={1}
      width={shape.size[0]}
      height={shape.size[1]}
    />
  )
})

The indicator component will receive the following props:

Name	Type	Description
shape	TLShape	The shape from page.shapes that is being rendered
meta	{}	The value provided to the Renderer's meta prop
user	TLUser	The user when shown in a multiplayer session
isSelected	boolean	Whether the current shape is selected (true if its id is in pageState.selectedIds)
isHovered	boolean	Whether the current shape is hovered (true if its id is pageState.hoveredId)

ShapeUtil

Next, create a "shape util" for your shape. This is a class that extends TLShapeUtil. The Renderer will use an instance of this class to answer questions about the shape: what it should look like, where it is on screen, whether it can rotate, etc.

// BoxUtil.ts

import { Utils, TLBounds, TLShapeUtil } from '@tldraw/core'
import { BoxComponent } from './BoxComponent'
import { BoxIndicator } from './BoxIndicator'
import type { BoxShape } from './BoxShape'

export class BoxUtil extends TLShapeUtil<BoxShape, SVGSVGElement> {
  Component = BoxComponent

  Indicator = BoxIndicator

  getBounds = (shape: BoxShape): TLBounds => {
    const [width, height] = shape.size

    const bounds = {
      minX: 0,
      maxX: width,
      minY: 0,
      maxY: height,
      width,
      height,
    }

    return Utils.translateBounds(bounds, shape.point)
  }
}

Set the Component field to your component and the Indicator field to your indicator component. Then define the getBounds method. This method will receive a shape and should return a TLBounds object.

You may also set the following fields:

Name	Type	Default	Description
showCloneHandles	boolean	false	Whether to display clone handles when the shape is the only selected shape
hideBounds	boolean	false	Whether to hide the bounds when the shape is the only selected shape
isStateful	boolean	false	Whether the shape has its own React state. When true, the shape will not be unmounted when off-screen

ShapeUtils Object

Finally, create a mapping of your project's shape utils and the type properties of their corresponding shapes. Pass this object to the Renderer's shapeUtils prop.

// App.tsx

const shapeUtils = {
  box: new BoxUtil(),
  circle: new CircleUtil(),
  text: new TextUtil(),
}

export function App() {
  // ...

  return <Renderer page={page} pageState={pageState} {...etc} shapeUtils={shapeUtils} />
}

Local Development

To start the development servers for the package and the advanced example:

• Run yarn to install dependencies.
• Run yarn start.
• Open localhost:5420.

You can also run:

• start:advanced to start development servers for the package and the advanced example.
• start:simple to start development servers for the package and the simple example.
• test to execute unit tests via Jest.
• docs to build the docs via ts-doc.
• build to build the package.

Example

See the example folder or this CodeSandbox example.

Community

Support

Need help? Please open an issue for support.

Discussion

Want to connect with other devs? Visit the Discord channel.

License

This project is licensed under MIT.

If you're using the library in a commercial product, please consider becoming a sponsor.

Author

• @steveruizok