@rasamjs/boolean

The optional editor adapter registers boolean commands through structural capabilities, with no editor runtime dependency.

Boolean path operations for rasam drawings: union, subtract, intersect and exclude. The result keeps curves: arcs and Bézier segments stay curves instead of turning into many short lines. Geometry comes from PathBool.js (path-bool), a peer of this package only, so apps that don't use boolean operations don't download it.

import { combinePaths, combineSelection } from '@rasamjs/boolean';

const square = drawing.rect({ x: 0, y: 0, width: 100, height: 100, fill: '#a5d8ff' });
const circle = drawing.circle({ cx: 100, cy: 50, r: 50, fill: '#ffd8a8' });
const shape = combinePaths([square, circle], 'union'); // one <path>, one undo step

// With a selection (rasam Selection, or anything with nodes and select()):
combineSelection(selection, 'subtract');

Operations

| Operation | Result | Style from | | ----------- | ---------------------------------------- | -------------------- | | union | Everything covered by any shape | The front-most shape | | subtract | The back-most shape minus all the others | The back-most shape | | intersect | Only what every shape covers | The front-most shape | | exclude | What an odd number of shapes covers | The front-most shape |

Front and back follow document order, so the result matches what you see. The new path takes the front-most shape's place in its parent. Every transform, including those of parent groups, is baked into its path data, so it has no transform attribute. Paint and presentation attributes (fill, stroke, opacity, dashes, class and style) come from the style source, and the path uses fill-rule="evenodd", which renders the result's holes correctly.

The operation is one change group labelled "Union", "Subtract", "Intersect" or "Exclude", so @rasamjs/history records one undo step that restores the original shapes. Pass prepare to name the result inside the same step. When the result is empty, for example intersecting shapes that don't overlap, nothing changes and the call returns null.

Shapes

Rectangles (including rounded corners), circles, ellipses, polygons, polylines and paths are supported; booleanShapes lists them. A polyline counts as its filled area, closed the way SVG fills it. Text, images, lines and groups are rejected; canCombine(nodes) tells you whether a set of nodes can be combined. Geometry attributes must be plain numbers, and an input's fill-rule="evenodd" attribute is honored; CSS fill-rule is not read.

outline(node, space) returns a shape's filled outline as path data in another node's user space, with transforms applied. It is useful on its own, for example to convert a shape to a path.

Requirements

@rasamjs/core, and path-bool 1.0.4 or a later 1.x release. PathBool.js describes itself as early in development; report reduced failure cases upstream. See API.md.