#  [](https://www.npmjs.com/package/@thi.ng/hdom-canvas)  [](https://mastodon.thi.ng/@toxi) > [!NOTE] > This is one of 210 standalone projects, maintained as part > of the [@thi.ng/umbrella](https://github.com/thi-ng/umbrella/) monorepo > and anti-framework. > > 🚀 Please help me to work full-time on these projects by [sponsoring me on > GitHub](https://github.com/sponsors/postspectacular). Thank you! ❤️ - [About](#about) - [Status](#status) - [BREAKING CHANGES 3.0.0](#breaking-changes-300) - [Related packages](#related-packages) - [Installation](#installation) - [Dependencies](#dependencies) - [Usage examples](#usage-examples) - [API](#api) - [How it works](#how-it-works) - [Restrictions & behavior controls](#restrictions--behavior-controls) - [HDPI support](#hdpi-support) - [SVG conversion](#svg-conversion) - [Supported shape types](#supported-shape-types) - [Authors](#authors) - [License](#license) ## About [@thi.ng/hdom](https://github.com/thi-ng/umbrella/tree/develop/packages/hdom) component wrapper for declarative canvas scenegraphs. This package provides a [re-usable canvas component](https://github.com/thi-ng/umbrella/tree/develop/packages/hdom-canvas/src/index.ts#L66), which accepts child nodes defining a scene tree of different shape types in standard [@thi.ng/hiccup](https://github.com/thi-ng/umbrella/tree/develop/packages/hiccup) syntax/format (i.e. nested arrays) and then translates these into canvas API draw calls during the hdom update process / cycle. ## Status **STABLE** - used in production [Search or submit any issues for this package](https://github.com/thi-ng/umbrella/issues?q=%5Bhdom-canvas%5D+in%3Atitle) ### BREAKING CHANGES 3.0.0 The actual tree traversal & drawing has been extracted to the new [@thi.ng/hiccup-canvas](https://github.com/thi-ng/umbrella/tree/develop/packages/hiccup-canvas) package for better re-usability, also outside without hdom. ## Related packages - [@thi.ng/geom](https://github.com/thi-ng/umbrella/tree/develop/packages/geom) - Functional, polymorphic API for 2D geometry types & SVG generation - [@thi.ng/hdom](https://github.com/thi-ng/umbrella/tree/develop/packages/hdom) - Lightweight vanilla ES6 UI component trees with customizable branch-local behaviors - [@thi.ng/hiccup-canvas](https://github.com/thi-ng/umbrella/tree/develop/packages/hiccup-canvas) - Hiccup shape tree renderer for vanilla Canvas 2D contexts - [@thi.ng/hiccup-svg](https://github.com/thi-ng/umbrella/tree/develop/packages/hiccup-svg) - SVG element functions for [@thi.ng/hiccup](https://github.com/thi-ng/umbrella/tree/develop/packages/hiccup) & related tooling - [@thi.ng/rdom-canvas](https://github.com/thi-ng/umbrella/tree/develop/packages/rdom-canvas) - [@thi.ng/rdom](https://github.com/thi-ng/umbrella/tree/develop/packages/rdom) component wrapper for [@thi.ng/hiccup-canvas](https://github.com/thi-ng/umbrella/tree/develop/packages/hiccup-canvas) and declarative canvas drawing ## Installation ```bash yarn add @thi.ng/hdom-canvas ``` ESM import: ```ts import * as hc from "@thi.ng/hdom-canvas"; ``` Browser ESM import: ```html ``` [JSDelivr documentation](https://www.jsdelivr.com/) Package sizes (brotli'd, pre-treeshake): ESM: 821 bytes ## Dependencies - [@thi.ng/api](https://github.com/thi-ng/umbrella/tree/develop/packages/api) - [@thi.ng/checks](https://github.com/thi-ng/umbrella/tree/develop/packages/checks) - [@thi.ng/diff](https://github.com/thi-ng/umbrella/tree/develop/packages/diff) - [@thi.ng/errors](https://github.com/thi-ng/umbrella/tree/develop/packages/errors) - [@thi.ng/hdom](https://github.com/thi-ng/umbrella/tree/develop/packages/hdom) - [@thi.ng/hiccup-canvas](https://github.com/thi-ng/umbrella/tree/develop/packages/hiccup-canvas) Note: @thi.ng/api is in _most_ cases a type-only import (not used at runtime) ## Usage examples 18 projects in this repo's [/examples](https://github.com/thi-ng/umbrella/tree/develop/examples) directory are using this package: | Screenshot | Description | Live demo | Source | |:-------------------------------------------------------------------------------------------------------------------------------------|:---------------------------------------------------------------------------------|:------------------------------------------------------------|:-----------------------------------------------------------------------------------------| | | Interactive inverse FFT toy synth | [Demo](https://demo.thi.ng/umbrella/fft-synth/) | [Source](https://github.com/thi-ng/umbrella/tree/develop/examples/fft-synth) | | | Convex hull & shape clipping of 2D polygons | [Demo](https://demo.thi.ng/umbrella/geom-convex-hull/) | [Source](https://github.com/thi-ng/umbrella/tree/develop/examples/geom-convex-hull) | | | Doodle w/ K-nearest neighbor search result visualization | [Demo](https://demo.thi.ng/umbrella/geom-knn/) | [Source](https://github.com/thi-ng/umbrella/tree/develop/examples/geom-knn) | | | K-nearest neighbor search in an hash grid | [Demo](https://demo.thi.ng/umbrella/geom-knn-hash/) | [Source](https://github.com/thi-ng/umbrella/tree/develop/examples/geom-knn-hash) | | | Poisson-disk shape-aware sampling, Voronoi & Minimum Spanning Tree visualization | [Demo](https://demo.thi.ng/umbrella/geom-voronoi-mst/) | [Source](https://github.com/thi-ng/umbrella/tree/develop/examples/geom-voronoi-mst) | | | Realtime analog clock demo | [Demo](https://demo.thi.ng/umbrella/hdom-canvas-clock/) | [Source](https://github.com/thi-ng/umbrella/tree/develop/examples/hdom-canvas-clock) | | | Interactive pattern drawing demo using transducers | [Demo](https://demo.thi.ng/umbrella/hdom-canvas-draw/) | [Source](https://github.com/thi-ng/umbrella/tree/develop/examples/hdom-canvas-draw) | | | 2D Bezier curve-guided particle system | [Demo](https://demo.thi.ng/umbrella/hdom-canvas-particles/) | [Source](https://github.com/thi-ng/umbrella/tree/develop/examples/hdom-canvas-particles) | | | Various hdom-canvas shape drawing examples & SVG conversion / export | [Demo](https://demo.thi.ng/umbrella/hdom-canvas-shapes/) | [Source](https://github.com/thi-ng/umbrella/tree/develop/examples/hdom-canvas-shapes) | | | Canvas based Immediate Mode GUI components | [Demo](https://demo.thi.ng/umbrella/imgui/) | [Source](https://github.com/thi-ng/umbrella/tree/develop/examples/imgui) | | | Minimal IMGUI usage example | [Demo](https://demo.thi.ng/umbrella/imgui-basics/) | [Source](https://github.com/thi-ng/umbrella/tree/develop/examples/imgui-basics) | | | Animated sine plasma effect visualized using contour lines | [Demo](https://demo.thi.ng/umbrella/iso-plasma/) | [Source](https://github.com/thi-ng/umbrella/tree/develop/examples/iso-plasma) | | | Basic rstream-gestures multi-touch demo | [Demo](https://demo.thi.ng/umbrella/multitouch/) | [Source](https://github.com/thi-ng/umbrella/tree/develop/examples/multitouch) | | | Unison wavetable synth with waveform editor | [Demo](https://demo.thi.ng/umbrella/ramp-synth/) | [Source](https://github.com/thi-ng/umbrella/tree/develop/examples/ramp-synth) | | | Animated Voronoi diagram, cubic splines & SVG download | [Demo](https://demo.thi.ng/umbrella/rotating-voronoi/) | [Source](https://github.com/thi-ng/umbrella/tree/develop/examples/rotating-voronoi) | | | 2D scenegraph & shape picking | [Demo](https://demo.thi.ng/umbrella/scenegraph/) | [Source](https://github.com/thi-ng/umbrella/tree/develop/examples/scenegraph) | | | 2D scenegraph & image map based geometry manipulation | [Demo](https://demo.thi.ng/umbrella/scenegraph-image/) | [Source](https://github.com/thi-ng/umbrella/tree/develop/examples/scenegraph-image) | | | Fork-join worker-based raymarch renderer (JS/CPU only) | [Demo](https://demo.thi.ng/umbrella/shader-ast-workers/) | [Source](https://github.com/thi-ng/umbrella/tree/develop/examples/shader-ast-workers) | ## API [Generated API docs](https://docs.thi.ng/umbrella/hdom-canvas/) ```ts import { start } from "@thi.ng/hdom"; import { canvas } from "@thi.ng/hdom-canvas"; start(() => { const t = Date.now() * 0.001; return [canvas, { width: 100, height: 100 }, ["circle", { fill: "red", stroke: "black" }, [50, 50], 25 + 25 * Math.sin(t)] ]; }); ``` Usage with [@thi.ng/geom](https://github.com/thi-ng/umbrella/tree/develop/packages/geom) shape primitives: ```ts import { start } from "@thi.ng/hdom"; import { canvas } from "@thi.ng/hdom-canvas"; import * as g from "@thi.ng/geom"; start(() => { const t = Date.now() * 0.001; return [canvas, { width: 100, height: 100 }, g.group( { translate: [50, 50], fill: "none" }, [ g.withAttribs( g.asPolygon(g.circle(50), 6), { rotate: t % Math.PI, stroke: "red" } ), g.star(25 + 25 * Math.sin(t), 6, [0.5, 1], { stroke: "blue" }), ] ) ]; }); ``` ## How it works The package provides a `canvas` component which uses the branch-local behavior implementation feature of [@thi.ng/hdom](https://github.com/thi-ng/umbrella/tree/develop/packages/hdom) v5.0.0 to support virtual SVG-like shape elements / components. These are defined as part of the main UI component tree just like any other component, but are then translated into canvas API draw commands during the hdom update process. Any embedded shape component functions receive the user context object as first arg, just like normal hdom components. Shape components are expressed in standard hiccup syntax (or as objects implementing the `IToHiccup()` interface, like the shape types provided by [@thi.ng/geom](https://github.com/thi-ng/umbrella/tree/develop/packages/geom)), and with the following... ### Restrictions & behavior controls - Shape component objects with life cycle methods are only partially supported, i.e. only the `render` & `release` methods are used. - For performance reasons `release` methods are disabled by default. If your shape tree contains stateful components which use the `release` life cycle method, you'll need to explicitly enable the canvas component's `__release` control attribute by setting it to `true`. - Currently no event listeners can be assigned to shapes (ignored), though this is planned for a future version. The canvas element itself can of course have event handlers as usual. For best performance it's recommended to ensure all resulting shapes elements are provided in already normalized hiccup format, i.e. ```ts [tag, {attribs}, ...] // or [tag, null, ...] ``` That way the `__normalize: false` control attribute can be added either to the canvas component itself (or to individual shapes / groups), and if present, will skip normalization of that element's children. Likewise, for animated scenes, the `__diff` control attribute should be set to `false` to skip unnecessary diffing and force redraws. To disable the automatic background clearing of the canvas, set the `__clear` attribute to `false`. ```ts import { canvas } from "@thi.ng/hdom-components"; [canvas, { width: 100, height: 100, __clear: false }, ...] ``` ### HDPI support The canvas component automatically adjusts its size for HDPI displays by adding CSS `width` & `height` properties and pre-scaling the drawing context accordingly before any shapes are processed. For fullscreen canvases simply set the `width` & `height` attribs to: ```ts import { canvas } from "@thi.ng/hdom-components"; [canvas, { width: window.innerWidth, height: window.innerHeight }, // shapes ... ] ``` ## SVG conversion Even though the element names & syntax are *very similar* to SVG elements, for performance reasons all geometry data given to each shape remains un-stringified (only styling attributes are). However, the [@thi.ng/hiccup-svg](https://github.com/thi-ng/umbrella/tree/develop/packages/hiccup-svg) package provides a `convertTree()` function which takes the arguably more "raw" shape format used by hdom-canvas and converts an entire shape tree into SVG compatible & serializable format. Note: the tree MUST first be normalized (if not already) using hdom-canvas' `normalizeTree()`. ```ts import { serialize } from "@thi.ng/hiccup"; import { convertTree, svg } from "@thi.ng/hiccup-svg"; import { normalizeTree } from "@thi.ng/hdom-canvas"; serialize( svg({ width: 100, height: 100}, convertTree( normalizeTree( {}, // default normalization options ["g", { fill: "red", stroke: "none", translate: [50, 50] }, ["circle", {}, [0, 0], 25], ["polygon", { fill: "white" }, [[-10,10],[10,10],[0,-10]] ] ] ) ) ) ); ``` ```xml ``` ## Supported shape types Please see the [@thi.ng/hiccup-canvas README](https://github.com/thi-ng/umbrella/tree/develop/packages/hiccup-canvas/README.md#supported-shape-types) for the full list of supported shapes, gradients, attributes, colors and transformations. ## Authors - [Karsten Schmidt](https://thi.ng) (Main author) - [Arthur Carabott](https://github.com/acarabott) If this project contributes to an academic publication, please cite it as: ```bibtex @misc{thing-hdom-canvas, title = "@thi.ng/hdom-canvas", author = "Karsten Schmidt and others", note = "https://thi.ng/hdom-canvas", year = 2018 } ``` ## License © 2018 - 2025 Karsten Schmidt // Apache License 2.0