# @jupyterlab/ui-components The [@jupyterlab/ui-components](https://jupyterlab.github.io/jupyterlab/modules/_ui_components_src_index_.html) package provides UI elements that are widely used in JupyterLab core, and that can be reused in your own extensions. For example, all of the icons in JupyterLab core can be reused via `LabIcon`. You can also use `LabIcon` to create your own custom icons that will be able to automatically change color to match the current JupyterLab theme. # `LabIcon` - set up and render icons `LabIcon` is the icon class used by JupyterLab, and is part of the new icon system introduced in JupyterLab v2.0. ## How JupyterLab handles icons The @jupyterlab/ui-components package provides icons to the rest of JupyterLab, in the form of a set of `LabIcon` instances (currently about 80). All of the icons in the core JupyterLab packages are rendered using one of these `LabIcon` instances. ## Using the icons in your own code You can use any of JupyterLab icons in your own code via an `import` statement. For example, to use `jupyterIcon` you would first do: ```typescript import { jupyterIcon } from '@jupyterlab/ui-components'; ``` ## How to render an icon into a DOM node Icons can be added as children to any `div` or `span` nodes using the `icon.element(...)` method (where `icon` is any instance of `LabIcon`). For example, to render the Jupyter icon you could do: ```typescript jupyterIcon.element({ container: elem, height: '16px', width: '16px', marginLeft: '2px' }); ``` where `elem` is any `HTMLElement` with a `div` or `span` tag. As shown in the above example, the icon can be styled by passing CSS parameters into `.element(...)`. Any valid CSS parameter can be used (one catch: snake case params do have to be converted to camel case: instead of `foo-bar: '8px'`, you’d need to use `fooBar: '8px'`. ## How to render an icon as a React component Icons can also be rendered using React. The `icon.react` parameter holds a standard React component that will display the icon on render. Like any React component, `icon.react` can be used in various ways. For example, here is how you would add the Jupyter icon to the render tree of another React component: ```jsx public render() { return (
"and here's a text node"
); } ``` Alternatively, you can just render the icon directly into any existing DOM node `elem` by using the `ReactDOM` module: ```typescript ReactDOM.render(jupyterIcon.react, elem); ``` If do you use `ReactDOM` to render, and if the `elem` node is ever removed from the DOM, you’ll first need to clean it up: ```typescript ReactDOM.unmountComponentAtNode(elem); ``` This cleanup step is not a special property of `LabIcon`, but is instead needed for any React component that is rendered directly at the top level by `ReactDOM`: failure to call `unmountComponentAtNode` can result in a [memory leak](https://stackoverflow.com/a/48198011/425458). ## How to create your own custom `LabIcon` You can create your own custom icon by constructing a new instance of `LabIcon`: ```typescript export const fooIcon = new LabIcon({ name: 'barpkg:foo', svgstr: '...' }); ``` where `name` should be of the form “your-pkg:icon-name”, and `svgstr` is the raw contents of your icon’s svg file. ## How to create a new `LabIcon` from an external svg file Although you can copy-and-paste an svg directly into the `LabIcon` constructor, the best practice is to keep the svg for each of your icons in its own separate svg file. You will need to have an `svg.d.ts` file at the root of your project’s `src` directory: ```typescript // svg.d.ts declare module '*.svg' { const value: string; export default value; } ``` You can then `import` the contents of an svg file: ```typescript import fooSvgstr from 'path-to-your/foo.svg'; export const fooIcon = new LabIcon({ name: 'barpkg:foo', svgstr: fooSvgstr }); ``` ## Sync icon color to JupyterLab theme Example svgs with class annotation can be found in ui-components/style/icons You can ensure that the colors of your custom `LabIcon` sync up to the colors of the current JuptyerLab theme by adding appropriate `class` annotations to each colored element of your icon's svg. In other words, each element of your svg that a `fill="..."` or a `stroke="..."` property should also have a `class="jp-icon"` property. ### Available icon classes Icon-related CSS classes are defined in ui-components/style/icons.css All colors shown are for the standard light/dark theme, mouse over for hex values. #### `jp-iconX`: contrast to theme background Most one-color icons in JupyterLab (including the sidebar and toolbar icons) are colored using the `jp-icon3` class. For light/dark themes, `jp-icon0` corresponds to the darkest/lighest background color, while `jp-icon1` is somewhat lighter/darker, and so forth. #### `jp-icon-accentX`: match to theme background For light/dark themes, `jp-icon-accent0` corresponds to the lighest/darkest background color, while `jp-icon-accent1` is somewhat darker/lighter, and so forth. ### Adding classes to a one-color icon For most simple, one-color icons, it is desirable for the icon's color to strongly constrast with that of the application's background. You can acheive this using one of the `jp-iconX` classes. **Example: check icon** _svg source:_ ```html ``` _rendered icon:_ ### Adding classes to a multi-colored icon For more complex icons, each element that needs to match the background should be annotated with a `jp-icon-accentX` class, while each element that needs to contrast with the background should be annotated with a `jp-iconX` class. **Example: close-circle icon** _svg source:_ ```html ``` _rendered icon:_ ## Background ### Icon handling in Jupyterlab Pre JupyterLab 2.0, most icons were created using the icons-as-css-background pattern: - Set up the icon’s svg as a `background-image` in CSS: ```css /* CSS */ .jp-FooIcon { background-image: url('path-to-your/foo.svg'); } ``` - Add the icon to the DOM by constructing an otherwise empty DOM node with the appropriate class: ```typescript // typescript const e = document.createElement('div'); e.className = 'jp-FooIcon'; document.body.append(e); ``` What you end up with is a single DOM node that has the “foo” icon as a background image. Post JupyterLab 2.0, nearly all icons in core are now created using [LabIcon](https://github.com/jupyterlab/jupyterlab/blob/f0153e0258b32674c9aec106383ddf7b618cebab/packages/ui-components/src/icon/labicon.tsx) and the icons-as-inline-svg pattern: - Construct a new instance of LabIcon from the icon’s name and svg: ```typescript // typescript // svgstr is the raw contents of an icon's svg file export const fooIcon = new LabIcon({ name: 'barpkg:foo', svgstr: '...' }); ``` - Add the icon to the DOM using the appropriate property of your LabIcon instance (either LabIcon.element() to directly create a DOM node, or LabIcon.react to get the icon as a react component): ```typescript // typescript const e = fooIcon.element(); document.body.append(e); ``` What you end up with is a DOM node (by default a ‘div’) that has an inline svg node as a child. ### `background-image` vs inline svg The big limitation of the old icon-as-css-background pattern is that svg images rendered as `background-image` are invisible to CSS. On the other hand, an icon rendered as an inline svg node is fully exposed to the CSS. This allows us to dynamically change icon styling as needed simply by modifying our CSS. Most importantly, this allows us to recolor icons according to Jupyterlab’s current theme.