Storycap

A Storybook Addon, Save the screenshot image of your stories :camera: via Puppeteer.

Storycap crawls your Storybook and takes screenshot images. It is primarily responsible for image generation necessary for Visual Testing such as reg-suit.

• Features
• Install
• Getting Started
  • Managed mode
    • Setup Storybook
    • Setup your stories(optional)
    • Run storycap Command
• API
  • withScreenshot
  • type ScreenshotOptions
  • type Variants
  • type Viewport
  • function isScreenshot
• Command Line Options
• Multiple PNGs from 1 story
  • Basic usage
  • Variants composition
  • Parallelisation across multiple computers
• Tips
  • Run with Docker
  • Full control the screenshot timing
• Chromium version
• Storybook compatibility
  • Storybook versions
  • UI frameworks
• Migration
• How it works
• Examples
• TODO
• Contributing
• License

Features

• :camera: Take screenshots of each stories. via Puppeteer.
• :zap: Extremely fast.
• :package: Zero configuration.
• :rocket: Provide flexible screenshot shooting options.
• :tada: Independent of any UI framework(React, Angular, Vue, etc...)

Install

$ npm install storycap

Or

$ npm install storycap puppeteer

Installing puppeteer is optional. See Chromium version to get more detail.

Getting Started

Storycap runs with 2 modes. One is "simple" and another is "managed".

With the simple mode, you don't need to configure your Storybook. All you need is give Storybook's URL, such as:

$ npx storycap http://localhost:9001

You can launch your server via --serverCmd option.

$ storycap --serverCmd "start-storybook -p 9001" http://localhost:9001

Of course, you can use pre-built Storybook:

$ build-storybook -o dist-storybook
$ storycap --serverCmd "npx http-server dist-storybook -p 9001" http://localhost:9001

Also, Storycap can crawls built and hosted Storybook pages:

$ storycap https://next--storybookjs.netlify.app/vue-kitchen-sink/

Managed mode

Setup Storybook

If you want to control how stories are captured (timing or size or etc...), use managed mode.

First, add storycap to your Storybook config file:

/* .storybook/main.js */

module.exports = {
  stories: ['../src/**/*.stories.@(js|mdx)'],
  addons: [
    '@storybook/addon-actions',
    '@storybook/addon-links',
    'storycap', // <-- Add storycap
  ],
};

Next, use withScreenshot decorator to tell how Storycap captures your stories.

/* .storybook/preview.js */

import { withScreenshot } from 'storycap';

export const decorators = [
  withScreenshot, // Registration the decorator is required
];

export const parameters = {
  // Global parameter is optional.
  screenshot: {
    // Put global screenshot parameters(e.g. viewport)
  },
};

Note: You can set configuration of screenshot with addParameters and screenshot key.

Note: Storycap also supports notation of legacy Storybook decorator such as addDecorator(withScreenshot({/* some options */}). But using decorator as function is deprecated and not recommended. See Storybook's migration guide if you want more details.

Setup your stories(optional)

And you can overwrite the global screenshot options in specific stories file via parameters.

import React from 'react';
import MyComponent from './MyComponent';

export default {
  title: 'MyComponent',
  parameters: {
    screenshot: {
      delay: 200,
    },
  },
};

export const normal = () => <MyComponent />;
export const small = () => <MyComponent text="small" />;
small.story = {
  parameters: {
    screenshot: {
      viewport: 'iPhone 5',
    },
  },
};

Of course Storycap works well with CSF 3.0 notation.

import React from 'react';
import MyComponent from './MyComponent';

export default {
  title: 'MyComponent',
  component: MyComponent,
  parameters: {
    screenshot: {
      delay: 200,
    },
  },
};

export const Normal = {};

export const Small = {
  args: {
    text: 'small',
  },
  parameters: {
    screenshot: {
      viewport: 'iPhone 5',
    },
  },
};

Run storycap Command

$ npx start-storybook -p 9009
$ npx storycap http://localhost:9009

Or you can exec with one-liner via --serverCmd option:

$ npx storycap http://localhost:9009 --serverCmd "start-storybook -p 9009"

API

withScreenshot

withScreenshot(opt?: ScreenshotOptions): Function;

A Storybook decorator to notify Storycap to captures stories.

Note: Using withScreenshot as function is deprecated. Use addParameters if you give screenshot options.

type ScreenshotOptions

ScreenshotOptions object is available as the value of the key screenshot of addParameters argument or withScreenshot argument.

interface ScreenshotOptions {
  delay?: number;                           // default 0 msec
  waitAssets?: boolean;                     // default true
  waitFor?: string | () => Promise<void>;   // default ""
  fullPage?: boolean;                       // default true
  hover?: string;                           // default ""
  focus?: string;                           // default ""
  click?: string;                           // default ""
  skip?: boolean;                           // default false
  viewport?: Viewport;
  viewports?: string[] | { [variantName]: Viewport };
  variants?: Variants;
  waitImages?: boolean;                     // default true
  omitBackground?: boolean;                 // default false
  captureBeyondViewport?: boolean;          // default true
  clip?: { x: number; y: number; width: number; height: number } | null; // default null
}

• delay: Waiting time [msec] before capturing.
• waitAssets: If set true, Storycap waits until all resources requested by the story, such as <img> or CSS background images, are finished.
• waitFor : If you set a function to return Promise, Storycap waits the promise is resolved. You can also set a name of global function that returns Promise.
• fullPage: If set true, Storycap captures the entire page of stories.
• focus: If set a valid CSS selector string, Storycap captures after focusing the element matched by the selector.
• hover: If set a valid CSS selector string, Storycap captures after hovering the element matched by the selector.
• click: If set a valid CSS selector string, Storycap captures after clicking the element matched by the selector.
• skip: If set true, Storycap cancels capturing corresponding stories.
• viewport, viewports: See type Viewport section below.
• variants: See type Variants section below.
• waitImages: Deprecated. Use waitAssets. If set true, Storycap waits until <img> in the story are loaded.
• omitBackground: If set true, Storycap omits the background of the page allowing for transparent screenshots. Note the storybook theme will need to be transparent as well.
• captureBeyondViewport: If set true, Storycap captures screenshot beyond the viewport. See also Puppeteer API docs.
• clip: If set, Storycap captures only the portion of the screen bounded by x/y/width/height.

type Variants

Variants is used to generate multiple PNGs from 1 story.

type Variants = {
  [variantName: string]: {
    extends?: string | string[]; // default: ""
    delay?: number;
    waitAssets?: boolean;
    waitFor?: string | () => Promise<void>;
    fullPage?: boolean;
    hover?: string;
    focus?: string;
    click?: string;
    skip?: boolean;
    viewport?: Viewport;
    waitImages?: boolean;
    omitBackground?: boolean;
    captureBeyondViewport?: boolean;
    clip?: { x: number; y: number; width: number; height: number } | null;
  };
};

• extends: If set other variant's name(or an array of names of them), this variant extends the other variant options. And this variant generates a PNG file with suffix such as _${parentVariantName}_${thisVariantName}.

type Viewport

Viewport is compatible for Puppeteer viewport interface.

type Viewport =
  | string
  | {
      width: number; // default: 800
      height: number; // default: 600
      deviceScaleFactor: ?number; // default: 1,
      isMobile?: boolean; // default: false,
      hasTouch?: boolean; // default: false,
      isLandscape?: boolean; // default: false,
    };

Note: You should choose a valid device name if set string.

Viewport values are available in viewports field such as:

addParameters({
  screenshot: {
    viewports: {
      large: {
        width: 1024,
        height: 768,
      },
      small: {
        width: 375,
        height: 668,
      },
      xsmall: {
        width: 320,
        height: 568,
      },
    },
  },
});

function isScreenshot

function isScreenshot(): boolean;

Returns whether current process runs in Storycap browser. It's useful to change your stories' behavior only in Storycap (e.g. disable JavaScript animation).

Command Line Options

usage: storycap [options] storybook_url

Options:
      --help                       Show help                                                                   [boolean]
      --version                    Show version number                                                         [boolean]
  -o, --outDir                     Output directory.                               [string] [default: "__screenshots__"]
  -p, --parallel                   Number of browsers to screenshot.                               [number] [default: 4]
  -f, --flat                       Flatten output filename.                                   [boolean] [default: false]
  -i, --include                    Including stories name rule.                                    [array] [default: []]
  -e, --exclude                    Excluding stories name rule.                                    [array] [default: []]
      --delay                      Waiting time [msec] before screenshot for each story.           [number] [default: 0]
  -V, --viewport                   Viewport.                                              [array] [default: ["800x600"]]
      --disableCssAnimation        Disable CSS animation and transition.                       [boolean] [default: true]
      --disableWaitAssets          Disable waiting for requested assets                       [boolean] [default: false]
      --trace                      Emit Chromium trace files per screenshot.                  [boolean] [default: false]
      --silent                                                                                [boolean] [default: false]
      --verbose                                                                               [boolean] [default: false]
      --forwardConsoleLogs         Forward in-page console logs to the user's console.        [boolean] [default: false]
      --serverCmd                  Command line to launch Storybook server.                       [string] [default: ""]
      --serverTimeout              Timeout [msec] for starting Storybook server.               [number] [default: 60000]
      --shard                      The sharding options for this run. In the format <shardNumber>/<totalShards>.
                                   <shardNumber> is a number between 1 and <totalShards>. <totalShards> is the total
                                   number of computers working.                                [string] [default: "1/1"]
      --captureTimeout             Timeout [msec] for capture a story.                          [number] [default: 5000]
      --captureMaxRetryCount       Number of count to retry to capture.                            [number] [default: 3]
      --metricsWatchRetryCount     Number of count to retry until browser metrics stable.       [number] [default: 1000]
      --viewportDelay              Delay time [msec] between changing viewport and capturing.    [number] [default: 300]
      --reloadAfterChangeViewport  Whether to reload after viewport changed.                  [boolean] [default: false]
      --stateChangeDelay           Delay time [msec] after changing element's state.               [number] [default: 0]
      --listDevices                List available device descriptors.                         [boolean] [default: false]
  -C, --chromiumChannel            Channel to search local Chromium. One of "puppeteer", "canary", "stable", "*"
                                                                                                 [string] [default: "*"]
      --chromiumPath               Executable Chromium path.                                      [string] [default: ""]
      --puppeteerLaunchConfig      JSON string of launch config for Puppeteer.
               [string] [default: "{ "args": ["--no-sandbox", "--disable-setuid-sandbox", "--disable-dev-shm-usage"] }"]

Examples:
  storycap http://localhost:9009
  storycap http://localhost:9009 -V 1024x768 -V 320x568
  storycap http://localhost:9009 -i "some-kind/a-story"
  storycap http://example.com/your-storybook -e "**/default" -V iPad
  storycap --serverCmd "start-storybook -p 3000" http://localhost:3000

Multiple PNGs from 1 story

By default, storycap generates 1 screenshot image from 1 story. Use variants if you want multiple PNGs(e.g. viewports, element's states variation, etc...) for 1 story.

Basic usage

For example:

import React from 'react';
import MyComponent from './MyButton';

export default {
  title: 'MyButton',
};

export const normal = () => <MyButton />;
normal.story = {
  parameters: {
    screenshot: {
      variants: {
        hovered: {
          hover: 'button.my-button',
        },
      },
    },
  },
};

The above configuration generates 2 PNGs:

• MyButton/normal.png
• MyButton/normal_hovered.png

The variant key, hovered in the above example, is used as suffix of the generated PNG file name. And the almost all ScreenshotOptions fields are available as fields of variant value.

Note: variants itself and viewports are prohibited as variant's field.

Variants composition

You can composite multiple variants via extends field.

normal.story = {
  parameters: {
    screenshot: {
      variants: {
        small: {
          viewport: 'iPhone 5',
        },
        hovered: {
          extends: 'small',
          hover: 'button.my-button',
        },
      },
    },
  },
};

The above example generates the following:

• MyButton/normal.png (default
• MyButton/normal_small.png (derived from the small variant
• MyButton/normal_hovered.png (derived from the hovered variant
• MyButton/normal_small_hovered.png (derived from the hovered and small variant

Note: You can extend some viewports with keys of viewports option because the viewports field is expanded to variants internally.

Parallelisation across multiple computers

To process more stories in parallel across multiple computers, the shard argument can be used.

The shard argument is a string of the format: <shardNumber>/<totalShards>. <shardNumber> is a number between 1 and <totalShards>, inclusive. <totalShards> is the total number of computers running the execution.

For example, a run with --shard 1/1 would be considered the default behaviour on a single computer. Two computers each running --shard 1/2 and --shard 2/2 respectively would split the stories across two computers.

Stories are distributed across shards in a round robin fashion when ordered by their ID. If a series of stories 'close together' are slower to screenshot than others, they should be distributed evenly.

Tips

Run with Docker

Use regviz/node-xcb.

Or create your Docker base image such as:

FROM node:12

RUN apt-get update -y
RUN apt-get install -yq gconf-service libasound2 libatk1.0-0 libc6 libcairo2 libcups2 libdbus-1-3 \
    libexpat1 libfontconfig1 libgcc1 libgconf-2-4 libgdk-pixbuf2.0-0 libglib2.0-0 libgtk-3-0 libnspr4 \
    libpango-1.0-0 libpangocairo-1.0-0 libstdc++6 libx11-6 libx11-xcb1 libxcb1 libxcomposite1 \
    libxcursor1 libxdamage1 libxext6 libxfixes3 libxi6 libxrandr2 libxrender1 libxss1 libxtst6 \
    ca-certificates fonts-liberation libappindicator1 libnss3 lsb-release xdg-utils wget

Full control the screenshot timing

Sometimes you may want to full-manage the timing of performing screenshot. Use the waitFor option if you think so. This string parameter should points a global function to return Promise.

For example, the following setting tells storycap to wait for resolving of fontLoading:

<!-- ./storybook/preview-head.html -->
<link rel="preload" href="/some-heavy-asset.woff" as="font" onload="this.setAttribute('loaded', 'loaded')" />
<script>
  function fontLoading() {
    const loaded = () => !!document.querySelector('link[rel="preload"][loaded="loaded"]');
    if (loaded()) return Promise.resolve();
    return new Promise((resolve, reject) => {
      const id = setInterval(() => {
        if (!loaded()) return;
        clearInterval(id);
        resolve();
      }, 50);
    });
  }
</script>

/* .storybook/config.js */
import { addParameters, addDecorator } from '@storybook/react';
import { withScreenshot } from 'storycap';

addDecorator(withScreenshot);
addParameters({
  screenshot: {
    waitFor: 'fontLoading',
  },
});

Chromium version

Since v3.0.0, Storycap does not use Puppeteer directly. Instead, Storycap searches Chromium binary in the following order:

1. Installed Puppeteer package (if you installed explicitly)
2. Canary Chrome installed locally
3. Stable Chrome installed locally

You can change search channel with --chromiumChannel option or set executable Chromium file path with --chromiumPath option.

Storybook compatibility

Storybook versions

Storycap is tested with the followings versions:

• Simple mode:
  • [x] Storybook v5.x
  • [x] Storybook v6.x
• Managed mode:
  • [x] Storybook v5.x
  • [x] Storybook v6.x

See also packages in examples directory.

UI frameworks

Storycap (with both simple and managed mode) is agnostic for specific UI frameworks(e.g. React, Angular, Vue.js, etc...). So you can use it with Storybook with your own favorite framework :smile: .

Migration

See migration guide if you already use storybook-chrome-screenshot or zisui.

How it works

Storycap accesses the launched page using Puppeteer.

TODO

The following tasks remain. Contributes are welcome :smiley:

• [x] Upgrade v2
• [x] Extract crawler as a NPM package.
• [ ] More unit testing.
• [ ] Capture with JS/CSS coverages.

Contributing

See CONTRIBUTING.md.

License

MIT © reg-viz