feat(Overlay): implement component

src/components/Overlay/Overlay.scss

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+@use '../variables';
+
+$block: '.#{variables.$ns}overlay';
+
+#{$block} {
+    position: absolute;
+    inset: 0;
+
+    display: flex;
+    visibility: hidden;
+    justify-content: center;
+    align-items: center;
+
+    isolation: isolate;
+
+    opacity: 0;
+
+    transition:
+        visibility 0.1s,
+        opacity 0.1s linear;
+
+    &_visible {
+        visibility: visible;
+
+        opacity: 1;
+    }
+
+    &__background {
+        position: absolute;
+        z-index: 0;
+        inset: 0;
+
+        opacity: 0.8;
+
+        &_style {
+            &_base {
+                background-color: var(--g-color-base-background);
+            }
+
+            &_float {
+                background-color: var(--g-color-base-float);
+            }
+        }
+    }
+
+    &__children {
+        z-index: 1;
+    }
+}

src/components/Overlay/Overlay.tsx

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+import React from 'react';
+
+import {block} from '../utils/cn';
+
+import './Overlay.scss';
+
+const b = block('overlay');
+
+export type OverlayBackground = 'base' | 'float';
+
+export interface OverlayProps {
+    className?: string;
+    background?: OverlayBackground;
+    visible?: boolean;
+    children?: React.ReactNode;
+}
+
+export function Overlay({className, background = 'base', visible = false, children}: OverlayProps) {
+    return (
+        <div className={b({visible}, className)}>
+            <div className={b('background', {style: background})} />
+            {children && <div className={b('children')}>{children}</div>}
+        </div>
+    );
+}

src/components/Overlay/README.md

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+<!--GITHUB_BLOCK-->
+
+# Overlay
+
+<!--/GITHUB_BLOCK-->
+
+```tsx
+import {Overlay} from '@gravity-ui/uikit';
+```
+
+The `Overlay` component renders an overlay over the parent element with relative position,
+i.e. parent element must have `position` set to `relative`.
+For example, it can be used to preserve the desired layout while loading data.
+
+```jsx
+import {Box, Overlay, Loader} from '@gravity-ui/uikit';
+
+<Box position="relative">
+  <div>Some content to hide under overlay</div>
+  <Overlay visible={loading}>
+    <Loader />
+  </Overlay>
+</Box>;
+```
+
+## Appearance
+
+### Background
+
+You can use `base` or `float` background colors.
+
+<!--GITHUB_BLOCK-->
+
+```tsx
+<Overlay background="base">
+<Overlay background="float">
+```
+
+<!--/GITHUB_BLOCK-->
+
+## Properties
+
+| Name       | Description                         |        Type        | Default |
+| :--------- | :---------------------------------- | :----------------: | :-----: |
+| className  | CSS class name of the root element  |      `string`      |         |
+| visible    | Overlay visibility state            |     `boolean`      | `false` |
+| background | Overlay background style            | `"base"` `"float"` | `base`  |
+| children   | Content, usually a Loader component | `React.ReactNode`  |         |

src/components/Overlay/__stories__/Docs.mdx

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+import {Meta, Markdown} from '@storybook/addon-docs';
+import * as Stories from './Overlay.stories';
+import Readme from '../README.md?raw';
+
+<Meta of={Stories} />
+
+<Markdown>{Readme}</Markdown>

src/components/Overlay/__stories__/Overlay.stories.scss

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+@use '../../variables';
+
+$block: '.#{variables.$ns}overlay-stories';
+
+#{$block} {
+    &__content {
+        width: fit-content;
+        padding: var(--g-spacing-1);
+    }
+
+    &__table table {
+        min-width: 763px;
+    }
+
+    &__button {
+        margin-block-start: var(--g-spacing-1);
+
+        & + & {
+            margin-inline-start: var(--g-spacing-1);
+        }
+    }
+}

src/components/Overlay/__stories__/Overlay.stories.tsx

@@ -0,0 +1,128 @@
+import React from 'react';
+
+import {ArrowsRotateRight} from '@gravity-ui/icons';
+import type {Meta, StoryObj} from '@storybook/react';
+
+import {Showcase} from '../../../demo/Showcase';
+import {ShowcaseItem} from '../../../demo/ShowcaseItem';
+import {Button} from '../../Button';
+import {Icon} from '../../Icon';
+import {Loader} from '../../Loader';
+import {Table as TableComponent} from '../../Table';
+import {Box} from '../../layout';
+import {block} from '../../utils/cn';
+import {Overlay} from '../Overlay';
+import type {OverlayProps} from '../Overlay';
+
+import {columns, data} from './data';
+import type {DataItem} from './data';
+
+import './Overlay.stories.scss';
+
+const b = block('overlay-stories');
+
+type Story = StoryObj<typeof Overlay>;
+
+export default {
+    title: 'Components/Utils/Overlay',
+    component: Overlay,
+} as Meta;
+
+export const Default: Story = {
+    args: {
+        visible: true,
+    },
+    render: (args) => {
+        return (
+            <Showcase>
+                <Box position="relative" className={b('content')}>
+                    <div>Example of overlay</div>
+                    <div>with loader</div>
+                    <Overlay {...args}>
+                        <Loader size="m" />
+                    </Overlay>
+                </Box>
+                <Box position="relative" className={b('content')}>
+                    <div>Example of overlay</div>
+                    <div>with text</div>
+                    <Overlay {...args}>Loading...</Overlay>
+                </Box>
+                <Box position="relative" className={b('content')}>
+                    <div>Example of overlay</div>
+                    <div>with icon</div>
+                    <Overlay {...args}>
+                        <Icon data={ArrowsRotateRight} />
+                    </Overlay>
+                </Box>
+                <Box position="relative" className={b('content')}>
+                    <div>Example of overlay</div>
+                    <div>without children</div>
+                    <Overlay {...args} />
+                </Box>
+            </Showcase>
+        );
+    },
+};
+
+export const Background: Story = {
+    args: {
+        visible: true,
+    },
+    render: (args) => {
+        return (
+            <Showcase>
+                <ShowcaseItem title="base">
+                    <Box position="relative" className={b('content')}>
+                        <div>I am an example</div>
+                        <div>content</div>
+                        <Overlay {...args} background="base" />
+                    </Box>
+                </ShowcaseItem>
+                <ShowcaseItem title="float">
+                    <Box position="relative" className={b('content')}>
+                        <div>I am an example</div>
+                        <div>content</div>
+                        <Overlay {...args} background="float" />
+                    </Box>
+                </ShowcaseItem>
+            </Showcase>
+        );
+    },
+};
+
+const TableView = (args: OverlayProps) => {
+    const [loading, setLoading] = React.useState(false);
+    const [loadedData, setData] = React.useState<DataItem[]>([]);
+
+    return (
+        <div className={b()}>
+            <Box position="relative" className={b('content')}>
+                <TableComponent className={b('table')} columns={columns} data={loadedData} />
+                <Overlay {...args} visible={loading}>
+                    <Loader size="m" />
+                </Overlay>
+            </Box>
+            <Button
+                className={b('button')}
+                disabled={loading}
+                onClick={() => {
+                    setLoading(true);
+                    setTimeout(() => {
+                        setLoading(false);
+                        setData(data);
+                    }, 1000);
+                }}
+            >
+                Load data
+            </Button>
+            <Button className={b('button')} disabled={loading} onClick={() => setData([])}>
+                Clear data
+            </Button>
+        </div>
+    );
+};
+
+export const Table: Story = {
+    args: {},
+    render: TableView,
+};

src/components/Overlay/__stories__/data.tsx

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+import React from 'react';
+
+import type {TableColumnConfig} from '../../Table';
+
+export interface DataItem {
+    name: string;
+    location?: {region: string; city?: string};
+    phone: string;
+    count: number;
+    date: string;
+    disabled?: boolean;
+}
+
+export const columns: TableColumnConfig<DataItem>[] = [
+    {
+        id: 'name',
+        name: 'Name',
+        template(item, i) {
+            if (i % 2 === 0) {
+                return item.name;
+            }
+            const [name, surname] = item.name.split(' ');
+            return (
+                <div>
+                    {name}
+                    <br />
+                    {surname}
+                </div>
+            );
+        },
+    },
+    {
+        id: 'location.region',
+        name: 'Region',
+    },
+    {
+        id: 'location.city',
+        name: 'City',
+    },
+    {
+        id: 'phone',
+        name: 'Phone',
+    },
+    {
+        id: 'count',
+        name: 'Count',
+        align: 'end',
+    },
+    {
+        id: 'date',
+        name: 'Date created',
+    },
+];
+
+export const data: DataItem[] = [
+    {
+        name: 'Nomlanga Compton',
+        location: {region: 'Liguria', city: 'Erli'},
+        phone: '+7 (923) 737-89-72',
+        count: 82,
+        date: '2019-03-15',
+    },
+    {
+        name: 'Paul Hatfield',
+        location: {region: 'Trentino-Alto Adige/Südtirol', city: 'Campitello di Fassa'},
+        phone: '+7 (900) 333-82-02',
+        count: 51,
+        date: '2019-11-23',
+    },
+    {
+        name: 'Phelan Daniel',
+        location: {region: 'Piedmont', city: 'Meugliano'},
+        phone: '+7 (925) 549-50-23',
+        count: 10,
+        date: '2019-05-14',
+    },
+    {
+        name: 'Hiram Mayer',
+        phone: '+7 (950) 372-56-84',
+        location: {region: 'Calabria'},
+        count: 54,
+        date: '2019-03-29',
+    },
+    {
+        name: 'Madeline Puckett',
+        phone: '+7 (908) 582-05-91',
+        count: 75,
+        date: '2019-02-01',
+        disabled: true,
+    },
+];

src/components/Overlay/index.ts

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+export * from './Overlay';

src/components/index.ts

@@ -25,6 +25,7 @@ export * from './List';
 export * from './Loader';
 export * from './Menu';
 export * from './Modal';
+export * from './Overlay';
 export * from './Pagination';
 export * from './Palette';
 export * from './UserLabel';