EuiBottomBar: allow customization of whether the component makes room for itself

CHANGELOG.md

@@ -6,6 +6,7 @@
 - Added more exports for `EuiBasicTable` types ([#4125](https://github.com/elastic/eui/pull/4125))
 - Updated types associated with `EuiMarkdownEditor` plugin dependencies ([4124](https://github.com/elastic/eui/pull/4124))
 - Upgraded dependencies related to `EuiMarkdownEditor`: `react-dropzone`, `rehype-*`, `remark-*`, and `unified` ([#4124](https://github.com/elastic/eui/pull/4124))
+- Added `affordForDisplacement` prop to `EuiBottomBar` ([#4156](https://github.com/elastic/eui/pull/4156))
 
 **Breaking changes**
 

src-docs/src/views/bottom_bar/bottom_bar.js

@@ -12,7 +12,7 @@ export default () => {
   const [showBar, setShowBar] = useState(false);
 
   const button = (
-    <EuiButton color="primary" onClick={() => setShowBar(!showBar)}>
+    <EuiButton color="primary" onClick={() => setShowBar((show) => !show)}>
       Toggle appearance of the bottom bar
     </EuiButton>
   );

src-docs/src/views/bottom_bar/bottom_bar_displacement.js

@@ -0,0 +1,58 @@
+import React, { useState } from 'react';
+
+import {
+  EuiBottomBar,
+  EuiButtonGroup,
+  EuiButtonEmpty,
+  EuiFlexGroup,
+  EuiFlexItem,
+} from '../../../../src/components';
+
+export default () => {
+  const [toggleIdSelected, setToggleIdSelected] = useState(null);
+
+  const toggleButtons = [
+    {
+      id: 'bottomBarStandard',
+      label: 'Show bottom bar',
+    },
+    {
+      id: 'bottomBarWithoutAffordForDisplacement',
+      label: 'Show bottom bar (without affordForDisplacement behavior)',
+    },
+  ];
+
+  const onChange = (optionId) => {
+    setToggleIdSelected(optionId);
+  };
+
+  return (
+    <div>
+      <EuiButtonGroup
+        legend="Bottom Bar demo toggle buttons group"
+        type="single"
+        buttonSize="m"
+        options={toggleButtons}
+        idSelected={toggleIdSelected}
+        onChange={(id) => onChange(id)}
+      />
+
+      {toggleIdSelected && (
+        <EuiBottomBar
+          affordForDisplacement={toggleIdSelected === 'bottomBarStandard'}>
+          <EuiFlexGroup justifyContent="flexEnd">
+            <EuiFlexItem grow={false}>
+              <EuiButtonEmpty
+                onClick={() => setToggleIdSelected(null)}
+                color="ghost"
+                size="s"
+                iconType="cross">
+                close
+              </EuiButtonEmpty>
+            </EuiFlexItem>
+          </EuiFlexGroup>
+        </EuiBottomBar>
+      )}
+    </div>
+  );
+};

src-docs/src/views/bottom_bar/bottom_bar_example.js

@@ -14,6 +14,14 @@ const bottomBarSnippet = `<EuiBottomBar paddingSize="s">
   <!-- Content goes here -->
 </EuiBottomBar>`;
 
+import BottomBarDisplacement from './bottom_bar_displacement';
+const bottomBarDisplacementSource = require('!!raw-loader!./bottom_bar_displacement');
+const bottomBarDisplacementHtml = renderToHtml(BottomBarDisplacement);
+
+const bottomBarDisplacementSnippet = `<EuiBottomBar affordForDisplacement={false}>
+  <!-- Content goes here -->
+</EuiBottomBar>`;
+
 export const BottomBarExample = {
   title: 'Bottom bar',
   sections: [
@@ -29,7 +37,7 @@ export const BottomBarExample = {
         },
       ],
       text: (
-        <div>
+        <>
           <p>
             <strong>EuiBottomBar</strong> is a simple wrapper component that
             does nothing but fix a bottom bar (usually filled with buttons) to
@@ -41,13 +49,41 @@ export const BottomBarExample = {
             Like many of our other wrapper components,{' '}
             <strong>EuiBottomBar</strong> accepts a{' '}
             <EuiCode>paddingSize</EuiCode> prop, which can be set to{' '}
-            <EuiCode>s / m / l / none</EuiCode>.
+            <EuiCode>s / m (default) / l / none</EuiCode>.
           </p>
-        </div>
+        </>
       ),
       props: { EuiBottomBar },
       snippet: bottomBarSnippet,
       demo: <BottomBar />,
     },
+    {
+      title: 'Displacement',
+      source: [
+        {
+          type: GuideSectionTypes.JS,
+          code: bottomBarDisplacementSource,
+        },
+        {
+          type: GuideSectionTypes.HTML,
+          code: bottomBarDisplacementHtml,
+        },
+      ],
+      text: (
+        <>
+          <p>
+            There is an <EuiCode>affordForDisplacement</EuiCode> prop
+            (defaulting to <EuiCode>true</EuiCode>), which determines whether
+            the component makes room for itself by adding bottom padding
+            equivalent to its own height on the document body element. Setting
+            this to <EuiCode>false</EuiCode> can be useful to minimize scrollbar
+            visibility but will cause the bottom bar to overlap body content.
+          </p>
+        </>
+      ),
+      props: { EuiBottomBar },
+      snippet: bottomBarDisplacementSnippet,
+      demo: <BottomBarDisplacement />,
+    },
   ],
 };

src/components/bottom_bar/__snapshots__/bottom_bar.test.tsx.snap

@@ -23,6 +23,40 @@ Array [
 ]
 `;
 
+exports[`EuiBottomBar props affordForDisplacement can be false 1`] = `
+Array [
+  <section
+    aria-label="Page level controls"
+    class="euiBottomBar euiBottomBar--paddingMedium"
+  >
+    <h2
+      class="euiScreenReaderOnly"
+    >
+      Page level controls
+    </h2>
+  </section>,
+  <p
+    aria-live="assertive"
+    class="euiScreenReaderOnly"
+  >
+    There is a new region landmark with page level controls at the end of the document.
+  </p>,
+]
+`;
+
+exports[`EuiBottomBar props bodyClassName is rendered 1`] = `
+<section
+  aria-label="Page level controls"
+  class="euiBottomBar euiBottomBar--paddingMedium"
+>
+  <h2
+    class="euiScreenReaderOnly"
+  >
+    Page level controls
+  </h2>
+</section>
+`;
+
 exports[`EuiBottomBar props paddingSize l is rendered 1`] = `
 Array [
   <section

src/components/bottom_bar/bottom_bar.test.tsx

@@ -19,15 +19,19 @@
 
 import React from 'react';
 import ReactDOM from 'react-dom';
-import { render } from 'enzyme';
-import { requiredProps } from '../../test/required_props';
+import { render, mount } from 'enzyme';
 import { keysOf } from '../common';
+import { requiredProps, takeMountedSnapshot } from '../../test';
 
 import { EuiBottomBar, paddingSizeToClassNameMap } from './bottom_bar';
 
 // @ts-ignore TODO: Temporary hack which we can remove once react-test-renderer supports portals.
 // More info at https://github.com/facebook/react/issues/11565.
-ReactDOM.createPortal = (node) => node;
+ReactDOM.createPortal = (children) => {
+  // hack to make enzyme treat the portal as a fragment
+  if (children == null) return [['nested']];
+  return children;
+};
 
 describe('EuiBottomBar', () => {
   test('is rendered', () => {
@@ -48,5 +52,18 @@ describe('EuiBottomBar', () => {
         });
       });
     });
+
+    test('affordForDisplacement can be false', () => {
+      const component = render(<EuiBottomBar affordForDisplacement={false} />);
+
+      expect(component).toMatchSnapshot();
+    });
+
+    test('bodyClassName is rendered', () => {
+      const component = mount(<EuiBottomBar bodyClassName={'customClass'} />);
+
+      expect(takeMountedSnapshot(component)).toMatchSnapshot();
+      expect(document.body.classList.contains('customClass')).toBe(true);
+    });
   });
 });

src/components/bottom_bar/bottom_bar.tsx

@@ -38,34 +38,73 @@ export const paddingSizeToClassNameMap: {
 
 interface Props extends CommonProps {
   /**
-   * Optional class applied to the body class
+   * Padding applied to the bar. Default is 'm'.
    */
-  bodyClassName?: string;
+  paddingSize: BottomBarPaddingSize;
+
+  /**
+   * Whether the component should apply padding on the document body element to afford for its own displacement height.
+   * Default is true.
+   */
+  affordForDisplacement: boolean;
 
   /**
-   * Padding applied to the bar
+   * Optional class applied to the body element on mount
    */
-  paddingSize?: BottomBarPaddingSize;
+  bodyClassName?: string;
 
   /**
-   * Customize the screen reader heading that helps users find this control. Default is "Page level controls".
+   * Customize the screen reader heading that helps users find this control. Default is 'Page level controls'.
    */
   landmarkHeading?: string;
 }
 
 export class EuiBottomBar extends Component<Props> {
+  static defaultProps = {
+    paddingSize: 'm',
+    affordForDisplacement: true,
+  };
+
   private bar: HTMLElement | null = null;
 
   componentDidMount() {
-    const height = this.bar ? this.bar.clientHeight : -1;
-    document.body.style.paddingBottom = `${height}px`;
+    if (this.props.affordForDisplacement) {
+      const height = this.bar ? this.bar.clientHeight : -1;
+      document.body.style.paddingBottom = `${height}px`;
+    }
+
     if (this.props.bodyClassName) {
       document.body.classList.add(this.props.bodyClassName);
     }
   }
 
+  componentDidUpdate(prevProps: Props) {
+    if (prevProps.affordForDisplacement !== this.props.affordForDisplacement) {
+      if (this.props.affordForDisplacement) {
+        // start affording for displacement
+        const height = this.bar ? this.bar.clientHeight : -1;
+        document.body.style.paddingBottom = `${height}px`;
+      } else {
+        // stop affording for displacement
+        document.body.style.paddingBottom = '';
+      }
+    }
+
+    if (prevProps.bodyClassName !== this.props.bodyClassName) {
+      if (prevProps.bodyClassName) {
+        document.body.classList.remove(prevProps.bodyClassName);
+      }
+      if (this.props.bodyClassName) {
+        document.body.classList.add(this.props.bodyClassName);
+      }
+    }
+  }
+
   componentWillUnmount() {
-    document.body.style.paddingBottom = '';
+    if (this.props.affordForDisplacement) {
+      document.body.style.paddingBottom = '';
+    }
+
     if (this.props.bodyClassName) {
       document.body.classList.remove(this.props.bodyClassName);
     }
@@ -75,9 +114,10 @@ export class EuiBottomBar extends Component<Props> {
     const {
       children,
       className,
-      paddingSize = 'm',
+      paddingSize,
       bodyClassName,
       landmarkHeading,
+      affordForDisplacement,
       ...rest
     } = this.props;