Fix dropdown menu positions when scrolling (#22916)

* Update react-overlays to latest version

* Fix breaking changes in dropdown menus

* Use react-overlays built-in arrow positioning feature
* Re-implemented `.dropdown-menu__arrow` to have a defined width and height to improve positioning
* Moved wrapping div (`.dropdown-menu` from `DropdownMenu` to `Dropdown`)
* Wrap button in a span to solve issue with ref
* Temporarily remove animations

* Fix breaking changes in emoji picker

* Wrap EmojiPickerMenu in a div where react-overlays’ ref is added

* Fix breaking changes in language dropdown

* Fix breaking changes in privacy dropdown

* Fix breaking changes in search form

* Add animations back using `@keyframes`

* Fix arrow color in light theme

* Fix linting issue

* Remove unused `mounted` state

* Remove `placement` state from components and redux

And remove the placement state from props of the menu components.

* Remove abolution position to fix flip issue

* Remove z-index to fix modals and overlay positions

* Fix lint issues

* Set placement in privacy and language components

Copy the placement state into the `PrivacyDropdown` and `LanguageDropdown` components, to apply correct styling to the buttons depending on which placement the Overlay has.

* Move `placement` state to correct component

11 files changed, 239 insertions, 242 deletions

diff --git a/app/javascript/mastodon/actions/dropdown_menu.js b/app/javascript/mastodon/actions/dropdown_menu.js
index fb6e55612..023151d4b 100644
--- a/app/javascript/mastodon/actions/dropdown_menu.js
+++ b/app/javascript/mastodon/actions/dropdown_menu.js
@@ -1,8 +1,8 @@
 export const DROPDOWN_MENU_OPEN = 'DROPDOWN_MENU_OPEN';
 export const DROPDOWN_MENU_CLOSE = 'DROPDOWN_MENU_CLOSE';
 
-export function openDropdownMenu(id, placement, keyboard, scroll_key) {
-  return { type: DROPDOWN_MENU_OPEN, id, placement, keyboard, scroll_key };
+export function openDropdownMenu(id, keyboard, scroll_key) {
+  return { type: DROPDOWN_MENU_OPEN, id, keyboard, scroll_key };
 }
 
 export function closeDropdownMenu(id) {
diff --git a/app/javascript/mastodon/components/dropdown_menu.js b/app/javascript/mastodon/components/dropdown_menu.js
index 4b4ad8355..5897aada8 100644
--- a/app/javascript/mastodon/components/dropdown_menu.js
+++ b/app/javascript/mastodon/components/dropdown_menu.js
@@ -2,9 +2,7 @@ import React from 'react';
 import PropTypes from 'prop-types';
 import ImmutablePropTypes from 'react-immutable-proptypes';
 import IconButton from './icon_button';
-import Overlay from 'react-overlays/lib/Overlay';
-import Motion from '../features/ui/util/optional_motion';
-import spring from 'react-motion/lib/spring';
+import Overlay from 'react-overlays/Overlay';
 import { supportsPassiveEvents } from 'detect-passive-events';
 import classNames from 'classnames';
 import { CircularProgress } from 'mastodon/components/loading_indicator';
@@ -24,9 +22,6 @@ class DropdownMenu extends React.PureComponent {
     scrollable: PropTypes.bool,
     onClose: PropTypes.func.isRequired,
     style: PropTypes.object,
-    placement: PropTypes.string,
-    arrowOffsetLeft: PropTypes.string,
-    arrowOffsetTop: PropTypes.string,
     openedViaKeyboard: PropTypes.bool,
     renderItem: PropTypes.func,
     renderHeader: PropTypes.func,
@@ -35,11 +30,6 @@ class DropdownMenu extends React.PureComponent {
 
   static defaultProps = {
     style: {},
-    placement: 'bottom',
-  };
-
-  state = {
-    mounted: false,
   };
 
   handleDocumentClick = e => {
@@ -56,8 +46,6 @@ class DropdownMenu extends React.PureComponent {
     if (this.focusedItem && this.props.openedViaKeyboard) {
       this.focusedItem.focus({ preventScroll: true });
     }
-
-    this.setState({ mounted: true });
   }
 
   componentWillUnmount () {
@@ -139,40 +127,28 @@ class DropdownMenu extends React.PureComponent {
   }
 
   render () {
-    const { items, style, placement, arrowOffsetLeft, arrowOffsetTop, scrollable, renderHeader, loading } = this.props;
-    const { mounted } = this.state;
+    const { items, scrollable, renderHeader, loading } = this.props;
 
     let renderItem = this.props.renderItem || this.renderItem;
 
     return (
-      <Motion defaultStyle={{ opacity: 0, scaleX: 0.85, scaleY: 0.75 }} style={{ opacity: spring(1, { damping: 35, stiffness: 400 }), scaleX: spring(1, { damping: 35, stiffness: 400 }), scaleY: spring(1, { damping: 35, stiffness: 400 }) }}>
-        {({ opacity, scaleX, scaleY }) => (
-          // It should not be transformed when mounting because the resulting
-          // size will be used to determine the coordinate of the menu by
-          // react-overlays
-          <div className={`dropdown-menu ${placement}`} style={{ ...style, opacity: opacity, transform: mounted ? `scale(${scaleX}, ${scaleY})` : null }} ref={this.setRef}>
-            <div className={`dropdown-menu__arrow ${placement}`} style={{ left: arrowOffsetLeft, top: arrowOffsetTop }} />
-
-            <div className={classNames('dropdown-menu__container', { 'dropdown-menu__container--loading': loading })}>
-              {loading && (
-                <CircularProgress size={30} strokeWidth={3.5} />
-              )}
-
-              {!loading && renderHeader && (
-                <div className='dropdown-menu__container__header'>
-                  {renderHeader(items)}
-                </div>
-              )}
-
-              {!loading && (
-                <ul className={classNames('dropdown-menu__container__list', { 'dropdown-menu__container__list--scrollable': scrollable })}>
-                  {items.map((option, i) => renderItem(option, i, { onClick: this.handleClick, onKeyPress: this.handleItemKeyPress }))}
-                </ul>
-              )}
-            </div>
+      <div className={classNames('dropdown-menu__container', { 'dropdown-menu__container--loading': loading })} ref={this.setRef}>
+        {loading && (
+          <CircularProgress size={30} strokeWidth={3.5} />
+        )}
+
+        {!loading && renderHeader && (
+          <div className='dropdown-menu__container__header'>
+            {renderHeader(items)}
           </div>
         )}
-      </Motion>
+
+        {!loading && (
+          <ul className={classNames('dropdown-menu__container__list', { 'dropdown-menu__container__list--scrollable': scrollable })}>
+            {items.map((option, i) => renderItem(option, i, { onClick: this.handleClick, onKeyPress: this.handleItemKeyPress }))}
+          </ul>
+        )}
+      </div>
     );
   }
 
@@ -197,7 +173,6 @@ export default class Dropdown extends React.PureComponent {
     isUserTouching: PropTypes.func,
     onOpen: PropTypes.func.isRequired,
     onClose: PropTypes.func.isRequired,
-    dropdownPlacement: PropTypes.string,
     openDropdownId: PropTypes.number,
     openedViaKeyboard: PropTypes.bool,
     renderItem: PropTypes.func,
@@ -213,13 +188,11 @@ export default class Dropdown extends React.PureComponent {
     id: id++,
   };
 
-  handleClick = ({ target, type }) => {
+  handleClick = ({ type }) => {
     if (this.state.id === this.props.openDropdownId) {
       this.handleClose();
     } else {
-      const { top } = target.getBoundingClientRect();
-      const placement = top * 2 < innerHeight ? 'bottom' : 'top';
-      this.props.onOpen(this.state.id, this.handleItemClick, placement, type !== 'click');
+      this.props.onOpen(this.state.id, this.handleItemClick, type !== 'click');
     }
   }
 
@@ -303,7 +276,6 @@ export default class Dropdown extends React.PureComponent {
       disabled,
       loading,
       scrollable,
-      dropdownPlacement,
       openDropdownId,
       openedViaKeyboard,
       children,
@@ -314,7 +286,6 @@ export default class Dropdown extends React.PureComponent {
     const open = this.state.id === openDropdownId;
 
     const button = children ? React.cloneElement(React.Children.only(children), {
-      ref: this.setTargetRef,
       onClick: this.handleClick,
       onMouseDown: this.handleMouseDown,
       onKeyDown: this.handleButtonKeyDown,
@@ -326,7 +297,6 @@ export default class Dropdown extends React.PureComponent {
         active={open}
         disabled={disabled}
         size={size}
-        ref={this.setTargetRef}
         onClick={this.handleClick}
         onMouseDown={this.handleMouseDown}
         onKeyDown={this.handleButtonKeyDown}
@@ -336,19 +306,27 @@ export default class Dropdown extends React.PureComponent {
 
     return (
       <React.Fragment>
-        {button}
-
-        <Overlay show={open} placement={dropdownPlacement} target={this.findTarget}>
-          <DropdownMenu
-            items={items}
-            loading={loading}
-            scrollable={scrollable}
-            onClose={this.handleClose}
-            openedViaKeyboard={openedViaKeyboard}
-            renderItem={renderItem}
-            renderHeader={renderHeader}
-            onItemClick={this.handleItemClick}
-          />
+        <span ref={this.setTargetRef}>
+          {button}
+        </span>
+        <Overlay show={open} offset={[5, 5]} placement={'bottom'} flip target={this.findTarget} popperConfig={{ strategy: 'fixed' }}>
+          {({ props, arrowProps, placement }) => (
+            <div {...props}>
+              <div className={`dropdown-animation dropdown-menu ${placement}`}>
+                <div className={`dropdown-menu__arrow ${placement}`} {...arrowProps} />
+                <DropdownMenu
+                  items={items}
+                  loading={loading}
+                  scrollable={scrollable}
+                  onClose={this.handleClose}
+                  openedViaKeyboard={openedViaKeyboard}
+                  renderItem={renderItem}
+                  renderHeader={renderHeader}
+                  onItemClick={this.handleItemClick}
+                />
+              </div>
+            </div>
+          )}
         </Overlay>
       </React.Fragment>
     );
diff --git a/app/javascript/mastodon/components/edited_timestamp/containers/dropdown_menu_container.js b/app/javascript/mastodon/components/edited_timestamp/containers/dropdown_menu_container.js
index e30c18372..16fe77a73 100644
--- a/app/javascript/mastodon/components/edited_timestamp/containers/dropdown_menu_container.js
+++ b/app/javascript/mastodon/components/edited_timestamp/containers/dropdown_menu_container.js
@@ -4,7 +4,6 @@ import { fetchHistory } from 'mastodon/actions/history';
 import DropdownMenu from 'mastodon/components/dropdown_menu';
 
 const mapStateToProps = (state, { statusId }) => ({
-  dropdownPlacement: state.getIn(['dropdown_menu', 'placement']),
   openDropdownId: state.getIn(['dropdown_menu', 'openId']),
   openedViaKeyboard: state.getIn(['dropdown_menu', 'keyboard']),
   items: state.getIn(['history', statusId, 'items']),
@@ -13,9 +12,9 @@ const mapStateToProps = (state, { statusId }) => ({
 
 const mapDispatchToProps = (dispatch, { statusId }) => ({
 
-  onOpen (id, onItemClick, dropdownPlacement, keyboard) {
+  onOpen (id, onItemClick, keyboard) {
     dispatch(fetchHistory(statusId));
-    dispatch(openDropdownMenu(id, dropdownPlacement, keyboard));
+    dispatch(openDropdownMenu(id, keyboard));
   },
 
   onClose (id) {
diff --git a/app/javascript/mastodon/containers/dropdown_menu_container.js b/app/javascript/mastodon/containers/dropdown_menu_container.js
index c45bab40b..bedd1c63f 100644
--- a/app/javascript/mastodon/containers/dropdown_menu_container.js
+++ b/app/javascript/mastodon/containers/dropdown_menu_container.js
@@ -6,13 +6,12 @@ import DropdownMenu from '../components/dropdown_menu';
 import { isUserTouching } from '../is_mobile';
 
 const mapStateToProps = state => ({
-  dropdownPlacement: state.getIn(['dropdown_menu', 'placement']),
   openDropdownId: state.getIn(['dropdown_menu', 'openId']),
   openedViaKeyboard: state.getIn(['dropdown_menu', 'keyboard']),
 });
 
 const mapDispatchToProps = (dispatch, { status, items, scrollKey }) => ({
-  onOpen(id, onItemClick, dropdownPlacement, keyboard) {
+  onOpen(id, onItemClick, keyboard) {
     if (status) {
       dispatch(fetchRelationships([status.getIn(['account', 'id'])]));
     }
@@ -21,7 +20,7 @@ const mapDispatchToProps = (dispatch, { status, items, scrollKey }) => ({
       status,
       actions: items,
       onClick: onItemClick,
-    }) : openDropdownMenu(id, dropdownPlacement, keyboard, scrollKey));
+    }) : openDropdownMenu(id, keyboard, scrollKey));
   },
 
   onClose(id) {
diff --git a/app/javascript/mastodon/features/compose/components/emoji_picker_dropdown.js b/app/javascript/mastodon/features/compose/components/emoji_picker_dropdown.js
index 8cca8af2a..76c9cda81 100644
--- a/app/javascript/mastodon/features/compose/components/emoji_picker_dropdown.js
+++ b/app/javascript/mastodon/features/compose/components/emoji_picker_dropdown.js
@@ -2,7 +2,7 @@ import React from 'react';
 import PropTypes from 'prop-types';
 import { defineMessages, injectIntl, FormattedMessage } from 'react-intl';
 import { EmojiPicker as EmojiPickerAsync } from '../../ui/util/async-components';
-import Overlay from 'react-overlays/lib/Overlay';
+import Overlay from 'react-overlays/Overlay';
 import classNames from 'classnames';
 import ImmutablePropTypes from 'react-immutable-proptypes';
 import { supportsPassiveEvents } from 'detect-passive-events';
@@ -154,9 +154,6 @@ class EmojiPickerMenu extends React.PureComponent {
     onClose: PropTypes.func.isRequired,
     onPick: PropTypes.func.isRequired,
     style: PropTypes.object,
-    placement: PropTypes.string,
-    arrowOffsetLeft: PropTypes.string,
-    arrowOffsetTop: PropTypes.string,
     intl: PropTypes.object.isRequired,
     skinTone: PropTypes.number.isRequired,
     onSkinTone: PropTypes.func.isRequired,
@@ -324,14 +321,13 @@ class EmojiPickerDropdown extends React.PureComponent {
   state = {
     active: false,
     loading: false,
-    placement: null,
   };
 
   setRef = (c) => {
     this.dropdown = c;
   }
 
-  onShowDropdown = ({ target }) => {
+  onShowDropdown = () => {
     this.setState({ active: true });
 
     if (!EmojiPicker) {
@@ -346,9 +342,6 @@ class EmojiPickerDropdown extends React.PureComponent {
         this.setState({ loading: false, active: false });
       });
     }
-
-    const { top } = target.getBoundingClientRect();
-    this.setState({ placement: top * 2 < innerHeight ? 'bottom' : 'top' });
   }
 
   onHideDropdown = () => {
@@ -382,7 +375,7 @@ class EmojiPickerDropdown extends React.PureComponent {
   render () {
     const { intl, onPickEmoji, onSkinTone, skinTone, frequentlyUsedEmojis, button } = this.props;
     const title = intl.formatMessage(messages.emoji);
-    const { active, loading, placement } = this.state;
+    const { active, loading } = this.state;
 
     return (
       <div className='emoji-picker-dropdown' onKeyDown={this.handleKeyDown}>
@@ -394,16 +387,22 @@ class EmojiPickerDropdown extends React.PureComponent {
           />}
         </div>
 
-        <Overlay show={active} placement={placement} target={this.findTarget}>
-          <EmojiPickerMenu
-            custom_emojis={this.props.custom_emojis}
-            loading={loading}
-            onClose={this.onHideDropdown}
-            onPick={onPickEmoji}
-            onSkinTone={onSkinTone}
-            skinTone={skinTone}
-            frequentlyUsedEmojis={frequentlyUsedEmojis}
-          />
+        <Overlay show={active} placement={'bottom'} target={this.findTarget} popperConfig={{ strategy: 'fixed' }}>
+          {({ props, placement })=> (
+            <div {...props} style={{ ...props.style, width: 299 }}>
+              <div className={`dropdown-animation ${placement}`}>
+                <EmojiPickerMenu
+                  custom_emojis={this.props.custom_emojis}
+                  loading={loading}
+                  onClose={this.onHideDropdown}
+                  onPick={onPickEmoji}
+                  onSkinTone={onSkinTone}
+                  skinTone={skinTone}
+                  frequentlyUsedEmojis={frequentlyUsedEmojis}
+                />
+              </div>
+            </div>
+          )}
         </Overlay>
       </div>
     );
diff --git a/app/javascript/mastodon/features/compose/components/language_dropdown.js b/app/javascript/mastodon/features/compose/components/language_dropdown.js
index bf56fd0fa..4254a4926 100644
--- a/app/javascript/mastodon/features/compose/components/language_dropdown.js
+++ b/app/javascript/mastodon/features/compose/components/language_dropdown.js
@@ -2,9 +2,7 @@ import React from 'react';
 import PropTypes from 'prop-types';
 import { injectIntl, defineMessages } from 'react-intl';
 import TextIconButton from './text_icon_button';
-import Overlay from 'react-overlays/lib/Overlay';
-import Motion from 'mastodon/features/ui/util/optional_motion';
-import spring from 'react-motion/lib/spring';
+import Overlay from 'react-overlays/Overlay';
 import { supportsPassiveEvents } from 'detect-passive-events';
 import classNames from 'classnames';
 import { languages as preloadedLanguages } from 'mastodon/initial_state';
@@ -22,10 +20,8 @@ const listenerOptions = supportsPassiveEvents ? { passive: true } : false;
 class LanguageDropdownMenu extends React.PureComponent {
 
   static propTypes = {
-    style: PropTypes.object,
     value: PropTypes.string.isRequired,
     frequentlyUsedLanguages: PropTypes.arrayOf(PropTypes.string).isRequired,
-    placement: PropTypes.string.isRequired,
     onClose: PropTypes.func.isRequired,
     onChange: PropTypes.func.isRequired,
     languages: PropTypes.arrayOf(PropTypes.arrayOf(PropTypes.string)),
@@ -37,7 +33,6 @@ class LanguageDropdownMenu extends React.PureComponent {
   };
 
   state = {
-    mounted: false,
     searchValue: '',
   };
 
@@ -50,7 +45,6 @@ class LanguageDropdownMenu extends React.PureComponent {
   componentDidMount () {
     document.addEventListener('click', this.handleDocumentClick, false);
     document.addEventListener('touchend', this.handleDocumentClick, listenerOptions);
-    this.setState({ mounted: true });
 
     // Because of https://github.com/react-bootstrap/react-bootstrap/issues/2614 we need
     // to wait for a frame before focusing
@@ -222,29 +216,22 @@ class LanguageDropdownMenu extends React.PureComponent {
   }
 
   render () {
-    const { style, placement, intl } = this.props;
-    const { mounted, searchValue } = this.state;
+    const { intl } = this.props;
+    const { searchValue } = this.state;
     const isSearching = searchValue !== '';
     const results = this.search();
 
     return (
-      <Motion defaultStyle={{ opacity: 0, scaleX: 0.85, scaleY: 0.75 }} style={{ opacity: spring(1, { damping: 35, stiffness: 400 }), scaleX: spring(1, { damping: 35, stiffness: 400 }), scaleY: spring(1, { damping: 35, stiffness: 400 }) }}>
-        {({ opacity, scaleX, scaleY }) => (
-          // It should not be transformed when mounting because the resulting
-          // size will be used to determine the coordinate of the menu by
-          // react-overlays
-          <div className={`language-dropdown__dropdown ${placement}`} style={{ ...style, opacity: opacity, transform: mounted ? `scale(${scaleX}, ${scaleY})` : null }} ref={this.setRef}>
-            <div className='emoji-mart-search'>
-              <input type='search' value={searchValue} onChange={this.handleSearchChange} onKeyDown={this.handleSearchKeyDown} placeholder={intl.formatMessage(messages.search)} />
-              <button type='button' className='emoji-mart-search-icon' disabled={!isSearching} aria-label={intl.formatMessage(messages.clear)} onClick={this.handleClear}>{!isSearching ? loupeIcon : deleteIcon}</button>
-            </div>
+      <div ref={this.setRef}>
+        <div className='emoji-mart-search'>
+          <input type='search' value={searchValue} onChange={this.handleSearchChange} onKeyDown={this.handleSearchKeyDown} placeholder={intl.formatMessage(messages.search)} />
+          <button type='button' className='emoji-mart-search-icon' disabled={!isSearching} aria-label={intl.formatMessage(messages.clear)} onClick={this.handleClear}>{!isSearching ? loupeIcon : deleteIcon}</button>
+        </div>
 
-            <div className='language-dropdown__dropdown__results emoji-mart-scroll' role='listbox' ref={this.setListRef}>
-              {results.map(this.renderItem)}
-            </div>
-          </div>
-        )}
-      </Motion>
+        <div className='language-dropdown__dropdown__results emoji-mart-scroll' role='listbox' ref={this.setListRef}>
+          {results.map(this.renderItem)}
+        </div>
+      </div>
     );
   }
 
@@ -266,14 +253,11 @@ class LanguageDropdown extends React.PureComponent {
     placement: 'bottom',
   };
 
-  handleToggle = ({ target }) => {
-    const { top } = target.getBoundingClientRect();
-
+  handleToggle = () => {
     if (this.state.open && this.activeElement) {
       this.activeElement.focus({ preventScroll: true });
     }
 
-    this.setState({ placement: top * 2 < innerHeight ? 'bottom' : 'top' });
     this.setState({ open: !this.state.open });
   }
 
@@ -293,13 +277,25 @@ class LanguageDropdown extends React.PureComponent {
     onChange(value);
   }
 
+  setTargetRef = c => {
+    this.target = c;
+  }
+
+  findTarget = () => {
+    return this.target;
+  }
+
+  handleOverlayEnter = (state) => {
+    this.setState({ placement: state.placement });
+  }
+
   render () {
     const { value, intl, frequentlyUsedLanguages } = this.props;
     const { open, placement } = this.state;
 
     return (
-      <div className={classNames('privacy-dropdown', { active: open })}>
-        <div className='privacy-dropdown__value'>
+      <div className={classNames('privacy-dropdown', placement, { active: open })}>
+        <div className='privacy-dropdown__value' ref={this.setTargetRef} >
           <TextIconButton
             className='privacy-dropdown__value-icon'
             label={value && value.toUpperCase()}
@@ -309,15 +305,20 @@ class LanguageDropdown extends React.PureComponent {
           />
         </div>
 
-        <Overlay show={open} placement={placement} target={this}>
-          <LanguageDropdownMenu
-            value={value}
-            frequentlyUsedLanguages={frequentlyUsedLanguages}
-            onClose={this.handleClose}
-            onChange={this.handleChange}
-            placement={placement}
-            intl={intl}
-          />
+        <Overlay show={open} placement={'bottom'} flip target={this.findTarget} popperConfig={{ strategy: 'fixed', onFirstUpdate: this.handleOverlayEnter }}>
+          {({ props, placement }) => (
+            <div {...props} style={{ ...props.style, width: 280 }}>
+              <div className={`dropdown-animation language-dropdown__dropdown ${placement}`} >
+                <LanguageDropdownMenu
+                  value={value}
+                  frequentlyUsedLanguages={frequentlyUsedLanguages}
+                  onClose={this.handleClose}
+                  onChange={this.handleChange}
+                  intl={intl}
+                />
+              </div>
+            </div>
+          )}
         </Overlay>
       </div>
     );
diff --git a/app/javascript/mastodon/features/compose/components/privacy_dropdown.js b/app/javascript/mastodon/features/compose/components/privacy_dropdown.js
index 1f0e998d3..09bbc8e99 100644
--- a/app/javascript/mastodon/features/compose/components/privacy_dropdown.js
+++ b/app/javascript/mastodon/features/compose/components/privacy_dropdown.js
@@ -2,9 +2,7 @@ import React from 'react';
 import PropTypes from 'prop-types';
 import { injectIntl, defineMessages } from 'react-intl';
 import IconButton from '../../../components/icon_button';
-import Overlay from 'react-overlays/lib/Overlay';
-import Motion from '../../ui/util/optional_motion';
-import spring from 'react-motion/lib/spring';
+import Overlay from 'react-overlays/Overlay';
 import { supportsPassiveEvents } from 'detect-passive-events';
 import classNames from 'classnames';
 import Icon from 'mastodon/components/icon';
@@ -29,15 +27,10 @@ class PrivacyDropdownMenu extends React.PureComponent {
     style: PropTypes.object,
     items: PropTypes.array.isRequired,
     value: PropTypes.string.isRequired,
-    placement: PropTypes.string.isRequired,
     onClose: PropTypes.func.isRequired,
     onChange: PropTypes.func.isRequired,
   };
 
-  state = {
-    mounted: false,
-  };
-
   handleDocumentClick = e => {
     if (this.node && !this.node.contains(e.target)) {
       this.props.onClose();
@@ -101,7 +94,6 @@ class PrivacyDropdownMenu extends React.PureComponent {
     document.addEventListener('click', this.handleDocumentClick, false);
     document.addEventListener('touchend', this.handleDocumentClick, listenerOptions);
     if (this.focusedItem) this.focusedItem.focus({ preventScroll: true });
-    this.setState({ mounted: true });
   }
 
   componentWillUnmount () {
@@ -118,31 +110,23 @@ class PrivacyDropdownMenu extends React.PureComponent {
   }
 
   render () {
-    const { mounted } = this.state;
-    const { style, items, placement, value } = this.props;
+    const { style, items, value } = this.props;
 
     return (
-      <Motion defaultStyle={{ opacity: 0, scaleX: 0.85, scaleY: 0.75 }} style={{ opacity: spring(1, { damping: 35, stiffness: 400 }), scaleX: spring(1, { damping: 35, stiffness: 400 }), scaleY: spring(1, { damping: 35, stiffness: 400 }) }}>
-        {({ opacity, scaleX, scaleY }) => (
-          // It should not be transformed when mounting because the resulting
-          // size will be used to determine the coordinate of the menu by
-          // react-overlays
-          <div className={`privacy-dropdown__dropdown ${placement}`} style={{ ...style, opacity: opacity, transform: mounted ? `scale(${scaleX}, ${scaleY})` : null }} role='listbox' ref={this.setRef}>
-            {items.map(item => (
-              <div role='option' tabIndex='0' key={item.value} data-index={item.value} onKeyDown={this.handleKeyDown} onClick={this.handleClick} className={classNames('privacy-dropdown__option', { active: item.value === value })} aria-selected={item.value === value} ref={item.value === value ? this.setFocusRef : null}>
-                <div className='privacy-dropdown__option__icon'>
-                  <Icon id={item.icon} fixedWidth />
-                </div>
-
-                <div className='privacy-dropdown__option__content'>
-                  <strong>{item.text}</strong>
-                  {item.meta}
-                </div>
-              </div>
-            ))}
+      <div style={{ ...style }} role='listbox' ref={this.setRef}>
+        {items.map(item => (
+          <div role='option' tabIndex='0' key={item.value} data-index={item.value} onKeyDown={this.handleKeyDown} onClick={this.handleClick} className={classNames('privacy-dropdown__option', { active: item.value === value })} aria-selected={item.value === value} ref={item.value === value ? this.setFocusRef : null}>
+            <div className='privacy-dropdown__option__icon'>
+              <Icon id={item.icon} fixedWidth />
+            </div>
+
+            <div className='privacy-dropdown__option__content'>
+              <strong>{item.text}</strong>
+              {item.meta}
+            </div>
           </div>
-        )}
-      </Motion>
+        ))}
+      </div>
     );
   }
 
@@ -168,7 +152,7 @@ class PrivacyDropdown extends React.PureComponent {
     placement: 'bottom',
   };
 
-  handleToggle = ({ target }) => {
+  handleToggle = () => {
     if (this.props.isUserTouching && this.props.isUserTouching()) {
       if (this.state.open) {
         this.props.onModalClose();
@@ -179,11 +163,9 @@ class PrivacyDropdown extends React.PureComponent {
         });
       }
     } else {
-      const { top } = target.getBoundingClientRect();
       if (this.state.open && this.activeElement) {
         this.activeElement.focus({ preventScroll: true });
       }
-      this.setState({ placement: top * 2 < innerHeight ? 'bottom' : 'top' });
       this.setState({ open: !this.state.open });
     }
   }
@@ -247,6 +229,18 @@ class PrivacyDropdown extends React.PureComponent {
     }
   }
 
+  setTargetRef = c => {
+    this.target = c;
+  }
+
+  findTarget = () => {
+    return this.target;
+  }
+
+  handleOverlayEnter = (state) => {
+    this.setState({ placement: state.placement });
+  }
+
   render () {
     const { value, container, disabled, intl } = this.props;
     const { open, placement } = this.state;
@@ -255,7 +249,7 @@ class PrivacyDropdown extends React.PureComponent {
 
     return (
       <div className={classNames('privacy-dropdown', placement, { active: open })} onKeyDown={this.handleKeyDown}>
-        <div className={classNames('privacy-dropdown__value', { active: this.options.indexOf(valueOption) === (placement === 'bottom' ? 0 : (this.options.length - 1)) })}>
+        <div className={classNames('privacy-dropdown__value', { active: this.options.indexOf(valueOption) === (placement === 'bottom' ? 0 : (this.options.length - 1)) })} ref={this.setTargetRef}>
           <IconButton
             className='privacy-dropdown__value-icon'
             icon={valueOption.icon}
@@ -272,14 +266,19 @@ class PrivacyDropdown extends React.PureComponent {
           />
         </div>
 
-        <Overlay show={open} placement={placement} target={this} container={container}>
-          <PrivacyDropdownMenu
-            items={this.options}
-            value={value}
-            onClose={this.handleClose}
-            onChange={this.handleChange}
-            placement={placement}
-          />
+        <Overlay show={open} placement={'bottom'} flip target={this.findTarget} container={container} popperConfig={{ strategy: 'fixed', onFirstUpdate: this.handleOverlayEnter }}>
+          {({ props, placement }) => (
+            <div {...props} style={{ ...props.style, width: 350, maxWidth: '100vw' }}>
+              <div className={`dropdown-animation privacy-dropdown__dropdown ${placement}`}>
+                <PrivacyDropdownMenu
+                  items={this.options}
+                  value={value}
+                  onClose={this.handleClose}
+                  onChange={this.handleChange}
+                />
+              </div>
+            </div>
+          )}
         </Overlay>
       </div>
     );
diff --git a/app/javascript/mastodon/features/compose/components/search.js b/app/javascript/mastodon/features/compose/components/search.js
index 8254fb607..5820f8ca2 100644
--- a/app/javascript/mastodon/features/compose/components/search.js
+++ b/app/javascript/mastodon/features/compose/components/search.js
@@ -1,9 +1,7 @@
 import React from 'react';
 import PropTypes from 'prop-types';
 import { defineMessages, injectIntl, FormattedMessage } from 'react-intl';
-import Overlay from 'react-overlays/lib/Overlay';
-import Motion from '../../ui/util/optional_motion';
-import spring from 'react-motion/lib/spring';
+import Overlay from 'react-overlays/Overlay';
 import { searchEnabled } from '../../../initial_state';
 import Icon from 'mastodon/components/icon';
 
@@ -14,31 +12,20 @@ const messages = defineMessages({
 
 class SearchPopout extends React.PureComponent {
 
-  static propTypes = {
-    style: PropTypes.object,
-  };
-
   render () {
-    const { style } = this.props;
     const extraInformation = searchEnabled ? <FormattedMessage id='search_popout.tips.full_text' defaultMessage='Simple text returns statuses you have written, favourited, boosted, or have been mentioned in, as well as matching usernames, display names, and hashtags.' /> : <FormattedMessage id='search_popout.tips.text' defaultMessage='Simple text returns matching display names, usernames and hashtags' />;
     return (
-      <div style={{ ...style, position: 'absolute', width: 285, zIndex: 2 }}>
-        <Motion defaultStyle={{ opacity: 0, scaleX: 0.85, scaleY: 0.75 }} style={{ opacity: spring(1, { damping: 35, stiffness: 400 }), scaleX: spring(1, { damping: 35, stiffness: 400 }), scaleY: spring(1, { damping: 35, stiffness: 400 }) }}>
-          {({ opacity, scaleX, scaleY }) => (
-            <div className='search-popout' style={{ opacity: opacity, transform: `scale(${scaleX}, ${scaleY})` }}>
-              <h4><FormattedMessage id='search_popout.search_format' defaultMessage='Advanced search format' /></h4>
-
-              <ul>
-                <li><em>#example</em> <FormattedMessage id='search_popout.tips.hashtag' defaultMessage='hashtag' /></li>
-                <li><em>@username@domain</em> <FormattedMessage id='search_popout.tips.user' defaultMessage='user' /></li>
-                <li><em>URL</em> <FormattedMessage id='search_popout.tips.user' defaultMessage='user' /></li>
-                <li><em>URL</em> <FormattedMessage id='search_popout.tips.status' defaultMessage='status' /></li>
-              </ul>
-
-              {extraInformation}
-            </div>
-          )}
-        </Motion>
+      <div className='search-popout'>
+        <h4><FormattedMessage id='search_popout.search_format' defaultMessage='Advanced search format' /></h4>
+
+        <ul>
+          <li><em>#example</em> <FormattedMessage id='search_popout.tips.hashtag' defaultMessage='hashtag' /></li>
+          <li><em>@username@domain</em> <FormattedMessage id='search_popout.tips.user' defaultMessage='user' /></li>
+          <li><em>URL</em> <FormattedMessage id='search_popout.tips.user' defaultMessage='user' /></li>
+          <li><em>URL</em> <FormattedMessage id='search_popout.tips.status' defaultMessage='status' /></li>
+        </ul>
+
+        {extraInformation}
       </div>
     );
   }
@@ -115,6 +102,10 @@ class Search extends React.PureComponent {
     this.setState({ expanded: false });
   }
 
+  findTarget = () => {
+    return this.searchForm;
+  }
+
   render () {
     const { intl, value, submitted } = this.props;
     const { expanded } = this.state;
@@ -140,8 +131,14 @@ class Search extends React.PureComponent {
           <Icon id='search' className={hasValue ? '' : 'active'} />
           <Icon id='times-circle' className={hasValue ? 'active' : ''} aria-label={intl.formatMessage(messages.placeholder)} />
         </div>
-        <Overlay show={expanded && !hasValue} placement='bottom' target={this} container={this}>
-          <SearchPopout />
+        <Overlay show={expanded && !hasValue} placement='bottom' target={this.findTarget} popperConfig={{ strategy: 'fixed' }}>
+          {({ props, placement }) => (
+            <div {...props} style={{ ...props.style, width: 285, zIndex: 2 }}>
+              <div className={`dropdown-animation ${placement}`}>
+                <SearchPopout />
+              </div>
+            </div>
+          )}
         </Overlay>
       </div>
     );
diff --git a/app/javascript/mastodon/reducers/dropdown_menu.js b/app/javascript/mastodon/reducers/dropdown_menu.js
index a78a11acc..51bf9375b 100644
--- a/app/javascript/mastodon/reducers/dropdown_menu.js
+++ b/app/javascript/mastodon/reducers/dropdown_menu.js
@@ -4,12 +4,12 @@ import {
   DROPDOWN_MENU_CLOSE,
 } from '../actions/dropdown_menu';
 
-const initialState = Immutable.Map({ openId: null, placement: null, keyboard: false, scroll_key: null });
+const initialState = Immutable.Map({ openId: null, keyboard: false, scroll_key: null });
 
 export default function dropdownMenu(state = initialState, action) {
   switch (action.type) {
   case DROPDOWN_MENU_OPEN:
-    return state.merge({ openId: action.id, placement: action.placement, keyboard: action.keyboard, scroll_key: action.scroll_key });
+    return state.merge({ openId: action.id, keyboard: action.keyboard, scroll_key: action.scroll_key });
   case DROPDOWN_MENU_CLOSE:
     return state.get('openId') === action.id ? state.set('openId', null).set('scroll_key', null) : state;
   default:
diff --git a/app/javascript/styles/mastodon-light/diff.scss b/app/javascript/styles/mastodon-light/diff.scss
index 928af8453..123fe0c67 100644
--- a/app/javascript/styles/mastodon-light/diff.scss
+++ b/app/javascript/styles/mastodon-light/diff.scss
@@ -285,22 +285,8 @@ html {
 .dropdown-menu {
   background: $white;
 
-  &__arrow {
-    &.left {
-      border-left-color: $white;
-    }
-
-    &.top {
-      border-top-color: $white;
-    }
-
-    &.bottom {
-      border-bottom-color: $white;
-    }
-
-    &.right {
-      border-right-color: $white;
-    }
+  &__arrow::before {
+    background-color: $white;
   }
 
   &__item {
diff --git a/app/javascript/styles/mastodon/components.scss b/app/javascript/styles/mastodon/components.scss
index 0439156f1..ad59303f4 100644
--- a/app/javascript/styles/mastodon/components.scss
+++ b/app/javascript/styles/mastodon/components.scss
@@ -363,8 +363,8 @@
   }
 }
 
-.dropdown-menu {
-  position: absolute;
+body > [data-popper-placement] {
+  z-index: 3;
 }
 
 .invisible {
@@ -1932,6 +1932,42 @@ a.account__display-name {
   text-decoration: none;
 }
 
+.dropdown-animation {
+  animation: dropdown 300ms cubic-bezier(0.1, 0.7, 0.1, 1);
+
+  @keyframes dropdown {
+    from {
+      opacity: 0;
+      transform: scaleX(0.85) scaleY(0.75);
+    }
+
+    to {
+      opacity: 1;
+      transform: scaleX(1) scaleY(1);
+    }
+  }
+
+  &.top {
+    transform-origin: bottom;
+  }
+
+  &.right {
+    transform-origin: left;
+  }
+
+  &.bottom {
+    transform-origin: top;
+  }
+
+  &.left {
+    transform-origin: right;
+  }
+
+  .reduce-motion & {
+    animation: none;
+  }
+}
+
 .dropdown {
   display: inline-block;
 }
@@ -2016,36 +2052,42 @@ a.account__display-name {
 
 .dropdown-menu__arrow {
   position: absolute;
-  width: 0;
-  height: 0;
-  border: 0 solid transparent;
 
-  &.left {
-    right: -5px;
-    margin-top: -5px;
-    border-width: 5px 0 5px 5px;
-    border-left-color: $ui-secondary-color;
+  &::before {
+    content: '';
+    display: block;
+    width: 14px;
+    height: 5px;
+    background-color: $ui-secondary-color;
+    mask-image: url("data:image/svg+xml;utf8,<svg width='14' height='5' xmlns='http://www.w3.org/2000/svg'><path d='M7 0L0 5h14L7 0z' fill='white'/></svg>");
   }
 
   &.top {
     bottom: -5px;
-    margin-left: -7px;
-    border-width: 5px 7px 0;
-    border-top-color: $ui-secondary-color;
+
+    &::before {
+      transform: rotate(180deg);
+    }
+  }
+
+  &.right {
+    left: -9px;
+
+    &::before {
+      transform: rotate(-90deg);
+    }
   }
 
   &.bottom {
     top: -5px;
-    margin-left: -7px;
-    border-width: 0 7px 5px;
-    border-bottom-color: $ui-secondary-color;
   }
 
-  &.right {
-    left: -5px;
-    margin-top: -5px;
-    border-width: 5px 5px 5px 0;
-    border-right-color: $ui-secondary-color;
+  &.left {
+    right: -9px;
+
+    &::before {
+      transform: rotate(90deg);
+    }
   }
 }
 
@@ -4524,7 +4566,6 @@ a.status-card.compact:hover {
 }
 
 .privacy-dropdown__dropdown {
-  position: absolute;
   background: $simple-background-color;
   box-shadow: 2px 4px 15px rgba($base-shadow-color, 0.4);
   border-radius: 4px;
@@ -4630,7 +4671,6 @@ a.status-card.compact:hover {
 
 .language-dropdown {
   &__dropdown {
-    position: absolute;
     background: $simple-background-color;
     box-shadow: 2px 4px 15px rgba($base-shadow-color, 0.4);
     border-radius: 4px;
@@ -4877,7 +4917,6 @@ a.status-card.compact:hover {
 .modal-root__modal {
   pointer-events: auto;
   display: flex;
-  z-index: 9999;
 }
 
 .video-modal__container {