message: Superposition UI: add "toggle selection" button to help
diff: @@ -13,6 +13,7 @@ import ArrowDownward from '@material-ui/icons/ArrowDownward';
  import ArrowUpward from '@material-ui/icons/ArrowUpward';
  import DeleteOutlined from '@material-ui/icons/DeleteOutlined';
  import Tune from '@material-ui/icons/Tune';
  +import Crop from '@material-ui/icons/Crop';
  import { CollapsableControls, PurePluginUIComponent } from '../base';
  import { Icon } from '../controls/icons';
  import { Button, ToggleButton, IconButton } from '../controls/common';
  @@ -263,6 +264,14 @@ export class SuperpositionControls extends PurePluginUIComponent<{}, Superpositi
  return entries;
  }
  + _toggleSelMode = () => {
  + this.plugin.selectionMode = !this.plugin.selectionMode;
  + }
  +
  + get toggleSelectionMode() {
  + return <IconButton svg={Crop} onClick={this._toggleSelMode} title={'Toggle Selection Mode'} style={{ background: 'transparent' }} />;
  + }
  +
  addByChains() {
  const entries = this.chainEntries;
  return <>
  @@ -270,7 +279,7 @@ export class SuperpositionControls extends PurePluginUIComponent<{}, Superpositi
  {entries.map((e, i) => this.lociEntry(e, i))}
  </div>}
  {entries.length < 2 && <div className='msp-control-offset msp-help-text'>
  - <div className='msp-help-description'><Icon svg={HelpOutline} inline />Add 2 or more selections from separate structures. Selections must be limited to single chains or parts of single chains.</div>
  + <div className='msp-help-description'><Icon svg={HelpOutline} inline />Add 2 or more selections {this.toggleSelectionMode} from separate structures. Selections must be limited to single chains or parts of single chains.</div>
  </div>}
  {entries.length > 1 && <Button title='Superpose structures by selected chains.' className='msp-btn-commit msp-btn-commit-on' onClick={this.superposeChains} style={{ marginTop: '1px' }}>
  Superpose
  @@ -285,7 +294,8 @@ export class SuperpositionControls extends PurePluginUIComponent<{}, Superpositi
  {entries.map((e, i) => this.atomsLociEntry(e, i))}
  </div>}
  {entries.length < 2 && <div className='msp-control-offset msp-help-text'>
  - <div className='msp-help-description'><Icon svg={HelpOutline} inline />Add 1 or more selections from separate structures. Selections must be limited to single atoms.</div>
  + <div className='msp-help-description'><Icon svg={HelpOutline} inline />Add 1 or more selections {this.toggleSelectionMode} from
  + separate structures. Selections must be limited to single atoms.</div>
  </div>}
  {entries.length > 1 && <Button title='Superpose structures by selected atoms.' className='msp-btn-commit msp-btn-commit-on' onClick={this.superposeAtoms} style={{ marginTop: '1px' }}>
  Superpose
  