Better looking checkboxes (#3345)

Also showing icon only on hover on control headers

superset/assets/javascripts/explore/components/Control.jsx

@@ -56,6 +56,7 @@ const defaultProps = {
 export default class Control extends React.PureComponent {
   constructor(props) {
     super(props);
+    this.state = { hovered: false };
     this.validate = this.validate.bind(this);
     this.onChange = this.onChange.bind(this);
   }
@@ -65,6 +66,9 @@ export default class Control extends React.PureComponent {
   onChange(value, errors) {
     this.validateAndSetValue(value, errors);
   }
+  setHover(hovered) {
+    this.setState({ hovered });
+  }
   validateAndSetValue(value, errors) {
     let validationErrors = this.props.validationErrors;
     let currentErrors = this.validate(value);
@@ -96,9 +100,14 @@ export default class Control extends React.PureComponent {
     const ControlType = controlMap[this.props.type];
     const divStyle = this.props.hidden ? { display: 'none' } : null;
     return (
-      <div style={divStyle}>
+      <div
+        style={divStyle}
+        onMouseEnter={this.setHover.bind(this, true)}
+        onMouseLeave={this.setHover.bind(this, false)}
+      >
         <ControlType
           onChange={this.onChange}
+          hovered={this.state.hovered}
           {...this.props}
         />
       </div>