Fix some smaller styling issues and bugs in Widgets Customizer

packages/block-editor/src/components/duotone-control/style.scss

@@ -11,6 +11,7 @@
 	.components-menu-group__label {
 		padding: $grid-unit-15 $grid-unit-15 0 $grid-unit-15;
 		width: 100%;
+		box-sizing: border-box;
 	}
 }
 

packages/customize-widgets/src/components/customize-widgets/index.js

@@ -57,7 +57,7 @@ export default function CustomizeWidgets( {
 	const popover =
 		parentContainer &&
 		createPortal(
-			<div ref={ popoverRef }>
+			<div className="customize-widgets-popover" ref={ popoverRef }>
 				<Popover.Slot />
 			</div>,
 			parentContainer

packages/customize-widgets/src/components/customize-widgets/use-clear-selected-block.js

@@ -10,6 +10,13 @@ import { store as blockEditorStore } from '@wordpress/block-editor';
  * many root nodes rather than just one in the post editor.
  * We need to listen to the focus events in all those roots, and also in
  * the preview iframe.
+ * This hook will clear the selected block when focusing outside the editor,
+ * with a few exceptions:
+ * 1. Focusing on popovers.
+ * 2. Focusing on the inspector.
+ * 3. Focusing on any modals/dialogs.
+ * These cases are normally triggered by user interactions from the editor,
+ * not by explicitly focusing outside the editor, hence no need for clearing.
  *
  * @param {Object} sidebarControl The sidebar control instance.
  * @param {Object} popoverRef The ref object of the popover node container.
@@ -38,7 +45,8 @@ export default function useClearSelectedBlock( sidebarControl, popoverRef ) {
 					// 3. It should also not exist in the container, inspector, nor the popover.
 					! container.contains( element ) &&
 					! popoverRef.current.contains( element ) &&
-					! inspectorContainer.contains( element )
+					! inspectorContainer.contains( element ) &&
+					! element.closest( '[role="dialog"]' )
 				) {
 					clearSelectedBlock();
 				}

packages/customize-widgets/src/style.scss

@@ -11,3 +11,10 @@
 .components-modal__screen-overlay {
 	z-index: 999999;
 }
+
+// Include reset CSS for the customizer.
+.customize-control-sidebar_block_editor,
+.customize-widgets-layout__inspector,
+.customize-widgets-popover {
+	@include reset;
+}