[form-builder] Optimize selectionchange event handlers in FormbuilderBlock/FormBuilderInline (#555)

Author: bjoerge

packages/@sanity/form-builder/src/inputs/BlockEditor-slate/FormBuilderBlock.js

@@ -110,6 +110,9 @@ export default class FormBuilderBlock extends React.Component {
   }
 
   handleSelectionChange = event => {
+    if (!this._editorNode.contains(event.target)) {
+      return
+    }
     const selection = document.getSelection()
     const isSelected = selection.containsNode
         && selection.containsNode(this.formBuilderBlock)

packages/@sanity/form-builder/src/inputs/BlockEditor-slate/FormBuilderInline.js

@@ -87,6 +87,9 @@ export default class FormBuilderInline extends React.Component {
   }
 
   handleSelectionChange = event => {
+    if (!this._editorNode.contains(event.target)) {
+      return
+    }
     const selection = document.getSelection()
     const isSelected = selection.containsNode
         && selection.containsNode(this.formBuilderInline)