Factor scale into adjustment of bubbled mouse events

packages/block-editor/src/components/iframe/index.js

@@ -40,15 +40,17 @@ function bubbleEvent( event, Constructor, frame ) {
 		init[ key ] = event[ key ];
 	}
 
-	// Check if the event is a MouseEvent generated within the iframe.
-	// If so, adjust the coordinates to be relative to the position of
-	// the iframe. This ensures that components such as Draggable
-	// receive coordinates relative to the window, instead of relative
-	// to the iframe. Without this, the Draggable event handler would
-	// result in components "jumping" position as soon as the user
-	// drags over the iframe.
+	// Check if the event is a MouseEvent generated within the iframe. If so,
+	// adjust the coordinates by the iframe’s position and scale. This ensures
+	// that components such as Draggable receive coordinates relative to the
+	// window, instead of relative to the iframe. Without this, such component’s
+	// would have to deal with "jumps" in the coordinates whenever the pointer
+	// enters or exits the iframe.
 	if ( event instanceof frame.contentDocument.defaultView.MouseEvent ) {
 		const rect = frame.getBoundingClientRect();
+		const scale = rect.width / frame.offsetWidth;
+		init.clientX *= scale;
+		init.clientY *= scale;
 		init.clientX += rect.left;
 		init.clientY += rect.top;
 	}