In the latest main (at least in v0.0.0-20230512135434-8571b25ff7cb), when a parent has focus, key.Events still arrive to children for some reason. This can be tested e.g. by modifying the key-input-tree example from giouiorg/include/files/architecture/main.go by making the second child respond only to "A" presses, like so:

func doKeyTree(ops *op.Ops, q event.Queue) {
	// Process events that arrived between the last frame and this one for every tag.
	for _, tag := range []*bool{&keyRoot, &keyChild1, &keyChild2} {
		for _, ev := range q.Events(tag) {
			switch ev := ev.(type) {
			case pointer.Event:
				switch ev.Type {
				case pointer.Release:
					// Request focus on this tag if the mouse click ended in our area.
					key.FocusOp{Tag: tag}.Add(ops)
				}
			case key.FocusEvent:
				// If this tag is focused, update the focused variable.
				if ev.Focus {
					focused = tag
				} else if focused == tag {
					focused = nil
				}
			case key.Event:
				// If we got a key.Event, it means that we are the foremost
				// handler for that key (based on the contents of our
				// key.InputOp's key.Set).
				*tag = ev.State == key.Press
			}
		}
	}

	// If nothing is focused, focus the root:
	if focused == nil {
		key.FocusOp{Tag: &keyRoot}.Add(ops)
		key.SoftKeyboardOp{Show: true}.Add(ops)
	}

	// Confine the rootArea of interest to a 200x200 rectangle.
	rootRect := clip.Rect(image.Rect(0, 0, 200, 200))
	rootArea := rootRect.Push(ops)
	keyDisplayForTag(ops, enterAndSpaceKeys, &keyRoot, rootRect)

	// Any clip areas we add before Pop-ing the root area
	// are considered its children.
	child1Rect := clip.Rect(image.Rect(25, 25, 175, 100))
	child1Area := child1Rect.Push(ops)
	keyDisplayForTag(ops, spaceKey, &keyChild1, child1Rect)
	child1Area.Pop()

	child2Rect := clip.Rect(image.Rect(100, 25, 175, 175))
	child2Area := child2Rect.Push(ops)
	keyDisplayForTag(ops, "A", &keyChild2, child2Rect) // THIS IS THE ONLY LINE I MODIFIED
	child2Area.Pop()

	rootArea.Pop()
	// Now anything we add is _not_ a child of the rootArea.
}

If the large widget (parent widget) has focus, the child 2 still get the "A" presses. This cannot be right.