Add a new children/descendants api as well as deeper element queries to ElementHandle

[tronical]

No description provided.

[ogoffart]

Should visit_element be removed. It is a bit redundent since you can do HasElementHandle::root_element(component).visit_descendants

(the only difference is that it visits the root)

[ogoffart]

Will it? All Clip elements? Why is that?

[tronical]

Maybe I'm missing something (I tried to cover that also in the test I added in search_api.rs), but the old code did this:

    pub fn is_visible(&self) -> bool {
        let item = self.borrow();
        let is_clipping = crate::item_rendering::is_clipping_item(item);
        let geometry = self.geometry();
        if is_clipping && (geometry.width() <= 0.01 as _ || geometry.height() <= 0.01 as _) {
            return false;
        }
        if let Some(parent) = self.parent_item() {
            parent.is_visible()
        } else {
            true
        }
    }

That suggests to me that is_clipping_item() returns true for Clip elements that are enabled for clipping (clip true) and the visible pass gives them the null width/height. So I think that'll return false.

The new code should return an empty clip rectangle from the call to absolute_clip_rect_and_geometry because of this:

      if crate::item_rendering::is_clipping_item(item) {
            clip = geometry.intersection(&clip).unwrap_or_default();
        }

And then the intersection of itself should be empty.

Should I add a direct unit test in here perhaps?

[tronical]

Should visit_element be removed. It is a bit redundent since you can do HasElementHandle::root_element(component).visit_descendants

(the only difference is that it visits the root)

Yes, I'm in favor of that - if you're okay with the rest of this API. I'd make that a separate change though.