Removable widgets flash "hovered" state to the previous widget for 1 frame after a widget is removed

[voidburn]

Hello community,

I have an issue that I cannot seem to solve: I have a grid with placement slots where vertices can be visually added and removed, something like this:

Vertices are placed with absolute positioning within the area, no Layout is involved. In the picture are two vertices, this is the pseudo-code of the Widget trait implementation for a Vertex:

impl Widget for Vertex {
    fn ui(self, ui: &mut Ui) -> Response {
        let response = ui.allocate_rect(cwd.ui_rect(), Sense::click());
        let font_id = TextStyle::Body.resolve(ui.style());

        if response.hovered() {
            ui.painter()
                .circle_filled(cwd.ui_pos(), cwd.ui_radius(), Color32::RED);
        } else {
            ui.painter()
                .circle_filled(cwd.ui_pos(), cwd.ui_radius(), Color32::GREEN);
        }

        ui.painter().text(
            cwd.ui_pos(),
            Align2::CENTER_CENTER,
            self.op.to_string(),
            font_id.clone(),
            Colors::RED,
        );

        response
    }
}

The problem I'm experiencing is that when I proceed to delete the vertex on the right, during the next frame the previous vertex (relative to the rendering order, in this case the left one) will flash RED as if the response to the input state of the old one jumped over to it.

I suppose these are egui::Ids at work within the input system, but I cannot find a way to prevent this. I tried to add a ui.id().with(vertex_uuid) thinking that would both work to propagate events between frames for the same widget, but also make sure that no two widgets have the same egui::id, but that did not work.

Any insight on how the Response system works and what I am doing wrong would be greatly appreciated.

[emilk]

Try wrapping your per-vertex ui-code in ui.push_id(vertex_uuid, …).

It would be nice with an API for allocating some space with a specific Id though, but alas we don't have that

[voidburn]

That worked like a charm! Thank you! This will come in handy in the future :)