Updating child widgets?

[timothyhollabaugh]

I have a custom widget that has a tree of child widgets, where the data of the child widgets is made up of both the widget's data and some of the widget's internal state. The event, lifecycle, update, layout, and paint methods all handle assembling these together.

In particular, the event method looks like this:

fn event(&mut self, ctx: &mut EventCtx, event: &Event, tools: &mut ToolTable, env: &Env) {
    let mut data = (self.state.to_owned(), tools.to_owned());

    self.widgets.event(ctx, event, &mut data, env);

    let (new_state, new_tools) = data;

    if !new_state.same(&self.state) {
        self.state = new_state;
    }

    if !new_tools.same(&new_tools) {
        *tools = new_tools;
    }
}

This works great, except that when the widget's internal state changes, the children do not get updated.

Does it make sense to add a request_update method on EventCtx? Or is there a better way to do this?

[rhzk]

Hi, you can use WidgetPod for this. I recommend you take a look at:
https://github.com/linebender/druid/blob/master/druid/src/widget/scroll.rs#L110
https://github.com/linebender/druid/blob/master/druid/src/widget/scroll.rs#L442
https://github.com/linebender/druid/blob/master/druid/src/widget/scroll.rs#L470

[timothyhollabaugh]

I'll take a look. I changed up my UI to avoid this problem, so I'll close this issue.

[raphlinus]

I'm going to reopen this, as I think a request_update method on EventCtx is something we really should have. I'll try to make a PR for it.

[cmyr]

thinking about this, my first thought is that you should be responsible for calling update in your own update call? If you're a container you are responsible for forwarding all calls to children as needed.

[raphlinus]

Yes, we discussed this on Zulip and the consensus is to just have the request_update call for the parent.