Problems setting focus to a View inside a View ... inside a Dialog

[jwodder]

The below code creates a dialog with a group of radio buttons followed by a set of checkboxes. I want the application to handle the Home and End keys as follows:

• When the user presses End, focus should jump to the dialog's "OK" button. This part works.

• When the user presses Home, focus should jump to the first radio button in the top group. This part only partially works. Specifically:

  • If focus is on a radio button, pressing Home jumps to the first radio button correctly.
  • If focus is on a radio button and then the user presses End, pressing Home immediately afterwards jumps to the first radio button correctly.
  • If focus is on a checkbox, pressing Home does nothing.
  • If focus is on a checkbox and then the user presses End, pressing Home immediately afterwards shifts the focus back to the previous checkbox instead of to the first radio button.

I'm at a loss as to how to fix the aberrant behaviors; it seems there's something about how focus-changing is implemented in cursive that I don't understand.

Note that, in my actual code, the form is dynamic, so the top group (the one whose first element should receive focus from Home) could be either a radio group or a checkbox group, so any solution should be able to handle both cases.

Code:

use cursive::{
    Cursive, View,
    direction::Direction,
    event::{EventResult, Key},
    view::{Finder, Nameable},
    views::{
        Checkbox, Dialog, DialogFocus, DummyView, LinearLayout, OnEventView, PaddedView,
        RadioGroup, TextView,
    },
};

fn main() {
    let mut siv = cursive::default();
    siv.add_global_callback('q', Cursive::quit);
    siv.add_global_callback('Q', Cursive::quit);
    siv.add_global_callback(Key::Esc, Cursive::quit);
    let mut layout = LinearLayout::vertical();

    layout.add_child(TextView::new("Flavors:"));
    let mut group = RadioGroup::<usize>::new();
    let mut sublayout = LinearLayout::vertical();
    for (i, opt) in [
        "Vanilla",
        "Chocolate",
        "Strawberry",
        "Cinnamon",
        "Butterscotch",
        "Peanut Butter Fudge",
        "Chili",
    ]
    .into_iter()
    .enumerate()
    {
        let mut button = group.button(i, opt);
        if i == 0 {
            let _ = button.select();
        }
        sublayout.add_child(button);
    }
    layout.add_child(PaddedView::lrtb(4, 0, 0, 0, sublayout).with_name("top_pad"));

    layout.add_child(DummyView);

    layout.add_child(TextView::new("Toppings:"));
    let mut sublayout = LinearLayout::vertical();
    for opt in ["Whipped Cream", "Hot Fudge", "Nuts", "Cherry", "Banana"] {
        let chkbox = Checkbox::new();
        let lbl = TextView::new(opt);
        sublayout.add_child(
            LinearLayout::horizontal()
                .child(chkbox)
                .child(DummyView)
                .child(lbl),
        );
    }
    layout.add_child(PaddedView::lrtb(4, 0, 0, 0, sublayout));

    siv.add_layer(
        OnEventView::new(Dialog::around(layout).button("OK", Cursive::quit))
            .on_pre_event_inner(Key::Home, |dialog, _| {
                dialog.set_focus(DialogFocus::Content);
                dialog.call_on_name("top_pad", |b: &mut PaddedView<LinearLayout>| {
                    b.take_focus(Direction::up())
                });
                Some(EventResult::Consumed(None))
            })
            .on_pre_event_inner(Key::End, |dialog, _| {
                dialog.set_focus(DialogFocus::Button(0));
                Some(EventResult::Consumed(None))
            }),
    );
    siv.run();
}

Dependencies:

cursive = "0.21.1"

[gyscos]

Hi, and thanks for the report!

Currently focus in cursive is not global, but decided per parent view. Each parent in your chain (dialog, layout, sublayout, sublayout's horizontal layout children) keeps its own focus state. So the manual way to ensure some view ends up "focused" is to make each parent in the chain focus the correct child down the chain.

take_focus is to tell a view that it just received focus, and that it should possibly update its own internal focus (in case it's a parent).

Here's what happens in your "Home" event handler:

• dialog.set_focus(DialogFocus::Content): update the dialog's own focus to the content.
• b.take_focus(Direction::up()): update the top sublayout's to behave as if it just received the focus coming from the top. This indeed leads to the top-most item being selected.

Note that layout itself was not updated, and still points to either the checkbox or the radio button. LinearLayouts can use set_focus_index, or you can make it "take focus from the top" and it'll work too.

All that gets more complex with more nested views, and even more if you want to focus a specific view in the middle, not just the top one. That's why there's also View::focus_view, which you can use on a view to focus the entire tree from itself all the way the down to a named view. So in your case, you could call dialog.focus_view(Selector::Name("top_pad")) and it'll make sure top_pad is selected all the way from the dialog itself. Then you can update top_pad's own internal focus. Or you could also directly name the first radio button and directly focus that.

... Well that's the theory. In practice I just saw that dialog was not properly focusing the content if you use it, so it would have left the focus on the button for example. I just pushed a commit to fix that, tell me if it works for you!

[jwodder]

I got it to work using both dialog.set_focus(Content) and dialog.focus_view(...) targeting the first radio button. Thanks for the help!