#Focus Builder

This page only introduces builder methods for configuring focus table. Complete explanation of focus mechanism see Focus Mechanism, runtime APIs for manipulating focus through ViewId see ViewId.

Actually exposed trait is:

pub trait FocusIndexBuilder {
    fn focus_scope(self, focus_scope: u32) -> Self;
    fn focus_index(self, focus_index: u32) -> Self;
}

#focus_index

focus_index adds view to focus table, and sets its sort value in Tab order.

use flor::view::builder::{EventBuilder, FocusIndexBuilder};
use flor_lys::label::label;

let name = label("Name")
    .focus_index(0)
    .on_focus(|_, virtual_index| {
        println!("focus virtual index: {virtual_index}");
    });

let confirm = label("Confirm").focus_index(1);

0 is legal sort value, don't understand it as canceling focus. Smaller numbers are visited by Tab first. Same sort value can also work, final sorting will still include ViewId and virtual focus number; however using clear incrementing values for same group of views is easier to maintain.

Not writing focus_index means not joining focus table. Such views won't be selected by Tab, also won't become view-level on_key_* focus target.

#focus_scope

focus_scope provides a sort offset for current view and its subtree. It's suitable for splitting page into several areas, letting each area internally number from 0.

use flor::view::builder::FocusIndexBuilder;
use flor::views;
use flor_lys::div::div;
use flor_lys::label::label;

let toolbar = div(views![
    label("Tool 1").focus_index(0),
    label("Tool 2").focus_index(1),
])
.focus_scope(100);

let content = div(views![
    label("Content 1").focus_index(0),
    label("Content 2").focus_index(1),
])
.focus_scope(200);

Final sort values above are:

focus_scope can nest, parent offset will continue accumulating to subtree.

Note: builder's focus_scope(u32) only affects sorting, doesn't limit Tab's runtime range. For popup layer, modal and similar focus isolation scenarios, use ViewId::push_focus_scope() and ViewId::pop_focus_scope(), mechanism explanation see Focus Mechanism.