Dense by design.

use densa_data::{
    Aggregate, CompareOp, Filter, GroupSpec, LiveTable, Order, Scalar, ViewSpec,
};

let mut table = LiveTable::new(schema, "symbol")?;
let movers = table.add_view(
    ViewSpec::new()
        .filter(Filter::compare("volume", CompareOp::Gt, Scalar::Int(1_000)))
        .sort_by("change_pct", Order::Descending),
)?;
let sectors = table.add_groups(
    GroupSpec::new().group_by("sector").aggregate(Aggregate::sum("volume")),
)?;

table.upsert(ticks)?;      // new symbols insert, known ones update
table.delete(&delisted)?;  // an array of keys

let view = table.view(movers).unwrap();  // in order, after every change
let totals = table.groups(sectors).unwrap().to_batch()?;  // one row per sector

use densa_fmt::write_fixed;
use densa_grid::{CellStyle, CellText, Color, GridSource};
use std::fmt::Write as _;

/// A monitoring table: one row per sensor.
struct Sensors<'a> {
    names: &'a [&'a str],
    celsius: &'a [f64],
}

impl GridSource for Sensors<'_> {
    fn rows(&self) -> usize {
        self.celsius.len()
    }

    // Called for every visible cell, every frame.
    fn cell(&self, row: usize, column: usize, text: &mut CellText) -> CellStyle {
        let value = self.celsius[row];
        if column == 0 {
            let _ = text.write_str(self.names[row]);
        } else {
            let _ = write_fixed(text, value, 1);
        }
        let hex = if value > 80.0 { 0xF87171 } else { 0xE2E8F0 };
        CellStyle { color: Color::srgb(hex), background: None }
    }
}

use densa_sync::triple_buffer;

let (mut writer, mut reader) = triple_buffer([0.0_f64; 64]);

// Producer thread: fill the back slot, then publish it.
std::thread::spawn(move || {
    writer.write(|rows| rows[0] = 101.25);
    writer.publish();
});

// UI thread, once per frame: switch to the newest snapshot.
if reader.update() {
    reader.read(|rows| draw(rows));
}