a rust tui to view amtrak train status
Greedy label collision detection for city names
City labels were getting overwritten by braille-rendered map features
(station markers, route lines, train circles). Fixed with two changes:
1. Greedy collision detection: compute approximate bounding boxes for
each label in geo-coordinate space, sorted by population priority.
Skip labels that overlap any previously placed label, train marker,
or station marker. Uses AABB intersection testing.
2. Render city labels as the topmost layer (layer 12) so text characters
aren't overwritten by braille dots drawn in later layers.
Labels are placed offset-right of the city coordinate with collision-
aware spacing. Dense areas (like the NEC corridor) will show only the
highest-population cities that fit without overlap.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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src/ui.rs
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src/ui.rs
···
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.map(|g| segments_to_lines(&g.roads, Color::Rgb(45, 48, 58)))
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.unwrap_or_default();
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// Cities visible based on zoom level and population
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let city_labels: Vec<(f64, f64, String)> = app
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.geo
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.as_ref()
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.map(|g| {
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let min_pop = if vp_width > 40.0 {
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2_000_000 // zoomed out: only major cities
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} else if vp_width > 20.0 {
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500_000
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} else if vp_width > 10.0 {
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100_000
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} else {
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30_000 // zoomed in: most cities
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};
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g.cities
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// City labels with greedy collision detection.
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// We approximate each label's bounding box in geo-coordinates and skip any
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// that would overlap a previously placed label or a train/station marker.
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let city_labels: Vec<(f64, f64, String)> = {
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// Approximate width of one character in geo-degrees.
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// Canvas area is (area.width - 2) chars wide (minus border), each braille
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// cell is 2 dots wide, but text chars occupy 1 full cell.
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let canvas_cols = (area.width.saturating_sub(2)) as f64;
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let char_w = if canvas_cols > 0.0 {
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vp_width / canvas_cols
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} else {
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1.0
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};
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let char_h = char_w * 2.0; // character cells are roughly 2x taller than wide in geo space
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+
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let min_pop = if vp_width > 40.0 {
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2_000_000
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} else if vp_width > 20.0 {
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500_000
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} else if vp_width > 10.0 {
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+
100_000
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} else {
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30_000
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};
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+
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// Occupied bounding boxes: (x_min, y_min, x_max, y_max)
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let mut occupied: Vec<(f64, f64, f64, f64)> = Vec::new();
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+
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// Reserve space for train markers (each ~2 chars wide)
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for dot in &dots {
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let pad = char_w * 2.0;
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let pad_h = char_h;
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occupied.push((
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dot.lon - pad,
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dot.lat - pad_h,
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dot.lon + pad,
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dot.lat + pad_h,
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));
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}
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+
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// Reserve space for station markers
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for s in &station_dots {
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let pad = char_w;
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let pad_h = char_h * 0.5;
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occupied.push((s.lon - pad, s.lat - pad_h, s.lon + pad, s.lat + pad_h));
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}
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+
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let candidates: Vec<_> = app
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.geo
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.as_ref()
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.map(|g| {
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g.cities
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.iter()
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.filter(|c| c.population >= min_pop)
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.filter(|c| vp.contains(c.lon, c.lat))
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.collect::<Vec<_>>()
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})
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.unwrap_or_default();
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+
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let mut result = Vec::new();
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for city in candidates {
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let lx = city.lon + char_w; // offset right of the point
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let ly = city.lat;
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let label_w = city.name.len() as f64 * char_w;
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let label_h = char_h;
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let bbox = (lx, ly - label_h * 0.5, lx + label_w, ly + label_h * 0.5);
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+
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// Check for collision with any occupied box
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let collides = occupied
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.iter()
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.filter(|c| c.population >= min_pop)
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.filter(|c| vp.contains(c.lon, c.lat))
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.map(|c| (c.lon, c.lat, c.name.clone()))
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.collect()
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})
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.unwrap_or_default();
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.any(|o| bbox.0 < o.2 && bbox.2 > o.0 && bbox.1 < o.3 && bbox.3 > o.1);
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+
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if !collides {
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occupied.push(bbox);
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result.push((lx, ly, city.name.clone()));
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}
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}
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result
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+
};
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let canvas = Canvas::default()
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.block(
···
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}
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}
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// Layer 8: City labels — offset slightly right/up to avoid sitting on features
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if show_cities {
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for (lon, lat, ref name) in &city_labels {
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ctx.print(
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*lon + vp_width * 0.004,
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*lat + vp_width * 0.002,
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Span::styled(
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name.clone(),
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Style::default().fg(Color::Rgb(130, 125, 115)),
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),
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);
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}
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}
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// Layer 9: Amtrak routes
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// Layer 8: Amtrak routes
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if show_routes {
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for &(x1, y1, x2, y2, color) in &route_lines {
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ctx.draw(&CanvasLine {
···
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),
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);
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}
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}
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}
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+
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// Layer 12: City labels — rendered LAST so text isn't overwritten by braille
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// Collision detection already filtered out labels that overlap trains/stations
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if show_cities {
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for (lon, lat, ref name) in &city_labels {
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ctx.print(
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*lon,
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*lat,
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Span::styled(name.clone(), Style::default().fg(Color::Rgb(140, 135, 120))),
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+
);
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}
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}
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})