Context-Aware Icon Colors for Terminal Weather

Mausam is a terminal weather tool — Rust, crossterm, tokio. The icon palette is small but the rule that drives it is the part I’m proud of.

Every status icon has a contextual color, not a fixed one. The sun is yellow at noon, dimmed at dusk, swapped for a moon at night. Rain icons are blue when cold, slate when warm. Wind glyphs use a steel-gray that doesn’t fight with the temperature gradient.

The state machine reads sunrise/sunset from the API response rather than using hardcoded hours. is_daytime_now(daily, &localtime) consults the actual local sunrise time, so winter mornings render the moon icon at 7am and summer evenings render the sun until well past 8pm. No magic numbers.

let (icon, desc, icon_color) =
    weather_icon(cur.weather_code, is_daytime_now(daily, &loc.localtime));

let wind_val = format!(
    "{} {:.0} {} {}",
    ICON_WIND.truecolor(150, 180, 210),
    cur.wind_speed_10m, wind_label(),
    wind_compass(cur.wind_direction_10m),
);

Truecolor is non-negotiable. The 16-color ANSI palette can’t render a sunset gradient; the temperature display needs a smooth ramp from teal-cool to amber-warm and that doesn’t fit in 16 slots. colored::truecolor(r, g, b) falls back gracefully on terminals that don’t support it, but every modern terminal in 2026 does.

Icon set is Nerd Font. \u{e30f} for sun, \u{f04b6} for moon, full set for wind compass, AQI leaf, gauge for pressure, eye for visibility, dewpoint indicator. The compact display computes a per-column padding width by stripping ANSI from each value before measuring — otherwise the box-drawing borders drift on color codes.

The whole render is two phases: pre-compute every string and its visual width, then derive the panel width from max(content widths) + gap. Nothing reflows after layout. Single render, single line of output.