nixos/settings/ui.nix

# settings/ui.nix — shared UI metrics.
#
# Single source of truth for corner rounding. Both the quickshell shell
# (settings/quickshell.nix -> Theme.qml) and hyprland's window decoration
# (settings/hyprland.nix) read `radius` from here, and every other rounding
# value is derived from it, so this one number rescales the roundness of the
# whole desktop — panels, cards, pills, hover rows and window corners.
#
# Derived values live next to their consumers:
#   Theme.radiusCard  = radius - panelGap  (concentric nesting, see Theme.qml)
#   Theme.radiusSmall = radius * 0.75
#   Theme.radiusTiny  = radius * 0.5
#   hyprland decoration.rounding = radius
{
  radius = 20;

  # ── Ink ladder ────────────────────────────────────────────────────────
  # base05 is the wallpaper's ink. base04 and base03 are THAT colour mixed
  # toward the background, not stylix's own base03/base04: those are three
  # independent slots off the image and routinely land in unrelated hues —
  # on walls/wallhaven-k8dqr6 the raw ladder is red (base03), blue (base04)
  # and cream (base05). Mixing gives one colour at three strengths, which is
  # the same trick quickshell's Theme.base01/base02 already use for surfaces.
  #
  # Read by settings/quickshell.nix (Theme.qml), settings/theming.nix
  # (hypr.lua, applied at runtime) and settings/hyprland.nix (the build-time
  # fallback), so the shell frame and hyprland's window borders are the same
  # colour rather than two slots that happen to be near each other.
  inkMuted = 0.30;   # base04 — secondary text, hyprland's active border
  inkFaint = 0.55;   # base03 — disabled text, hyprland's inactive border

  # Mix two "rrggbb" strings. t = 0 keeps `a`, t = 1 lands on `b`.
  mixHex = a: b: t:
    let
      digits = "0123456789abcdef";
      val = ch: {
        "0"=0; "1"=1; "2"=2; "3"=3; "4"=4; "5"=5; "6"=6; "7"=7;
        "8"=8; "9"=9; "a"=10; "b"=11; "c"=12; "d"=13; "e"=14; "f"=15;
        "A"=10; "B"=11; "C"=12; "D"=13; "E"=14; "F"=15;
      }.${ch};
      byte = s: i: val (builtins.substring i 1 s) * 16
                 + val (builtins.substring (i + 1) 1 s);
      chan = i:
        let
          n = builtins.floor (byte a i + (byte b i - byte a i) * t + 0.5);
          hi = n / 16;
        in builtins.substring hi 1 digits + builtins.substring (n - hi * 16) 1 digits;
    in chan 0 + chan 2 + chan 4;
}