Match filename tint lightness in every canonical theme and focus state

1 files changed, 71 insertions, 2 deletions

diff --git a/src/pardes.zig b/src/pardes.zig
index b6d6ed8f..51c9c3db 100644
--- a/src/pardes.zig
+++ b/src/pardes.zig
@@ -2939,8 +2939,10 @@ pub const Theme = struct {
     // editor palettes keep working; ChromeTheme resolves their legacy defaults.
     tag_active_bg: ?[3]u8 = null,
     tag_active_fg: ?[3]u8 = null,
-    /// Quiet filename/output-name accent; directories and commands keep tag ink.
+    /// Filename/output-name accent, also used by the Tty command.
     tag_name_fg: ?[3]u8 = null,
+    /// Active tint; absence preserves the shared name tint or active tag ink.
+    tag_active_name_fg: ?[3]u8 = null,
     border: ?[3]u8 = null,
     search_bg: ?[3]u8 = null,
     search_fg: ?[3]u8 = null,
@@ -3049,6 +3051,51 @@ test "native themes keep text and UI roles readable on their own surfaces" {
     }
 }
 
+test "native filename tints change hue without changing perceived lightness" {
+    const Perceptual = struct {
+        fn lab(rgb: [3]u8) [3]f64 {
+            var linear: [3]f64 = undefined;
+            for (rgb, 0..) |channel, i| {
+                const value = @as(f64, @floatFromInt(channel)) / 255;
+                linear[i] = if (value <= 0.04045) value / 12.92 else std.math.pow(f64, (value + 0.055) / 1.055, 2.4);
+            }
+            const r = linear[0];
+            const g = linear[1];
+            const b = linear[2];
+            const l = std.math.cbrt(0.4122214708 * r + 0.5363325363 * g + 0.0514459929 * b);
+            const m = std.math.cbrt(0.2119034982 * r + 0.6806995451 * g + 0.1073969566 * b);
+            const n = std.math.cbrt(0.0883024619 * r + 0.2817188376 * g + 0.6299787005 * b);
+            return .{
+                0.2104542553 * l + 0.7936177850 * m - 0.0040720468 * n,
+                1.9779984951 * l - 2.4285922050 * m + 0.4505937099 * n,
+                0.0259040371 * l + 0.7827717662 * m - 0.8086757660 * n,
+            };
+        }
+    };
+    for (themes[0..native_theme_count]) |th| {
+        try std.testing.expect(th.tag_name_fg != null and th.tag_active_name_fg != null);
+        const chrome = ChromeTheme.fromTheme(&th);
+        const pairs = [2][2][3]u8{
+            .{ chrome.tag_fg, chrome.tag_name_fg },
+            .{ chrome.tag_active_fg, chrome.tag_active_name_fg },
+        };
+        for (pairs) |pair| {
+            const base = Perceptual.lab(pair[0]);
+            const name = Perceptual.lab(pair[1]);
+            // Half a lightness point allows 8-bit quantization without a
+            // basename becoming visibly brighter or darker than its tag.
+            try std.testing.expectApproxEqAbs(base[0], name[0], 0.005);
+            const base_chroma = @sqrt(base[1] * base[1] + base[2] * base[2]);
+            const name_chroma = @sqrt(name[1] * name[1] + name[2] * name[2]);
+            try std.testing.expect(base_chroma > 0.005 and name_chroma > 0.02);
+            // A normalized dot product <= cos(60 degrees) means a clear
+            // hue difference, independent of saturation or lightness.
+            const hue_cosine = (base[1] * name[1] + base[2] * name[2]) / (base_chroma * name_chroma);
+            try std.testing.expect(hue_cosine <= 0.5);
+        }
+    }
+}
+
 test "native dark palettes choose near-black or deliberately soft contrast" {
     for (themes[0..native_theme_count]) |th| {
         if (themeContrast(th.bg.?, .{ 0, 0, 0 }) > 10) continue; // light paper
@@ -3122,6 +3169,7 @@ test "legacy ThemeFile documents inherit Pardes UI roles without new fields" {
     defer std.zon.parse.free(std.testing.allocator, parsed);
     try std.testing.expectEqual(@as(?[3]u8, null), parsed.tag_active_bg);
     try std.testing.expectEqual(@as(?[3]u8, null), parsed.tag_name_fg);
+    try std.testing.expectEqual(@as(?[3]u8, null), parsed.tag_active_name_fg);
     try std.testing.expectEqual(@as(?[3]u8, null), parsed.search_bg);
     const chrome = ChromeTheme.fromTheme(&parsed);
     try std.testing.expectEqual(parsed.tag_bg, chrome.tag_active_bg);
@@ -3131,6 +3179,27 @@ test "legacy ThemeFile documents inherit Pardes UI roles without new fields" {
     try std.testing.expectEqual(parsed.fg.?, chrome.diagnostic_error);
 }
 
+test "custom filename tints preserve optional active fallback precedence" {
+    var theme = themes[0];
+    theme.tag_name_fg = null;
+    theme.tag_active_name_fg = null;
+    var chrome = ChromeTheme.fromTheme(&theme);
+    try std.testing.expectEqual(theme.tag_fg, chrome.tag_name_fg);
+    try std.testing.expectEqual(theme.tag_active_fg.?, chrome.tag_active_name_fg);
+    theme.tag_name_fg = .{ 120, 130, 140 };
+    chrome = ChromeTheme.fromTheme(&theme);
+    try std.testing.expectEqual(theme.tag_name_fg.?, chrome.tag_name_fg);
+    try std.testing.expectEqual(theme.tag_name_fg.?, chrome.tag_active_name_fg);
+    theme.tag_active_name_fg = .{ 150, 160, 170 };
+    chrome = ChromeTheme.fromTheme(&theme);
+    try std.testing.expectEqual(theme.tag_name_fg.?, chrome.tag_name_fg);
+    try std.testing.expectEqual(theme.tag_active_name_fg.?, chrome.tag_active_name_fg);
+    theme.tag_name_fg = null;
+    chrome = ChromeTheme.fromTheme(&theme);
+    try std.testing.expectEqual(theme.tag_fg, chrome.tag_name_fg);
+    try std.testing.expectEqual(theme.tag_active_name_fg.?, chrome.tag_active_name_fg);
+}
+
 comptime {
     if (themes.len > std.math.maxInt(u16) + 1)
         @compileError("runtime config theme index no longer fits u16");
@@ -3209,7 +3278,7 @@ pub const ChromeTheme = struct {
             .tag_active_bg = th.tag_active_bg orelse th.tag_bg,
             .tag_active_fg = th.tag_active_fg orelse th.tag_fg,
             .tag_name_fg = th.tag_name_fg orelse th.tag_fg,
-            .tag_active_name_fg = th.tag_name_fg orelse (th.tag_active_fg orelse th.tag_fg),
+            .tag_active_name_fg = th.tag_active_name_fg orelse (th.tag_name_fg orelse (th.tag_active_fg orelse th.tag_fg)),
             .border = th.border orelse th.scroll_track,
             .search_bg = th.search_bg orelse th.sel_bg,
             .search_fg = th.search_fg orelse th.sel_fg,