tui: hardcode xterm palette, shimmer blends between fg and bg (#4957)

Instead of querying all 256 terminal colors on startup, which was slow
in some terminals, hardcode the default xterm palette.

Additionally, tweak the shimmer so that it blends between default_fg and
default_bg, instead of "dark gray" (according to the terminal) and pure
white (regardless of terminal theme).

Author: nornagon-openai

codex-rs/tui/src/shimmer.rs

@@ -8,10 +8,8 @@ use ratatui::style::Style;
 use ratatui::text::Span;
 
 use crate::color::blend;
+use crate::terminal_palette::default_bg;
 use crate::terminal_palette::default_fg;
-use crate::terminal_palette::terminal_palette;
-
-const FALLBACK_DARK_GRAY: (u8, u8, u8) = (103, 103, 103);
 
 static PROCESS_START: OnceLock<Instant> = OnceLock::new();
 
@@ -35,11 +33,11 @@ pub(crate) fn shimmer_spans(text: &str) -> Vec<Span<'static>> {
     let has_true_color = supports_color::on_cached(supports_color::Stream::Stdout)
         .map(|level| level.has_16m)
         .unwrap_or(false);
-    let band_half_width = 3.0;
+    let band_half_width = 5.0;
 
     let mut spans: Vec<Span<'static>> = Vec::with_capacity(chars.len());
-    let default_fg = default_fg();
-    let palette_dark_gray = terminal_palette().map(|palette| palette[8]);
+    let base_color = default_fg().unwrap_or((128, 128, 128));
+    let highlight_color = default_bg().unwrap_or((255, 255, 255));
     for (i, ch) in chars.iter().enumerate() {
         let i_pos = i as isize + padding as isize;
         let pos = pos as isize;
@@ -52,11 +50,8 @@ pub(crate) fn shimmer_spans(text: &str) -> Vec<Span<'static>> {
             0.0
         };
         let style = if has_true_color {
-            let base = palette_dark_gray
-                .or(default_fg)
-                .unwrap_or(FALLBACK_DARK_GRAY);
             let highlight = t.clamp(0.0, 1.0);
-            let (r, g, b) = blend((255, 255, 255), base, highlight);
+            let (r, g, b) = blend(highlight_color, base_color, highlight * 0.9);
             // Allow custom RGB colors, as the implementation is thoughtfully
             // adjusting the level of the default foreground color.
             #[allow(clippy::disallowed_methods)]

codex-rs/tui/src/style.rs

@@ -1,8 +1,7 @@
 use crate::color::blend;
 use crate::color::is_light;
-use crate::color::perceptual_distance;
+use crate::terminal_palette::best_color;
 use crate::terminal_palette::default_bg;
-use crate::terminal_palette::terminal_palette;
 use ratatui::style::Color;
 use ratatui::style::Style;
 
@@ -25,25 +24,5 @@ pub fn user_message_bg(terminal_bg: (u8, u8, u8)) -> Color {
     } else {
         (255, 255, 255)
     };
-    let bottom = terminal_bg;
-    let Some(color_level) = supports_color::on_cached(supports_color::Stream::Stdout) else {
-        return Color::default();
-    };
-
-    let target = blend(top, bottom, 0.1);
-    if color_level.has_16m {
-        let (r, g, b) = target;
-        Color::Rgb(r, g, b)
-    } else if color_level.has_256
-        && let Some(palette) = terminal_palette()
-        && let Some((i, _)) = palette.into_iter().enumerate().min_by(|(_, a), (_, b)| {
-            perceptual_distance(*a, target)
-                .partial_cmp(&perceptual_distance(*b, target))
-                .unwrap_or(std::cmp::Ordering::Equal)
-        })
-    {
-        Color::Indexed(i as u8)
-    } else {
-        Color::default()
-    }
+    best_color(blend(top, terminal_bg, 0.1))
 }