Fix some theme colors & drill summary delete continue

src/ui/components/typing_area.rs

@@ -26,6 +26,117 @@ struct RenderToken {
     is_line_break: bool,
 }
 
+fn color_to_rgb(color: ratatui::style::Color) -> (u8, u8, u8) {
+    use ratatui::style::Color;
+    match color {
+        Color::Reset => (0, 0, 0),
+        Color::Black => (0, 0, 0),
+        Color::Red => (205, 49, 49),
+        Color::Green => (13, 188, 121),
+        Color::Yellow => (229, 229, 16),
+        Color::Blue => (36, 114, 200),
+        Color::Magenta => (188, 63, 188),
+        Color::Cyan => (17, 168, 205),
+        Color::Gray => (229, 229, 229),
+        Color::DarkGray => (102, 102, 102),
+        Color::LightRed => (241, 76, 76),
+        Color::LightGreen => (35, 209, 139),
+        Color::LightYellow => (245, 245, 67),
+        Color::LightBlue => (59, 142, 234),
+        Color::LightMagenta => (214, 112, 214),
+        Color::LightCyan => (41, 184, 219),
+        Color::White => (255, 255, 255),
+        Color::Rgb(r, g, b) => (r, g, b),
+        Color::Indexed(i) => {
+            if i < 16 {
+                const ANSI16: [(u8, u8, u8); 16] = [
+                    (0, 0, 0),
+                    (128, 0, 0),
+                    (0, 128, 0),
+                    (128, 128, 0),
+                    (0, 0, 128),
+                    (128, 0, 128),
+                    (0, 128, 128),
+                    (192, 192, 192),
+                    (128, 128, 128),
+                    (255, 0, 0),
+                    (0, 255, 0),
+                    (255, 255, 0),
+                    (0, 0, 255),
+                    (255, 0, 255),
+                    (0, 255, 255),
+                    (255, 255, 255),
+                ];
+                ANSI16[i as usize]
+            } else if i <= 231 {
+                let idx = i - 16;
+                let r = idx / 36;
+                let g = (idx % 36) / 6;
+                let b = idx % 6;
+                let cv = |n: u8| if n == 0 { 0 } else { 55 + n * 40 };
+                (cv(r), cv(g), cv(b))
+            } else {
+                let v = 8 + (i - 232) * 10;
+                (v, v, v)
+            }
+        }
+    }
+}
+
+fn relative_luminance(color: ratatui::style::Color) -> f64 {
+    let (r, g, b) = color_to_rgb(color);
+    let to_linear = |c: u8| {
+        let x = c as f64 / 255.0;
+        if x <= 0.03928 {
+            x / 12.92
+        } else {
+            ((x + 0.055) / 1.055).powf(2.4)
+        }
+    };
+    0.2126 * to_linear(r) + 0.7152 * to_linear(g) + 0.0722 * to_linear(b)
+}
+
+fn contrast_ratio(a: ratatui::style::Color, b: ratatui::style::Color) -> f64 {
+    let la = relative_luminance(a);
+    let lb = relative_luminance(b);
+    let (hi, lo) = if la >= lb { (la, lb) } else { (lb, la) };
+    (hi + 0.05) / (lo + 0.05)
+}
+
+fn choose_cursor_colors(colors: &crate::ui::theme::ThemeColors) -> (ratatui::style::Color, ratatui::style::Color) {
+    use ratatui::style::Color;
+
+    let base_bg = colors.bg();
+    let mut cursor_bg = colors.text_cursor_bg();
+
+    // Ensure cursor block stands out from the typing area's background.
+    if contrast_ratio(cursor_bg, base_bg) < 1.8 {
+        let mut best_bg = cursor_bg;
+        let mut best_ratio = contrast_ratio(cursor_bg, base_bg);
+        for candidate in [colors.accent(), colors.focused_key(), colors.warning(), Color::Black, Color::White] {
+            let ratio = contrast_ratio(candidate, base_bg);
+            if ratio > best_ratio {
+                best_bg = candidate;
+                best_ratio = ratio;
+            }
+        }
+        cursor_bg = best_bg;
+    }
+
+    // Pick most readable fg on top of chosen cursor background.
+    let mut cursor_fg = colors.text_cursor_fg();
+    let mut best_ratio = contrast_ratio(cursor_fg, cursor_bg);
+    for candidate in [colors.fg(), colors.bg(), Color::Black, Color::White] {
+        let ratio = contrast_ratio(candidate, cursor_bg);
+        if ratio > best_ratio {
+            cursor_fg = candidate;
+            best_ratio = ratio;
+        }
+    }
+
+    (cursor_fg, cursor_bg)
+}
+
 /// Expand target chars into render tokens, handling whitespace display.
 fn build_render_tokens(target: &[char]) -> Vec<RenderToken> {
     let mut tokens = Vec::new();
@@ -71,6 +182,7 @@ fn build_render_tokens(target: &[char]) -> Vec<RenderToken> {
 impl Widget for TypingArea<'_> {
     fn render(self, area: Rect, buf: &mut Buffer) {
         let colors = &self.theme.colors;
+        let (cursor_fg, cursor_bg) = choose_cursor_colors(colors);
         let tokens = build_render_tokens(&self.drill.target);
 
         // Group tokens into lines, splitting on line_break tokens
@@ -90,9 +202,9 @@ impl Widget for TypingArea<'_> {
                 }
             } else if idx == self.drill.cursor {
                 Style::default()
-                    .fg(colors.text_cursor_fg())
-                    .bg(colors.text_cursor_bg())
-                    .add_modifier(Modifier::REVERSED | Modifier::BOLD)
+                    .fg(cursor_fg)
+                    .bg(cursor_bg)
+                    .add_modifier(Modifier::BOLD)
             } else {
                 Style::default().fg(colors.text_pending())
             };