fix: match ghostty pane default colors to host terminal theme

1 files changed, 143 insertions, 0 deletions

diff --git a/src/terminal_theme.rs b/src/terminal_theme.rs
new file mode 100644
index 00000000..e0b4b9d5
--- /dev/null
+++ b/src/terminal_theme.rs
@@ -0,0 +1,143 @@
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+pub struct RgbColor {
+    pub r: u8,
+    pub g: u8,
+    pub b: u8,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+pub struct TerminalTheme {
+    pub foreground: Option<RgbColor>,
+    pub background: Option<RgbColor>,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum DefaultColorKind {
+    Foreground,
+    Background,
+}
+
+pub const HOST_COLOR_QUERY_SEQUENCE: &str = "\x1b]10;?\x1b\\\x1b]11;?\x1b\\";
+
+impl TerminalTheme {
+    pub fn with_color(mut self, kind: DefaultColorKind, color: RgbColor) -> Self {
+        match kind {
+            DefaultColorKind::Foreground => self.foreground = Some(color),
+            DefaultColorKind::Background => self.background = Some(color),
+        }
+        self
+    }
+
+    pub fn is_empty(self) -> bool {
+        self.foreground.is_none() && self.background.is_none()
+    }
+}
+
+pub fn parse_default_color_response(sequence: &str) -> Option<(DefaultColorKind, RgbColor)> {
+    let body = sequence.strip_prefix("\x1b]")?;
+    let body = body
+        .strip_suffix("\x1b\\")
+        .or_else(|| body.strip_suffix('\u{7}'))?;
+    let (command, value) = body.split_once(';')?;
+    let kind = match command {
+        "10" => DefaultColorKind::Foreground,
+        "11" => DefaultColorKind::Background,
+        _ => return None,
+    };
+    Some((kind, parse_rgb_color(value)?))
+}
+
+#[cfg_attr(not(feature = "ghostty-vt"), allow(dead_code))]
+pub fn osc_set_default_color_sequence(kind: DefaultColorKind, color: RgbColor) -> String {
+    let command = match kind {
+        DefaultColorKind::Foreground => 10,
+        DefaultColorKind::Background => 11,
+    };
+    format!(
+        "\x1b]{command};rgb:{:02x}/{:02x}/{:02x}\x1b\\",
+        color.r, color.g, color.b
+    )
+}
+
+fn parse_rgb_color(value: &str) -> Option<RgbColor> {
+    if let Some(rgb) = value.strip_prefix("rgb:") {
+        let mut parts = rgb.split('/');
+        return Some(RgbColor {
+            r: parse_hex_component(parts.next()?)?,
+            g: parse_hex_component(parts.next()?)?,
+            b: parse_hex_component(parts.next()?)?,
+        })
+        .filter(|_| parts.next().is_none());
+    }
+
+    if let Some(hex) = value.strip_prefix('#') {
+        let digits = hex.len() / 3;
+        if !matches!(digits, 1..=4) || hex.len() != digits * 3 {
+            return None;
+        }
+        return Some(RgbColor {
+            r: parse_hex_component(&hex[..digits])?,
+            g: parse_hex_component(&hex[digits..digits * 2])?,
+            b: parse_hex_component(&hex[digits * 2..])?,
+        });
+    }
+
+    None
+}
+
+fn parse_hex_component(component: &str) -> Option<u8> {
+    if component.is_empty()
+        || component.len() > 4
+        || !component.chars().all(|ch| ch.is_ascii_hexdigit())
+    {
+        return None;
+    }
+    let value = u32::from_str_radix(component, 16).ok()?;
+    let max = (1u32 << (component.len() * 4)) - 1;
+    Some(((value * 255 + (max / 2)) / max) as u8)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parses_st_terminated_rgb_response() {
+        let parsed = parse_default_color_response("\x1b]10;rgb:cccc/dddd/eeee\x1b\\");
+        assert_eq!(
+            parsed,
+            Some((
+                DefaultColorKind::Foreground,
+                RgbColor {
+                    r: 0xcc,
+                    g: 0xdd,
+                    b: 0xee,
+                },
+            ))
+        );
+    }
+
+    #[test]
+    fn parses_bel_terminated_hash_response() {
+        let parsed = parse_default_color_response("\x1b]11;#123456\u{7}");
+        assert_eq!(
+            parsed,
+            Some((
+                DefaultColorKind::Background,
+                RgbColor {
+                    r: 0x12,
+                    g: 0x34,
+                    b: 0x56,
+                },
+            ))
+        );
+    }
+
+    #[test]
+    fn scales_short_hex_components() {
+        assert_eq!(parse_hex_component("f"), Some(255));
+        assert_eq!(parse_hex_component("80"), Some(128));
+        assert_eq!(parse_hex_component("800"), Some(128));
+        assert_eq!(parse_hex_component("8000"), Some(128));
+    }
+}