core: implement querying with OSC 4

src/config/Config.zig

@@ -551,15 +551,16 @@ keybind: Keybinds = .{},
 @"shell-integration-features": ShellIntegrationFeatures = .{},
 
 /// Sets the reporting format for OSC sequences that request color information.
-/// Ghostty currently supports OSC 10 (foreground) and OSC 11 (background) queries,
+/// Ghostty currently supports OSC 10 (foreground), OSC 11 (background), and OSC
-/// and by default the reported values are scaled-up RGB values, where each component
+/// 4 (256 color palette) queries, and by default the reported values are
-/// are 16 bits. This is how most terminals report these values. However, some legacy
+/// scaled-up RGB values, where each component are 16 bits. This is how most
-/// applications may require 8-bit, unscaled, components. We also support turning off
+/// terminals report these values. However, some legacy applications may require
-/// reporting alltogether. The components are lowercase hex values.
+/// 8-bit, unscaled, components. We also support turning off reporting
+/// alltogether. The components are lowercase hex values.
 ///
 /// Allowable values are:
 ///
-///   * "none" - OSC 10/11 queries receive no reply
+///   * "none" - OSC 4/10/11 queries receive no reply
 ///   * "8-bit" - Color components are return unscaled, i.e. rr/gg/bb
 ///   * "16-bit" - Color components are returned scaled, e.g. rrrr/gggg/bbbb
 ///

src/inspector/termio.zig

@@ -241,6 +241,25 @@ pub const VTEvent = struct {
                 try alloc.dupeZ(u8, @tagName(value)),
             ),
 
+            .Union => |u| if (u.tag_type) |Tag| {
+                const tag_name = @tagName(@as(Tag, value));
+                inline for (u.fields) |field| {
+                    if (std.mem.eql(u8, field.name, tag_name)) {
+                        const s = if (field.type == void)
+                            try alloc.dupeZ(u8, tag_name)
+                        else
+                            try std.fmt.allocPrintZ(alloc, "{s}={}", .{
+                                tag_name,
+                                @field(value, field.name),
+                            });
+
+                        try md.put(key, s);
+                    }
+                }
+            } else {
+                @compileError("Unions must have a tag");
+            },
+
             else => switch (Value) {
                 u8 => try md.put(
                     key,

src/terminal/osc.zig

@@ -94,9 +94,10 @@ pub const Command = union(enum) {
         value: []const u8,
     },
 
-    /// OSC 10 and OSC 11 default color report.
+    /// OSC 4, OSC 10, and OSC 11 default color report.
     report_default_color: struct {
-        /// OSC 10 requests the foreground color, OSC 11 the background color.
+        /// OSC 4 requests a palette color, OSC 10 requests the foreground
+        /// color, OSC 11 the background color.
         kind: DefaultColorKind,
 
         /// We must reply with the same string terminator (ST) as used in the
@@ -104,14 +105,16 @@ pub const Command = union(enum) {
         terminator: Terminator = .st,
     },
 
-    pub const DefaultColorKind = enum {
+    pub const DefaultColorKind = union(enum) {
         foreground,
         background,
+        palette: u8,
 
         pub fn code(self: DefaultColorKind) []const u8 {
             return switch (self) {
                 .foreground => "10",
                 .background => "11",
+                .palette => "4",
             };
         }
     };
@@ -199,6 +202,7 @@ pub const Parser = struct {
         @"133",
         @"2",
         @"22",
+        @"4",
         @"5",
         @"52",
         @"7",
@@ -224,6 +228,10 @@ pub const Parser = struct {
         clipboard_kind,
         clipboard_kind_end,
 
+        // Get/set color palette index
+        color_palette_index,
+        color_palette_index_end,
+
         // Expect a string parameter. param_str must be set as well as
         // buf_start.
         string,
@@ -277,6 +285,7 @@ pub const Parser = struct {
                 '0' => self.state = .@"0",
                 '1' => self.state = .@"1",
                 '2' => self.state = .@"2",
+                '4' => self.state = .@"4",
                 '5' => self.state = .@"5",
                 '7' => self.state = .@"7",
                 else => self.state = .invalid,
@@ -348,6 +357,39 @@ pub const Parser = struct {
                 else => self.state = .invalid,
             },
 
+            .@"4" => switch (c) {
+                ';' => {
+                    self.state = .color_palette_index;
+                    self.buf_start = self.buf_idx;
+                },
+                else => self.state = .invalid,
+            },
+
+            .color_palette_index => switch (c) {
+                '0'...'9' => {},
+                ';' => {
+                    if (std.fmt.parseUnsigned(u8, self.buf[self.buf_start .. self.buf_idx - 1], 10)) |num| {
+                        self.state = .color_palette_index_end;
+                        self.temp_state = .{ .num = num };
+                    } else |err| switch (err) {
+                        error.Overflow => self.state = .invalid,
+                        error.InvalidCharacter => unreachable,
+                    }
+                },
+                else => self.state = .invalid,
+            },
+
+            .color_palette_index_end => switch (c) {
+                '?' => {
+                    self.command = .{ .report_default_color = .{
+                        .kind = .{ .palette = @intCast(self.temp_state.num) },
+                    } };
+
+                    self.complete = true;
+                },
+                else => self.state = .invalid,
+            },
+
             .@"5" => switch (c) {
                 '2' => self.state = .@"52",
                 else => self.state = .invalid,
@@ -921,3 +963,17 @@ test "OSC: report default background color" {
     try testing.expectEqual(cmd.report_default_color.kind, .background);
     try testing.expectEqual(cmd.report_default_color.terminator, .bel);
 }
+
+test "OSC: get palette color" {
+    const testing = std.testing;
+
+    var p: Parser = .{};
+
+    const input = "4;1;?";
+    for (input) |ch| p.next(ch);
+
+    const cmd = p.end('\x1b').?;
+    try testing.expect(cmd == .report_default_color);
+    try testing.expectEqual(cmd.report_default_color.kind, .{ .palette = 1 });
+    try testing.expectEqual(cmd.report_default_color.terminator, .st);
+}

src/termio/Exec.zig

@@ -2150,8 +2150,8 @@ const StreamHandler = struct {
         }
     }
 
-    /// Implements OSC 10 and OSC 11, which reports default foreground and
+    /// Implements OSC 4, OSC 10, and OSC 11, which reports palette color,
-    /// background color respectively.
+    /// default foreground color, and background color respectively.
     pub fn reportDefaultColor(
         self: *StreamHandler,
         kind: terminal.osc.Command.DefaultColorKind,
@@ -2162,6 +2162,7 @@ const StreamHandler = struct {
         const color = switch (kind) {
             .foreground => self.default_foreground_color,
             .background => self.default_background_color,
+            .palette => |i| self.terminal.color_palette[i],
         };
 
         var msg: termio.Message = .{ .write_small = .{} };