terminal: support mode 2031

src/Surface.zig

@@ -838,18 +838,21 @@ pub fn handleMessage(self: *Surface, msg: Message) !void {
 
         .renderer_health => |health| self.updateRendererHealth(health),
 
-        .report_color_scheme => {
+        .report_color_scheme => try self.reportColorScheme(),
-            const output = switch (self.color_scheme) {
-                .light => "\x1B[?997;2n",
-                .dark => "\x1B[?997;1n",
-            };
-
-            _ = self.io_thread.mailbox.push(.{ .write_stable = output }, .{ .forever = {} });
-            try self.io_thread.wakeup.notify();
-        },
     }
 }
 
+/// Sends a DSR response for the current color scheme to the pty.
+fn reportColorScheme(self: *const Surface) !void {
+    const output = switch (self.color_scheme) {
+        .light => "\x1B[?997;2n",
+        .dark => "\x1B[?997;1n",
+    };
+
+    _ = self.io_thread.mailbox.push(.{ .write_stable = output }, .{ .forever = {} });
+    try self.io_thread.wakeup.notify();
+}
+
 /// Call this when modifiers change. This is safe to call even if modifiers
 /// match the previous state.
 ///
@@ -2804,7 +2807,19 @@ fn dragLeftClickBefore(
 /// Call to notify Ghostty that the color scheme for the terminal has
 /// changed.
 pub fn colorSchemeCallback(self: *Surface, scheme: apprt.ColorScheme) !void {
+    // If our scheme didn't change, then we don't do anything.
+    if (self.color_scheme == scheme) return;
+
+    // Set our new scheme
     self.color_scheme = scheme;
+
+    // If mode 2031 is on, then we report the change live.
+    const report = report: {
+        self.renderer_state.mutex.lock();
+        defer self.renderer_state.mutex.unlock();
+        break :report self.renderer_state.terminal.modes.get(.report_color_scheme);
+    };
+    if (report) try self.reportColorScheme();
 }
 
 fn posToViewport(self: Surface, xpos: f64, ypos: f64) terminal.point.Viewport {

src/terminal/modes.zig

@@ -215,6 +215,7 @@ const entries: []const ModeEntry = &.{
     .{ .name = "bracketed_paste", .value = 2004 },
     .{ .name = "synchronized_output", .value = 2026 },
     .{ .name = "grapheme_cluster", .value = 2027 },
+    .{ .name = "report_color_scheme", .value = 2031 },
 };
 
 test {