termio: report color scheme synchronously

The reporting of color scheme was handled asynchronously by queuing a
handler in the surface. This could lead to race conditions where the
DSR is reported after subsequent VT sequences.

Fixes #5922

src/Surface.zig

@@ -1073,8 +1073,6 @@ pub fn handleMessage(self: *Surface, msg: Message) !void {
 
         .scrollbar => |scrollbar| self.updateScrollbar(scrollbar),
 
-        .report_color_scheme => |force| self.reportColorScheme(force),
-
         .present_surface => try self.presentSurface(),
 
         .password_input => |v| try self.passwordInput(v),
@@ -1386,26 +1384,6 @@ fn passwordInput(self: *Surface, v: bool) !void {
     try self.queueRender();
 }
 
-/// Sends a DSR response for the current color scheme to the pty. If
-/// force is false then we only send the response if the terminal mode
-/// 2031 is enabled.
-fn reportColorScheme(self: *Surface, force: bool) void {
-    if (!force) {
-        self.renderer_state.mutex.lock();
-        defer self.renderer_state.mutex.unlock();
-        if (!self.renderer_state.terminal.modes.get(.report_color_scheme)) {
-            return;
-        }
-    }
-
-    const output = switch (self.config_conditional_state.theme) {
-        .light => "\x1B[?997;2n",
-        .dark => "\x1B[?997;1n",
-    };
-
-    self.queueIo(.{ .write_stable = output }, .unlocked);
-}
-
 fn searchCallback(event: terminal.search.Thread.Event, ud: ?*anyopaque) void {
     // IMPORTANT: This function is run on the SEARCH THREAD! It is NOT SAFE
     // to access anything other than values that never change on the surface.
@@ -5039,7 +5017,7 @@ pub fn colorSchemeCallback(self: *Surface, scheme: apprt.ColorScheme) !void {
     self.notifyConfigConditionalState();
 
     // If mode 2031 is on, then we report the change live.
-    self.reportColorScheme(false);
+    self.queueIo(.{ .color_scheme_report = .{ .force = false } }, .unlocked);
 }
 
 pub fn posToViewport(self: Surface, xpos: f64, ypos: f64) terminal.point.Coordinate {

src/apprt/surface.zig

@@ -63,11 +63,6 @@ pub const Message = union(enum) {
     /// Health status change for the renderer.
     renderer_health: renderer.Health,
 
-    /// Report the color scheme. The bool parameter is whether to force or not.
-    /// If force is true, the color scheme should be reported even if mode
-    /// 2031 is not set.
-    report_color_scheme: bool,
-
     /// Tell the surface to present itself to the user. This may require raising
     /// a window and switching tabs.
     present_surface: void,

src/termio/Termio.zig

@@ -165,6 +165,7 @@ pub const DerivedConfig = struct {
     osc_color_report_format: configpkg.Config.OSCColorReportFormat,
     clipboard_write: configpkg.ClipboardAccess,
     enquiry_response: []const u8,
+    conditional_state: configpkg.ConditionalState,
 
     pub fn init(
         alloc_gpa: Allocator,
@@ -185,6 +186,7 @@ pub const DerivedConfig = struct {
             .osc_color_report_format = config.@"osc-color-report-format",
             .clipboard_write = config.@"clipboard-write",
             .enquiry_response = try alloc.dupe(u8, config.@"enquiry-response"),
+            .conditional_state = config._conditional_state,
 
             // This has to be last so that we copy AFTER the arena allocations
             // above happen (Zig assigns in order).
@@ -712,6 +714,25 @@ fn processOutputLocked(self: *Termio, buf: []const u8) void {
     }
 }
 
+/// Sends a DSR response for the current color scheme to the pty.
+pub fn colorSchemeReport(self: *Termio, td: *ThreadData, force: bool) !void {
+    self.renderer_state.mutex.lock();
+    defer self.renderer_state.mutex.unlock();
+
+    try self.colorSchemeReportLocked(td, force);
+}
+
+pub fn colorSchemeReportLocked(self: *Termio, td: *ThreadData, force: bool) !void {
+    if (!force and !self.renderer_state.terminal.modes.get(.report_color_scheme)) {
+        return;
+    }
+    const output = switch (self.config.conditional_state.theme) {
+        .light => "\x1B[?997;2n",
+        .dark => "\x1B[?997;1n",
+    };
+    try self.queueWrite(td, output, false);
+}
+
 /// ThreadData is the data created and stored in the termio thread
 /// when the thread is started and destroyed when the thread is
 /// stopped.

src/termio/Thread.zig

@@ -311,6 +311,7 @@ fn drainMailbox(
 
         log.debug("mailbox message={s}", .{@tagName(message)});
         switch (message) {
+            .color_scheme_report => |v| try io.colorSchemeReport(data, v.force),
             .crash => @panic("crash request, crashing intentionally"),
             .change_config => |config| {
                 defer config.alloc.destroy(config.ptr);

src/termio/message.zig

@@ -16,6 +16,12 @@ pub const Message = union(enum) {
     /// in the future.
     pub const WriteReq = MessageData(u8, 38);
 
+    /// Request a color scheme report is sent to the pty.
+    color_scheme_report: struct {
+        /// Force write the current color scheme
+        force: bool,
+    },
+
     /// Purposely crash the renderer. This is used for testing and debugging.
     /// See the "crash" binding action.
     crash: void,

src/termio/stream_handler.zig

@@ -119,7 +119,7 @@ pub const StreamHandler = struct {
         };
 
         // The config could have changed any of our colors so update mode 2031
-        self.surfaceMessageWriter(.{ .report_color_scheme = false });
+        self.messageWriter(.{ .color_scheme_report = .{ .force = false } });
     }
 
     inline fn surfaceMessageWriter(
@@ -871,7 +871,7 @@ pub const StreamHandler = struct {
                 self.messageWriter(msg);
             },
 
-            .color_scheme => self.surfaceMessageWriter(.{ .report_color_scheme = true }),
+            .color_scheme => self.messageWriter(.{ .color_scheme_report = .{ .force = true } }),
         }
     }
 
@@ -956,7 +956,7 @@ pub const StreamHandler = struct {
         try self.setMouseShape(.text);
 
         // Reset resets our palette so we report it for mode 2031.
-        self.surfaceMessageWriter(.{ .report_color_scheme = false });
+        self.messageWriter(.{ .color_scheme_report = .{ .force = false } });
 
         // Clear the progress bar
         self.progressReport(.{ .state = .remove });