mode 2031 should send updates on any color palette change

Related #2755

From the mode 2031 spec[1]:

> Send CSI ? 2031 h to the terminal to enable unsolicited DSR (device status
> report) messages for color palette updates and CSI ? 2031 l respectively to
> disable it again.
>
> The sent out DSR looks equivalent to the already above mentioned. This
> notification is not just sent when dark/light mode has been changed by the
> operating system / desktop, but also if the user explicitly changed color
> scheme, e.g. by configuration.

My reading of this paired with the original discussion is that this is
meant to be sent out for anything that could possibly change terminal
colors.

Previous to this commit, we only sent out the DSR when the actual system
light/dark mode changed. This commit changes it to send out the DSR on
any operation that _may_ change the terminal colors.

[1]: https://contour-terminal.org/vt-extensions/color-palette-update-notifications/#example-source-code

src/Surface.zig

@@ -820,7 +820,13 @@ pub fn handleMessage(self: *Surface, msg: Message) !void {
             }, .unlocked);
         },
 
-        .color_change => |change| try self.rt_app.performAction(
+        .color_change => |change| {
+            // On any color change, we have to report for mode 2031
+            // if it is enabled.
+            self.reportColorScheme(false);
+
+            // Notify our apprt
+            try self.rt_app.performAction(
                 .{ .surface = self },
                 .color_change,
                 .{
@@ -834,7 +840,8 @@ pub fn handleMessage(self: *Surface, msg: Message) !void {
                     .g = change.color.g,
                     .b = change.color.b,
                 },
-        ),
+            );
+        },
 
         .set_mouse_shape => |shape| {
             log.debug("changing mouse shape: {}", .{shape});
@@ -898,7 +905,7 @@ pub fn handleMessage(self: *Surface, msg: Message) !void {
 
         .renderer_health => |health| self.updateRendererHealth(health),
 
-        .report_color_scheme => try self.reportColorScheme(),
+        .report_color_scheme => |force| self.reportColorScheme(force),
 
         .present_surface => try self.presentSurface(),
 
@@ -935,8 +942,18 @@ fn passwordInput(self: *Surface, v: bool) !void {
     try self.queueRender();
 }
 
-/// Sends a DSR response for the current color scheme to the pty.
+/// Sends a DSR response for the current color scheme to the pty. If
-fn reportColorScheme(self: *Surface) !void {
+/// 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",
@@ -3643,12 +3660,7 @@ pub fn colorSchemeCallback(self: *Surface, scheme: apprt.ColorScheme) !void {
     self.notifyConfigConditionalState();
 
     // If mode 2031 is on, then we report the change live.
-    const report = report: {
+    self.reportColorScheme(false);
-        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();
 }
 
 pub fn posToViewport(self: Surface, xpos: f64, ypos: f64) terminal.point.Coordinate {

src/apprt/surface.zig

@@ -58,8 +58,10 @@ pub const Message = union(enum) {
     /// Health status change for the renderer.
     renderer_health: renderer.Health,
 
-    /// Report the color scheme
+    /// Report the color scheme. The bool parameter is whether to force or not.
-    report_color_scheme: void,
+    /// 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.

src/termio/stream_handler.zig

@@ -126,6 +126,9 @@ pub const StreamHandler = struct {
         if (self.default_cursor) self.setCursorStyle(.default) catch |err| {
             log.warn("failed to set default cursor style: {}", .{err});
         };
+
+        // The config could have changed any of our colors so update mode 2031
+        self.surfaceMessageWriter(.{ .report_color_scheme = false });
     }
 
     inline fn surfaceMessageWriter(
@@ -767,7 +770,7 @@ pub const StreamHandler = struct {
                 self.messageWriter(msg);
             },
 
-            .color_scheme => self.surfaceMessageWriter(.{ .report_color_scheme = {} }),
+            .color_scheme => self.surfaceMessageWriter(.{ .report_color_scheme = true }),
         }
     }
 
@@ -892,6 +895,9 @@ pub const StreamHandler = struct {
     ) !void {
         self.terminal.fullReset();
         try self.setMouseShape(.text);
+
+        // Reset resets our palette so we report it for mode 2031.
+        self.surfaceMessageWriter(.{ .report_color_scheme = false });
     }
 
     pub fn queryKittyKeyboard(self: *StreamHandler) !void {