feat: add DSR 996 color scheme query support

Handle CSI ? 996 n (DSR 996) in deviceStatusPrivate. When color scheme
updates are enabled (DECSET 2031), fires OnRequestColorSchemeQuery so
the host application can respond with the current color scheme.

- Add OnRequestColorSchemeQueryEmitter to InputHandler
- Add case 996 to deviceStatusPrivate (gated on ColorSchemeUpdates mode)
- Expose OnRequestColorSchemeQuery event on Terminal
- Add tests at both InputHandler and Terminal levels

Fixes #31

Co-authored-by: Ona <no-reply@ona.com>

Author: ona-automations

inputhandler.go

@@ -98,8 +98,9 @@ type InputHandler struct {
 	OnRequestBellEmitter          EventEmitter[struct{}]
 	OnRequestResetEmitter         EventEmitter[struct{}]
 	OnRequestRefreshRowsEmitter   EventEmitter[RowRange]
-	OnColorEmitter                EventEmitter[[]ColorEvent]
-	OnRequestSyncScrollBarEmitter EventEmitter[struct{}]
+	OnColorEmitter                     EventEmitter[[]ColorEvent]
+	OnRequestSyncScrollBarEmitter      EventEmitter[struct{}]
+	OnRequestColorSchemeQueryEmitter   EventEmitter[struct{}]
 }
 
 // NewInputHandler creates an InputHandler and registers all parser handlers.
@@ -547,4 +548,5 @@ func (h *InputHandler) Dispose() {
 	h.OnRequestRefreshRowsEmitter.Dispose()
 	h.OnColorEmitter.Dispose()
 	h.OnRequestSyncScrollBarEmitter.Dispose()
+	h.OnRequestColorSchemeQueryEmitter.Dispose()
 }

inputhandler_csi.go

@@ -497,10 +497,15 @@ func (h *InputHandler) deviceStatus(params *Params) bool {
 
 func (h *InputHandler) deviceStatusPrivate(params *Params) bool {
 	buf := h.activeBuffer()
-	if params.Params[0] == 6 {
+	switch params.Params[0] {
+	case 6:
 		y := buf.Y + 1
 		x := buf.X + 1
 		h.coreService.TriggerDataEvent(fmt.Sprintf("\x1b[?%d;%dR", y, x), false, false)
+	case 996:
+		if h.coreService.DecPrivateModes.ColorSchemeUpdates {
+			h.OnRequestColorSchemeQueryEmitter.Fire(struct{}{})
+		}
 	}
 	return true
 }

inputhandler_csi_test.go

@@ -1516,3 +1516,80 @@ func TestWindowOptionsPopIconNameEmptyStack(t *testing.T) {
 	}
 }
 
+func TestDSR996ColorSchemeQuery(t *testing.T) {
+	t.Parallel()
+
+	t.Run("fires_when_color_scheme_updates_enabled", func(t *testing.T) {
+		t.Parallel()
+		h := newTestInputHandler(80, 24)
+		fired := 0
+		h.OnRequestColorSchemeQueryEmitter.Event(func(struct{}) {
+			fired++
+		})
+
+		// Enable color scheme updates (DECSET 2031).
+		h.ParseString("\x1b[?2031h")
+		// Send DSR 996.
+		h.ParseString("\x1b[?996n")
+
+		if fired != 1 {
+			t.Errorf("expected OnRequestColorSchemeQuery to fire once, got %d", fired)
+		}
+	})
+
+	t.Run("does_not_fire_when_color_scheme_updates_disabled", func(t *testing.T) {
+		t.Parallel()
+		h := newTestInputHandler(80, 24)
+		fired := 0
+		h.OnRequestColorSchemeQueryEmitter.Event(func(struct{}) {
+			fired++
+		})
+
+		// Do NOT enable color scheme updates — send DSR 996 directly.
+		h.ParseString("\x1b[?996n")
+
+		if fired != 0 {
+			t.Errorf("expected OnRequestColorSchemeQuery not to fire, got %d", fired)
+		}
+	})
+
+	t.Run("does_not_fire_after_color_scheme_updates_reset", func(t *testing.T) {
+		t.Parallel()
+		h := newTestInputHandler(80, 24)
+		fired := 0
+		h.OnRequestColorSchemeQueryEmitter.Event(func(struct{}) {
+			fired++
+		})
+
+		// Enable then disable color scheme updates.
+		h.ParseString("\x1b[?2031h")
+		h.ParseString("\x1b[?2031l")
+		// Send DSR 996.
+		h.ParseString("\x1b[?996n")
+
+		if fired != 0 {
+			t.Errorf("expected OnRequestColorSchemeQuery not to fire after reset, got %d", fired)
+		}
+	})
+
+	t.Run("dsr6_still_works", func(t *testing.T) {
+		t.Parallel()
+		h := newTestInputHandler(80, 24)
+		var response string
+		h.coreService.OnDataEmitter.Event(func(s string) {
+			response = s
+		})
+
+		// Move cursor to row 5, col 10.
+		h.ParseString("\x1b[5;10H")
+		// Send DSR 6 (cursor position report).
+		h.ParseString("\x1b[?6n")
+
+		expected := "\x1b[?5;10R"
+		if response != expected {
+			t.Errorf("DSR 6 response = %q, want %q", response, expected)
+		}
+	})
+}
+
+

terminal.go

@@ -40,14 +40,15 @@ type Terminal struct {
 	inputHandler      *InputHandler
 
 	// Public event emitters (forwarded from sub-components).
-	OnBellEmitter           EventEmitter[struct{}]
-	OnTitleChangeEmitter    EventEmitter[string]
-	OnIconNameChangeEmitter EventEmitter[string]
-	OnLineFeedEmitter       EventEmitter[struct{}]
-	OnCursorMoveEmitter     EventEmitter[struct{}]
-	OnResizeEmitter         EventEmitter[BufferResizeEvent]
-	OnScrollEmitter         EventEmitter[int]
-	OnRenderEmitter         EventEmitter[RowRange]
+	OnBellEmitter                    EventEmitter[struct{}]
+	OnTitleChangeEmitter             EventEmitter[string]
+	OnIconNameChangeEmitter          EventEmitter[string]
+	OnLineFeedEmitter                EventEmitter[struct{}]
+	OnCursorMoveEmitter              EventEmitter[struct{}]
+	OnResizeEmitter                  EventEmitter[BufferResizeEvent]
+	OnScrollEmitter                  EventEmitter[int]
+	OnRenderEmitter                  EventEmitter[RowRange]
+	OnRequestColorSchemeQueryEmitter EventEmitter[struct{}]
 }
 
 // New creates a new Terminal with the given options.
@@ -84,6 +85,7 @@ func New(opts ...Option) *Terminal {
 	ih.OnLineFeedEmitter.Event(func(struct{}) { t.OnLineFeedEmitter.Fire(struct{}{}) })
 	ih.OnCursorMoveEmitter.Event(func(struct{}) { t.OnCursorMoveEmitter.Fire(struct{}{}) })
 	ih.OnRequestRefreshRowsEmitter.Event(func(r RowRange) { t.OnRenderEmitter.Fire(r) })
+	ih.OnRequestColorSchemeQueryEmitter.Event(func(struct{}) { t.OnRequestColorSchemeQueryEmitter.Fire(struct{}{}) })
 
 	// Forward buffer service events.
 	bufSvc.OnResizeEmitter.Event(func(e BufferResizeEvent) { t.OnResizeEmitter.Fire(e) })
@@ -252,6 +254,12 @@ func (t *Terminal) OnRender(fn func(RowRange)) Disposable {
 	return t.OnRenderEmitter.Event(fn)
 }
 
+// OnRequestColorSchemeQuery subscribes to DSR 996 color scheme query events.
+// Fired when the client sends CSI ? 996 n while color scheme updates (DECSET 2031) are enabled.
+func (t *Terminal) OnRequestColorSchemeQuery(fn func()) Disposable {
+	return t.OnRequestColorSchemeQueryEmitter.Event(func(struct{}) { fn() })
+}
+
 // OnColor subscribes to color palette query/set/restore events (OSC 4/10/11/12).
 func (t *Terminal) OnColor(fn func([]ColorEvent)) Disposable {
 	return t.inputHandler.OnColorEmitter.Event(fn)
@@ -401,4 +409,5 @@ func (t *Terminal) Dispose() {
 	t.OnResizeEmitter.Dispose()
 	t.OnScrollEmitter.Dispose()
 	t.OnRenderEmitter.Dispose()
+	t.OnRequestColorSchemeQueryEmitter.Dispose()
 }

terminal_test.go

@@ -1179,4 +1179,45 @@ func TestTerminalOnA11yChar(t *testing.T) {
 	d.Dispose()
 }
 
+func TestTerminalOnRequestColorSchemeQuery(t *testing.T) {
+	t.Parallel()
+	term := newTestTerminal(80, 24)
+	fired := 0
+	term.OnRequestColorSchemeQuery(func() {
+		fired++
+	})
+
+	// Enable color scheme updates and send DSR 996.
+	term.WriteString("\x1b[?2031h")
+	term.WriteString("\x1b[?996n")
+
+	if fired != 1 {
+		t.Errorf("expected OnRequestColorSchemeQuery to fire once via Terminal, got %d", fired)
+	}
+}
+
+func TestTerminalOnRequestColorSchemeQueryDispose(t *testing.T) {
+	t.Parallel()
+	term := newTestTerminal(80, 24)
+	fired := 0
+	d := term.OnRequestColorSchemeQuery(func() {
+		fired++
+	})
+
+	// Enable color scheme updates and send DSR 996.
+	term.WriteString("\x1b[?2031h")
+	term.WriteString("\x1b[?996n")
+	if fired != 1 {
+		t.Fatalf("expected 1 fire before dispose, got %d", fired)
+	}
+
+	// Dispose the listener and send again.
+	d.Dispose()
+	term.WriteString("\x1b[?996n")
+	if fired != 1 {
+		t.Errorf("expected no additional fires after dispose, got %d", fired)
+	}
+}
+
+