fix(term): use bare set OSC 22 so pointer shapes work on Ghostty

The tracker emitted the kitty push/pop stack form (ESC]22;>shape and
ESC]22;<). Ghostty's OSC 22 parser treats the whole payload after "22;"
as a literal shape name, so ">shape" is not a valid shape and is dropped
— the pointer never changed on Ghostty (and any other set-only terminal).

Switch to the portable bare set form: set the shape on enter
(ESC]22;shape) and restore the base by setting "default" on leave. kitty
and Ghostty both honor this. The trade-off is that we assume the base
shape is "default" rather than restoring a non-default prior shape; the
push/pop helpers remain exported for callers that target kitty and want
exact save/restore.

Author: natemoo-re

specs/renderer-spec.md

@@ -974,26 +974,30 @@ if (r.cursor) stdout.write(r.cursor);
 4. When the shape changed, populates `result.cursor` with the OSC 22 bytes that
    effect the transition. When nothing changed, `result.cursor` is absent.
 
-**Save and restore (kitty stack).** Transitions use the kitty pointer-shape
-_stack_ rather than bare set, so the terminal's prior shape is preserved:
+**Setting and restoring.** Transitions use the bare _set_ form of OSC 22 for
+portability — kitty and Ghostty both honor it, whereas the kitty push/pop
+_stack_ extension is silently ignored by set-only terminals (Ghostty parses the
+whole payload after `22;` as a literal shape name, so a `>`/`<` prefix is not a
+valid shape and is dropped):
 
-- Entering an element with a declared shape pushes it (`OSC 22 ; >shape ST`).
-- Returning to no declared shape pops back to what the terminal had before
-  (`OSC 22 ; < ST`).
+- Entering an element with a declared shape sets it (`OSC 22 ; shape ST`).
+- Returning to no declared shape restores the base by setting `default`
+  (`OSC 22 ; default ST`).
 
-This means the renderer never needs to know or assume the terminal's base shape;
-the stack restores it.
+The base shape is assumed to be `default` (the ordinary pointer); the renderer
+does not attempt to restore a non-default prior shape. Callers targeting kitty
+exclusively who want exact save/restore can drive the push/pop helpers manually.
 
 **Capability detection and graceful degradation.** Before relying on tracking,
 the caller MAY query support. The OSC 22 query is sent through the normal output
 path (it is a separate, caller-initiated byte sequence, not part of `output`),
 and the terminal's reply arrives on the **input** stream, where it is decoded as
 a `PointerShapeEvent` (see [Input Specification](input-spec.md), Section 5.1).
 Correlating the reply with the query is the caller's responsibility, preserving
-the renderer/input independence (INV-7). Terminals that do not implement OSC 22
-(or implement only the set operation, such as Ghostty) never reply and may not
-honor push/pop; on these terminals tracking degrades to a no-op or a best-effort
-set, and the absence of a reply within a timeout is the unsupported signal.
+the renderer/input independence (INV-7). Because tracking uses the bare set
+form, it works on set-only terminals (such as Ghostty) as well as kitty; only
+terminals that do not implement OSC 22 at all ignore it entirely, and the
+absence of a reply within a timeout is the unsupported signal.
 
 **OSC 22 byte helpers.** The byte sequences above are produced by small,
 caller-usable helpers (set, push, pop, and query builders). These are the first

term.ts

@@ -1,10 +1,6 @@
 import { isOpen, type Op, pack } from "./ops.ts";
 import { type BoundingBox, createTermNative } from "./term-native.ts";
-import {
-  type CursorShape,
-  POPPOINTERSHAPE,
-  PUSHPOINTERSHAPE,
-} from "./termcodes.ts";
+import { type CursorShape, POINTERSHAPE } from "./termcodes.ts";
 
 export interface TermOptions {
   height: number;
@@ -105,7 +101,7 @@ export async function createTerm(options: TermOptions): Promise<Term> {
   let wasDown = false;
   let lastRenderAt: number | undefined;
   let wasAnimating = false;
-  let cursorShape: CursorShape | null = null;
+  let cursorShape: CursorShape = "default";
 
   return {
     render(ops: Op[], options?: RenderOptions): RenderResult {
@@ -171,7 +167,10 @@ export async function createTerm(options: TermOptions): Promise<Term> {
 
       let cursor: Uint8Array | undefined;
       if (options?.trackCursor) {
-        let active: CursorShape | null = null;
+        // Set-only OSC 22: the base is "default" (kitty and Ghostty both honor
+        // a bare set; the kitty push/pop stack is ignored by set-only terminals
+        // like Ghostty).
+        let active: CursorShape = "default";
         if (overIds.length > 0) {
           let shapes = new Map<string, CursorShape>();
           for (let op of ops) {
@@ -188,10 +187,7 @@ export async function createTerm(options: TermOptions): Promise<Term> {
           }
         }
         if (active !== cursorShape) {
-          let parts: Uint8Array[] = [];
-          if (cursorShape !== null) parts.push(POPPOINTERSHAPE());
-          if (active !== null) parts.push(PUSHPOINTERSHAPE(active));
-          cursor = concat(parts);
+          cursor = POINTERSHAPE(active);
           cursorShape = active;
         }
       }
@@ -222,15 +218,3 @@ export async function createTerm(options: TermOptions): Promise<Term> {
     },
   };
 }
-
-function concat(parts: Uint8Array[]): Uint8Array {
-  let total = 0;
-  for (let part of parts) total += part.length;
-  let out = new Uint8Array(total);
-  let offset = 0;
-  for (let part of parts) {
-    out.set(part, offset);
-    offset += part.length;
-  }
-  return out;
-}

test/cursor.test.ts

@@ -8,8 +8,7 @@ function shown(bytes: Uint8Array | undefined): string | undefined {
   return bytes === undefined ? undefined : decoder.decode(bytes);
 }
 
-const PUSH = (shape: string) => `\x1b]22;>${shape}\x1b\\`;
-const POP = `\x1b]22;<\x1b\\`;
+const SET = (shape: string) => `\x1b]22;${shape}\x1b\\`;
 
 // ┌─root (40x10, ltr)──────────────────┐
 // │┌─btn (20x10)──┐┌─field (20x10)───┐│
@@ -51,12 +50,12 @@ describe("pointer shape tracking", () => {
     expect(result.cursor).toBeUndefined();
   });
 
-  it("pushes the shape when the pointer enters a declaring element", () => {
+  it("sets the shape when the pointer enters a declaring element", () => {
     let result = term.render(layout(), {
       pointer: { x: 5, y: 5, down: false },
       trackCursor: true,
     });
-    expect(shown(result.cursor)).toBe(PUSH("pointer"));
+    expect(shown(result.cursor)).toBe(SET("pointer"));
   });
 
   it("emits nothing on a subsequent frame over the same element", () => {
@@ -71,7 +70,7 @@ describe("pointer shape tracking", () => {
     expect(result.cursor).toBeUndefined();
   });
 
-  it("pops then pushes when moving between elements of different shapes", () => {
+  it("sets the new shape when moving between elements of different shapes", () => {
     term.render(layout(), {
       pointer: { x: 5, y: 5, down: false },
       trackCursor: true,
@@ -80,10 +79,10 @@ describe("pointer shape tracking", () => {
       pointer: { x: 25, y: 5, down: false },
       trackCursor: true,
     });
-    expect(shown(result.cursor)).toBe(POP + PUSH("text"));
+    expect(shown(result.cursor)).toBe(SET("text"));
   });
 
-  it("pops when the pointer leaves all declaring elements", () => {
+  it("restores default when the pointer leaves all declaring elements", () => {
     term.render(layout(), {
       pointer: { x: 5, y: 5, down: false },
       trackCursor: true,
@@ -92,16 +91,16 @@ describe("pointer shape tracking", () => {
       pointer: { x: 100, y: 100, down: false },
       trackCursor: true,
     });
-    expect(shown(result.cursor)).toBe(POP);
+    expect(shown(result.cursor)).toBe(SET("default"));
   });
 
-  it("pops when the pointer is removed entirely", () => {
+  it("restores default when the pointer is removed entirely", () => {
     term.render(layout(), {
       pointer: { x: 5, y: 5, down: false },
       trackCursor: true,
     });
     let result = term.render(layout(), { trackCursor: true });
-    expect(shown(result.cursor)).toBe(POP);
+    expect(shown(result.cursor)).toBe(SET("default"));
   });
 
   it("uses the topmost (innermost) declaring element's shape", () => {
@@ -123,7 +122,7 @@ describe("pointer shape tracking", () => {
       pointer: { x: 2, y: 2, down: false },
       trackCursor: true,
     });
-    expect(shown(result.cursor)).toBe(PUSH("pointer"));
+    expect(shown(result.cursor)).toBe(SET("pointer"));
   });
 
   it("emits nothing when the hovered element declares no shape", () => {