From cdf98eaa3d7eb775e25f191398f1ee0cc20dbc52 Mon Sep 17 00:00:00 2001
From: Nate Moore <git@natemoo.re>
Date: Thu, 4 Jun 2026 00:32:53 -0500
Subject: [PATCH] test: failing repro for signed-margin

---
 test/signed-margin.test.ts | 79 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 79 insertions(+)
 create mode 100644 test/signed-margin.test.ts

diff --git a/test/signed-margin.test.ts b/test/signed-margin.test.ts
new file mode 100644
index 0000000..021ca66
--- /dev/null
+++ b/test/signed-margin.test.ts
@@ -0,0 +1,79 @@
+import { describe, expect, it } from "./suite.ts";
+import { createTerm } from "../term.ts";
+import { close, fixed, grow, open, type OpenElement, text } from "../ops.ts";
+
+import { print } from "./print.ts";
+
+const decode = (b: Uint8Array) => new TextDecoder().decode(b);
+
+// Proposed (not-yet-implemented) signed offset prop. Cast through this so the
+// ops still type-check while `margin` is silently ignored by the current build.
+type Margin = { left?: number; right?: number; top?: number; bottom?: number };
+const withMargin = (
+  layout: NonNullable<OpenElement["layout"]>,
+  margin: Margin,
+): NonNullable<OpenElement["layout"]> =>
+  ({ ...layout, margin }) as NonNullable<OpenElement["layout"]>;
+
+describe("layout margin (signed offset)", () => {
+  it("positive marginLeft shifts the box origin without shrinking content", async () => {
+    let term = await createTerm({ width: 20, height: 4 });
+    let r = term.render([
+      open("root", {
+        layout: { width: grow(), height: grow(), direction: "ttb" },
+      }),
+      open("box", {
+        layout: withMargin({ width: fixed(8), direction: "ttb" }, { left: 2 }),
+      }),
+      text("Hello W"),
+      close(),
+      close(),
+    ]);
+    // pins: box origin moves right by 2 cells (margin offsets position, not content)
+    expect(r.info.get("box")!.bounds.x).toBe(2);
+    // pins: full 7-cell text still fits on ONE line (margin must not consume width)
+    expect(r.info.get("box")!.bounds.height).toBe(1);
+  });
+
+  it("negative marginLeft pulls the box before the parent origin and clips", async () => {
+    let term = await createTerm({ width: 20, height: 4 });
+    let r = term.render([
+      open("root", {
+        layout: { width: fixed(6), height: grow(), direction: "ttb" },
+        clip: { horizontal: true },
+      }),
+      open("box", {
+        layout: withMargin(
+          { width: fixed(12), direction: "ttb" },
+          { left: -3 },
+        ),
+      }),
+      text("Hello World"),
+      close(),
+      close(),
+    ]);
+    let first = print(decode(r.output), 20, 4).split("\n")[0];
+    // pins: leftmost 3 cells fall outside the parent and are clipped away
+    expect(first.slice(0, 6)).toBe("lo Wor");
+  });
+
+  it("negative margin keeps box geometry sane (no unsigned overflow)", async () => {
+    let term = await createTerm({ width: 20, height: 6 });
+    let r = term.render([
+      open("root", {
+        layout: { width: grow(), height: grow(), direction: "ttb" },
+      }),
+      open("box", {
+        layout: withMargin(
+          { width: fixed(11), direction: "ttb" },
+          { left: -3 },
+        ),
+      }),
+      text("Hello World"),
+      close(),
+      close(),
+    ]);
+    // pins: the box origin is pulled left by 3 cells (negative offset is signed)
+    expect(r.info.get("box")!.bounds.x).toBe(-3);
+  });
+});
-- 
2.51.2