feat: add contextual layer inspector

renderer/rotated-rect.test.ts

@@ -0,0 +1,40 @@
+import { describe, expect, test } from "bun:test";
+import { rotatedRectBounds, rotatedRectCorners } from "./rotated-rect";
+
+describe("rotated rectangle geometry", () => {
+  test("interprets rotation as radians and keeps the center anchored", () => {
+    const corners = rotatedRectCorners({ x: 10, y: 20, w: 40, h: 20 }, Math.PI / 2);
+
+    expectPoint(corners[0], { x: 40, y: 10 });
+    expectPoint(corners[1], { x: 40, y: 50 });
+    expectPoint(corners[2], { x: 20, y: 10 });
+    expectPoint(corners[3], { x: 20, y: 50 });
+    expect((corners[0].x + corners[3].x) / 2).toBeCloseTo(30);
+    expect((corners[0].y + corners[3].y) / 2).toBeCloseTo(30);
+  });
+
+  test("expands axis-aligned clipping bounds around a rotated quad", () => {
+    const bounds = rotatedRectBounds({ x: 10, y: 20, w: 40, h: 20 }, Math.PI / 2);
+
+    expect(bounds.x).toBeCloseTo(20);
+    expect(bounds.y).toBeCloseTo(10);
+    expect(bounds.w).toBeCloseTo(20);
+    expect(bounds.h).toBeCloseTo(40);
+  });
+
+  test("preserves an unrotated rectangle exactly", () => {
+    const rect = { x: 10, y: 20, w: 40, h: 20 };
+    expect(rotatedRectBounds(rect, 0)).toBe(rect);
+    expect(rotatedRectCorners(rect, 0)).toEqual([
+      { x: 10, y: 20 },
+      { x: 50, y: 20 },
+      { x: 10, y: 40 },
+      { x: 50, y: 40 },
+    ]);
+  });
+});
+
+function expectPoint(actual: { x: number; y: number }, expected: { x: number; y: number }) {
+  expect(actual.x).toBeCloseTo(expected.x);
+  expect(actual.y).toBeCloseTo(expected.y);
+}