[Init] Initial commit - NetMesh terminal manager

components/terminal/runtime/rendererDprWatch.test.ts

@@ -0,0 +1,158 @@
+import assert from "node:assert/strict";
+import { test } from "node:test";
+import {
+  type MediaQueryListLike,
+  watchDevicePixelRatio,
+} from "./rendererDprWatch";
+
+class FakeMediaQueryList implements MediaQueryListLike {
+  readonly query: string;
+  modernListeners: Array<() => void> = [];
+  legacyListeners: Array<() => void> = [];
+  private readonly supportsModern: boolean;
+
+  constructor(query: string, supportsModern = true) {
+    this.query = query;
+    this.supportsModern = supportsModern;
+    if (!supportsModern) {
+      // Strip the modern API to emulate legacy environments.
+      this.addEventListener = undefined;
+      this.removeEventListener = undefined;
+    }
+  }
+
+  addEventListener? = (_type: "change", listener: () => void) => {
+    this.modernListeners.push(listener);
+  };
+
+  removeEventListener? = (_type: "change", listener: () => void) => {
+    this.modernListeners = this.modernListeners.filter((l) => l !== listener);
+  };
+
+  addListener = (listener: () => void) => {
+    this.legacyListeners.push(listener);
+  };
+
+  removeListener = (listener: () => void) => {
+    this.legacyListeners = this.legacyListeners.filter((l) => l !== listener);
+  };
+
+  trigger() {
+    for (const l of [...this.modernListeners, ...this.legacyListeners]) l();
+  }
+
+  get listenerCount() {
+    return this.modernListeners.length + this.legacyListeners.length;
+  }
+}
+
+function makeEnv(initialDpr: number, supportsModern = true) {
+  let dpr = initialDpr;
+  const created: FakeMediaQueryList[] = [];
+  return {
+    created,
+    getDevicePixelRatio: () => dpr,
+    matchMedia: (query: string) => {
+      const mql = new FakeMediaQueryList(query, supportsModern);
+      created.push(mql);
+      return mql;
+    },
+    setDpr: (value: number) => {
+      dpr = value;
+    },
+  };
+}
+
+test("registers a change listener for the current devicePixelRatio", () => {
+  const env = makeEnv(1);
+  watchDevicePixelRatio({
+    getDevicePixelRatio: env.getDevicePixelRatio,
+    matchMedia: env.matchMedia,
+    onChange: () => {},
+  });
+
+  assert.equal(env.created.length, 1);
+  assert.equal(env.created[0].query, "(resolution: 1dppx)");
+  assert.equal(env.created[0].listenerCount, 1);
+});
+
+test("invokes onChange when the media query reports a change", () => {
+  const env = makeEnv(1);
+  let calls = 0;
+  watchDevicePixelRatio({
+    getDevicePixelRatio: env.getDevicePixelRatio,
+    matchMedia: env.matchMedia,
+    onChange: () => {
+      calls += 1;
+    },
+  });
+
+  env.setDpr(2);
+  env.created[0].trigger();
+
+  assert.equal(calls, 1);
+});
+
+test("re-registers for the new ratio so subsequent changes still fire", () => {
+  const env = makeEnv(1);
+  let calls = 0;
+  watchDevicePixelRatio({
+    getDevicePixelRatio: env.getDevicePixelRatio,
+    matchMedia: env.matchMedia,
+    onChange: () => {
+      calls += 1;
+    },
+  });
+
+  env.setDpr(2);
+  env.created[0].trigger();
+
+  assert.equal(env.created.length, 2);
+  assert.equal(env.created[1].query, "(resolution: 2dppx)");
+  // The stale listener must be detached so it cannot double-fire.
+  assert.equal(env.created[0].listenerCount, 0);
+
+  env.setDpr(3);
+  env.created[1].trigger();
+
+  assert.equal(calls, 2);
+});
+
+test("cleanup stops further onChange callbacks", () => {
+  const env = makeEnv(1);
+  let calls = 0;
+  const stop = watchDevicePixelRatio({
+    getDevicePixelRatio: env.getDevicePixelRatio,
+    matchMedia: env.matchMedia,
+    onChange: () => {
+      calls += 1;
+    },
+  });
+
+  stop();
+
+  assert.equal(env.created[0].listenerCount, 0);
+  env.created[0].trigger();
+  assert.equal(calls, 0);
+});
+
+test("falls back to addListener/removeListener when addEventListener is unavailable", () => {
+  const env = makeEnv(1, /* supportsModern */ false);
+  let calls = 0;
+  const stop = watchDevicePixelRatio({
+    getDevicePixelRatio: env.getDevicePixelRatio,
+    matchMedia: env.matchMedia,
+    onChange: () => {
+      calls += 1;
+    },
+  });
+
+  assert.equal(env.created[0].legacyListeners.length, 1);
+  env.created[0].trigger();
+  assert.equal(calls, 1);
+
+  stop();
+  // After cleanup the most recently registered query has no listeners.
+  const latest = env.created[env.created.length - 1];
+  assert.equal(latest.listenerCount, 0);
+});