1 files changed, 156 insertions, 0 deletions
diff --git a/gfx/layers/apz/test/mochitest/helper_relative_scroll_smoothness.html b/gfx/layers/apz/test/mochitest/helper_relative_scroll_smoothness.html
new file mode 100644
index 0000000000..3f895c37d8
--- /dev/null
+++ b/gfx/layers/apz/test/mochitest/helper_relative_scroll_smoothness.html
@@ -0,0 +1,156 @@
+<!DOCTYPE html>
+<html>
+<meta charset="utf-8">
+<script src="/tests/SimpleTest/EventUtils.js"></script>
+<script src="/tests/SimpleTest/NativeKeyCodes.js"></script>
+<script src="/tests/SimpleTest/paint_listener.js"></script>
+<script src="apz_test_utils.js"></script>
+<script src="apz_test_native_event_utils.js"></script>
+<title>What happens if main thread scrolls?</title>
+<style>
+html, body { margin: 0; }
+
+html {
+  background:
+    repeating-linear-gradient(45deg, transparent 0, transparent 100px, rgba(0,0,0,0.1) 0, rgba(0,0,0,0.1) 200px),
+    repeating-linear-gradient(-45deg, transparent 0, transparent 100px, rgba(0,0,0,0.1) 0, rgba(0,0,0,0.1) 200px),
+    repeating-linear-gradient(to bottom, transparent 0, transparent 500px, rgba(0,0,0,0.4) 0, rgba(0,0,0,0.4) 1000px),
+    repeating-linear-gradient(to bottom, hsl(0, 60%, 80%), hsl(0, 60%, 80%) 200px, hsl(70, 60%, 80%) 0, hsl(70, 60%, 80%) 400px, hsl(140, 60%, 80%) 0, hsl(140, 60%, 80%) 600px, hsl(210, 60%, 80%) 0, hsl(210, 60%, 80%) 800px),
+    white;
+  background-size:
+    283px 283px,
+    283px 283px,
+    100px 1000px,
+    100px 800px;
+}
+
+body {
+  height: 10000px;
+}
+</style>
+
+<script>
+const searchParams = new URLSearchParams(location.search);
+let strict = searchParams.get("strict") == "true";
+
+var intervalId;
+// Start periodic content expansions after we get a scroll event triggered by
+// a key press in test() function below, otherwise we may have same scroll
+// offsets caused by this script before we start scrolling.
+window.addEventListener("scroll",  () => {
+  var offset = 0;
+  var initialBodyHeight = 10000;
+  intervalId = setInterval(() => {
+    // "Add content" at the top. We do this by making the body longer and adjusting the background position.
+    offset += 10;
+    document.documentElement.style.backgroundPosition = `0px ${offset}px`;
+    document.body.style.height = `${initialBodyHeight + offset}px`;
+
+    switch (searchParams.get("scroll-method")) {
+      case "scrollBy":
+        window.scrollBy(0, 10);
+        break;
+      case "scrollTop":
+        document.scrollingElement.scrollTop += 10;
+        break;
+      case "scrollTo":
+        window.scrollTo(0, window.scrollY + 10);
+        break;
+      default:
+        ok(false, "Unsupported scroll method: " + searchParams.get("scroll-method"));
+        break;
+    }
+
+    // Simulate some jank.
+    var freezeDurationInMilliseconds = 100;
+    var startTime = Date.now();
+    while (Date.now() - startTime < freezeDurationInMilliseconds) {} // eslint-disable-line no-empty
+  }, 300);
+}, { once: true });
+
+
+async function test() {
+  // Once this content starts scrolling, it triggers a 100ms jank every 300ms so
+  // sending arrow down keys for 1500ms will cause some jank.
+  const TEST_DURATION_MS = 1500;
+  const timeAtStart = performance.now();
+  while (performance.now() - timeAtStart < TEST_DURATION_MS) {
+    switch (searchParams.get("input-type")) {
+      case "key":
+        synthesizeKey("KEY_ArrowDown");
+        break;
+      case "native-key":
+        const DownArrowKeyCode = nativeArrowDownKey();
+        ok(synthesizeNativeKey(KEYBOARD_LAYOUT_EN_US,
+                               DownArrowKeyCode, {}  /* no modifier */,
+                               "", ""),
+          "Dispatched an down arrow key event");
+        break;
+      case "wheel":
+        await synthesizeNativeWheel(window, 50, 50, 0, -50);
+        break;
+      default:
+        ok(false, "Unsupported input type: " + searchParams.get("input-type"));
+        break;
+    }
+    await promiseFrame(window);
+  }
+
+  // Stop the periodic expansions.
+  clearInterval(intervalId);
+
+  const records = collectSampledScrollOffsets(document.scrollingElement);
+
+  let previousRecord = { scrollOffsetY: 0, sampledTimeStamp: 0 };
+  let scrollStartTime = null;
+  for (const record of records) {
+    // Ignore offsets before scrolling.
+    if (record.scrollOffsetY == 0) {
+      continue;
+    }
+    // Ignore offsets after TEST_DURATION_MS has elapsed since the
+    // start of scrolling. Note that the sampled timestamps are
+    // in microseconds.
+    if (!scrollStartTime) {
+      scrollStartTime = record.sampledTimeStamp;
+    } else if (((record.sampledTimeStamp - scrollStartTime) / 1000) > TEST_DURATION_MS) {
+      break;
+    }
+    ok(
+      strict
+        ? (record.scrollOffsetY > previousRecord.scrollOffsetY)
+        : (record.scrollOffsetY >= previousRecord.scrollOffsetY),
+      "scroll offset should be " +
+      (strict ? "strictly monotonically increasing " : "nondecreasing ") +
+      "previous offset: " + previousRecord.scrollOffsetY +
+      ", offset: " + record.scrollOffsetY
+    );
+    ok(
+      record.sampledTimeStamp > previousRecord.sampledTimeStamp,
+      "sampled time stamp should be strictly monotonically increasing " +
+      "previous timestamp: " + previousRecord.sampledTimeStamp +
+      ", timestamp: " + record.sampledTimeStamp
+    );
+    previousRecord = record;
+  }
+}
+
+function isOnChaosMode() {
+  return SpecialPowers.Services.env.get("MOZ_CHAOSMODE");
+}
+
+if (searchParams.get("input-type") == "native-key" &&
+    getPlatform() != "mac" && getPlatform() != "windows") {
+  ok(true, "Skipping test because native key events are not supported on " +
+     getPlatform());
+  subtestDone();
+} else if (searchParams.get("input-type") == "native-key" &&
+           getPlatform() == "mac" && isOnChaosMode()) {
+  ok(true, "Skipping native-key tests on verify runs on Mac");
+  subtestDone();
+} else {
+  waitUntilApzStable()
+  .then(test)
+  .then(subtestDone, subtestFailed);
+}
+</script>