Bug 1863194 - Do not terminate wheel transaction on browsing context change. r=hiro,smaug,webdriver-reviewers,Sasha

We should continue to use a wheel transaction for wheel events when the browsing context changes from the current context. Avoiding the override of the event target with the current wheel transaction can halt a page scroll when the mouse moves over content in a different presentation context. Differential Revision: https://phabricator.services.mozilla.com/D205495
2024-04-25 12:16:40 +00:00 · 2024-04-25 12:16:40 +00:00 · 455ab11833
--- a/gfx/layers/apz/test/mochitest/helper_scroll_over_subframe.html
+++ b/gfx/layers/apz/test/mochitest/helper_scroll_over_subframe.html
@ -0,0 +1,146 @@
+<!DOCTYPE html>
+<html>
+  <title>A scroll over an iframe should not terminate the wheel transaction</title>
+  <script type="application/javascript" src="apz_test_utils.js"></script>
+  <script type="application/javascript" src="apz_test_native_event_utils.js"></script>
+  <script src="/tests/SimpleTest/paint_listener.js"></script>
+<head>
+<style>
+body {
+  height: 250vh;
+  width: 100%;
+  margin: 0;
+  padding: 0;
+}
+
+#spacer {
+  height: 50px;
+  width: 100vw;
+  background: yellow;
+}
+
+#subframe {
+  width: 80vw;
+  height: 60vh;
+}
+</style>
+</head>
+<body>
+  <div id="spacer"></div>
+  <iframe id="subframe">
+  </iframe>
+</body>
+<script>
+const searchParams = new URLSearchParams(location.search);
+
+async function scrollWithPan() {
+  await NativePanHandler.promiseNativePanEvent(
+    document.scrollingElement,
+    50,
+    30,
+    0,
+    NativePanHandler.delta,
+    NativePanHandler.beginPhase,
+  );
+
+  await NativePanHandler.promiseNativePanEvent(
+    document.scrollingElement,
+    50,
+    30,
+    0,
+    NativePanHandler.delta,
+    NativePanHandler.updatePhase,
+  );
+
+  await NativePanHandler.promiseNativePanEvent(
+    document.scrollingElement,
+    50,
+    30,
+    0,
+    NativePanHandler.delta,
+    NativePanHandler.endPhase,
+  );
+}
+
+async function scrollWithWheel() {
+  await promiseMoveMouseAndScrollWheelOver(document.scrollingElement, 50, 30,
+                                           false, 100);
+}
+
+async function test() {
+  let iframeURL =
+       SimpleTest.getTestFileURL("helper_scroll_over_subframe_child.html");
+
+  switch (searchParams.get("oop")) {
+    case "true":
+      iframeURL = iframeURL.replace(window.location.origin, "https://example.com/");
+      break;
+    default:
+      break;
+  }
+
+  const iframeLoadPromise = promiseOneEvent(subframe, "load", null);
+  subframe.src = iframeURL;
+  await iframeLoadPromise;
+
+  await SpecialPowers.spawn(subframe, [], async () => {
+    await content.wrappedJSObject.waitUntilApzStable();
+    await SpecialPowers.contentTransformsReceived(content);
+  });
+
+  let childWindowReceivedWheelEvent = false;
+
+  window.addEventListener("message", e => {
+    if (e.data == "child-received-wheel-event") {
+      childWindowReceivedWheelEvent = true;
+    }
+  });
+
+  await SpecialPowers.spawn(subframe, [], () => {
+    let target = content.document.getElementById("target")
+    target.style.backgroundColor = "green";
+    content.getComputedStyle(target).backgroundColor;
+    target.addEventListener("wheel", () => {
+      target.style.backgroundColor = "red";
+      content.getComputedStyle(target).backgroundColor;
+    });
+    return new Promise(resolve => resolve());
+  });
+
+  await promiseFrame();
+
+  let transformEndPromise = promiseTransformEnd();
+
+  // Scroll over the iframe
+  switch (searchParams.get("scroll")) {
+    case "wheel":
+      await scrollWithWheel();
+      break;
+    case "pan":
+      await scrollWithPan();
+      break;
+    default:
+      ok(false, "Unsupported scroll value: " + searchParams.get("scroll"));
+      break;
+  }
+
+  await transformEndPromise;
+
+  // Wait an extra frame to ensure any message from the child has
+  // extra time to be sent to the parent.
+  await promiseFrame();
+
+  let res = await SpecialPowers.spawn(subframe, [], () => {
+    let target = content.document.getElementById("target")
+    return target.style.backgroundColor;
+  });
+
+  await promiseFrame();
+
+  // We should not have fired a wheel event to the element in the iframe
+  ok(!childWindowReceivedWheelEvent, "Child window should not receive wheel events");
+  is(res, "green", "OOP iframe does not halt user scroll of parent");
+}
+waitUntilApzStable().then(test).then(subtestDone, subtestFailed);
+</script>
+</html>
--- a/gfx/layers/apz/test/mochitest/helper_scroll_over_subframe_child.html
+++ b/gfx/layers/apz/test/mochitest/helper_scroll_over_subframe_child.html
@ -0,0 +1,29 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<script src="/tests/SimpleTest/SimpleTest.js"></script>
+<script src="/tests/SimpleTest/paint_listener.js"></script>
+<script src="apz_test_utils.js"></script>
+<style>
+body {
+  margin: 0px;
+}
+
+#target {
+  width: 100%;
+  height: 100vh;
+  background: blue;
+  overflow: scroll;
+}
+</style>
+</head>
+<body>
+<div id="target">
+</div>
+</body>
+<script>
+  window.addEventListener("wheel", () => {
+    window.parent.postMessage("child-received-wheel-event", "*");
+  });
+</script>
+</html>
--- a/gfx/layers/apz/test/mochitest/test_group_wheelevents.html
+++ b/gfx/layers/apz/test/mochitest/test_group_wheelevents.html
@ -20,6 +20,13 @@ var prefs = [
  ["mousewheel.transaction.timeout", 0],
 ];

+var wheel_transaction_prefs = [
+  ["dom.event.wheel-event-groups.enabled", true],
+  ["mousewheel.transaction.timeout", 10000],
+  ["apz.test.mac.synth_wheel_input", true],
+  ...getSmoothScrollPrefs("wheel"),
+];
+
 // For helper_scroll_over_scrollbar, we need to set a pref to force
 // layerization of the scrollbar track to reproduce the bug being fixed.
 // Otherwise, the bug only manifests with overlay scrollbars on macOS,
@ -48,6 +55,10 @@ var subtests = [
    prefs: [["general.smoothScroll", false],
             ["apz.test.mac.synth_wheel_input", true]]},
  {"file": "helper_scroll_anchoring_on_wheel.html", prefs: smoothness_prefs},
+  {"file": "helper_scroll_over_subframe.html?scroll=wheel", prefs: wheel_transaction_prefs},
+  {"file": "helper_scroll_over_subframe.html?oop=true&scroll=wheel", prefs: wheel_transaction_prefs},
+  {"file": "helper_scroll_over_subframe.html?scroll=pan", prefs: wheel_transaction_prefs},
+  {"file": "helper_scroll_over_subframe.html?oop=true&scroll=pan", prefs: wheel_transaction_prefs},
 ];

 subtests.push(...buildRelativeScrollSmoothnessVariants("wheel", ["scrollBy", "scrollTo", "scrollTop"]));
--- a/layout/base/PresShell.cpp
+++ b/layout/base/PresShell.cpp
@ -12100,13 +12100,6 @@ void PresShell::EventHandler::EventTargetData::UpdateWheelEventTarget(
    return;
  }

-  // If the browsing context is no longer the same as the context of the
-  // current wheel transaction, do not override the event target.
-  if (!groupFrame->PresContext() || !groupFrame->PresShell() ||
-      groupFrame->PresContext() != GetPresContext()) {
-    return;
-  }
-
  // If dom.event.wheel-event-groups.enabled is set and whe have a stored
  // event target from the wheel transaction, override the event target.
  SetFrameAndComputePresShellAndContent(groupFrame, aGUIEvent);
--- a/remote/webdriver-bidi/modules/windowglobal/input.sys.mjs
+++ b/remote/webdriver-bidi/modules/windowglobal/input.sys.mjs
@ -34,6 +34,10 @@ class InputModule extends WindowGlobalBiDiModule {
    const actionChain = lazy.action.Chain.fromJSON(this.#actionState, actions);

    await actionChain.dispatch(this.#actionState, this.messageHandler.window);
+
+    // Terminate the current wheel transaction if there is one. Wheel
+    // transactions should not live longer than a single action chain.
+    ChromeUtils.endWheelTransaction();
  }

  async releaseActions() {