Bug 1941683: Update the viewport cache when a CacheDomain::APZ update happens r=eeejay

Differential Revision: https://phabricator.services.mozilla.com/D234256

accessible/generic/LocalAccessible.cpp

@@ -4174,7 +4174,8 @@ already_AddRefed<AccAttributes> LocalAccessible::BundleFieldsForCache(
     }
   }
 
-  if ((aCacheDomain & (CacheDomain::Text | CacheDomain::ScrollPosition) ||
+  if ((aCacheDomain & (CacheDomain::Text | CacheDomain::ScrollPosition |
+                       CacheDomain::APZ) ||
        boundsChanged) &&
       mDoc) {
     mDoc->SetViewportCacheDirty(true);

accessible/tests/browser/states/browser.toml

@@ -4,8 +4,11 @@ support-files = [
   "head.js",
   "!/accessible/tests/browser/shared-head.js",
   "!/accessible/tests/mochitest/*.js",
+  "!/gfx/layers/apz/test/mochitest/apz_test_native_event_utils.js",
 ]
 
+["browser_test_APZ.js"]
+
 ["browser_test_link.js"]
 https_first_disabled = true
 skip-if = ["verify"]

accessible/tests/browser/states/browser_test_APZ.js

@@ -0,0 +1,97 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+Services.scriptloader.loadSubScript(
+  "chrome://mochitests/content/browser/gfx/layers/apz/test/mochitest/apz_test_native_event_utils.js",
+  this
+);
+
+/**
+ * Test accessible is has correct offscreen state before and after
+ * APZ.
+ */
+addAccessibleTask(
+  `
+  <div id="test" style="background:green; height: 100px; width: 100px;">I am square</div>
+  <div style="height: 70vh;">hello world I am large</div><br>
+  <h1 id="heading" style="display: inline-block;">I am a heading</h1>
+  `,
+  async function (browser, accDoc) {
+    const test = findAccessibleChildByID(accDoc, "test");
+    const heading = findAccessibleChildByID(accDoc, "heading");
+
+    info("Verifying offscreen state");
+    await untilCacheOk(() => {
+      const [states] = getStates(test);
+      return (states & STATE_OFFSCREEN) == 0;
+    }, "test div should be ON screen");
+    await untilCacheOk(() => {
+      const [states] = getStates(heading);
+      return (states & STATE_OFFSCREEN) == 0;
+    }, "heading should be ON screen");
+
+    info("Pinch zooming...");
+    await SpecialPowers.spawn(browser, [], async () => {
+      const visualScrollPromise = new Promise(resolve => {
+        content.window.visualViewport.addEventListener("scroll", resolve, {
+          once: true,
+        });
+      });
+      const utils = SpecialPowers.getDOMWindowUtils(content.window);
+      utils.setResolutionAndScaleTo(2);
+      utils.scrollToVisual(
+        200,
+        200,
+        utils.UPDATE_TYPE_MAIN_THREAD,
+        utils.SCROLL_MODE_INSTANT
+      );
+      await visualScrollPromise;
+    });
+    info("Verifying offscreen state");
+    await untilCacheOk(() => {
+      const [states] = getStates(test);
+      return (states & STATE_OFFSCREEN) != 0;
+    }, "test div should be OFF screen");
+    await untilCacheOk(() => {
+      const [states] = getStates(heading);
+      return (states & STATE_OFFSCREEN) != 0;
+    }, "heading should be OFF screen");
+
+    info("Scrolling to bottom of page...");
+    // We have to use the APZ scroll util here, we can't rely on
+    // body.scrollTo, because the thing that we've created scroll
+    // bars on is the visual viewport "element".
+    await SpecialPowers.spawn(browser, [], async () => {
+      const visualScrollPromise = new Promise(resolve => {
+        content.window.visualViewport.addEventListener("scroll", resolve, {
+          once: true,
+        });
+      });
+      const utils = SpecialPowers.getDOMWindowUtils(content.window);
+      utils.scrollToVisual(
+        0,
+        content.visualViewport.height,
+        utils.UPDATE_TYPE_MAIN_THREAD,
+        utils.SCROLL_MODE_INSTANT
+      );
+      await visualScrollPromise;
+    });
+
+    info("Verifying offscreen state");
+    await untilCacheOk(() => {
+      const [states] = getStates(test);
+      return (states & STATE_OFFSCREEN) != 0;
+    }, "test div should be OFF screen");
+
+    await untilCacheOk(() => {
+      const [states] = getStates(heading);
+      return (states & STATE_OFFSCREEN) == 0;
+    }, "heading should be ON screen");
+  },
+  // APZ only happens on the top-level document, which means iframe tests
+  // will assert differently than classic remote doc tests.
+  { iframe: false, remoteIframe: false }
+);