weblayer: adds ScrollOffsetCallback

This allows tracking the scrollTop of the page.

BUG=1109035
TEST=covered by tests

Change-Id: I34dd29cacb2569704176d8d3027347cdbd9be734
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2422650
Commit-Queue: Scott Violet <sky@chromium.org>
Reviewed-by: Bo <boliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#809596}

weblayer/browser/android/javatests/BUILD.gn

@@ -30,6 +30,7 @@ android_library("weblayer_java_tests") {
     "src/org/chromium/weblayer/test/OnTabRemovedTabListCallbackImpl.java",
     "src/org/chromium/weblayer/test/ProfileTest.java",
     "src/org/chromium/weblayer/test/RenderingTest.java",
+    "src/org/chromium/weblayer/test/ScrollOffsetCallbackTest.java",
     "src/org/chromium/weblayer/test/SmokeTest.java",
     "src/org/chromium/weblayer/test/TabCallbackTest.java",
     "src/org/chromium/weblayer/test/TabListCallbackTest.java",

weblayer/browser/android/javatests/src/org/chromium/weblayer/test/ScrollOffsetCallbackTest.java

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.weblayer.test;
+
+import androidx.test.filters.SmallTest;
+
+import org.junit.Assert;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import org.chromium.base.test.util.CallbackHelper;
+import org.chromium.content_public.browser.test.util.TestThreadUtils;
+import org.chromium.weblayer.ScrollOffsetCallback;
+import org.chromium.weblayer.shell.InstrumentationActivity;
+
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+
+/**
+ * Test for ScrollOffsetCallback.
+ */
+@RunWith(WebLayerJUnit4ClassRunner.class)
+public class ScrollOffsetCallbackTest {
+    @Rule
+    public InstrumentationActivityTestRule mActivityTestRule =
+            new InstrumentationActivityTestRule();
+
+    @Test
+    @SmallTest
+    @MinWebLayerVersion(87)
+    public void testBasic() throws Throwable {
+        final String url = mActivityTestRule.getTestDataURL("tall_page.html");
+        InstrumentationActivity activity = mActivityTestRule.launchShellWithUrl(url);
+
+        // As registering for scroll offsets requires sending a message to the renderer, and
+        // requires viz to be in a particular state, ensuring scrolls will generate a message is a
+        // bit finicky. This tries to adjust the top-offset 10 times before giving up.
+        CallbackHelper callbackHelper = new CallbackHelper();
+        ScrollOffsetCallback scrollOffsetCallback = new ScrollOffsetCallback() {
+            @Override
+            public void onVerticalScrollOffsetChanged(int scrollOffset) {
+                callbackHelper.notifyCalled();
+            }
+        };
+        TestThreadUtils.runOnUiThreadBlocking(() -> {
+            activity.getBrowser().getActiveTab().registerScrollOffsetCallback(scrollOffsetCallback);
+        });
+
+        boolean gotInitialScroll = false;
+        for (int i = 1; i < 10 && !gotInitialScroll; ++i) {
+            mActivityTestRule.executeScriptSync("window.scroll(0, " + (i * 100) + ");", false);
+            try {
+                callbackHelper.waitForCallback(
+                        "Waiting for initial scroll", 0, 1, 100, TimeUnit.MILLISECONDS);
+                gotInitialScroll = true;
+            } catch (TimeoutException e) {
+            }
+        }
+        if (!gotInitialScroll) {
+            Assert.fail("Was unable to get initial scroll, failing");
+        }
+
+        // Scroll back to the origin.
+        CallbackHelper scrollBackCallbackHelper = new CallbackHelper();
+        ScrollOffsetCallback scrollBackOffsetCallback = new ScrollOffsetCallback() {
+            @Override
+            public void onVerticalScrollOffsetChanged(int scrollOffset) {
+                if (scrollOffset == 0) {
+                    scrollBackCallbackHelper.notifyCalled();
+                }
+            }
+        };
+        TestThreadUtils.runOnUiThreadBlocking(() -> {
+            activity.getBrowser().getActiveTab().registerScrollOffsetCallback(
+                    scrollBackOffsetCallback);
+        });
+        mActivityTestRule.executeScriptSync("window.scroll(0, 0);", false);
+        scrollBackCallbackHelper.waitForFirst();
+        TestThreadUtils.runOnUiThreadBlocking(() -> {
+            activity.getBrowser().getActiveTab().unregisterScrollOffsetCallback(
+                    scrollOffsetCallback);
+        });
+
+        // At this point scrollOffsetCallback is still registered. If this code were to remove the
+        // callback the renderer might temporarily disable scroll-offsets notification, which
+        // could potentially lead to raciness. In other words, best to leave it for future
+        // assertions.
+    }
+
+    // NOTE: if adding another test, you'll likely want to make testBasic() a setUp type function
+    // that is shared.
+}

weblayer/browser/java/org/chromium/weblayer_private/TabImpl.java

@@ -41,6 +41,8 @@ import org.chromium.components.find_in_page.FindMatchRectsDetails;
 import org.chromium.components.find_in_page.FindResultBar;
 import org.chromium.components.infobars.InfoBar;
 import org.chromium.components.url_formatter.UrlFormatter;
+import org.chromium.content_public.browser.GestureListenerManager;
+import org.chromium.content_public.browser.GestureStateListenerWithScroll;
 import org.chromium.content_public.browser.LoadUrlParams;
 import org.chromium.content_public.browser.NavigationHandle;
 import org.chromium.content_public.browser.SelectionClient;
@@ -134,6 +136,9 @@ public final class TabImpl extends ITab.Stub implements LoginPrompt.Observer {
 
     private Set<FaviconCallbackProxy> mFaviconCallbackProxies = new HashSet<>();
 
+    // Only non-null if scroll offsets have been requested.
+    private @Nullable GestureStateListenerWithScroll mGestureStateListenerWithScroll;
+
     private static class InternalAccessDelegateImpl
             implements ViewEventSink.InternalAccessDelegate {
         @Override
@@ -570,6 +575,31 @@ public final class TabImpl extends ITab.Stub implements LoginPrompt.Observer {
         TabImplJni.get().setTranslateTargetLanguage(mNativeTab, targetLanguage);
     }
 
+    @Override
+    public void setScrollOffsetsEnabled(boolean enabled) {
+        if (enabled) {
+            if (mGestureStateListenerWithScroll == null) {
+                mGestureStateListenerWithScroll = new GestureStateListenerWithScroll() {
+                    @Override
+                    public void onScrollOffsetOrExtentChanged(
+                            int scrollOffsetY, int scrollExtentY) {
+                        try {
+                            mClient.onVerticalScrollOffsetChanged(scrollOffsetY);
+                        } catch (RemoteException e) {
+                            throw new APICallException(e);
+                        }
+                    }
+                };
+                GestureListenerManager.fromWebContents(mWebContents)
+                        .addListener(mGestureStateListenerWithScroll);
+            }
+        } else if (mGestureStateListenerWithScroll != null) {
+            GestureListenerManager.fromWebContents(mWebContents)
+                    .removeListener(mGestureStateListenerWithScroll);
+            mGestureStateListenerWithScroll = null;
+        }
+    }
+
     public void removeFaviconCallbackProxy(FaviconCallbackProxy proxy) {
         mFaviconCallbackProxies.remove(proxy);
     }
@@ -873,6 +903,9 @@ public final class TabImpl extends ITab.Stub implements LoginPrompt.Observer {
             }
         }
 
+        // This is called to ensure a listener is removed from the WebContents.
+        setScrollOffsetsEnabled(false);
+
         if (mTabCallbackProxy != null) {
             mTabCallbackProxy.destroy();
             mTabCallbackProxy = null;

weblayer/browser/java/org/chromium/weblayer_private/interfaces/ITab.aidl

@@ -72,4 +72,7 @@ interface ITab {
   void setGoogleAccountsCallbackClient(IGoogleAccountsCallbackClient client) = 23;
   IFaviconFetcher createFaviconFetcher(IFaviconFetcherClient client) = 24;
   void setTranslateTargetLanguage(in String targetLanguage) = 25;
+
+  // Added in 87
+  void setScrollOffsetsEnabled(in boolean enabled) = 26;
 }

weblayer/browser/java/org/chromium/weblayer_private/interfaces/ITabClient.aidl

@@ -43,4 +43,7 @@ interface ITabClient {
   // Added in M85
   void onScrollNotification(
           in int notificationType, in float currentScrollRatio) = 10;
+
+  // Added in M87
+  void onVerticalScrollOffsetChanged(in int offset) = 11;
 }

weblayer/public/java/BUILD.gn

@@ -79,6 +79,7 @@ android_library("java") {
     "org/chromium/weblayer/Profile.java",
     "org/chromium/weblayer/RemoteFragment.java",
     "org/chromium/weblayer/ScrollNotificationType.java",
+    "org/chromium/weblayer/ScrollOffsetCallback.java",
     "org/chromium/weblayer/SettingType.java",
     "org/chromium/weblayer/SiteSettingsActivity.java",
     "org/chromium/weblayer/SiteSettingsFragment.java",

weblayer/public/java/org/chromium/weblayer/ScrollOffsetCallback.java

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.weblayer;
+
+/**
+ * Callback notified when the vertical location of the content of a Tab changes. The value reported
+ * by the callback corresponds to the 'scrollTop' html property.
+ *
+ * WARNING: use of this API necessitates additional cross process ipc that impacts overall
+ * performance. Only use when absolutely necessary.
+ *
+ * Because of WebLayer's multi-process architecture, this function can not be used to reliably
+ * synchronize the painting of other Views with WebLayer's Views. It's entirely possible one will
+ * render before or after the other.
+ *
+ * @since 87
+ */
+public abstract class ScrollOffsetCallback {
+    /**
+     * Called when the scroll offset of the content of a Tab changes.
+     */
+    public abstract void onVerticalScrollOffsetChanged(int scrollOffset);
+}

weblayer/public/java/org/chromium/weblayer/Tab.java

@@ -55,6 +55,7 @@ public class Tab {
     private Profile.DownloadCallbackClientImpl mDownloadCallbackClient;
     private FullscreenCallbackClientImpl mFullscreenCallbackClient;
     private NewTabCallback mNewTabCallback;
+    private final ObserverList<ScrollOffsetCallback> mScrollOffsetCallbacks;
     // Id from the remote side.
     private final int mId;
 
@@ -65,6 +66,7 @@ public class Tab {
         mFindInPageController = null;
         mMediaCaptureController = null;
         mCallbacks = null;
+        mScrollOffsetCallbacks = null;
         mId = 0;
     }
 
@@ -79,6 +81,7 @@ public class Tab {
         }
 
         mCallbacks = new ObserverList<TabCallback>();
+        mScrollOffsetCallbacks = new ObserverList<ScrollOffsetCallback>();
         mNavigationController = NavigationController.create(mImpl);
         mFindInPageController = new FindInPageController(mImpl);
         mMediaCaptureController = new MediaCaptureController(mImpl);
@@ -353,6 +356,48 @@ public class Tab {
         mCallbacks.removeObserver(callback);
     }
 
+    /**
+     * Registers {@link callback} to be notified when the scroll offset changes. <b>WARNING:</b>
+     * adding a {@link ScrollOffsetCallback} impacts performance, ensure
+     * {@link ScrollOffsetCallback} are only installed when needed. See {@link ScrollOffsetCallback}
+     * for more details.
+     *
+     * @param callback The ScrollOffsetCallback to notify
+     *
+     * @since 87
+     */
+    public void registerScrollOffsetCallback(@NonNull ScrollOffsetCallback callback) {
+        ThreadCheck.ensureOnUiThread();
+        throwIfDestroyed();
+        if (WebLayer.getSupportedMajorVersionInternal() < 87) {
+            throw new UnsupportedOperationException();
+        }
+        if (mScrollOffsetCallbacks.isEmpty()) {
+            try {
+                mImpl.setScrollOffsetsEnabled(true);
+            } catch (RemoteException e) {
+                throw new APICallException(e);
+            }
+        }
+        mScrollOffsetCallbacks.addObserver(callback);
+    }
+
+    public void unregisterScrollOffsetCallback(@NonNull ScrollOffsetCallback callback) {
+        ThreadCheck.ensureOnUiThread();
+        throwIfDestroyed();
+        if (WebLayer.getSupportedMajorVersionInternal() < 87) {
+            throw new UnsupportedOperationException();
+        }
+        mScrollOffsetCallbacks.removeObserver(callback);
+        if (mScrollOffsetCallbacks.isEmpty()) {
+            try {
+                mImpl.setScrollOffsetsEnabled(false);
+            } catch (RemoteException e) {
+                throw new APICallException(e);
+            }
+        }
+    }
+
     /**
      * Take a screenshot of this tab and return it as a Bitmap.
      * This API captures only the web content, not any Java Views, including the
@@ -821,6 +866,14 @@ public class Tab {
                 callback.onScrollNotification(notificationType, currentScrollRatio);
             }
         }
+
+        @Override
+        public void onVerticalScrollOffsetChanged(int value) {
+            StrictModeWorkaround.apply();
+            for (ScrollOffsetCallback callback : mScrollOffsetCallbacks) {
+                callback.onVerticalScrollOffsetChanged(value);
+            }
+        }
     }
 
     private static final class ErrorPageCallbackClientImpl extends IErrorPageCallbackClient.Stub {