Implement SmartText selection.

content/public/android/java/src/org/chromium/content/browser/ContextSelectionClient.java

+// Copyright 2017 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.content.browser;
+
+import android.support.annotation.IntDef;
+import android.text.TextUtils;
+
+import org.chromium.base.annotations.CalledByNative;
+import org.chromium.base.annotations.JNINamespace;
+import org.chromium.content_public.browser.WebContents;
+import org.chromium.ui.base.WindowAndroid;
+import org.chromium.ui.touch_selection.SelectionEventType;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+/**
+ * A class that controls the classification of the textual selection.
+ * It requests the selection together with its surrounding text from the focused frame and sends it
+ * to ContextSelectionProvider which does the classification itself.
+ */
+@JNINamespace("content")
+public class ContextSelectionClient implements SelectionClient {
+    @IntDef({CLASSIFY, SUGGEST_AND_CLASSIFY})
+    @Retention(RetentionPolicy.SOURCE)
+    private @interface RequestType {}
+
+    // Request to obtain the type (e.g. phone number, e-mail address) and the most
+    // appropriate operation for the selected text.
+    private static final int CLASSIFY = 0;
+
+    // Request to obtain the type (e.g. phone number, e-mail address), the most
+    // appropriate operation for the selected text and a better selection boundaries.
+    private static final int SUGGEST_AND_CLASSIFY = 1;
+
+    // The maximal number of characters on the left and on the right from the current selection.
+    // Used for surrounding text request.
+    private static final int NUM_EXTRA_CHARS = 100;
+
+    private long mNativeContextSelectionClient;
+    private ContextSelectionProvider mProvider;
+    private ContextSelectionProvider.ResultCallback mCallback;
+
+    /**
+     * Creates the ContextSelectionClient. Returns null in case ContextSelectionProvider
+     * does not exist in the system.
+     */
+    public static ContextSelectionClient create(ContextSelectionProvider.ResultCallback callback,
+            WindowAndroid windowAndroid, WebContents webContent) {

[Ted C, 2017/03/30 00:12:40]

s/webContent/webContents

[Tima Vaisburd, 2017/03/30 01:03:13]

Done.

+        ContextSelectionProvider provider =
+                ContentClassFactory.get().createContextSelectionProvider(callback, windowAndroid);

[Ted C, 2017/03/30 00:12:39]

FYI, the window android associated with a WebContents can change if you move
them between windows, so this has the potential to break for you in unexpected
ways in the future.

You'd be better off keeping a reference to WebContents in this file and passing
the WindowAndroid into the provider API calls to handle this case where your
WebContents is reparented across windows.

[Tima Vaisburd, 2017/03/30 01:03:13]

Yes, thank you. I will need to do either that or just use the application
context.
So far I could not figure out which one should be used to get the default
TextClassifier.

+
+        // ContextSelectionProvider might not exist.
+        if (provider == null) return null;
+
+        return new ContextSelectionClient(provider, callback, webContent);
+    }
+
+    private ContextSelectionClient(ContextSelectionProvider provider,
+            ContextSelectionProvider.ResultCallback callback, WebContents webContents) {
+        mProvider = provider;
+        mCallback = callback;
+        mNativeContextSelectionClient = nativeInit(webContents);
+    }
+
+    @CalledByNative
+    private void onNativeSideDestroyed(long nativeContextSelectionClient) {
+        assert nativeContextSelectionClient == mNativeContextSelectionClient;
+        mNativeContextSelectionClient = 0;
+        mProvider.cancelAllRequests();
+    }
+
+    // SelectionClient implementation
+    @Override
+    public void onSelectionChanged(String selection) {}
+
+    @Override
+    public void onSelectionEvent(int eventType, float posXPix, float posYPix) {
+        switch (eventType) {
+            case SelectionEventType.SELECTION_HANDLES_SHOWN:
+                // This event is sent when the long press is detected which causes
+                // selection to appear for the first time. Temporarily hiding the
+                // handles that happens e.g. during scroll does not affect this event.
+                requestSurroundingText(SUGGEST_AND_CLASSIFY);
+                break;
+
+            case SelectionEventType.SELECTION_HANDLES_CLEARED:
+                // The ActionMode should be stopped when this event comes.
+                cancelAllRequests();
+                break;
+
+            case SelectionEventType.SELECTION_HANDLE_DRAG_STOPPED:
+                // This event is sent after a user stopped dragging one of the
+                // selection handles, i.e. stopped modifying the selection.
+                requestSurroundingText(CLASSIFY);
+                break;
+
+            default:
+                break; // ignore
+        }
+    }
+
+    @Override
+    public void showUnhandledTapUIIfNeeded(int x, int y) {}
+
+    @Override
+    public boolean sendsSelectionPopupUpdates() {
+        return true;
+    }
+
+    private void cancelAllRequests() {
+        if (mNativeContextSelectionClient != 0) {
+            nativeCancelAllRequests(mNativeContextSelectionClient);
+        }
+
+        mProvider.cancelAllRequests();
+    }
+
+    private void requestSurroundingText(@RequestType int callbackData) {
+        if (mNativeContextSelectionClient == 0) {
+            onSurroundingTextReceived(callbackData, "", 0, 0);
+            return;
+        }
+
+        nativeRequestSurroundingText(mNativeContextSelectionClient, NUM_EXTRA_CHARS, callbackData);
+    }
+
+    @CalledByNative
+    private void onSurroundingTextReceived(
+            @RequestType int callbackData, String text, int start, int end) {
+        if (TextUtils.isEmpty(text)) {
+            mCallback.onClassified(new ContextSelectionProvider.Result());
+            return;
+        }
+
+        switch (callbackData) {
+            case SUGGEST_AND_CLASSIFY:
+                mProvider.sendSuggestAndClassifyRequest(text, start, end);
+                break;
+
+            case CLASSIFY:
+                mProvider.sendClassifyRequest(text, start, end);
+                break;
+
+            default:
+                assert false : "Unexpected callback data";
+                break;
+        }
+    }
+
+    private native long nativeInit(WebContents webContents);
+    private native void nativeRequestSurroundingText(
+            long nativeContextSelectionClient, int numExtraCharacters, int callbackData);
+    private native void nativeCancelAllRequests(long nativeContextSelectionClient);
+}