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.Log;
+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 {

[Tima Vaisburd, 2017/03/10 20:42:37]

A better naming suggestion is welcome.

+    private static final String TAG = "ContextSelClient"; // 20 char limit
+
+    @IntDef({CLASSIFY, SUGGEST_AND_CLASSIFY})
+    @Retention(RetentionPolicy.SOURCE)
+    private @interface RequestType {}
+
+    private static final int CLASSIFY = 0;

[boliu, 2017/03/11 00:37:52]

comment on what these actually does?

[Tima Vaisburd, 2017/03/20 05:06:04]

Not done yet.

[Tima Vaisburd, 2017/03/21 02:07:01]

Done.

+    private static final int SUGGEST_AND_CLASSIFY = 1;
+
+    // The callback that would receive the information from ContextSelectionProvider.
+    private class ProviderCallback implements ContextSelectionProvider.ResultCallback {

[boliu, 2017/03/11 00:37:52]

What's the point of this class?

[Tima Vaisburd, 2017/03/20 05:06:04]

See my reply below.

+        @Override
+        public void onClassified(ContextSelectionProvider.Result result) {
+            mOuterCallback.onClassified(result);
+        }
+    };
+
+    private long mNativeContextSelectionClient;
+    private ContextSelectionProvider mProvider;
+    private ProviderCallback mProviderCallback;
+    private ContextSelectionProvider.ResultCallback mOuterCallback;
+
+    /**
+     * 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) {
+        Log.v(TAG, "create");

[boliu, 2017/03/11 00:37:52]

remove random logs

[Tima Vaisburd, 2017/03/20 05:06:04]

Done.

+
+        ContextSelectionClient client = new ContextSelectionClient(callback);
+        if (!client.initialize(windowAndroid, webContent)) client = null;
+        return client;
+    }
+
+    private ContextSelectionClient(ContextSelectionProvider.ResultCallback callback) {
+        mOuterCallback = callback;
+    }
+
+    private boolean initialize(WindowAndroid windowAndroid, WebContents webContents) {
+        Log.v(TAG, "initialize");

[boliu, 2017/03/11 00:37:52]

ditto

[Tima Vaisburd, 2017/03/20 05:06:04]

Done.

+        // We make a chain of callbacks: this class receiive result from provider through
+        // mProviderCallback and passes the info to embedder with mOuterCallback.
+        mProviderCallback = new ProviderCallback();
+        mProvider = ContentClassFactory.get().createContextSelectionProvider(
+                mProviderCallback, windowAndroid);
+
+        // ContextSelectionProvider might not exist.
+        if (mProvider == null) {
+            Log.v(TAG, "initialize: no provider");
+            return false;
+        }
+
+        mNativeContextSelectionClient = nativeInit(webContents);
+        return mNativeContextSelectionClient != 0;

[boliu, 2017/03/11 00:37:52]

how can this ever be 0?

you can check null provider in create, then you don't need initialize at all?

[Tima Vaisburd, 2017/03/20 05:06:04]

When the C++ new fails. I tried to make something new and original and this was
a bad idea. Changed to return true.
 
I could have one callback pointer (the one that's called mOuterCallback here) to
be stored in two places:
one in this class and one in provider. Provider will then call directly into
SelectionPopupController
and this class too, in parallel. I wanted to avoid this, but maybe it is not
that bad? Then I could avoid initialize(), indeed.

[boliu, 2017/03/20 20:27:25]

yeah, why not just use the same object?

[Tima Vaisburd, 2017/03/21 02:07:01]

Done.

+    }
+
+    @CalledByNative
+    private void onNativeSideDestroyed(long nativeContextSelectionClient) {

[boliu, 2017/03/11 00:37:52]

what if there are pending requests here?

[Tima Vaisburd, 2017/03/20 05:06:04]

They will be executed and eventually passed to SelectionPopupController, did I
miss some bad consequence?

[boliu, 2017/03/20 20:27:25]

Document that you chose this over cancelling pending requests

[Tima Vaisburd, 2017/03/21 02:07:01]

When the native side is destroyed we do not care about the requests because we
are going to destroy the UI, correct?
In this case it would be better to cancel.

+        assert nativeContextSelectionClient == mNativeContextSelectionClient;
+        mNativeContextSelectionClient = 0;
+    }
+
+    // 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:

[boliu, 2017/03/11 00:37:52]

I think what happens in each case is super unintuitive, and needs to be
documented extensively.

eg what prevents this just going from an infinite loop? eg suggest triggers
HANDLES_SHOWN again which triggers another suggest?

[Tima Vaisburd, 2017/03/20 05:06:04]

I tried to add some comments, but I think this is yet another argument in favor
of
the interface in the form "do this" rather to "react to the event". A reasonable
explanation would speak in terms of SelectionPopupController, not this class.

HANDLES_SHOWN are only generated by long press. Changing an existing selection
or hiding and showing it does not cause a new HANDLES_SHOWN event.

+                requestSurroundingText(SUGGEST_AND_CLASSIFY);
+                break;
+
+            case SelectionEventType.SELECTION_HANDLES_CLEARED:
+                cancelAllRequests();
+                break;
+
+            case SelectionEventType.SELECTION_HANDLE_DRAG_STOPPED:
+                requestSurroundingText(CLASSIFY);
+                break;
+
+            default:
+                break; // ignore
+        }
+    }
+
+    @Override
+    public void showUnhandledTapUIIfNeeded(int x, int y) {}
+
+    @Override
+    public boolean sendsMenuUpdates() {
+        return true;
+    }
+
+    private void cancelAllRequests() {
+        if (mNativeContextSelectionClient != 0) {
+            nativeCancelAllRequests(mNativeContextSelectionClient);
+        }
+
+        mProvider.cancelAllRequests();
+    }
+
+    private void requestSurroundingText(@RequestType int callbackData) {
+        Log.v(TAG, "requestSurroundingText");
+        if (mNativeContextSelectionClient == 0) {
+            onSurroundingTextReceived(callbackData, "", 0, 0);
+            return;
+        }
+
+        nativeRequestSurroundingText(mNativeContextSelectionClient, callbackData);
+    }
+
+    @CalledByNative
+    private void onSurroundingTextReceived(
+            @RequestType int callbackData, String text, int start, int end) {
+        if (TextUtils.isEmpty(text)) {
+            mOuterCallback.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 callbackData);
+    private native void nativeCancelAllRequests(long nativeContextSelectionClient);
+}