michael@0: /* -*- Mode: Java; c-basic-offset: 4; tab-width: 20; indent-tabs-mode: nil; -*-
michael@0:  * This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: package org.mozilla.gecko.gfx;
michael@0: 
michael@0: import org.mozilla.gecko.GeckoAppShell;
michael@0: import org.mozilla.gecko.GeckoEvent;
michael@0: import org.mozilla.gecko.EventDispatcher;
michael@0: import org.mozilla.gecko.util.GeckoEventListener;
michael@0: 
michael@0: import org.json.JSONException;
michael@0: import org.json.JSONObject;
michael@0: 
michael@0: import android.graphics.PointF;
michael@0: import android.os.Handler;
michael@0: import android.util.Log;
michael@0: 
michael@0: class SubdocumentScrollHelper implements GeckoEventListener {
michael@0:     private static final String LOGTAG = "GeckoSubdocScroll";
michael@0: 
michael@0:     private static String MESSAGE_PANNING_OVERRIDE = "Panning:Override";
michael@0:     private static String MESSAGE_CANCEL_OVERRIDE = "Panning:CancelOverride";
michael@0:     private static String MESSAGE_SCROLL = "Gesture:Scroll";
michael@0:     private static String MESSAGE_SCROLL_ACK = "Gesture:ScrollAck";
michael@0: 
michael@0:     private final Handler mUiHandler;
michael@0:     private final EventDispatcher mEventDispatcher;
michael@0: 
michael@0:     /* This is the amount of displacement we have accepted but not yet sent to JS; this is
michael@0:      * only valid when mOverrideScrollPending is true. */
michael@0:     private final PointF mPendingDisplacement;
michael@0: 
michael@0:     /* When this is true, we're sending scroll events to JS to scroll the active subdocument. */
michael@0:     private boolean mOverridePanning;
michael@0: 
michael@0:     /* When this is true, we have received an ack for the last scroll event we sent to JS, and
michael@0:      * are ready to send the next scroll event. Note we only ever have one scroll event inflight
michael@0:      * at a time. */
michael@0:     private boolean mOverrideScrollAck;
michael@0: 
michael@0:     /* When this is true, we have a pending scroll that we need to send to JS; we were unable
michael@0:      * to send it when it was initially requested because mOverrideScrollAck was not true. */
michael@0:     private boolean mOverrideScrollPending;
michael@0: 
michael@0:     /* When this is true, the last scroll event we sent actually did some amount of scrolling on
michael@0:      * the subdocument; we use this to decide when we have reached the end of the subdocument. */
michael@0:     private boolean mScrollSucceeded;
michael@0: 
michael@0:     SubdocumentScrollHelper(EventDispatcher eventDispatcher) {
michael@0:         // mUiHandler will be bound to the UI thread since that's where this constructor runs
michael@0:         mUiHandler = new Handler();
michael@0:         mPendingDisplacement = new PointF();
michael@0: 
michael@0:         mEventDispatcher = eventDispatcher;
michael@0:         registerEventListener(MESSAGE_PANNING_OVERRIDE);
michael@0:         registerEventListener(MESSAGE_CANCEL_OVERRIDE);
michael@0:         registerEventListener(MESSAGE_SCROLL_ACK);
michael@0:     }
michael@0: 
michael@0:     void destroy() {
michael@0:         unregisterEventListener(MESSAGE_PANNING_OVERRIDE);
michael@0:         unregisterEventListener(MESSAGE_CANCEL_OVERRIDE);
michael@0:         unregisterEventListener(MESSAGE_SCROLL_ACK);
michael@0:     }
michael@0: 
michael@0:     private void registerEventListener(String event) {
michael@0:         mEventDispatcher.registerEventListener(event, this);
michael@0:     }
michael@0: 
michael@0:     private void unregisterEventListener(String event) {
michael@0:         mEventDispatcher.unregisterEventListener(event, this);
michael@0:     }
michael@0: 
michael@0:     boolean scrollBy(PointF displacement) {
michael@0:         if (! mOverridePanning) {
michael@0:             return false;
michael@0:         }
michael@0: 
michael@0:         if (! mOverrideScrollAck) {
michael@0:             mOverrideScrollPending = true;
michael@0:             mPendingDisplacement.x += displacement.x;
michael@0:             mPendingDisplacement.y += displacement.y;
michael@0:             return true;
michael@0:         }
michael@0: 
michael@0:         JSONObject json = new JSONObject();
michael@0:         try {
michael@0:             json.put("x", displacement.x);
michael@0:             json.put("y", displacement.y);
michael@0:         } catch (JSONException e) {
michael@0:             Log.e(LOGTAG, "Error forming subwindow scroll message: ", e);
michael@0:         }
michael@0:         GeckoAppShell.sendEventToGecko(GeckoEvent.createBroadcastEvent(MESSAGE_SCROLL, json.toString()));
michael@0: 
michael@0:         mOverrideScrollAck = false;
michael@0:         mOverrideScrollPending = false;
michael@0:         // clear the |mPendingDisplacement| after serializing |displacement| to
michael@0:         // JSON because they might be the same object
michael@0:         mPendingDisplacement.x = 0;
michael@0:         mPendingDisplacement.y = 0;
michael@0: 
michael@0:         return true;
michael@0:     }
michael@0: 
michael@0:     void cancel() {
michael@0:         mOverridePanning = false;
michael@0:     }
michael@0: 
michael@0:     boolean scrolling() {
michael@0:         return mOverridePanning;
michael@0:     }
michael@0: 
michael@0:     boolean lastScrollSucceeded() {
michael@0:         return mScrollSucceeded;
michael@0:     }
michael@0: 
michael@0:     // GeckoEventListener implementation
michael@0: 
michael@0:     @Override
michael@0:     public void handleMessage(final String event, final JSONObject message) {
michael@0:         // This comes in on the Gecko thread; hand off the handling to the UI thread.
michael@0:         mUiHandler.post(new Runnable() {
michael@0:             @Override
michael@0:             public void run() {
michael@0:                 try {
michael@0:                     if (MESSAGE_PANNING_OVERRIDE.equals(event)) {
michael@0:                         mOverridePanning = true;
michael@0:                         mOverrideScrollAck = true;
michael@0:                         mOverrideScrollPending = false;
michael@0:                         mScrollSucceeded = true;
michael@0:                     } else if (MESSAGE_CANCEL_OVERRIDE.equals(event)) {
michael@0:                         mOverridePanning = false;
michael@0:                     } else if (MESSAGE_SCROLL_ACK.equals(event)) {
michael@0:                         mOverrideScrollAck = true;
michael@0:                         mScrollSucceeded = message.getBoolean("scrolled");
michael@0:                         if (mOverridePanning && mOverrideScrollPending) {
michael@0:                             scrollBy(mPendingDisplacement);
michael@0:                         }
michael@0:                     }
michael@0:                 } catch (Exception e) {
michael@0:                     Log.e(LOGTAG, "Exception handling message", e);
michael@0:                 }
michael@0:             }
michael@0:         });
michael@0:     }
michael@0: }