1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/mobile/android/base/gfx/SubdocumentScrollHelper.java Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,148 @@
1.4 +/* -*- Mode: Java; c-basic-offset: 4; tab-width: 20; indent-tabs-mode: nil; -*-
1.5 + * This Source Code Form is subject to the terms of the Mozilla Public
1.6 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.7 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.8 +
1.9 +package org.mozilla.gecko.gfx;
1.10 +
1.11 +import org.mozilla.gecko.GeckoAppShell;
1.12 +import org.mozilla.gecko.GeckoEvent;
1.13 +import org.mozilla.gecko.EventDispatcher;
1.14 +import org.mozilla.gecko.util.GeckoEventListener;
1.15 +
1.16 +import org.json.JSONException;
1.17 +import org.json.JSONObject;
1.18 +
1.19 +import android.graphics.PointF;
1.20 +import android.os.Handler;
1.21 +import android.util.Log;
1.22 +
1.23 +class SubdocumentScrollHelper implements GeckoEventListener {
1.24 + private static final String LOGTAG = "GeckoSubdocScroll";
1.25 +
1.26 + private static String MESSAGE_PANNING_OVERRIDE = "Panning:Override";
1.27 + private static String MESSAGE_CANCEL_OVERRIDE = "Panning:CancelOverride";
1.28 + private static String MESSAGE_SCROLL = "Gesture:Scroll";
1.29 + private static String MESSAGE_SCROLL_ACK = "Gesture:ScrollAck";
1.30 +
1.31 + private final Handler mUiHandler;
1.32 + private final EventDispatcher mEventDispatcher;
1.33 +
1.34 + /* This is the amount of displacement we have accepted but not yet sent to JS; this is
1.35 + * only valid when mOverrideScrollPending is true. */
1.36 + private final PointF mPendingDisplacement;
1.37 +
1.38 + /* When this is true, we're sending scroll events to JS to scroll the active subdocument. */
1.39 + private boolean mOverridePanning;
1.40 +
1.41 + /* When this is true, we have received an ack for the last scroll event we sent to JS, and
1.42 + * are ready to send the next scroll event. Note we only ever have one scroll event inflight
1.43 + * at a time. */
1.44 + private boolean mOverrideScrollAck;
1.45 +
1.46 + /* When this is true, we have a pending scroll that we need to send to JS; we were unable
1.47 + * to send it when it was initially requested because mOverrideScrollAck was not true. */
1.48 + private boolean mOverrideScrollPending;
1.49 +
1.50 + /* When this is true, the last scroll event we sent actually did some amount of scrolling on
1.51 + * the subdocument; we use this to decide when we have reached the end of the subdocument. */
1.52 + private boolean mScrollSucceeded;
1.53 +
1.54 + SubdocumentScrollHelper(EventDispatcher eventDispatcher) {
1.55 + // mUiHandler will be bound to the UI thread since that's where this constructor runs
1.56 + mUiHandler = new Handler();
1.57 + mPendingDisplacement = new PointF();
1.58 +
1.59 + mEventDispatcher = eventDispatcher;
1.60 + registerEventListener(MESSAGE_PANNING_OVERRIDE);
1.61 + registerEventListener(MESSAGE_CANCEL_OVERRIDE);
1.62 + registerEventListener(MESSAGE_SCROLL_ACK);
1.63 + }
1.64 +
1.65 + void destroy() {
1.66 + unregisterEventListener(MESSAGE_PANNING_OVERRIDE);
1.67 + unregisterEventListener(MESSAGE_CANCEL_OVERRIDE);
1.68 + unregisterEventListener(MESSAGE_SCROLL_ACK);
1.69 + }
1.70 +
1.71 + private void registerEventListener(String event) {
1.72 + mEventDispatcher.registerEventListener(event, this);
1.73 + }
1.74 +
1.75 + private void unregisterEventListener(String event) {
1.76 + mEventDispatcher.unregisterEventListener(event, this);
1.77 + }
1.78 +
1.79 + boolean scrollBy(PointF displacement) {
1.80 + if (! mOverridePanning) {
1.81 + return false;
1.82 + }
1.83 +
1.84 + if (! mOverrideScrollAck) {
1.85 + mOverrideScrollPending = true;
1.86 + mPendingDisplacement.x += displacement.x;
1.87 + mPendingDisplacement.y += displacement.y;
1.88 + return true;
1.89 + }
1.90 +
1.91 + JSONObject json = new JSONObject();
1.92 + try {
1.93 + json.put("x", displacement.x);
1.94 + json.put("y", displacement.y);
1.95 + } catch (JSONException e) {
1.96 + Log.e(LOGTAG, "Error forming subwindow scroll message: ", e);
1.97 + }
1.98 + GeckoAppShell.sendEventToGecko(GeckoEvent.createBroadcastEvent(MESSAGE_SCROLL, json.toString()));
1.99 +
1.100 + mOverrideScrollAck = false;
1.101 + mOverrideScrollPending = false;
1.102 + // clear the |mPendingDisplacement| after serializing |displacement| to
1.103 + // JSON because they might be the same object
1.104 + mPendingDisplacement.x = 0;
1.105 + mPendingDisplacement.y = 0;
1.106 +
1.107 + return true;
1.108 + }
1.109 +
1.110 + void cancel() {
1.111 + mOverridePanning = false;
1.112 + }
1.113 +
1.114 + boolean scrolling() {
1.115 + return mOverridePanning;
1.116 + }
1.117 +
1.118 + boolean lastScrollSucceeded() {
1.119 + return mScrollSucceeded;
1.120 + }
1.121 +
1.122 + // GeckoEventListener implementation
1.123 +
1.124 + @Override
1.125 + public void handleMessage(final String event, final JSONObject message) {
1.126 + // This comes in on the Gecko thread; hand off the handling to the UI thread.
1.127 + mUiHandler.post(new Runnable() {
1.128 + @Override
1.129 + public void run() {
1.130 + try {
1.131 + if (MESSAGE_PANNING_OVERRIDE.equals(event)) {
1.132 + mOverridePanning = true;
1.133 + mOverrideScrollAck = true;
1.134 + mOverrideScrollPending = false;
1.135 + mScrollSucceeded = true;
1.136 + } else if (MESSAGE_CANCEL_OVERRIDE.equals(event)) {
1.137 + mOverridePanning = false;
1.138 + } else if (MESSAGE_SCROLL_ACK.equals(event)) {
1.139 + mOverrideScrollAck = true;
1.140 + mScrollSucceeded = message.getBoolean("scrolled");
1.141 + if (mOverridePanning && mOverrideScrollPending) {
1.142 + scrollBy(mPendingDisplacement);
1.143 + }
1.144 + }
1.145 + } catch (Exception e) {
1.146 + Log.e(LOGTAG, "Exception handling message", e);
1.147 + }
1.148 + }
1.149 + });
1.150 + }
1.151 +}
