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comparison: mobile/android/base/gfx/SubdocumentScrollHelper.java
mobile/android/base/gfx/SubdocumentScrollHelper.java
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| 1 /* -*- Mode: Java; c-basic-offset: 4; tab-width: 20; indent-tabs-mode: nil; -*- | |
| 2 * This Source Code Form is subject to the terms of the Mozilla Public | |
| 3 * License, v. 2.0. If a copy of the MPL was not distributed with this | |
| 4 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ | |
| 5 | |
| 6 package org.mozilla.gecko.gfx; | |
| 7 | |
| 8 import org.mozilla.gecko.GeckoAppShell; | |
| 9 import org.mozilla.gecko.GeckoEvent; | |
| 10 import org.mozilla.gecko.EventDispatcher; | |
| 11 import org.mozilla.gecko.util.GeckoEventListener; | |
| 12 | |
| 13 import org.json.JSONException; | |
| 14 import org.json.JSONObject; | |
| 15 | |
| 16 import android.graphics.PointF; | |
| 17 import android.os.Handler; | |
| 18 import android.util.Log; | |
| 19 | |
| 20 class SubdocumentScrollHelper implements GeckoEventListener { | |
| 21 private static final String LOGTAG = "GeckoSubdocScroll"; | |
| 22 | |
| 23 private static String MESSAGE_PANNING_OVERRIDE = "Panning:Override"; | |
| 24 private static String MESSAGE_CANCEL_OVERRIDE = "Panning:CancelOverride"; | |
| 25 private static String MESSAGE_SCROLL = "Gesture:Scroll"; | |
| 26 private static String MESSAGE_SCROLL_ACK = "Gesture:ScrollAck"; | |
| 27 | |
| 28 private final Handler mUiHandler; | |
| 29 private final EventDispatcher mEventDispatcher; | |
| 30 | |
| 31 /* This is the amount of displacement we have accepted but not yet sent to JS; this is | |
| 32 * only valid when mOverrideScrollPending is true. */ | |
| 33 private final PointF mPendingDisplacement; | |
| 34 | |
| 35 /* When this is true, we're sending scroll events to JS to scroll the active subdocument. */ | |
| 36 private boolean mOverridePanning; | |
| 37 | |
| 38 /* When this is true, we have received an ack for the last scroll event we sent to JS, and | |
| 39 * are ready to send the next scroll event. Note we only ever have one scroll event inflight | |
| 40 * at a time. */ | |
| 41 private boolean mOverrideScrollAck; | |
| 42 | |
| 43 /* When this is true, we have a pending scroll that we need to send to JS; we were unable | |
| 44 * to send it when it was initially requested because mOverrideScrollAck was not true. */ | |
| 45 private boolean mOverrideScrollPending; | |
| 46 | |
| 47 /* When this is true, the last scroll event we sent actually did some amount of scrolling on | |
| 48 * the subdocument; we use this to decide when we have reached the end of the subdocument. */ | |
| 49 private boolean mScrollSucceeded; | |
| 50 | |
| 51 SubdocumentScrollHelper(EventDispatcher eventDispatcher) { | |
| 52 // mUiHandler will be bound to the UI thread since that's where this constructor runs | |
| 53 mUiHandler = new Handler(); | |
| 54 mPendingDisplacement = new PointF(); | |
| 55 | |
| 56 mEventDispatcher = eventDispatcher; | |
| 57 registerEventListener(MESSAGE_PANNING_OVERRIDE); | |
| 58 registerEventListener(MESSAGE_CANCEL_OVERRIDE); | |
| 59 registerEventListener(MESSAGE_SCROLL_ACK); | |
| 60 } | |
| 61 | |
| 62 void destroy() { | |
| 63 unregisterEventListener(MESSAGE_PANNING_OVERRIDE); | |
| 64 unregisterEventListener(MESSAGE_CANCEL_OVERRIDE); | |
| 65 unregisterEventListener(MESSAGE_SCROLL_ACK); | |
| 66 } | |
| 67 | |
| 68 private void registerEventListener(String event) { | |
| 69 mEventDispatcher.registerEventListener(event, this); | |
| 70 } | |
| 71 | |
| 72 private void unregisterEventListener(String event) { | |
| 73 mEventDispatcher.unregisterEventListener(event, this); | |
| 74 } | |
| 75 | |
| 76 boolean scrollBy(PointF displacement) { | |
| 77 if (! mOverridePanning) { | |
| 78 return false; | |
| 79 } | |
| 80 | |
| 81 if (! mOverrideScrollAck) { | |
| 82 mOverrideScrollPending = true; | |
| 83 mPendingDisplacement.x += displacement.x; | |
| 84 mPendingDisplacement.y += displacement.y; | |
| 85 return true; | |
| 86 } | |
| 87 | |
| 88 JSONObject json = new JSONObject(); | |
| 89 try { | |
| 90 json.put("x", displacement.x); | |
| 91 json.put("y", displacement.y); | |
| 92 } catch (JSONException e) { | |
| 93 Log.e(LOGTAG, "Error forming subwindow scroll message: ", e); | |
| 94 } | |
| 95 GeckoAppShell.sendEventToGecko(GeckoEvent.createBroadcastEvent(MESSAGE_SCROLL, json.toString())); | |
| 96 | |
| 97 mOverrideScrollAck = false; | |
| 98 mOverrideScrollPending = false; | |
| 99 // clear the |mPendingDisplacement| after serializing |displacement| to | |
| 100 // JSON because they might be the same object | |
| 101 mPendingDisplacement.x = 0; | |
| 102 mPendingDisplacement.y = 0; | |
| 103 | |
| 104 return true; | |
| 105 } | |
| 106 | |
| 107 void cancel() { | |
| 108 mOverridePanning = false; | |
| 109 } | |
| 110 | |
| 111 boolean scrolling() { | |
| 112 return mOverridePanning; | |
| 113 } | |
| 114 | |
| 115 boolean lastScrollSucceeded() { | |
| 116 return mScrollSucceeded; | |
| 117 } | |
| 118 | |
| 119 // GeckoEventListener implementation | |
| 120 | |
| 121 @Override | |
| 122 public void handleMessage(final String event, final JSONObject message) { | |
| 123 // This comes in on the Gecko thread; hand off the handling to the UI thread. | |
| 124 mUiHandler.post(new Runnable() { | |
| 125 @Override | |
| 126 public void run() { | |
| 127 try { | |
| 128 if (MESSAGE_PANNING_OVERRIDE.equals(event)) { | |
| 129 mOverridePanning = true; | |
| 130 mOverrideScrollAck = true; | |
| 131 mOverrideScrollPending = false; | |
| 132 mScrollSucceeded = true; | |
| 133 } else if (MESSAGE_CANCEL_OVERRIDE.equals(event)) { | |
| 134 mOverridePanning = false; | |
| 135 } else if (MESSAGE_SCROLL_ACK.equals(event)) { | |
| 136 mOverrideScrollAck = true; | |
| 137 mScrollSucceeded = message.getBoolean("scrolled"); | |
| 138 if (mOverridePanning && mOverrideScrollPending) { | |
| 139 scrollBy(mPendingDisplacement); | |
| 140 } | |
| 141 } | |
| 142 } catch (Exception e) { | |
| 143 Log.e(LOGTAG, "Exception handling message", e); | |
| 144 } | |
| 145 } | |
| 146 }); | |
| 147 } | |
| 148 } |
