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/* -*- Mode: Java; c-basic-offset: 4; tab-width: 20; indent-tabs-mode: nil; -*-
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
package org.mozilla.gecko.ui;
import android.graphics.PointF;
import android.os.Handler;
import android.util.Log;
import org.json.JSONException;
import org.json.JSONObject;
class SubdocumentScrollHelper {
private static final String LOGTAG = "GeckoSubdocumentScrollHelper";
private final PanZoomController mPanZoomController;
private final Handler mUiHandler;
/* This is the amount of displacement we have accepted but not yet sent to JS; this is
* only valid when mOverrideScrollPending is true. */
private final PointF mPendingDisplacement;
/* When this is true, we're sending scroll events to JS to scroll the active subdocument. */
private boolean mOverridePanning;
/* When this is true, we have received an ack for the last scroll event we sent to JS, and
* are ready to send the next scroll event. Note we only ever have one scroll event inflight
* at a time. */
private boolean mOverrideScrollAck;
/* When this is true, we have a pending scroll that we need to send to JS; we were unable
* to send it when it was initially requested because mOverrideScrollAck was not true. */
private boolean mOverrideScrollPending;
/* When this is true, the last scroll event we sent actually did some amount of scrolling on
* the subdocument; we use this to decide when we have reached the end of the subdocument. */
private boolean mScrollSucceeded;
SubdocumentScrollHelper(PanZoomController controller) {
mPanZoomController = controller;
// mUiHandler will be bound to the UI thread since that's where this constructor runs
mUiHandler = new Handler();
mPendingDisplacement = new PointF();
}
void destroy() {
}
boolean scrollBy(PointF displacement) {
if (! mOverridePanning) {
return false;
}
if (! mOverrideScrollAck) {
mOverrideScrollPending = true;
mPendingDisplacement.x += displacement.x;
mPendingDisplacement.y += displacement.y;
return true;
}
JSONObject json = new JSONObject();
try {
json.put("x", displacement.x);
json.put("y", displacement.y);
} catch (JSONException e) {
Log.e(LOGTAG, "Error forming subwindow scroll message: ", e);
}
mOverrideScrollAck = false;
mOverrideScrollPending = false;
// clear the |mPendingDisplacement| after serializing |displacement| to
// JSON because they might be the same object
mPendingDisplacement.x = 0;
mPendingDisplacement.y = 0;
return true;
}
void cancel() {
mOverridePanning = false;
}
boolean scrolling() {
return mOverridePanning;
}
boolean lastScrollSucceeded() {
return mScrollSucceeded;
}
}
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