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// Copyright (C) 2013 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package com.google.gerrit.client.diff;
import com.google.gerrit.client.Gerrit;
import com.google.gerrit.client.diff.LineMapper.LineOnOtherInfo;
import com.google.gwt.user.client.Timer;
import net.codemirror.lib.CodeMirror;
import net.codemirror.lib.CodeMirror.Viewport;
import net.codemirror.lib.ScrollInfo;
class ScrollSynchronizer {
private DiffTable diffTable;
private LineMapper mapper;
private ScrollCallback active;
void init(DiffTable diffTable,
CodeMirror cmA, CodeMirror cmB,
LineMapper mapper) {
this.diffTable = diffTable;
this.mapper = mapper;
cmA.on("scroll", new ScrollCallback(cmA, cmB, DisplaySide.A));
cmB.on("scroll", new ScrollCallback(cmB, cmA, DisplaySide.B));
}
private void updateScreenHeader(ScrollInfo si) {
if (si.getTop() == 0 && !Gerrit.isHeaderVisible()) {
Gerrit.setHeaderVisible(true);
diffTable.updateFileCommentVisibility(false);
} else if (si.getTop() > 0.5 * si.getClientHeight()
&& Gerrit.isHeaderVisible()) {
Gerrit.setHeaderVisible(false);
diffTable.updateFileCommentVisibility(true);
}
}
class ScrollCallback implements Runnable {
private final CodeMirror src;
private final CodeMirror dst;
private final DisplaySide srcSide;
private final Timer fixup;
private int state;
ScrollCallback(CodeMirror src, CodeMirror dst, DisplaySide srcSide) {
this.src = src;
this.dst = dst;
this.srcSide = srcSide;
this.fixup = new Timer() {
@Override
public void run() {
if (active == ScrollCallback.this) {
fixup();
}
}
};
}
@Override
public void run() {
if (active == null) {
active = this;
fixup.scheduleRepeating(20);
}
if (active == this) {
ScrollInfo si = src.getScrollInfo();
updateScreenHeader(si);
dst.scrollTo(si.getLeft(), si.getTop());
state = 0;
}
}
private void fixup() {
switch (state) {
case 0:
state = 1;
break;
case 1:
state = 2;
return;
case 2:
active = null;
fixup.cancel();
return;
}
// Since CM doesn't always take the height of line widgets into
// account when calculating scrollInfo when scrolling too fast (e.g.
// throw scrolling), simply setting scrollTop to be the same doesn't
// guarantee alignment.
//
// Iterate over the viewport to find the first line that isn't part of
// an insertion or deletion gap, for which isAligned() will be true.
// We then manually examine if the lines that should be aligned are at
// the same height. If not, perform additional scrolling.
Viewport fromTo = src.getViewport();
for (int line = fromTo.getFrom(); line <= fromTo.getTo(); line++) {
LineOnOtherInfo info = mapper.lineOnOther(srcSide, line);
if (info.isAligned()) {
double sy = src.heightAtLine(line);
double dy = dst.heightAtLine(info.getLine());
if (Math.abs(dy - sy) >= 1) {
dst.scrollToY(dst.getScrollInfo().getTop() + (dy - sy));
}
break;
}
}
}
}
}