389 lines
11 KiB
JavaScript
389 lines
11 KiB
JavaScript
/**
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* This code is mostly from the old Etherpad. Please help us to comment this code.
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* This helps other people to understand this code better and helps them to improve it.
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* TL;DR COMMENTS ON THIS FILE ARE HIGHLY APPRECIATED
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*/
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/**
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* Copyright 2009 Google Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS-IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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function makeVirtualLineView(lineNode)
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{
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// how much to jump forward or backward at once in a charSeeker before
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// constructing a DOM node and checking the coordinates (which takes a
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// significant fraction of a millisecond). From the
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// coordinates and the approximate line height we can estimate how
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// many lines we have moved. We risk being off if the number of lines
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// we move is on the order of the line height in pixels. Fortunately,
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// when the user boosts the font-size they increase both.
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var maxCharIncrement = 20;
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var seekerAtEnd = null;
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function getNumChars()
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{
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return lineNode.textContent.length;
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}
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function getNumVirtualLines()
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{
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if (!seekerAtEnd)
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{
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var seeker = makeCharSeeker();
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seeker.forwardByWhile(maxCharIncrement);
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seekerAtEnd = seeker;
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}
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return seekerAtEnd.getVirtualLine() + 1;
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}
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function getVLineAndOffsetForChar(lineChar)
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{
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var seeker = makeCharSeeker();
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seeker.forwardByWhile(maxCharIncrement, null, lineChar);
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var theLine = seeker.getVirtualLine();
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seeker.backwardByWhile(8, function()
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{
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return seeker.getVirtualLine() == theLine;
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});
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seeker.forwardByWhile(1, function()
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{
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return seeker.getVirtualLine() != theLine;
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});
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var lineStartChar = seeker.getOffset();
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return {
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vline: theLine,
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offset: (lineChar - lineStartChar)
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};
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}
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function getCharForVLineAndOffset(vline, offset)
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{
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// returns revised vline and offset as well as absolute char index within line.
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// if offset is beyond end of line, for example, will give new offset at end of line.
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var seeker = makeCharSeeker();
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// go to start of line
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seeker.binarySearch(function()
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{
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return seeker.getVirtualLine() >= vline;
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});
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var lineStart = seeker.getOffset();
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var theLine = seeker.getVirtualLine();
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// go to offset, overshooting the virtual line only if offset is too large for it
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seeker.forwardByWhile(maxCharIncrement, null, lineStart + offset);
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// get back into line
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seeker.backwardByWhile(1, function()
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{
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return seeker.getVirtualLine() != theLine;
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}, lineStart);
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var lineChar = seeker.getOffset();
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var theOffset = lineChar - lineStart;
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// handle case of last virtual line; should be able to be at end of it
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if (theOffset < offset && theLine == (getNumVirtualLines() - 1))
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{
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var lineLen = getNumChars();
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theOffset += lineLen - lineChar;
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lineChar = lineLen;
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}
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return {
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vline: theLine,
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offset: theOffset,
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lineChar: lineChar
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};
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}
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return {
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getNumVirtualLines: getNumVirtualLines,
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getVLineAndOffsetForChar: getVLineAndOffsetForChar,
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getCharForVLineAndOffset: getCharForVLineAndOffset,
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makeCharSeeker: function()
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{
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return makeCharSeeker();
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}
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};
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function deepFirstChildTextNode(nd)
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{
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nd = nd.firstChild;
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while (nd && nd.firstChild) nd = nd.firstChild;
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if (nd.data) return nd;
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return null;
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}
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function makeCharSeeker( /*lineNode*/ )
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{
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function charCoords(tnode, i)
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{
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var container = tnode.parentNode;
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// treat space specially; a space at the end of a virtual line
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// will have weird coordinates
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var isSpace = (tnode.nodeValue.charAt(i) === " ");
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if (isSpace)
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{
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if (i == 0)
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{
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if (container.previousSibling && deepFirstChildTextNode(container.previousSibling))
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{
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tnode = deepFirstChildTextNode(container.previousSibling);
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i = tnode.length - 1;
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container = tnode.parentNode;
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}
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else
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{
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return {
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top: container.offsetTop,
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left: container.offsetLeft
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};
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}
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}
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else
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{
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i--; // use previous char
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}
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}
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var charWrapper = document.createElement("SPAN");
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// wrap the character
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var tnodeText = tnode.nodeValue;
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var frag = document.createDocumentFragment();
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frag.appendChild(document.createTextNode(tnodeText.substring(0, i)));
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charWrapper.appendChild(document.createTextNode(tnodeText.substr(i, 1)));
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frag.appendChild(charWrapper);
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frag.appendChild(document.createTextNode(tnodeText.substring(i + 1)));
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container.replaceChild(frag, tnode);
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var result = {
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top: charWrapper.offsetTop,
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left: charWrapper.offsetLeft + (isSpace ? charWrapper.offsetWidth : 0),
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height: charWrapper.offsetHeight
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};
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while (container.firstChild) container.removeChild(container.firstChild);
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container.appendChild(tnode);
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return result;
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}
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var lineText = lineNode.textContent;
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var lineLength = lineText.length;
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var curNode = null;
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var curChar = 0;
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var curCharWithinNode = 0
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var curTop;
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var curLeft;
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var approxLineHeight;
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var whichLine = 0;
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function nextNode()
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{
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var n = curNode;
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if (!n) n = lineNode.firstChild;
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else n = n.nextSibling;
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while (n && !deepFirstChildTextNode(n))
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{
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n = n.nextSibling;
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}
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return n;
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}
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function prevNode()
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{
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var n = curNode;
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if (!n) n = lineNode.lastChild;
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else n = n.previousSibling;
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while (n && !deepFirstChildTextNode(n))
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{
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n = n.previousSibling;
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}
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return n;
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}
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var seeker;
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if (lineLength > 0)
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{
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curNode = nextNode();
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var firstCharData = charCoords(deepFirstChildTextNode(curNode), 0);
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approxLineHeight = firstCharData.height;
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curTop = firstCharData.top;
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curLeft = firstCharData.left;
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function updateCharData(tnode, i)
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{
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var coords = charCoords(tnode, i);
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whichLine += Math.round((coords.top - curTop) / approxLineHeight);
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curTop = coords.top;
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curLeft = coords.left;
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}
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seeker = {
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forward: function(numChars)
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{
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var oldChar = curChar;
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var newChar = curChar + numChars;
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if (newChar > (lineLength - 1)) newChar = lineLength - 1;
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while (curChar < newChar)
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{
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var curNodeLength = deepFirstChildTextNode(curNode).length;
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var toGo = curNodeLength - curCharWithinNode;
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if (curChar + toGo > newChar || !nextNode())
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{
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// going to next node would be too far
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var n = newChar - curChar;
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if (n >= toGo) n = toGo - 1;
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curChar += n;
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curCharWithinNode += n;
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break;
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}
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else
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{
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// go to next node
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curChar += toGo;
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curCharWithinNode = 0;
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curNode = nextNode();
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}
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}
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updateCharData(deepFirstChildTextNode(curNode), curCharWithinNode);
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return curChar - oldChar;
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},
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backward: function(numChars)
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{
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var oldChar = curChar;
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var newChar = curChar - numChars;
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if (newChar < 0) newChar = 0;
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while (curChar > newChar)
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{
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if (curChar - curCharWithinNode <= newChar || !prevNode())
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{
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// going to prev node would be too far
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var n = curChar - newChar;
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if (n > curCharWithinNode) n = curCharWithinNode;
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curChar -= n;
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curCharWithinNode -= n;
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break;
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}
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else
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{
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// go to prev node
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curChar -= curCharWithinNode + 1;
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curNode = prevNode();
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curCharWithinNode = deepFirstChildTextNode(curNode).length - 1;
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}
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}
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updateCharData(deepFirstChildTextNode(curNode), curCharWithinNode);
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return oldChar - curChar;
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},
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getVirtualLine: function()
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{
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return whichLine;
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},
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getLeftCoord: function()
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{
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return curLeft;
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}
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};
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}
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else
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{
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curLeft = lineNode.offsetLeft;
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seeker = {
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forward: function(numChars)
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{
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return 0;
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},
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backward: function(numChars)
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{
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return 0;
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},
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getVirtualLine: function()
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{
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return 0;
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},
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getLeftCoord: function()
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{
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return curLeft;
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}
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};
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}
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seeker.getOffset = function()
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{
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return curChar;
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};
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seeker.getLineLength = function()
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{
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return lineLength;
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};
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seeker.toString = function()
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{
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return "seeker[curChar: " + curChar + "(" + lineText.charAt(curChar) + "), left: " + seeker.getLeftCoord() + ", vline: " + seeker.getVirtualLine() + "]";
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};
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function moveByWhile(isBackward, amount, optCondFunc, optCharLimit)
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{
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var charsMovedLast = null;
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var hasCondFunc = ((typeof optCondFunc) == "function");
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var condFunc = optCondFunc;
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var hasCharLimit = ((typeof optCharLimit) == "number");
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var charLimit = optCharLimit;
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while (charsMovedLast !== 0 && ((!hasCondFunc) || condFunc()))
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{
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var toMove = amount;
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if (hasCharLimit)
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{
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var untilLimit = (isBackward ? curChar - charLimit : charLimit - curChar);
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if (untilLimit < toMove) toMove = untilLimit;
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}
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if (toMove < 0) break;
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charsMovedLast = (isBackward ? seeker.backward(toMove) : seeker.forward(toMove));
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}
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}
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seeker.forwardByWhile = function(amount, optCondFunc, optCharLimit)
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{
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moveByWhile(false, amount, optCondFunc, optCharLimit);
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}
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seeker.backwardByWhile = function(amount, optCondFunc, optCharLimit)
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{
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moveByWhile(true, amount, optCondFunc, optCharLimit);
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}
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seeker.binarySearch = function(condFunc)
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{
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// returns index of boundary between false chars and true chars;
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// positions seeker at first true char, or else last char
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var trueFunc = condFunc;
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var falseFunc = function()
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{
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return !condFunc();
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};
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seeker.forwardByWhile(20, falseFunc);
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seeker.backwardByWhile(20, trueFunc);
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seeker.forwardByWhile(10, falseFunc);
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seeker.backwardByWhile(5, trueFunc);
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seeker.forwardByWhile(1, falseFunc);
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return seeker.getOffset() + (condFunc() ? 0 : 1);
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}
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return seeker;
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}
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}
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exports.makeVirtualLineView = makeVirtualLineView;
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