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<!DOCTYPE html>
<!--
Copyright (c) 2013 The Chromium Authors. All rights reserved.
Use of this source code is governed by a BSD-style license that can be
found in the LICENSE file.
-->
<link rel="import" href="/tracing/base/base.html">
<script>
'use strict';
/**
* @fileoverview Provides a caching layer for elided text values.
*/
tr.exportTo('tr.ui.b', function() {
/**
* Cache for elided strings.
* Moved from the ElidedTitleCache protoype to a "global" for speed
* (variable reference is 100x faster).
* key: String we wish to elide.
* value: Another dict whose key is width
* and value is an ElidedStringWidthPair.
*/
var elidedTitleCacheDict = {};
var elidedTitleCache = new ElidedTitleCache();
/**
* A cache for elided strings.
* @constructor
*/
function ElidedTitleCache() {
// TODO(jrg): possibly obsoleted with the elided string cache.
// Consider removing.
this.textWidthMap = {};
}
ElidedTitleCache.prototype = {
/**
* Return elided text.
*
* @param {ctx} Context The graphics context.
* @param {pixWidth} Pixel width.
* @param {title} Original title text.
* @param {width} Drawn width in world coords.
* @param {sliceDuration} Where the title must fit (in world coords).
* @return {ElidedStringWidthPair} Elided string and width.
*/
get: function(ctx, pixWidth, title, width, sliceDuration) {
var elidedDict = elidedTitleCacheDict[title];
if (!elidedDict) {
elidedDict = {};
elidedTitleCacheDict[title] = elidedDict;
}
var elidedDictForPixWidth = elidedDict[pixWidth];
if (!elidedDictForPixWidth) {
elidedDict[pixWidth] = {};
elidedDictForPixWidth = elidedDict[pixWidth];
}
var stringWidthPair = elidedDictForPixWidth[sliceDuration];
if (stringWidthPair === undefined) {
var newtitle = title;
var elided = false;
while (this.labelWidthWorld(ctx, newtitle, pixWidth) > sliceDuration) {
if (newtitle.length * 0.75 < 1)
break;
newtitle = newtitle.substring(0, newtitle.length * 0.75);
elided = true;
}
if (elided && newtitle.length > 3)
newtitle = newtitle.substring(0, newtitle.length - 3) + '...';
stringWidthPair = new ElidedStringWidthPair(
newtitle, this.labelWidth(ctx, newtitle));
elidedDictForPixWidth[sliceDuration] = stringWidthPair;
}
return stringWidthPair;
},
quickMeasureText_: function(ctx, text) {
var w = this.textWidthMap[text];
if (!w) {
w = ctx.measureText(text).width;
this.textWidthMap[text] = w;
}
return w;
},
labelWidth: function(ctx, title) {
return this.quickMeasureText_(ctx, title) + 2;
},
labelWidthWorld: function(ctx, title, pixWidth) {
return this.labelWidth(ctx, title) * pixWidth;
}
};
/**
* A pair representing an elided string and world-coordinate width
* to draw it.
* @constructor
*/
function ElidedStringWidthPair(string, width) {
this.string = string;
this.width = width;
}
return {
ElidedTitleCache: ElidedTitleCache
};
});
</script>
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