| <!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="/base/base.html"> |
| <script> |
| 'use strict'; |
| |
| /** |
| * @fileoverview Provides a caching layer for elided text values. |
| */ |
| tv.exportTo('tv.c', 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> |
