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| 1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. | |
| 2 // Use of this source code is governed by a BSD-style license that can be | |
| 3 // found in the LICENSE file. | |
| 4 | |
| 5 #ifndef UI_BASE_L10N_TIME_FORMAT_H_ | |
| 6 #define UI_BASE_L10N_TIME_FORMAT_H_ | |
| 7 | |
| 8 #include "base/basictypes.h" | |
| 9 #include "base/strings/string16.h" | |
| 10 #include "ui/base/ui_base_export.h" | |
| 11 | |
| 12 namespace base { | |
| 13 class Time; | |
| 14 class TimeDelta; | |
| 15 } | |
| 16 | |
| 17 namespace ui { | |
| 18 | |
| 19 // Methods to format time values as strings. | |
| 20 class UI_BASE_EXPORT TimeFormat { | |
| 21 public: | |
| 22 enum Format { | |
| 23 FORMAT_DURATION, // Plain duration, e.g. in English: "2 minutes". | |
| 24 FORMAT_REMAINING, // Remaining time, e.g. in English: "2 minutes left". | |
| 25 FORMAT_ELAPSED, // Elapsed time, e.g. in English: "2 minutes ago". | |
| 26 FORMAT_COUNT // Enum size counter, not a format. Must be last. | |
| 27 }; | |
| 28 | |
| 29 enum Length { | |
| 30 LENGTH_SHORT, // Short format, e.g. in English: sec/min/hour/day. | |
| 31 LENGTH_LONG, // Long format, e.g. in English: second/minute/hour/day. | |
| 32 LENGTH_COUNT // Enum size counter, not a length. Must be last. | |
| 33 }; | |
| 34 | |
| 35 // Return a localized string of approximate time duration, formatted as a | |
| 36 // single number, e.g. in English "2 hours ago". Currently, all combinations | |
| 37 // of format and length except (FORMAT_ELAPSED, LENGTH_LONG) are implemented | |
| 38 // but it's easy to add this, if required. | |
| 39 static base::string16 Simple(Format format, | |
| 40 Length length, | |
| 41 const base::TimeDelta& delta); | |
| 42 | |
| 43 // Return a localized string of more precise time duration, either formatted | |
| 44 // as a single value or as two values: for a time delta of e.g. 2h19m either | |
| 45 // "2 hours" or "2 hours and 19 minutes" could be returned in English. | |
| 46 // Two-value output can be forced by setting |cutoff| to -1. Single-value | |
| 47 // output can be forced by using Simple() or setting |cutoff| to 0. | |
| 48 // Otherwise, choice of format happens automatically and the value of |cutoff| | |
| 49 // determines the largest numeric value that may appear in a single-value | |
| 50 // format -- for lower numeric values, a second unit is added to increase | |
| 51 // precision. (Applied to the examples above, a |cutoff| of 2 or smaller | |
| 52 // would yield the first string and a |cutoff| of 3 or larger would return the | |
| 53 // second string.) | |
| 54 // | |
| 55 // The aim of this logic is to reduce rounding errors (that in single-value | |
| 56 // representation can amount up to 33% of the true time duration) while at the | |
| 57 // same time avoiding over-precise time outputs such as e.g. "56 minutes 29 | |
| 58 // seconds". The relative rounding error is guaranteed to be less than 0.5 / | |
| 59 // |cutoff| (e.g. 5% for a |cutoff| of 10) and a second unit is only used when | |
| 60 // necessary to achieve the precision guarantee. | |
| 61 // | |
| 62 // Currently, the only combination of format and length that is implemented is | |
| 63 // (FORMAT_DURATION, LENGTH_LONG), but it's easy to add others if required. | |
| 64 // | |
| 65 // Note: To allow pre-, post- and infixes which can be inflected depending on | |
| 66 // either the first or the second value, two separate translation strings | |
| 67 // (IDS_TIME_*_1ST and IDS_TIME_*_2ND) are used per [plurality] times [pair of | |
| 68 // units] and are concatenated after having been formatted individually. The | |
| 69 // separator between first unit and second unit (a blank in English) is | |
| 70 // included in IDS_TIME_*_1ST. | |
| 71 static base::string16 Detailed(Format format, | |
| 72 Length length, | |
| 73 int cutoff, | |
| 74 const base::TimeDelta& delta); | |
| 75 | |
| 76 // For displaying a relative time in the past. This method returns either | |
| 77 // "Today", "Yesterday", or an empty string if it's older than that. Returns | |
| 78 // the empty string for days in the future. | |
| 79 // | |
| 80 // TODO(brettw): This should be able to handle days in the future like | |
| 81 // "Tomorrow". | |
| 82 // TODO(tc): This should be able to do things like "Last week". This | |
| 83 // requires handling singluar/plural for all languages. | |
| 84 // | |
| 85 // The second parameter is optional, it is midnight of "Now" for relative day | |
| 86 // computations: Time::Now().LocalMidnight() | |
| 87 // If NULL, the current day's midnight will be retrieved, which can be | |
| 88 // slow. If many items are being processed, it is best to get the current | |
| 89 // time once at the beginning and pass it for each computation. | |
| 90 static base::string16 RelativeDate(const base::Time& time, | |
| 91 const base::Time* optional_midnight_today); | |
| 92 | |
| 93 private: | |
| 94 DISALLOW_IMPLICIT_CONSTRUCTORS(TimeFormat); | |
| 95 }; | |
| 96 | |
| 97 } // namespace ui | |
| 98 | |
| 99 #endif // UI_BASE_L10N_TIME_FORMAT_H_ | |
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