Thursday, July 8, 2010

Sapphire – Focus on Localization

If you have missed the introduction to Sapphire, make sure to read it first… Introduction to Sapphire

Localization is like build systems, something that most developers prefer not to think about. Unfortunately, the developer must take explicit steps to manually externalize all user-visible strings for the software to be localizable. The localizable strings go into a separate file and the code references them by a key. The developer must come up with a key and then must manage the list of externalized strings so that it stays in sync with the code. Some tools have been developed to make this a little easier, but two types of problems remain very common:

  1. Strings that should be externalized are not. It’s too easy for the developer to put the string directly into code and then forget to externalize it later.
  2. The string resource files get out of sync with code. The case where the resource file is missing a string is easy enough to catch at runtime. The case where resource files contain orphaned strings not referenced in code is much harder to detect.

Since Sapphire is a UI framework, localization is very important. Since Sapphire is focused on ease of use and developer productivity, relying on current methods of localization is not satisfactory.

Localizable strings largely occur in two places in Sapphire. You see them in the model annotations (such as the @Label annotation) and you see them throughout the UI definition files. Sapphire’s approach is to allow the developer to leave the strings in their original language at point of use. The string resource files that will be translated are created at build time. The build system takes the original string and applies a function to it to generate a key for the string resources file. The same function is applied at runtime to derive the key to lookup the translated string.

The critical concept is that the developer does not take any explicit steps to enable localization. It just happens under the covers.

The nature of the function that is used to derive the string resources file key is not particularly important as long as the resulting key is not overly long and is reasonably free from collisions. The current implementation takes the original string, chops it off at 20 characters and replaces some characters that are illegal in a property file key with an underscore. Decent approach for the first cut, but we will likely replace it with an md5 hash in the first version of Sapphire to ship at Eclipse Foundation.

On top of the automatic externalization, Sapphire is architected to minimize the number of strings that must be externalized in the first place. In particular, when the developer specifies a property label, the string is expected to be all in lower case (except where acronyms or proper nouns are used). Sapphire is able to transform the capitalization of the label to make it suitable for different contexts. Three modes of capitalization are supported:

  1. NO_CAPS:  Basically the original string as specified by developer. This is most frequently used for embedding inside validation messages.
  2. FIRST_WORD_ONLY:  This is your typical label in the UI. The colon is added by the UI renderer where appropriate.
  3. TITLE_STYLE:  This is typically used in column headers, section headers, dialog titles, etc.

The current capitalization algorithm works well for English and reasonably well for other languages, but it will need to be made pluggable in the future.

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