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MozReview-Commit-ID: 9zP6j7COEiJ --HG-- extra : rebase_source : 35b44964d38f53f62522d0709b18d7dfa1ca8a9a
97 lines
3.6 KiB
ReStructuredText
97 lines
3.6 KiB
ReStructuredText
Startup
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=======
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There are cases where it may be important to understand how Gecko locale management
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acts during the startup.
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Below is the description of the `server` mode, since the `client` mode is starting
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with no data and doesn't perform any operations waiting for the parent to fill
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basic locale lists (`requested` and `appLocales`) and then maintain them in a
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unidirectional way.
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Data Types
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----------
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There are two primary data types involved in negotiating locales during startup:
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`requested` and `available`.
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Throughout the startup different sources for this lists become available, and
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in result the values for those lists change.
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Data Sources
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------------
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There are three primary sources that become available during the bootstrap.
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1) Packaged locale lists stored in files :js:`update.locale` and :js:`multilocale.txt`.
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2) User preferences read from the profile.
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3) Language packs installed in user profile or system wide.
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Bootstrap
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---------
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1) Packaged Data
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^^^^^^^^^^^^^^^^
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In the `server` mode Gecko starts with no knowledge of `available` or `requested`
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locales.
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Initially, all fields are resolved lazily, so no data for available, requested,
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default or resolved locales is retrieved.
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If any code queries any of the APIs, it triggers the initial data fetching
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and language negotiation.
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The initial request comes from the XPCLocale which is initializing
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the first JS context and needs to know which locale the JS context should use as
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the default.
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At that moment :js:`LocaleService` fetches the list of available locales, using
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packaged locales which are retrieved via :js:`multilocale.txt` file in the toolkit's
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package.
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This gives LocaleService information about which locales are initially available.
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Notice that this happens before any of the language packs gets registered, so
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at that point Gecko only knows about packaged locales.
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For requested locales, the initial request comes before user profile preferences
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are being read, so the data is being fetched using packaged preferences.
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In case of Desktop Firefox the :js:`intl.locale.requested` pref will be not set,
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which means Gecko will use the default locale which is retrieved from
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:js:`update.locale` file (also packaged).
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This means that the initial result of language negotiation is between packaged
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locales as available and the default requested locale.
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2) Profile Prefs Read
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^^^^^^^^^^^^^^^^^^^^^
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Next, the profile is being read and if the user set any requested locales,
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LocaleService updates its list of requested locales and broadcasts
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:js:`intl:requested-locales-changed` event.
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This may lead to language renegotiation if the requested locale is one of the packaged
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ones. In that case, :js:`intl:app-locales-changed` will be broadcasted.
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3) Language Packs Registered
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Finally, the AddonManager registers all the language packs, they get added to
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:js:`L10nRegistry` and in result LocaleService's available locales get updated.
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That triggers language negotiation and, if the language from the language pack
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is used in the requested list, final list of locales is being set.
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All of that happens before any UI is being built, but there's no guarantee of this
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order being preserved, so it is important to understand that, depending on where the
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code is used during the startup, it may receive different list of locales.
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In order to maintain the correct locale settings it is important to set an observer
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on :js:`intl:app-locales-changed` and update the code when the locale list changes.
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That ensures the code always uses the best possible locale selection during startup,
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but also during runtime in case user changes their requested locale list, or
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language packs are updated/removed on the fly.
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