doc: add translation strings policy

doc/README.md

@@ -55,6 +55,7 @@ The Bitcoin repo's [root README](https://github.com/bitcoin/bitcoin/blob/master/
 - [Release Process](release-process.md)
 - [Source Code Documentation (External Link)](https://dev.visucore.com/bitcoin/doxygen/)
 - [Translation Process](translation_process.md)
+- [Translation Strings Policy](translation_strings_policy.md)
 - [Unit Tests](unit-tests.md)
 - [Unauthenticated REST Interface](REST-interface.md)
 - [BIPS](bips.md)

doc/translation_strings_policy.md

@@ -0,0 +1,72 @@
+Translation Strings Policy
+===========================
+
+This document provides guidelines for internationalization of the Bitcoin Core software. 
+
+How to translate?
+------------------
+
+To mark a message as translatable
+
+- In GUI source code (under `src/qt`): use `tr("...")`
+
+- In non-GUI source code (under `src`): use `_("...")`
+
+No internationalization is used for e.g. developer scripts outside `src`.
+
+Strings to be translated
+-------------------------
+
+On a high level, these strings are to be translated:
+
+- GUI strings, anything that appears in a dialog or window
+
+- Command-line option documentation
+
+### GUI strings
+
+Anything that appears to the user in the GUI is to be translated. This includes labels, menu items, button texts, tooltips and window titles.
+This includes messages passed to the GUI through the UI interface through `InitMessage`, `ThreadSafeMessageBox` or `ShowProgress`.
+
+### Command-line options
+
+Documentation for the command line options in the output of `--help` should be translated as well.
+
+Make sure that default values do not end up in the string, but use string formatting like `strprintf(_("Threshold for disconnecting misbehaving peers (default: %u)"), 100)`. Putting default values in strings has led to accidental translations in the past, and forces the string to be retranslated every time the value changes.
+
+Do not translate messages that are only shown to developers, such as those that only appear when `--help-debug` is used.
+
+General recommendations
+------------------------
+
+### Avoid unnecessary translation strings
+
+Try not to burden translators with translating messages that are e.g. slight variations of other messages.
+In the GUI, avoid the use of text where an icon or symbol will do.
+Make sure that placeholder texts in forms don't end up in the list of strings to be translated (use `<string notr="true">`).
+
+### Make translated strings understandable
+
+Try to write translation strings in an understandable way, for both the user and the translator. Avoid overly technical or detailed messages
+
+### Do not translate internal errors
+
+Do not translate internal errors, or log messages, or messages that appear on the RPC interface. If an error is to be shown to the user,
+use a generic message, then log the detailed message to the log. E.g. "Error: A fatal internal error occurred, see debug.log for details".
+This helps troubleshooting; if the error is the same for everyone, the likelihood is increased that it can be found using a search engine.
+
+### Avoid fragments
+
+Avoid dividing up a message into fragments. Translators see every string separately, so may misunderstand the context if the messages are not self-contained.
+
+### Avoid HTML in translation strings
+
+There have been difficulties with use of HTML in translation strings; translators should not be able to accidentally affect the formatting of messages.
+This may sometimes be at conflict with the recommendation in the previous section.
+
+### String freezes
+
+During a string freeze (often before a major release), no translation strings are to be added, modified or removed.
+
+This can be checked by executing `make translate` in the `src` directory, then verifying that `bitcoin_en.ts` remains unchanged.
+