Preliminary i18n implementation as outlined in JEP 16 (#2140)

setting up internationalization for log and UI messages

See i18n README for details

Squashed to resolve CRLF, tab-indent issues.

Author: JCEmmons

.gitignore

@@ -33,3 +33,6 @@ src
 Read the Docs
 config.rst
 
+/.project
+/.pydevproject
+

bower.json

@@ -9,6 +9,7 @@
     "es6-promise": "~1.0",
     "font-awesome": "components/font-awesome#~4.7.0",
     "google-caja": "5669",
+    "jed": "~1.1.1",
     "jquery": "components/jquery#~2.0",
     "jquery-typeahead": "~2.0.0",
     "jquery-ui": "components/jqueryui#~1.10",
@@ -19,6 +20,8 @@
     "preact-compat": "https://unpkg.com/preact-compat@^3.14.3/dist/preact-compat.min.js",
     "proptypes": "https://unpkg.com/proptypes@^0.14.4/index.js",
     "requirejs": "~2.1",
+    "requirejs-text": "~2.0.15",
+    "requirejs-plugins": "~1.0.3",
     "text-encoding": "~0.1",
     "underscore": "components/underscore#~1.8.3",
     "xterm.js": "sourcelair/xterm.js#~2.8.1"

notebook/i18n/README.md

@@ -0,0 +1,122 @@
+# Implementation Notes for Internationalization of Jupyter Notebook
+
+This is a prototype implementation of i18n features for Jupyter notebook, and should not
+yet be considered ready for production use.  I have tried to focus on the public user
+interfaces in the notebook for the first cut, while leaving much of the console messages
+behind, as their usefulness in a translated environment is questionable at best.
+
+### Using a prototype translated version
+
+In order to use this preliminary version, you need to do things after installing the
+notebook as normal:
+
+1. Set the LANG environment variable in your shell to "xx_XX" or just "xx".  
+where "xx" is the language code you're wanting to run in. If you're
+running on Windows, I've found the easiest way to do this is to use Windows PowerShell,
+and run the command:
+
+`${Env:LANG} = "xx_XX"` 
+
+2. Set the preferred language for web pages in your browser to YourLanguage (xx). At the moment,
+it has to be first in the list.
+
+3. Run the `jupyter notebook` command to start the notebook.
+
+### Message extraction:
+
+I have split out the translatable material for the notebook into 3 POT, as follows:
+
+notebook/i18n/notebook.pot - Console and startup messages, basically anything that is
+	produced by Python code.
+	
+notebook/i18n/nbui.pot - User interface strings, as extracted from the Jinja2 templates
+	in notebook/templates/*.html
+	
+noteook/i18n/nbjs.pot - JavaScript strings and dialogs, which contain much of the visible
+	user interface for Jupyter notebook.
+	
+To extract the messages from the source code whenever new material is added, use the
+`pybabel` command to extract messages from the source code as follows:
+( assuming you are in the base directory for Jupyter notebook )
+
+`pybabel extract -F notebook/i18n/babel_notebook.cfg -o notebook/i18n/notebook.pot --no-wrap --project Jupyter .`
+`pybabel extract -F notebook/i18n/babel_nbui.cfg -o notebook/i18n/nbui.pot --no-wrap --project Jupyter .`
+`pybabel extract -F notebook/i18n/babel_nbjs.cfg -o notebook/i18n/nbjs.pot --no-wrap --project Jupyter .`
+
+(Note: there is a '.' at the end of these commands, and it has to be there...)
+
+After this is complete you have 3 POT files that you can give to a translator for your favorite language.
+Babel's documentation has instructions on how to integrate this into your setup.py so that eventually
+we can just do:
+
+`setup.py extract_messages`
+
+I hope to get this working at some point in the near future.
+
+### Post translation procedures
+
+After the source material has been translated, you should have 3 PO files with the same base names
+as the POT files above.  Put them in `notebook/i18n/${LANG}/LC_MESSAGES`, where ${LANG} is the language
+code for your desired language ( i.e. German = "de", Japanese = "ja", etc. ).  The first 2 files then
+need to be converted from PO to MO format for use at runtime. There are many different ways to do
+this, but pybabel has an option to do this as follows:
+
+`pybabel compile -D notebook -f -l ${LANG} -i notebook/i18n/${LANG}/LC_MESSAGES/notebook.po -o notebook/i18n/${LANG}/notebook.mo`
+
+`pybabel compile -D nbui -f -l ${LANG} -i notebook/i18n/${LANG}/LC_MESSAGES/nbui.po -o notebook/i18n/${LANG}/nbui.mo`
+
+The nbjs.po needs to be converted to JSON for use within the JavaScript code.  I'm using po2json for this, as follows:
+
+`po2json -p -F -f jed1.x -d nbjs notebook/i18n/${LANG}/LC_MESSAGES/nbjs.po notebook/i18n/${LANG}/LC_MESSAGES/nbjs.json`
+
+The conversions from PO to MO probably can and should be done during setup.py.
+
+When new languages get added, their language codes should be added to notebook/i18n/nbjs.json
+under the "supported_languages" element.
+
+### Tips for Jupyter developers
+
+The biggest "mistake" I found while doing i18n enablement was the habit of constructing UI messages
+from English "piece parts".  For example, code like:
+
+
+`var msg = "Enter a new " + type + "name:"`
+
+where "type" is either "file", "directory", or "notebook"....
+
+is problematic when doing translations, because the surrounding text may need to vary
+depending on the inserted word. In this case, you need to switch it and use complete phrases,
+as follows:
+
+```javascript
+var rename_msg = function (type) {
+    switch(type) {
+        case 'file': return _("Enter a new file name:");
+        case 'directory': return _("Enter a new directory name:");
+        case 'notebook': return _("Enter a new notebook name:");
+        default: return _("Enter a new name:");
+    }
+}
+```
+
+Also you need to remember that adding an "s" or "es" to an English word to
+create the plural form doesn't translate well.  Some languages have as many as 5 or 6 different
+plural forms for differing numbers, so using an API such as ngettext() is necessary in order
+to handle these cases properly.
+
+### Known issues
+
+1. Right now there are two different places where the desired language is set.  At startup time, the Jupyter console's messages pay attention to the setting of the ${LANG} environment variable
+as set in the shell at startup time.  Unfortunately, this is also the time where the Jinja2
+environment is set up, which means that the template stuff will always come from this setting.
+We really want to be paying attention to the browser's settings for the stuff that happens in the
+browser, so we need to be able to retrieve this information after the browser is started and somehow
+communicate this back to Jinja2.  So far, I haven't yet figured out how to do this, which means that if the ${LANG} at startup doesn't match the browser's settings, you could potentially get a mix
+of languages in the UI ( never a good thing ).
+
+2. We will need to decide if console messages should be translatable, and enable them if desired.
+3. The keyboard shorcut editor was implemented after the i18n work was completed, so that portion
+does not have translation support at this time.
+
+Any questions or comments please let me know @JCEmmons on github ([email protected])
+

notebook/i18n/babel_nbjs.cfg

@@ -0,0 +1,11 @@
+[javascript: notebook/static/base/js/*.js]
+extract_messages = $._, i18n.msg._
+
+[javascript: notebook/static/notebook/js/*.js]
+extract_messages = $._, i18n.msg._
+
+[javascript: notebook/static/notebook/js/celltoolbarpresets/*.js]
+extract_messages = $._, i18n.msg._
+
+[javascript: notebook/static/tree/js/*.js]
+extract_messages = $._, i18n.msg._

notebook/i18n/babel_nbui.cfg

@@ -0,0 +1,4 @@
+[jinja2: notebook/templates/**.html]
+ encoding = utf-8
+[extractors] 
+ jinja2 = jinja2.ext:babel_extract

notebook/i18n/babel_notebook.cfg

@@ -0,0 +1,2 @@
+[python: notebook/*.py]
+[python: notebook/services/contents/*.py]

notebook/i18n/nbjs.json

@@ -0,0 +1,12 @@
+{
+	"domain": "nbjs",
+	"supported_languages": [
+	],
+	"locale_data": {
+		"nbjs": {
+			"": {
+				"domain": "nbjs"
+         	}
+		}
+	}
+}