QGC uses the standard Qt Linguist mechanisms for string translation. QGC uses crowd sourced string translation through a Crowdin project for translation.
Run this command to update the translations files for both Qt and Json. Crowdin will automatically pull these up and submit a pull request back when new translations are available.
These are coded using the standard Qt tr() for C++ and qsTr() for Qml mechanisms.
QGC uses json files internally for metadata. These files need to be translated as well. There is a python json parser which is used to find all the json files in the source tree and pull all the strings out for translation. This parser outputs the localization file for json strings in Qt .ts file format.
In order for the parser to know which strings must be translated additional keys must be available at the root object level.
Important: Json files which have the same name are not allowed. Since the name is used as the context for the translation lookup it must be unique. The parse will throw an error if it finds duplicate file names.
Important: The root file name for the json file must be the same as the root filename for the Qt resource alias. This due to the fact that the root filename is used as the translation context. The json parser reads files from the file system and sees file system names. Whereas the QGC C++ code reads json files from the QT resource system and see the file alias as the full path and root name.
The parser supports two known file types: "MAVCmdInfo" and "FactMetaData". If your json file is one of these types you should place a fileType key at the root with one of these values. This will cause the parser to use these defaults for instructions:
"translateKeys": "label,enumStrings,friendlyName,description",
"arrayIDKeys": "rawName,comment"
"translateKeys": "shortDescription,longDescription,enumStrings"
"arrayIDKeys": "name"
For this case dont include the fileType key/value pair. And include the followings keys (as needed) in the root object:
translateKeysThis key is a string which is a list of all the keys which should be translated.arrayIDKeysThe json localization parser provides additional information to the translator about where this string came from in the json hierarchy. If there is an array in the json, just displaying an array index as to where this came from is not that helpful. In most cases there is a key within each array element for which the value is unique. If this is the case then specify this key name(s) as the value forarrayIDKeys.
This is used when you have two strings in the same file which are equal, but there meaning ar different enough that when translated they may each have their own different translation. In order to specific that you include a special prefix marker in the string which includes comments to the translator to explain the specifics of the string.
"foo": "#loc.disambiguation#This is the foo version of baz#baz"
"bar": "#loc.disambiguation#This is the bar version of baz#baz"
In the example above "baz" is the string which is the same for two different keys. The prefix #loc.disambiguation# indicates a disambiguation is to follow which is the string between the next set of #s.
Crowdin is configured to automatically sychronize the qgc.ts file once a day. So it will pick up any new changes automatically. Once it has processed those changes it will submit a pull request back with the translations.