How to translate the plugin into Your language
Unzip the downloaded Plugin onto your harddisk.
It contains the following folders:
Inside the "language" folder, copy the "en-GB" folder and name the copy according to your language, e.g. "hu-HU" for Hungary.
There are two language files in that folder, rename them from "en-GB.*" to e.g. "hu-HU.*", like so:
2. Translating the language files
Now open the files one by one with a text editor. Note the editor must support UTF-8; a good choice (on Windows) is NotePad++ (that's the editor i used myself).
In the header, change the Author to your name:
Then go through the files and translate every string/text to your language. Make sure to leave the " (double quotes) at the beginning and end of the texts intact.
3. Including your translation
The next thing to do is tell Joomla to copy your folder to the right place when installing the plugin. To do this, you need to edit the gpxtrackmap.xml file in the main directory. Close to the beginning there's a section called "languages". Add two new "language" tags in there for your translated files, like so:
4. Translating html templates
To translate the html template files (the ones that the plugin uses to build the html code for the included track maps), do the following:
Copy the "de-DE" folder that is in the "gpxtrackmap" folder (!). Rename it to your language, eg. "hu-HU".
That should then look like this:
Now translate the template1..5 files. There are only a few bits of localized texts in there, if at all. This is a part of template2.html:
Note: to translate from the English versions, copy the template<n>.html files directly from the gpxtrackmap folder into your language folder, these are the English ones.
5. Including translated templates
Go back to the gpxtrackmap.xml file in the main folder. At the top there is a section called "files". Add a new "folder" tag there as follows:
This will tell the Joomla installer to copy your translated templates as well.
6. Testing the translation
Zip the entire folder (the one "above" the gpxtrackmap folder) and name it something like "plg_content_gpxtrackmap_v1.1.1-hu.zip". Upload and install that to your Joomla site (like you would with any other extension).
Go to the plugin options in the backend and check if everything is translated correctly.
Also go to the frontend to an article with a track map to see whether the templates are fine.
If necessary, edit and correct the files and re-upload & re-check.
7. Publishing the translation
When your translation is complete and finished, it would be very kind if you could send it to me so i can include it in the next release of the plugin (the zip file you used for upload is fine).
Needless to say, i will credit you for your work!
...so now - happy translating! :-)