Generate code with libMEI
Verovio uses a forked version of LibMEI, a library that generates code directly from the MEI schema. It can be adapted to generate code in any language. For Verovio, it is used to generate C++ code. The code generated with LibMEI is included in the Verovio repository in the ./libmei directory and the LibMEI repository does not need to be cloned for building Verovio.
Whenever the MEI schema is modified, this code needs to be re-generated in order to integrate these changes. However, since Verovio implements only a small subset of the MEI schema, this really needs to be done only for the changes in the schema that touch features supported by Verovio. This means that the code within the ./libmei directory should never be edited by hand because any change will be overwritten by the LibMEI output when the code generated from the schema needs to be updated and LibMEI is run again.
Running LibMEI
In order to update to code generated with LibMEI, you need to clone the forked version of LibMEI.
LibMEI takes a compiled ODD as input. You need to run, from the LibMEI directory:
python tools/parseschema2.py -l vrv -o /path/to/the/verovio/directory -i tools/includes/vrv mei/develop/mei-verovio_compiled.odd
You need to set to option -o to point to the Verovio directory where the ./libmei files will be written.
Customization
Verovio currently uses an MEI customization that added or modified a few elements. It is defined in the ./mei/develop/mei-verovio.xml file. If you want to makes changes to it, you can make them there. You will need to re-generate the ./mei/develop/mei-verovio_compiled.odd ODD file. This can be done using the Edirom MEI Garage. Alternatively, you can also use the MEI command-line script. To do so, you will need to a clone of the MEI repository, copy your customization file (e.g., mei-verovio.xml) into it and do:
ant init
ant -lib lib/saxon/saxon9he.jar -Dcustomization.path=mei-verovio.xml
The ODD file will be written to ./dist/schemata/mei-verovio_compiled.odd, which you can use as new input file for LibMEI.