Separate translations for QMimeTypeDatabase

Currently, translations are embedded into the mimetype database itself. Consider switching it to use the Qt translation system (.ts / .qm files).

API / Use cases

Currently, the mimetype database contains various translations that are exposed via QMimeType::comment(). The chosen translation is determined via the default QLocale().

Qt uses QMimeType::comment() itself in file dialogs (e.g. QXdgDesktopPortalFileDialog, and QFileSystemModel(via QAbstractFileIconProviderPrivate::getFileType).

Proposal

Remove the translations from the embedded .xml file, and instead provide them as part of the qtbase translations.

Advantages

Reduction of Qt Core binary size.

The mimetype database to be loaded would be significantly smaller - without translations, the default database size on file system shrinks from 2515 KB to 313 KB. Qt Core binary size is reduced by 5% (from 5.398 KB to 5.105 KB in a release build on Windows).

Consistent translations

Using .ts/.pm files would make the handling of translations consistent with the translations of other parts of the user interfaces, for instance for file-dialogs.

Disadvantages

Behavior change

This would be a behavior change.

Challenges

The freedesktop.xml database currently contains translations for 57 locales. qtbase currently only features translations for 29 locales.

Conversion tool

TODO: extract translations from .xml into .ts file, for instance with Apache xalan or Python's lxml. This could then be run in qttranslations whenever qtbase_xz.ts is updated.