Style incompatibility in Gedit 47

[jakobwenzel]

Gedit 47 seems to contain some breaking changes related to theming. There are changes both in installing themes, as well as the actual theme files.

See https://gitlab.gnome.org/GNOME/gedit/-/blob/master/NEWS and https://gedit-technology.github.io/developer-docs/extra/libgedit-gtksourceview/style-scheme-file-format.html

Breaking changes that I found are:

• The button to manually install a theme is gone (breaking Alternative Installation in the readme)
• Themes are now searched in .local/share/libgedit-gtksourceview-300/styles
• There are two attribute changes in the style-scheme opening tag:
  • The version attribute is no longer supported
  • There is a new required attribute, kind, specifying whether this is a light or dark theme.
• The author tag is no longer supported.

Sadly, theme files modified like this seem to be incompatible with gnome-text-editor (46.3). I'm unsure whether gnome-text-editor will make matching changes to its themes.