Registers the PreviewWidget for addition directly into GML. Fixes
its previous double Frame borders. Also standardizes the Apply and
Reset buttons as DialogButtons and spaces them consistently with
other apps. Gives the TabWidget some tasteful container margins.
This patch introduces two new buttons to apply the current theme being
edited to the whole system and to reset to the previously selected
on disk system theme.
This is quite a radical change. The previous UI was very easy to add new
properties to (just add to the FooRole enum and it automatically
works), but not so nice to use: A ComboBox for selecting a property,
and then a box to edit that property's value. This makes it difficult
to compare different properties or edit multiple together without a lot
of back-and-forth.
This new design gives each property its own editing widgets, with those
categorized into several tabs. To try and avoid increasing the
maintenance burden for this, the UI is generated from the
`windows_tab`, `widgets_tab` and `syntax_highlighting_tab` variables,
which are basically just lists of which properties go in that tab. One
of the `FooProperty.gml` files is loaded to create each property's
widgets.
Now that the GML formatter is both perserving comments and also mostly
agrees to the existing GML style, it can be used to auto-format all the
GML files in the system. This commit does not only contain the scripts
for running the formatting on CI and the pre-commit hook, but also
initially formats all the existing GML files so that the hook is
successfull.
The GUI for this is a bit odd, especially since we only have one flag,
but otherwise adding new flags would require modifying ThemeEditor. At
least it is consistent with the other theme properties.
