GObject enforces the following restrictions on property overrides:
- must only add abilities: if the parent class supports
readability/writability then the subclass must also support them.
Subclasses are free to add readability/writability.
- must not add additional restrictions: if the parent class doesn't
have construct/construct-only restrictions then the subclass must
not add them. Subclasses are free to remove restrictions.
The problem with the previous implementation is that the check against
adding construct/construct-only restrictions was being done even if the
property was not previously writable. As an example:
"readable" and "writable only on construct"
was considered as being more restrictive than
"read only".
This patch tweaks the check to allow the addition of
construct/construct-only restrictions for properties that were
previously read-only and are now being made writable.
https://bugzilla.gnome.org/show_bug.cgi?id=666615
af24dbc12a