This bug is present both in 2.28 and master (I first noticed it when writing a PyGTK app). The gobject.property helper class does not correctly pass along the min/max values it was created with to the _install_properties method in the GObjectMeta metaclass.

The problem lies in the get_pspec_args method (line 301 in both master and 2.28, I believe): for all types accepting min/max values, the method returns self._get_minimum() and self._get_maximum(). Instead, it should return self.minimum and self.maximum, which are set by __init__ either to the user-supplied values or the defaults provided by _get_minimum() and get_maximum().

I have tested the patch on my own installation and it seems to work: setting a value out of range no longer calls a custom setter, instead displaying a warning about the value being out-of-range, which is the expected behaviour, and what happens when you declare the property with __gproperties__ directly.

This is a single-line pure-Python code change, so I request that the change be applied both to the master and 2.x branches.