name : _propertyhelper.py # -*- Mode: Python; py-indent-offset: 4 -*- # pygobject - Python bindings for the GObject library # Copyright (C) 2007 Johan Dahlin # # gi/_propertyhelper.py: GObject property wrapper/helper # # This library is free software; you can redistribute it and/or # modify it under the terms of the GNU Lesser General Public # License as published by the Free Software Foundation; either # version 2.1 of the License, or (at your option) any later version. # # This library is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU # Lesser General Public License for more details. # # You should have received a copy of the GNU Lesser General Public # License along with this library; if not, see <http://www.gnu.org/licenses/>. import sys import traceback from . import _gi from ._constants import \ TYPE_NONE, TYPE_INTERFACE, TYPE_CHAR, TYPE_UCHAR, \ TYPE_BOOLEAN, TYPE_INT, TYPE_UINT, TYPE_LONG, \ TYPE_ULONG, TYPE_INT64, TYPE_UINT64, TYPE_ENUM, TYPE_FLAGS, \ TYPE_FLOAT, TYPE_DOUBLE, TYPE_STRING, \ TYPE_POINTER, TYPE_BOXED, TYPE_PARAM, TYPE_OBJECT, \ TYPE_PYOBJECT, TYPE_GTYPE, TYPE_STRV, TYPE_VARIANT G_MAXFLOAT = _gi.G_MAXFLOAT G_MAXDOUBLE = _gi.G_MAXDOUBLE G_MININT = _gi.G_MININT G_MAXINT = _gi.G_MAXINT G_MAXUINT = _gi.G_MAXUINT G_MINLONG = _gi.G_MINLONG G_MAXLONG = _gi.G_MAXLONG G_MAXULONG = _gi.G_MAXULONG if sys.version_info >= (3, 0): _basestring = str _long = int else: _basestring = basestring _long = long class Property(object): """Creates a new Property which when used in conjunction with GObject subclass will create a Python property accessor for the GObject ParamSpec. :param callable getter: getter to get the value of the property :param callable setter: setter to set the value of the property :param type type: type of property :param default: default value, must match the property type. :param str nick: short description :param str blurb: long description :param GObject.ParamFlags flags: parameter flags :keyword minimum: minimum allowed value (int, float, long only) :keyword maximum: maximum allowed value (int, float, long only) .. code-block:: python class MyObject(GObject.Object): prop = GObject.Property(type=str) obj = MyObject() obj.prop = 'value' obj.prop # now is 'value' The API is similar to the builtin :py:func:`property`: .. code-block:: python class AnotherObject(GObject.Object): value = 0 @GObject.Property def prop(self): 'Read only property.' return 1 @GObject.Property(type=int) def propInt(self): 'Read-write integer property.' return self.value @propInt.setter def propInt(self, value): self.value = value """ _type_from_pytype_lookup = { # Put long_ first in case long_ and int are the same so int clobbers long_ _long: TYPE_LONG, int: TYPE_INT, bool: TYPE_BOOLEAN, float: TYPE_DOUBLE, str: TYPE_STRING, object: TYPE_PYOBJECT, } _min_value_lookup = { TYPE_UINT: 0, TYPE_ULONG: 0, TYPE_UINT64: 0, # Remember that G_MINFLOAT and G_MINDOUBLE are something different. TYPE_FLOAT: -G_MAXFLOAT, TYPE_DOUBLE: -G_MAXDOUBLE, TYPE_INT: G_MININT, TYPE_LONG: G_MINLONG, TYPE_INT64: -2 ** 63, } _max_value_lookup = { TYPE_UINT: G_MAXUINT, TYPE_ULONG: G_MAXULONG, TYPE_INT64: 2 ** 63 - 1, TYPE_UINT64: 2 ** 64 - 1, TYPE_FLOAT: G_MAXFLOAT, TYPE_DOUBLE: G_MAXDOUBLE, TYPE_INT: G_MAXINT, TYPE_LONG: G_MAXLONG, } _default_lookup = { TYPE_INT: 0, TYPE_UINT: 0, TYPE_LONG: 0, TYPE_ULONG: 0, TYPE_INT64: 0, TYPE_UINT64: 0, TYPE_STRING: '', TYPE_FLOAT: 0.0, TYPE_DOUBLE: 0.0, } class __metaclass__(type): def __repr__(self): return "<class 'GObject.Property'>" def __init__(self, getter=None, setter=None, type=None, default=None, nick='', blurb='', flags=_gi.PARAM_READWRITE, minimum=None, maximum=None): self.name = None if type is None: type = object self.type = self._type_from_python(type) self.default = self._get_default(default) self._check_default() if not isinstance(nick, _basestring): raise TypeError("nick must be a string") self.nick = nick if not isinstance(blurb, _basestring): raise TypeError("blurb must be a string") self.blurb = blurb # Always clobber __doc__ with blurb even if blurb is empty because # we don't want the lengthy Property class documentation showing up # on instances. self.__doc__ = blurb self.flags = flags # Call after setting blurb for potential __doc__ usage. if getter and not setter: setter = self._readonly_setter elif setter and not getter: getter = self._writeonly_getter elif not setter and not getter: getter = self._default_getter setter = self._default_setter self.getter(getter) # do not call self.setter() here, as this defines the property name # already self.fset = setter if minimum is not None: if minimum < self._get_minimum(): raise TypeError( "Minimum for type %s cannot be lower than %d" % (self.type, self._get_minimum())) else: minimum = self._get_minimum() self.minimum = minimum if maximum is not None: if maximum > self._get_maximum(): raise TypeError( "Maximum for type %s cannot be higher than %d" % (self.type, self._get_maximum())) else: maximum = self._get_maximum() self.maximum = maximum self._exc = None def __repr__(self): return '<GObject Property %s (%s)>' % ( self.name or '(uninitialized)', _gi.type_name(self.type)) def __get__(self, instance, klass): if instance is None: return self self._exc = None # Simply return the result of fget directly, no need to go through GObject. # See: https://bugzilla.gnome.org/show_bug.cgi?id=723872 # We catch and print any exception occurring within the fget for compatibility # prior to the fast path addition from bug 723872, this should eventually # be removed and exceptions raised directly to the caller as in: # https://bugzilla.gnome.org/show_bug.cgi?id=575652 try: value = self.fget(instance) except Exception: traceback.print_exc() value = None if self._exc: exc = self._exc self._exc = None raise exc return value def __set__(self, instance, value): if instance is None: raise TypeError self._exc = None instance.set_property(self.name, value) if self._exc: exc = self._exc self._exc = None raise exc def __call__(self, fget): """Allows application of the getter along with init arguments.""" return self.getter(fget) def getter(self, fget): """Set the getter function to fget. For use as a decorator.""" if fget.__doc__: # Always clobber docstring and blurb with the getter docstring. self.blurb = fget.__doc__ self.__doc__ = fget.__doc__ self.fget = fget return self def setter(self, fset): """Set the setter function to fset. For use as a decorator.""" self.fset = fset # with a setter decorator, we must ignore the name of the method in # install_properties, as this does not need to be a valid property name # and does not define the property name. So set the name here. if not self.name: self.name = self.fget.__name__ return self def _type_from_python(self, type_): if type_ in self._type_from_pytype_lookup: return self._type_from_pytype_lookup[type_] elif (isinstance(type_, type) and issubclass(type_, (_gi.GObject, _gi.GEnum, _gi.GFlags, _gi.GBoxed, _gi.GInterface))): return type_.__gtype__ elif type_ in (TYPE_NONE, TYPE_INTERFACE, TYPE_CHAR, TYPE_UCHAR, TYPE_INT, TYPE_UINT, TYPE_BOOLEAN, TYPE_LONG, TYPE_ULONG, TYPE_INT64, TYPE_UINT64, TYPE_FLOAT, TYPE_DOUBLE, TYPE_POINTER, TYPE_BOXED, TYPE_PARAM, TYPE_OBJECT, TYPE_STRING, TYPE_PYOBJECT, TYPE_GTYPE, TYPE_STRV, TYPE_VARIANT): return type_ else: raise TypeError("Unsupported type: %r" % (type_,)) def _get_default(self, default): if default is not None: return default return self._default_lookup.get(self.type, None) def _check_default(self): ptype = self.type default = self.default if (ptype == TYPE_BOOLEAN and (default not in (True, False))): raise TypeError( "default must be True or False, not %r" % (default,)) elif ptype == TYPE_PYOBJECT: if default is not None: raise TypeError("object types does not have default values") elif ptype == TYPE_GTYPE: if default is not None: raise TypeError("GType types does not have default values") elif _gi.type_is_a(ptype, TYPE_ENUM): if default is None: raise TypeError("enum properties needs a default value") elif not _gi.type_is_a(default, ptype): raise TypeError("enum value %s must be an instance of %r" % (default, ptype)) elif _gi.type_is_a(ptype, TYPE_FLAGS): if not _gi.type_is_a(default, ptype): raise TypeError("flags value %s must be an instance of %r" % (default, ptype)) elif _gi.type_is_a(ptype, TYPE_STRV) and default is not None: if not isinstance(default, list): raise TypeError("Strv value %s must be a list" % repr(default)) for val in default: if type(val) not in (str, bytes): raise TypeError("Strv value %s must contain only strings" % str(default)) elif _gi.type_is_a(ptype, TYPE_VARIANT) and default is not None: if not hasattr(default, '__gtype__') or not _gi.type_is_a(default, TYPE_VARIANT): raise TypeError("variant value %s must be an instance of %r" % (default, ptype)) def _get_minimum(self): return self._min_value_lookup.get(self.type, None) def _get_maximum(self): return self._max_value_lookup.get(self.type, None) # # Getter and Setter # def _default_setter(self, instance, value): setattr(instance, '_property_helper_' + self.name, value) def _default_getter(self, instance): return getattr(instance, '_property_helper_' + self.name, self.default) def _readonly_setter(self, instance, value): self._exc = TypeError("%s property of %s is read-only" % ( self.name, type(instance).__name__)) def _writeonly_getter(self, instance): self._exc = TypeError("%s property of %s is write-only" % ( self.name, type(instance).__name__)) # # Public API # def get_pspec_args(self): ptype = self.type if ptype in (TYPE_INT, TYPE_UINT, TYPE_LONG, TYPE_ULONG, TYPE_INT64, TYPE_UINT64, TYPE_FLOAT, TYPE_DOUBLE): args = self.minimum, self.maximum, self.default elif (ptype == TYPE_STRING or ptype == TYPE_BOOLEAN or ptype.is_a(TYPE_ENUM) or ptype.is_a(TYPE_FLAGS) or ptype.is_a(TYPE_VARIANT)): args = (self.default,) elif ptype in (TYPE_PYOBJECT, TYPE_GTYPE): args = () elif ptype.is_a(TYPE_OBJECT) or ptype.is_a(TYPE_BOXED): args = () else: raise NotImplementedError(ptype) return (self.type, self.nick, self.blurb) + args + (self.flags,) def install_properties(cls): """ Scans the given class for instances of Property and merges them into the classes __gproperties__ dict if it exists or adds it if not. """ gproperties = cls.__dict__.get('__gproperties__', {}) props = [] for name, prop in cls.__dict__.items(): if isinstance(prop, Property): # not same as the built-in # if a property was defined with a decorator, it may already have # a name; if it was defined with an assignment (prop = Property(...)) # we set the property's name to the member name if not prop.name: prop.name = name # we will encounter the same property multiple times in case of # custom setter methods if prop.name in gproperties: if gproperties[prop.name] == prop.get_pspec_args(): continue raise ValueError('Property %s was already found in __gproperties__' % prop.name) gproperties[prop.name] = prop.get_pspec_args() props.append(prop) if not props: return cls.__gproperties__ = gproperties if 'do_get_property' in cls.__dict__ or 'do_set_property' in cls.__dict__: for prop in props: if prop.fget != prop._default_getter or prop.fset != prop._default_setter: raise TypeError( "GObject subclass %r defines do_get/set_property" " and it also uses a property with a custom setter" " or getter. This is not allowed" % (cls.__name__,)) def obj_get_property(self, pspec): name = pspec.name.replace('-', '_') return getattr(self, name, None) cls.do_get_property = obj_get_property def obj_set_property(self, pspec, value): name = pspec.name.replace('-', '_') prop = getattr(cls, name, None) if prop: prop.fset(self, value) cls.do_set_property = obj_set_property