2 Creates functions at import time that are mixed into the
3 Accessibility.Accessible base class to make it more Pythonic.
5 Based on public domain code originally posted at
6 U{http://wwwx.cs.unc.edu/~parente/cgi-bin/RuntimeClassMixins}.
8 @var _ACCESSIBLE_CACHE: Pairs hash values for accessible objects to
9 L{_PropertyCache} bags. We do not store actual accessibles in the dictionary
10 because that would +1 their ref counts and cause __del__ to never be called
11 which is the method we rely on to properly invalidate cache entries.
12 @type _ACCESSIBLE_CACHE: dictionary
13 @var _CACHE_LEVEL: Current level of caching enabled. Checked dynamically by
15 @type _CACHE_LEVEL: integer
17 @author: Peter Parente
18 @organization: IBM Corporation
19 @copyright: Copyright (c) 2005, 2007 IBM Corporation
22 This library is free software; you can redistribute it and/or
23 modify it under the terms of the GNU Library General Public
24 License as published by the Free Software Foundation; either
25 version 2 of the License, or (at your option) any later version.
27 This library is distributed in the hope that it will be useful,
28 but WITHOUT ANY WARRANTY; without even the implied warranty of
29 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
30 Library General Public License for more details.
32 You should have received a copy of the GNU Library General Public
33 License along with this library; if not, write to the
34 Free Software Foundation, Inc., 59 Temple Place - Suite 330,
35 Boston, MA 02111-1307, USA.
37 Portions of this code originally licensed and copyright (c) 2005, 2007
38 IBM Corporation under the BSD license, available at
39 U{http://www.opensource.org/licenses/bsd-license.php}
49 _ACCESSIBLE_CACHE = {}
52 class _PropertyCache(object):
53 '''Fixed-size bag class for holding cached values.'''
54 __slots__ = ('name', 'description', 'rolename')
58 Gets the current level of caching.
60 @return: None indicating no caching is in effect.
61 L{constants.CACHE_INTERFACES} indicating all interface query results are
62 cached. L{constants.CACHE_PROPERTIES} indicating all basic accessible
63 properties are cached.
68 def setCacheLevel(val):
70 Sets the desired level of caching for all accessible objects created after
71 this function is invoked. Immediately clears the current accessible cache.
73 @param val: None indicating no caching is in effect.
74 L{constants.CACHE_INTERFACES} indicating all interface query results are
75 cached. L{constants.CACHE_PROPERTIES} indicating all basic accessible
76 properties are cached plus all interfaces.
80 if _CACHE_LEVEL != val:
81 # empty our accessible cache
82 _ACCESSIBLE_CACHE.clear()
83 # need to register/unregister for listeners depending on caching level
84 if val == constants.CACHE_PROPERTIES:
85 r = registry.Registry()
86 r.registerEventListener(_updateCache, *constants.CACHE_EVENTS)
88 r = registry.Registry()
89 r.deregisterEventListener(_updateCache, *constants.CACHE_EVENTS)
93 '''Forces a clear of the entire cache.'''
94 _ACCESSIBLE_CACHE.clear()
96 def printCache(template='%s'):
98 Prints the contents of the cache.
100 @param template: Format string to use when printing
101 @type template: string
103 print template % _ACCESSIBLE_CACHE
105 def _updateCache(event):
107 Invalidates an entry in the cache when the hash value of a source of an event
108 matches an entry in the cache.
110 @param event: One of the L{constants.CACHE_EVENTS} event types
111 @type event: L{event.Event}
114 del _ACCESSIBLE_CACHE[hash(event.source)]
118 def _makeQuery(interface):
120 Builds a function querying to a specific interface and returns it.
122 @param interface: Class representing an AT-SPI interface
123 @type interface: class
124 @return: Function querying to the given interface
129 Queries an object for another interface.
131 @return: An object with the desired interface
133 @raise NotImplementedError: When the desired interface is not supported
135 iid = utils.getInterfaceIID(interface)
137 i = self._icache[iid]
139 # interface not cached
141 except AttributeError:
142 # determine if we're caching
143 caching = _CACHE_LEVEL is not None
145 # initialize the cache
148 # check if our cached result was an interface, or an indicator that the
149 # interface is not supported
151 raise NotImplementedError
156 # do the query remotely
157 i = self.queryInterface(iid)
159 i = i._narrow(interface)
163 # cache that the interface is not supported
165 self._icache[iid] = None
166 raise NotImplementedError
169 # cache the narrow'ed result, but only if we're caching for this object
170 self._icache[iid] = i
175 def _makeExceptionHandler(func):
177 Builds a function calling the one it wraps in try/except statements catching
180 @return: Function calling the method being wrapped
183 def _inner(self, *args, **kwargs):
185 # try calling the original func
186 rv = func(self, *args, **kwargs)
187 if isinstance(rv, ORBit.CORBA.Object): rv.ref()
189 except ORBit.CORBA.NO_IMPLEMENT, e:
190 # raise Python exception
191 raise NotImplementedError(e)
192 except ORBit.CORBA.Exception, e:
193 # raise Python exception
197 def _mixInterfaces(cls, interfaces):
199 Add methods for querying to interfaces other than the base accessible to
202 @param cls: Class to mix interface methods into
204 @param interfaces: Classes representing AT-SPI interfaces
205 @type interfaces: list of class
207 # create functions in this module for all interfaces listed in constants
208 for interface in interfaces:
209 # build name of converter from the name of the interface
210 name = 'query%s' % utils.getInterfaceName(interface)
211 # build a function that queries to the given interface
212 func = _makeQuery(interface)
213 # build a new method that is a clone of the original function
214 method = new.function(func.func_code, func.func_globals, name,
215 func.func_defaults, func.func_closure)
216 # add the method to the given class
217 setattr(cls, name, method)
219 def _mixExceptions(cls):
221 Wraps all methods and properties in a class with handlers for CORBA
224 @param cls: Class to mix interface methods into
227 # get a method type as a reference from a known method
228 method_type = Accessibility.Accessible.getRole.__class__
229 # loop over all names in the new class
230 for name in cls.__dict__.keys():
231 obj = cls.__dict__[name]
232 # check if we're on a protected or private method
233 if name.startswith('_'):
235 # check if we're on a method
236 elif isinstance(obj, method_type):
237 # wrap the function in an exception handler
238 method = _makeExceptionHandler(obj)
239 # add the wrapped function to the class
240 setattr(cls, name, method)
241 # check if we're on a property
242 elif isinstance(obj, property):
243 # wrap the getters and setters
245 func = getattr(cls, obj.fget.__name__)
246 getter = _makeExceptionHandler(func)
250 func = getattr(cls, obj.fset.__name__)
251 setter = _makeExceptionHandler(func)
254 setattr(cls, name, property(getter, setter))
256 def _mixClass(cls, new_cls, ignore=[]):
258 Adds the methods in new_cls to cls. After mixing, all instances of cls will
259 have the new methods. If there is a method name clash, the method already in
260 cls will be prefixed with '_mix_' before the new method of the same name is
263 @note: _ is not the prefix because if you wind up with __ in front of a
264 variable, it becomes private and mangled when an instance is created.
265 Difficult to invoke from the mixin class.
267 @param cls: Existing class to mix features into
269 @param new_cls: Class containing features to add
271 @param ignore: Ignore these methods from the mixin
272 @type ignore: iterable
274 # loop over all names in the new class
275 for name, func in new_cls.__dict__.items():
278 if isinstance(func, types.FunctionType):
279 # build a new function that is a clone of the one from new_cls
280 method = new.function(func.func_code, func.func_globals, name,
281 func.func_defaults, func.func_closure)
283 # check if a method of the same name already exists in the target
284 old_method = getattr(cls, name)
285 except AttributeError:
288 # rename the old method so we can still call it if need be
289 setattr(cls, '_mix_'+name, old_method)
290 # add the clone to cls
291 setattr(cls, name, method)
292 elif isinstance(func, staticmethod):
294 # check if a method of the same name already exists in the target
295 old_method = getattr(cls, name)
296 except AttributeError:
299 # rename the old method so we can still call it if need be
300 setattr(cls, '_mix_'+name, old_method)
301 setattr(cls, name, func)
302 elif isinstance(func, property):
304 # check if a method of the same name already exists in the target
305 old_prop = getattr(cls, name)
306 except AttributeError:
309 # IMPORTANT: We save the old property before overwriting it, even
310 # though we never end up calling the old prop from our mixin class.
311 # If we don't save the old one, we seem to introduce a Python ref count
312 # problem where the property get/set methods disappear before we can
313 # use them at a later time. This is a minor waste of memory because
314 # a property is a class object and we only overwrite a few of them.
315 setattr(cls, '_mix_'+name, old_prop)
316 setattr(cls, name, func)
318 class _AccessibleMixin(object):
320 Defines methods to be added to the Accessibility.Accessible class. The
321 features defined here will be added to the Accessible class at run time so
322 that all instances of Accessible have them (i.e. there is no need to
323 explicitly wrap an Accessible in this class or derive a new class from it.)
325 @cvar SLOTTED_CLASSES: Mapping from raw Accessibility class to a new class
326 having the slots defined by L{SLOTS}
327 @type SLOTTED_CLASSES: dictionary
328 @cvar SLOTS: All slots to create
332 SLOTS = ('_icache', 'user_data')
336 Creates a new class mimicking the one requested, but with extra named
337 defined in __slots__. The _cache attribute is used internally for interface
338 caching. The user_data field may be populated with whatever data structure
339 a client wishes to use. Neither is set to a default value by default.
341 Note that we can't simply mix __slots__ into this class because __slots__
342 has an effect only at class creation time.
344 We also do not completely obliterate __slots__ to allow __dict__ to be
345 instantiated as normal as reducing the initialization and memory overhead
346 of the millions of accessible objects that are created is a good thing for
349 @param cls: Accessibility object class
351 @return: Instance of the new class
355 # check if we've already created a new version of the class
356 new_cls = _AccessibleMixin.SLOTTED_CLASSES[cls]
358 # create the new class if not
359 new_cls = type(cls.__name__, (cls,),
360 {'__module__' : cls.__module__,
361 '__slots__' : _AccessibleMixin.SLOTS})
362 _AccessibleMixin.SLOTTED_CLASSES[cls] = new_cls
363 obj = cls._mix___new__(new_cls)
368 Decrements the reference count on the accessible object when there are no
369 Python references to this object. This provides automatic reference
370 counting for AT-SPI objects. Also removes this object from the cache if
371 we're caching properties.
374 del _ACCESSIBLE_CACHE[hash(self)]
384 Iterator that yields one accessible child per iteration. If an exception is
385 encountered, None is yielded instead.
387 @return: A child accessible
388 @rtype: Accessibility.Accessible
390 for i in xrange(self.childCount):
392 yield self.getChildAtIndex(i)
398 Gets a human readable representation of the accessible.
400 @return: Role and name information for the accessible
404 return '[%s | %s]' % (self.getRoleName(), self.name)
408 def __nonzero__(self):
410 @return: True, always
415 def __getitem__(self, index):
417 Thin wrapper around getChildAtIndex.
419 @param index: Index of desired child
421 @return: Accessible child
422 @rtype: Accessibility.Accessible
431 return self.getChildAtIndex(index)
435 Thin wrapper around childCount.
437 @return: Number of child accessibles
440 return self.childCount
444 Gets the name of the accessible from the cache if it is available,
445 otherwise, fetches it remotely.
447 @return: Name of the accessible
450 if _CACHE_LEVEL != constants.CACHE_PROPERTIES:
451 return self._get_name()
453 cache = _ACCESSIBLE_CACHE
458 # no cached info for this object yet
459 name = self._get_name()
460 pc = _PropertyCache()
464 except AttributeError:
465 # no cached name for this object yet
466 name = self._get_name()
470 name = property(_get_name, Accessibility.Accessible._set_name)
472 def getRoleName(self):
474 Gets the unlocalized role name of the accessible from the cache if it is
475 available, otherwise, fetches it remotely.
477 @return: Role name of the accessible
480 if _CACHE_LEVEL != constants.CACHE_PROPERTIES:
481 return self._mix_getRoleName()
483 cache = _ACCESSIBLE_CACHE
486 return cache[h].rolename
488 # no cached info for this object yet
489 rolename = self._mix_getRoleName()
490 pc = _PropertyCache()
491 pc.rolename = rolename
494 except AttributeError, e:
495 # no cached name for this object yet
496 rolename = self._mix_getRoleName()
497 cache[h].rolename = rolename
500 def _get_description(self):
502 Gets the description of the accessible from the cache if it is available,
503 otherwise, fetches it remotely.
505 @return: Description of the accessible
508 if _CACHE_LEVEL != constants.CACHE_PROPERTIES:
509 return self._get_description()
511 cache = _ACCESSIBLE_CACHE
514 return cache[h].description
516 # no cached info for this object yet
517 description = self._get_description()
518 pc = _PropertyCache()
519 pc.description = description
522 except AttributeError:
523 # no cached name for this object yet
524 description = self._get_description()
525 cache[h].description = description
528 description = property(_get_description,
529 Accessibility.Accessible._set_description)
531 def getIndexInParent(self):
533 Gets the index of this accessible in its parent. Uses the implementation of
534 this method provided by the Accessibility.Accessible object, but checks the
535 bound of the value to ensure it is not outside the range of childCount
536 reported by this accessible's parent.
538 @return: Index of this accessible in its parent
541 i = self._mix_getIndexInParent()
543 # correct for out-of-bounds index reporting
544 return min(self.parent.childCount-1, i)
545 except AttributeError:
546 # return sentinel if there is no parent
549 def getApplication(self):
551 Gets the most-parent accessible (the application) of this accessible. Tries
552 using the getApplication method introduced in AT-SPI 1.7.0 first before
553 resorting to traversing parent links.
555 @warning: Cycles involving more than the previously traversed accessible
556 are not detected by this code.
557 @return: Application object
558 @rtype: Accessibility.Application
561 return self._mix_getApplication()
562 except AttributeError:
566 while curr.parent is not None and (not curr.parent == curr):
571 # return None if the application isn't reachable for any reason
574 class _RelationMixin(object):
576 Defines methods to be added to the Relation class. At this time it only
577 overrides L{_RelationMixin.getTarget} which by the IDL's standard is
578 supposed to return CORBA.Objects but we expect LAccessibility.Accessible
579 objects (see http://bugzilla.gnome.org/show_bug.cgi?id=435833).
580 This seems to be a problem especially with the Java implementation of CORBA.
582 def getTarget(self, index):
584 Overrides the regular getTarget to return Accessibility.Accessible
587 @return: The 'nth' target of this Relation.
588 @rtype: Accessibility.Accessible
590 target = self._mix_getTarget(index)
592 return target._narrow(Accessibility.Accessible)
594 # 1. mix the exception handlers into all queryable interfaces
595 map(_mixExceptions, constants.ALL_INTERFACES)
596 # 2. mix the exception handlers into other Accessibility objects
597 map(_mixExceptions, [Accessibility.StateSet])
598 # 3. mix the new functions
599 _mixClass(Accessibility.Accessible, _AccessibleMixin,
600 ['_get_name', '_get_description'])
601 # 4. mix queryInterface convenience methods
602 _mixInterfaces(Accessibility.Accessible, constants.ALL_INTERFACES)
603 # 5. mix Relation class
604 _mixClass(Accessibility.Relation, _RelationMixin)