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)]
120 Builds a function querying to a specific interface and returns it.
122 @param iid: Interface identifier to use when querying
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
136 i = self._icache[iid]
138 # interface not cached
141 # determine if we're caching
142 caching = _CACHE_LEVEL is not None
144 # initialize the cache
147 # check if our cached result was an interface, or an indicator that the
148 # interface is not supported
150 raise NotImplementedError
155 # do the query remotely
156 i = self.queryInterface(iid)
160 # cache that the interface is not supported
162 self._icache[iid] = None
163 raise NotImplementedError
165 # not needed according to ORBit2 spec, but makes Java queries work
166 # more reliably according to Orca experience
167 i = i._narrow(i.__class__)
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 return func(self, *args, **kwargs)
187 except ORBit.CORBA.NO_IMPLEMENT, e:
188 # raise Python exception
189 raise NotImplementedError(e)
190 except ORBit.CORBA.Exception, e:
191 # raise Python exception
195 def _mixInterfaces(cls, interfaces):
197 Add methods for querying to interfaces other than the base accessible to
200 @param cls: Class to mix interface methods into
202 @param interfaces: Classes representing AT-SPI interfaces
203 @type interfaces: list of class
205 # create functions in this module for all interfaces listed in constants
206 for interface in interfaces:
207 # build name of converter from the name of the interface
208 name = 'query%s' % utils.getInterfaceName(interface)
209 # build a function that queries to the given interface
210 func = _makeQuery(utils.getInterfaceIID(interface))
211 # build a new method that is a clone of the original function
212 method = new.function(func.func_code, func.func_globals, name,
213 func.func_defaults, func.func_closure)
214 # add the method to the given class
215 setattr(cls, name, method)
217 def _mixExceptions(cls):
219 Wraps all methods and properties in a class with handlers for CORBA
222 @param cls: Class to mix interface methods into
225 # get a method type as a reference from a known method
226 method_type = Accessibility.Accessible.getRole.__class__
227 # loop over all names in the new class
228 for name in cls.__dict__.keys():
229 obj = cls.__dict__[name]
230 # check if we're on a protected or private method
231 if name.startswith('_'):
233 # check if we're on a method
234 elif isinstance(obj, method_type):
235 # wrap the function in an exception handler
236 method = _makeExceptionHandler(obj)
237 # add the wrapped function to the class
238 setattr(cls, name, method)
239 # check if we're on a property
240 elif isinstance(obj, property):
241 # wrap the getters and setters
243 func = getattr(cls, obj.fget.__name__)
244 getter = _makeExceptionHandler(func)
248 func = getattr(cls, obj.fset.__name__)
249 setter = _makeExceptionHandler(func)
252 setattr(cls, name, property(getter, setter))
254 def _mixClass(cls, new_cls, ignore=[]):
256 Adds the methods in new_cls to cls. After mixing, all instances of cls will
257 have the new methods. If there is a method name clash, the method already in
258 cls will be prefixed with '_mix_' before the new method of the same name is
261 @note: _ is not the prefix because if you wind up with __ in front of a
262 variable, it becomes private and mangled when an instance is created.
263 Difficult to invoke from the mixin class.
265 @param cls: Existing class to mix features into
267 @param new_cls: Class containing features to add
269 @param ignore: Ignore these methods from the mixin
270 @type ignore: iterable
272 # loop over all names in the new class
273 for name, func in new_cls.__dict__.items():
276 if isinstance(func, types.FunctionType):
277 # build a new function that is a clone of the one from new_cls
278 method = new.function(func.func_code, func.func_globals, name,
279 func.func_defaults, func.func_closure)
281 # check if a method of the same name already exists in the target
282 old_method = getattr(cls, name)
283 except AttributeError:
286 # rename the old method so we can still call it if need be
287 setattr(cls, '_mix_'+name, old_method)
288 # add the clone to cls
289 setattr(cls, name, method)
290 elif isinstance(func, staticmethod):
292 # check if a method of the same name already exists in the target
293 old_method = getattr(cls, name)
294 except AttributeError:
297 # rename the old method so we can still call it if need be
298 setattr(cls, '_mix_'+name, old_method)
299 setattr(cls, name, func)
300 elif isinstance(func, property):
302 # check if a method of the same name already exists in the target
303 old_prop = getattr(cls, name)
304 except AttributeError:
307 # IMPORTANT: We save the old property before overwriting it, even
308 # though we never end up calling the old prop from our mixin class.
309 # If we don't save the old one, we seem to introduce a Python ref count
310 # problem where the property get/set methods disappear before we can
311 # use them at a later time. This is a minor waste of memory because
312 # a property is a class object and we only overwrite a few of them.
313 setattr(cls, '_mix_'+name, old_prop)
314 setattr(cls, name, func)
316 class _AccessibleMixin(object):
318 Defines methods to be added to the Accessibility.Accessible class. The
319 features defined here will be added to the Accessible class at run time so
320 that all instances of Accessible have them (i.e. there is no need to
321 explicitly wrap an Accessible in this class or derive a new class from it.)
323 @cvar SLOTTED_CLASSES: Mapping from raw Accessibility class to a new class
324 having the slots defined by L{SLOTS}
325 @type SLOTTED_CLASSES: dictionary
326 @cvar SLOTS: All slots to create
334 Creates a new class mimicking the one requested, but with an extra _cache
335 attribute set in the __slots__ tuple. This field can be set to a dictionary
336 or other object to allow caching to occur.
338 Note that we can't simply mix __slots__ into this class because __slots__
339 has an effect only at class creation time.
341 @param cls: Accessibility object class
343 @return: Instance of the new class
347 # check if we've already created a new version of the class
348 new_cls = _AccessibleMixin.SLOTTED_CLASSES[cls]
350 # create the new class if not
351 new_cls = type(cls.__name__, (cls,),
352 {'__module__' : cls.__module__,
353 '__slots__' : _AccessibleMixin.SLOTS})
354 _AccessibleMixin.SLOTTED_CLASSES[cls] = new_cls
355 obj = cls._mix___new__(new_cls)
356 # don't create the interface cache until we need it
362 Decrements the reference count on the accessible object when there are no
363 Python references to this object. This provides automatic reference
364 counting for AT-SPI objects. Also removes this object from the cache if
365 we're caching properties.
368 del _ACCESSIBLE_CACHE[hash(self)]
378 Iterator that yields one accessible child per iteration. If an exception is
379 encountered, None is yielded instead.
381 @return: A child accessible
382 @rtype: Accessibility.Accessible
384 for i in xrange(self.childCount):
386 yield self.getChildAtIndex(i)
392 Gets a human readable representation of the accessible.
394 @return: Role and name information for the accessible
398 return '[%s | %s]' % (self.getRoleName(), self.name)
402 def __nonzero__(self):
404 @return: True, always
409 def __getitem__(self, index):
411 Thin wrapper around getChildAtIndex.
413 @param index: Index of desired child
415 @return: Accessible child
416 @rtype: Accessibility.Accessible
418 return self.getChildAtIndex(index)
422 Thin wrapper around childCount.
424 @return: Number of child accessibles
427 return self.childCount
431 Gets the name of the accessible from the cache if it is available,
432 otherwise, fetches it remotely.
434 @return: Name of the accessible
437 if _CACHE_LEVEL != constants.CACHE_PROPERTIES:
438 return self._get_name()
440 cache = _ACCESSIBLE_CACHE
445 # no cached info for this object yet
446 name = self._get_name()
447 pc = _PropertyCache()
451 except AttributeError:
452 # no cached name for this object yet
453 name = self._get_name()
457 name = property(_get_name, Accessibility.Accessible._set_name)
459 def getRoleName(self):
461 Gets the unlocalized role name of the accessible from the cache if it is
462 available, otherwise, fetches it remotely.
464 @return: Role name of the accessible
467 if _CACHE_LEVEL != constants.CACHE_PROPERTIES:
468 return self._mix_getRoleName()
470 cache = _ACCESSIBLE_CACHE
473 return cache[h].rolename
475 # no cached info for this object yet
476 rolename = self._mix_getRoleName()
477 pc = _PropertyCache()
478 pc.rolename = rolename
481 except AttributeError, e:
482 # no cached name for this object yet
483 rolename = self._mix_getRoleName()
484 cache[h].rolename = rolename
487 def _get_description(self):
489 Gets the description of the accessible from the cache if it is available,
490 otherwise, fetches it remotely.
492 @return: Description of the accessible
495 if _CACHE_LEVEL != constants.CACHE_PROPERTIES:
496 return self._get_description()
498 cache = _ACCESSIBLE_CACHE
501 return cache[h].description
503 # no cached info for this object yet
504 description = self._get_description()
505 pc = _PropertyCache()
506 pc.description = description
509 except AttributeError:
510 # no cached name for this object yet
511 description = self._get_description()
512 cache[h].description = description
515 description = property(_get_description,
516 Accessibility.Accessible._set_description)
518 def getIndexInParent(self):
520 Gets the index of this accessible in its parent. Uses the implementation of
521 this method provided by the Accessibility.Accessible object, but checks the
522 bound of the value to ensure it is not outside the range of childCount
523 reported by this accessible's parent.
525 @return: Index of this accessible in its parent
528 i = self._mix_getIndexInParent()
530 # correct for out-of-bounds index reporting
531 return min(self.parent.childCount-1, i)
532 except AttributeError:
533 # return sentinel if there is no parent
536 def getApplication(self):
538 Gets the most-parent accessible (the application) of this accessible. Tries
539 using the getApplication method introduced in AT-SPI 1.7.0 first before
540 resorting to traversing parent links.
542 @warning: Cycles involving more than the previously traversed accessible
543 are not detected by this code.
544 @return: Application object
545 @rtype: Accessibility.Application
548 return self._mix_getApplication()
549 except AttributeError:
553 while curr.parent is not None and (not curr.parent == curr):
558 # return None if the application isn't reachable for any reason
561 # 1. mix the exception handlers into all queryable interfaces
562 map(_mixExceptions, constants.ALL_INTERFACES)
563 # 2. mix the exception handlers into other Accessibility objects
564 map(_mixExceptions, [Accessibility.StateSet])
565 # 3. mix the new functions
566 _mixClass(Accessibility.Accessible, _AccessibleMixin,
567 ['_get_name', '_get_description'])
568 # 4. mix queryInterface convenience methods
569 _mixInterfaces(Accessibility.Accessible, constants.ALL_INTERFACES)