pyx/attr.py

   1 # -*- coding: ISO-8859-1 -*-
   2 #
   3 #
   4 # Copyright (C) 2003-2004 Jörg Lehmann <joergl@users.sourceforge.net>
   5 # Copyright (C) 2003-2004 Michael Schindler <m-schindler@users.sourceforge.net>
   6 # Copyright (C) 2003-2004 André Wobst <wobsta@users.sourceforge.net>
   7 #
   8 # This file is part of PyX (http://pyx.sourceforge.net/).
   9 #
  10 # PyX is free software; you can redistribute it and/or modify
  11 # it under the terms of the GNU General Public License as published by
  12 # the Free Software Foundation; either version 2 of the License, or
  13 # (at your option) any later version.
  14 #
  15 # PyX is distributed in the hope that it will be useful,
  16 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 # GNU General Public License for more details.
  19 #
  20 # You should have received a copy of the GNU General Public License
  21 # along with PyX; if not, write to the Free Software
  22 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
  23
  24 # check for an isinstance which accepts both a class and a sequence of classes
  25 # as second argument and emulate this behaviour if necessary
  26 try:
  27     isinstance(1, (int, float))
  28 except TypeError:
  29     # workaround for Python 2.1
  30     _isinstance = isinstance
  31     def isinstance(instance, clsarg):
  32         import types
  33         if _isinstance(clsarg, types.ClassType):
  34             return _isinstance(instance, clsarg)
  35         for cls in clsarg:
  36             if _isinstance(instance, cls):
  37                 return 1
  38         return 0
  39
  40 #
  41 # some helper functions for the attribute handling
  42 #
  43
  44 def mergeattrs(attrs):
  45     """perform merging of the attribute list attrs as defined by the
  46     merge methods of the attributes"""
  47     newattrs = []
  48     for a in attrs:
  49         # XXX Do we really need this test?
  50         if isinstance(a, attr):
  51             newattrs = a.merge(newattrs)
  52         else:
  53             raise TypeError("only instances of class attr.attr are allowed")
  54     return newattrs
  55
  56
  57 def getattrs(attrs, getclasses):
  58     """return all attributes in the attribute list attrs, which are
  59     instances of one of the classes in getclasses"""
  60     return [attr for attr in attrs if isinstance(attr, tuple(getclasses))]
  61
  62
  63 def checkattrs(attrs, allowedclasses):
  64     """check whether only attributes which are instances of classes in
  65     allowedclasses are present in the attribute list attrs; if not it
  66     raises a TypeError"""
  67     if len(attrs) != len(getattrs(attrs, allowedclasses)):
  68         for attr1, attr2 in zip(attrs, getattrs(attrs, allowedclasses)):
  69             if attr1 is not attr2:
  70                 raise TypeError("instance %r not allowed" % attr1)
  71         else:
  72             raise TypeError("instance %r not allowed" % attrs[len(getattrs(attrs, allowedclasses))])
  73
  74 #
  75 # attr class and simple descendants
  76 #
  77
  78 class attr:
  79
  80     """ attr is the base class of all attributes, i.e., colors, decorators,
  81     styles, text attributes and trafos"""
  82
  83     def merge(self, attrs):
  84         """merge self into list of attrs
  85
  86         self may either be appended to attrs or inserted at a proper position
  87         immediately before a dependent attribute. Attributes of the same type
  88         should be removed, if redundant. Note that it is safe to modify
  89         attrs."""
  90
  91         attrs.append(self)
  92         return attrs
  93
  94
  95 class exclusiveattr(attr):
  96
  97     """an attribute which swallows all but the last of the same type (specified
  98     by the exlusiveclass argument to the constructor) in an attribute list"""
  99
 100     def __init__(self, exclusiveclass):
 101         self.exclusiveclass = exclusiveclass
 102
 103     def merge(self, attrs):
 104         attrs = [attr for attr in attrs if not isinstance(attr, self.exclusiveclass)]
 105         attrs.append(self)
 106         return attrs
 107
 108
 109 class sortbeforeattr(attr):
 110
 111     """an attribute which places itself previous to all attributes given
 112     in the beforetheclasses argument to the constructor"""
 113
 114     def __init__(self, beforetheclasses):
 115         self.beforetheclasses = tuple(beforetheclasses)
 116
 117     def merge(self, attrs):
 118         first = 1
 119         result = []
 120         for attr in attrs:
 121             if first and isinstance(attr, self.beforetheclasses):
 122                 result.append(self)
 123                 first = 0
 124             result.append(attr)
 125         if first:
 126             result.append(self)
 127         return result
 128
 129
 130 class sortbeforeexclusiveattr(attr):
 131
 132     """an attribute which swallows all but the last of the same type (specified
 133     by the exlusiveclass argument to the constructor) in an attribute list and
 134     places itself previous to all attributes given in the beforetheclasses
 135     argument to the constructor"""
 136
 137     def __init__(self, exclusiveclass, beforetheclasses):
 138         self.exclusiveclass = exclusiveclass
 139         self.beforetheclasses = tuple(beforetheclasses)
 140
 141     def merge(self, attrs):
 142         first = 1
 143         result = []
 144         for attr in attrs:
 145             if first and isinstance(attr, self.beforetheclasses):
 146                 result.append(self)
 147                 first = 0
 148             if not isinstance(attr, self.exclusiveclass):
 149                 result.append(attr)
 150         if first:
 151             result.append(self)
 152         return result
 153
 154
 155 class clearclass(attr):
 156
 157     """a special attribute which allows to remove all predecessing attributes of
 158     the same type in an attribute list"""
 159
 160     def __init__(self, clearclass):
 161         self.clearclass = clearclass
 162
 163     def merge(self, attrs):
 164         return [attr for attr in attrs if not isinstance(attr, self.clearclass)]
 165
 166
 167 class _clear(attr):
 168
 169     """a special attribute which removes all predecessing attributes
 170     in an attribute list"""
 171
 172     def merge(self, attrs):
 173         return []
 174
 175 # we define the attribute "clear", an instance of "_clear",
 176 # which can be used to remove all predecessing attributes
 177 # in an attribute list
 178
 179 clear = _clear()
 180
 181 #
 182 # changeable attrs
 183 #
 184
 185 def selectattrs(attrs, index, total):
 186     """performs select calls for all changeable attributes and
 187     returns the resulting attribute list
 188     - attrs should be a list containing attributes and changeable
 189       attributes
 190     - index should be an unsigned integer
 191     - total should be a positive number
 192     - valid sections fullfill 0<=index<total
 193     - returns None, when attrs is None
 194     - returns None, when a changeable attribute returns None"""
 195     if attrs is None:
 196         return None
 197     result = []
 198     for a in attrs:
 199         if isinstance(a, changeattr):
 200             select = a.select(index, total)
 201             if select is None:
 202                 return None
 203             result.append(select)
 204         else:
 205             result.append(a)
 206     return result
 207
 208
 209 def selectattr(attr, index, total):
 210     """as select, but for a single attribute"""
 211     if isinstance(attr, changeattr):
 212         select = attr.select(index, total)
 213         if select is None:
 214             return None
 215         return select
 216     else:
 217         return attr
 218
 219
 220 class changeattr:
 221
 222     """changeattr is the base class of all changeable attributes"""
 223
 224     def select(self, index, total):
 225         """returns an attribute for a given index out of a total number
 226         if attributes to be provided
 227         - index should be an unsigned integer
 228         - total should be a positive number
 229         - valid selections fullfill 0 <= index < total
 230         - the select method may raise a ValueError, when the
 231           changeable attribute does not allow for a requested
 232           selection"""
 233
 234         raise RuntimeError("not implemented")
 235
 236
 237 class changelist(changeattr):
 238
 239     """a changeable attribute over a list of attribute choises"""
 240
 241     def __init__(self, attrs, cyclic=1):
 242         """initializes the instance
 243         - attrs is a list of attributes to cycle
 244         - If cyclic is set, we restart from the beginning after
 245           the end of the list has been reached; otherwise
 246           selecting beyond the end of the list returns None"""
 247         self.attrs = attrs
 248         self.cyclic = cyclic
 249
 250     def select(self, index, total):
 251         if self.cyclic:
 252             return self.attrs[index % len(self.attrs)]
 253         elif index < len(self.attrs):
 254             return self.attrs[index]
 255         else:
 256             return None
 257