Add CssListProperty.

kivy/properties.pyx

@@ -169,7 +169,7 @@ __all__ = ('Property',
            'NumericProperty', 'StringProperty', 'ListProperty',
            'ObjectProperty', 'BooleanProperty', 'BoundedNumericProperty',
            'OptionProperty', 'ReferenceListProperty', 'AliasProperty',
-           'DictProperty')
+           'DictProperty', 'CssListProperty')
 
 from weakref import ref
 
@@ -177,6 +177,8 @@ cdef float g_dpi = -1
 cdef float g_density = -1
 cdef float g_fontscale = -1
 
+NUMERIC_FORMATS = ('in', 'px', 'dp', 'sp', 'pt', 'cm', 'mm')
+
 cpdef float dpi2px(value, ext):
     # 1in = 2.54cm = 25.4mm = 72pt = 12pc
     global g_dpi, g_density, g_fontscale
@@ -201,7 +203,6 @@ cpdef float dpi2px(value, ext):
     elif ext == 'mm':
         return rv * g_dpi / 25.4
 
-
 cdef class Property:
     '''Base class for building more complex properties.
 
@@ -1081,3 +1082,84 @@ cdef class AliasProperty(Property):
         if obj.__storage[self._name]['setter'](obj, value):
             obj.__storage[self._name]['value'] = self.get(obj)
             self.dispatch(obj)
+
+cdef class CssListProperty(Property):
+    '''A ListProperty that mimics the css way of defining numeric values such
+    as padding, margin, etc.
+
+    Accepts a list of 1, 2 or 4 Numeric arguments or a single Numeric argument.
+
+    CssListProperty([1]) represents [1, 1, 1, 1].
+    CssListProperty([1, 2]) represents [1, 1, 2, 2].
+    CssListProperty(['1px', (2, 'px'), 3, 4.0]) represents [1, 2, 3, 4.0].
+    CssListProperty(5) represents [5, 5, 5, 5].
+
+    .. versionadded:: 1.7.0
+    '''
+
+    def __init__(self, defaultvalue=None, **kw):
+        defaultvalue = defaultvalue or [0, 0, 0, 0]
+        super(CssListProperty, self).__init__(defaultvalue, **kw)
+
+    cdef check(self, EventDispatcher obj, value):
+        if Property.check(self, obj, value):
+            return True
+        if type(value) not in (int, float, long, list, tuple, str):
+            err = '%s.%s accepts only int/float/long/list/tuple/str (got %r)'
+            raise ValueError(err % (obj.__class__.__name__, self.name, value))
+
+    cdef convert(self, EventDispatcher obj, x):
+        if x is None:
+            return x
+
+        tp = type(x)
+        if tp is list or tp is tuple:
+            l = len(x)
+            if l == 1:
+                y = self._convert_numeric(obj, x[0])
+                return [y, y, y, y]
+            elif l == 2:
+                if x[1] in NUMERIC_FORMATS:
+                    # defaultvalue is a list or tuple representing one value
+                    y = self._convert_numeric(obj, x)
+                    return [y, y, y, y]
+                else:
+                    y = self._convert_numeric(obj, x[0])
+                    z = self._convert_numeric(obj, x[1])
+                    return [y, y, z, z]
+            elif l == 4:
+                return [self._convert_numeric(obj, y) for y in x]
+            else:
+                err = '%s.%s must have 1, 2 or 4 components (got %r)'
+                raise ValueError(err % (obj.__class__.__name__, self.name, x))
+        elif tp is int or tp is long or tp is float or tp is str:
+            y = self._convert_numeric(obj, x)
+            return [y, y, y, y]
+        else:
+            raise ValueError('%s.%s has an invalid format (got %r)' % (
+                obj.__class__.__name__,
+                self.name, x))
+
+    cdef _convert_numeric(self, EventDispatcher obj, x):
+        tp = type(x)
+        if tp is int or tp is float or tp is long:
+            return x
+        if tp is tuple or tp is list:
+            if len(x) != 2:
+                raise ValueError('%s.%s must have 2 components (got %r)' % (
+                    obj.__class__.__name__,
+                    self.name, x))
+            return self.parse_list(obj, x[0], <str>x[1])
+        elif tp is str:
+            return self.parse_str(obj, x)
+        else:
+            raise ValueError('%s.%s have an invalid format (got %r)' % (
+                obj.__class__.__name__,
+                self.name, x))
+
+    cdef float parse_str(self, EventDispatcher obj, value):
+        return self.parse_list(obj, value[:-2], <str>value[-2:])
+
+    cdef float parse_list(self, EventDispatcher obj, value, str ext):
+        return dpi2px(value, ext)
+