Initial snow flake layout implementation

sugar/canvas/Makefile.am

@@ -10,4 +10,5 @@ sugar_PYTHON =			\
 	Menu.py			\
 	MenuIcon.py		\
 	MenuShell.py		\
+	SnowflakeLayout.py	\
 	Timeline.py

sugar/canvas/SnowflakeLayout.py

@@ -0,0 +1,62 @@
+import math
+
+import cairo
+
+class SnowflakeLayout:
+	_BASE_RADIUS = 65
+	_CHILDREN_FACTOR = 1
+	_FLAKE_DISTANCE = 6
+	_BORDER = 20
+
+	def __init__(self):
+		self._root = None
+		self._children = []
+
+	def set_root(self, icon):
+		self._root = icon
+
+	def add_child(self, icon):
+		self._children.append(icon)
+		self._layout()
+
+	def remove_child(self, icon):
+		self._children.remove(icon)
+		self._layout()
+
+	def _layout_root(self):
+		[width, height] = self._root.get_size_request()
+
+		matrix = cairo.Matrix(1, 0, 0, 1, 0, 0)
+		matrix.translate(self._cx, self._cy)
+		self._root.set_transform(matrix)
+
+	def _layout_child(self, child, index):
+		r = self._r
+		if (len(self._children) > 10):
+			r += SnowflakeLayout._FLAKE_DISTANCE * (index % 3)
+
+		angle = 2 * math.pi / len(self._children) * index
+
+		x = self._cx + math.cos(angle) * r
+		y = self._cy + math.sin(angle) * r
+
+		matrix = cairo.Matrix(1, 0, 0, 1, 0, 0)
+		matrix.translate(x, y)
+		child.set_transform(matrix)
+
+	def _layout(self):
+		self._r = SnowflakeLayout._BASE_RADIUS + \
+				  SnowflakeLayout._CHILDREN_FACTOR * len(self._children)
+
+		c = self._r + SnowflakeLayout._BORDER + \
+			SnowflakeLayout._FLAKE_DISTANCE * 2 
+
+		self._cx = c
+		self._cy = c
+
+		self._layout_root()
+
+		index = 0
+		for child in self._children:
+			self._layout_child(child, index)
+			index += 1