sugar-toolkit-gtk3/sugar/graphics/snowflakebox.py

import math

import cairo
import hippo

_BASE_RADIUS = 65
_CHILDREN_FACTOR = 1
_FLAKE_DISTANCE = 6

class SnowflakeBox(hippo.CanvasBox, hippo.CanvasItem):
	__gtype_name__ = 'SugarSnowflakeBox'
	def __init__(self, **kwargs):
		hippo.CanvasBox.__init__(self, **kwargs)
		self._root = None

	def set_root(self, icon):
		self._root = icon

	def _get_center(self):
		[width, height] = self.get_allocation()
		return [width / 2, height / 2]

	def _get_radius(self):
		return _BASE_RADIUS + _CHILDREN_FACTOR * self._get_n_children()

	def _layout_root(self):
		[width, height] = self._root.get_allocation()
		[cx, cy] = self._get_center()

		x = cx - (width / 2)
		y = cy - (height / 2)

		self.move(self._root, int(x), int(y))

	def _get_n_children(self):
		return len(self.get_children()) - 1

	def _layout_child(self, child, index):
		r = self._get_radius()
		if (self._get_n_children() > 10):
			r += _FLAKE_DISTANCE * (index % 3)

		angle = 2 * math.pi * index / self._get_n_children()

		[width, height] = child.get_allocation()
		[cx, cy] = self._get_center()

		x = cx + math.cos(angle) * r - (width / 2)
		y = cy + math.sin(angle) * r - (height / 2)

		self.move(child, int(x), int(y))

	def do_get_width_request(self):
		hippo.CanvasBox.do_get_width_request(self)

		max_child_size = 0
		for child in self.get_children():
			width = child.get_width_request()
			height = child.get_height_request(width)
			max_child_size = max (max_child_size, width)
			max_child_size = max (max_child_size, height)

		return self._get_radius() * 2 +	\
			   max_child_size + _FLAKE_DISTANCE * 2

	def do_get_height_request(self, width):
		hippo.CanvasBox.do_get_height_request(self, width)
		return width

	def do_allocate(self, width, height):
		hippo.CanvasBox.do_allocate(self, width, height)

		self._layout_root()

		index = 0
		for child in self.get_children():
			if child != self._root:
				self._layout_child(child, index)
				index += 1