sugar-toolkit-gtk3/sugar/canvas/SnowflakeLayout.py

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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