def draw_path(self, points=None, corner_radius=0):
"""Sets up a Cairo path for the outline of a polygon on the given
Cairo context.
@param points: the coordinates of the corners of the polygon,
in clockwise or counter-clockwise order, or C{None} if we are
about to use the C{points} property of the class.
@param corner_radius: if zero, an ordinary polygon will be drawn.
If positive, the corners of the polygon will be rounded with
the given radius.
"""
if points is None:
points = self.points
self.context.new_path()
if len(points) < 2:
# Well, a polygon must have at least two corner points
return
ctx = self.context
if corner_radius <= 0:
# No rounded corners, this is simple
ctx.move_to(*points[-1])
for point in points:
ctx.line_to(*point)
return
# Rounded corners. First, we will take each side of the
# polygon and find what the corner radius should be on
# each corner. If the side is longer than 2r (where r is
# equal to corner_radius), the radius allowed by that side
# is r; if the side is shorter, the radius is the length
# of the side / 2. For each corner, the final corner radius
# is the smaller of the radii on the two sides adjacent to
# the corner.
points = [Point(*point) for point in points]
side_vecs = [
v - u for u, v in consecutive_pairs(points, circular=True)
]
half_side_lengths = [side.length() / 2 for side in side_vecs]
corner_radii = [corner_radius] * len(points)
for idx in range(len(corner_radii)):
prev_idx = -1 if idx == 0 else idx - 1
radii = [
corner_radius, half_side_lengths[prev_idx],
half_side_lengths[idx]
]
corner_radii[idx] = min(radii)
# Okay, move to the last corner, adjusted by corner_radii[-1]
# towards the first corner
ctx.move_to(*(points[-1].towards(points[0], corner_radii[-1])))
# Now, for each point in points, draw a line towards the
# corner, stopping before it in a distance of corner_radii[idx],
# then draw the corner
u = points[-1]
for idx, (v, w) in enumerate(consecutive_pairs(points, True)):
radius = corner_radii[idx]
ctx.line_to(*v.towards(u, radius))
aux1 = v.towards(u, radius / 2)
aux2 = v.towards(w, radius / 2)
ctx.curve_to(aux1.x, aux1.y, aux2.x, aux2.y,
*v.towards(w, corner_radii[idx]))
u = v
def draw_path(self, points=None, corner_radius=0):
"""Sets up a Cairo path for the outline of a polygon on the given
Cairo context.
@param points: the coordinates of the corners of the polygon,
in clockwise or counter-clockwise order, or C{None} if we are
about to use the C{points} property of the class.
@param corner_radius: if zero, an ordinary polygon will be drawn.
If positive, the corners of the polygon will be rounded with
the given radius.
"""
if points is None:
points = self.points
self.context.new_path()
if len(points) < 2:
# Well, a polygon must have at least two corner points
return
ctx = self.context
if corner_radius <= 0:
# No rounded corners, this is simple
ctx.move_to(*points[-1])
for point in points:
ctx.line_to(*point)
return
# Rounded corners. First, we will take each side of the
# polygon and find what the corner radius should be on
# each corner. If the side is longer than 2r (where r is
# equal to corner_radius), the radius allowed by that side
# is r; if the side is shorter, the radius is the length
# of the side / 2. For each corner, the final corner radius
# is the smaller of the radii on the two sides adjacent to
# the corner.
points = [Point(*point) for point in points]
side_vecs = [v-u for u, v in consecutive_pairs(points, circular=True)]
half_side_lengths = [side.length() / 2 for side in side_vecs]
corner_radii = [corner_radius] * len(points)
for idx in xrange(len(corner_radii)):
prev_idx = -1 if idx == 0 else idx - 1
radii = [corner_radius, half_side_lengths[prev_idx],
half_side_lengths[idx]]
corner_radii[idx] = min(radii)
# Okay, move to the last corner, adjusted by corner_radii[-1]
# towards the first corner
ctx.move_to(*(points[-1].towards(points[0], corner_radii[-1])))
# Now, for each point in points, draw a line towards the
# corner, stopping before it in a distance of corner_radii[idx],
# then draw the corner
u = points[-1]
for idx, (v, w) in enumerate(consecutive_pairs(points, True)):
radius = corner_radii[idx]
ctx.line_to(*v.towards(u, radius))
aux1 = v.towards(u, radius / 2)
aux2 = v.towards(w, radius / 2)
ctx.curve_to(aux1.x, aux1.y, aux2.x, aux2.y,
*v.towards(w, corner_radii[idx]))
u = v