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178 lines
6.0 KiB
Python
178 lines
6.0 KiB
Python
"""
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Enums representing sets of strings that Matplotlib uses as input parameters.
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Matplotlib often uses simple data types like strings or tuples to define a
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concept; e.g. the line capstyle can be specified as one of 'butt', 'round',
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or 'projecting'. The classes in this module are used internally and serve to
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document these concepts formally.
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As an end-user you will not use these classes directly, but only the values
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they define.
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"""
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from enum import Enum
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from matplotlib import _docstring
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class JoinStyle(str, Enum):
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"""
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Define how the connection between two line segments is drawn.
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For a visual impression of each *JoinStyle*, `view these docs online
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<JoinStyle>`, or run `JoinStyle.demo`.
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Lines in Matplotlib are typically defined by a 1D `~.path.Path` and a
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finite ``linewidth``, where the underlying 1D `~.path.Path` represents the
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center of the stroked line.
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By default, `~.backend_bases.GraphicsContextBase` defines the boundaries of
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a stroked line to simply be every point within some radius,
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``linewidth/2``, away from any point of the center line. However, this
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results in corners appearing "rounded", which may not be the desired
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behavior if you are drawing, for example, a polygon or pointed star.
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**Supported values:**
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.. rst-class:: value-list
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'miter'
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the "arrow-tip" style. Each boundary of the filled-in area will
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extend in a straight line parallel to the tangent vector of the
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centerline at the point it meets the corner, until they meet in a
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sharp point.
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'round'
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stokes every point within a radius of ``linewidth/2`` of the center
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lines.
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'bevel'
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the "squared-off" style. It can be thought of as a rounded corner
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where the "circular" part of the corner has been cut off.
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.. note::
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Very long miter tips are cut off (to form a *bevel*) after a
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backend-dependent limit called the "miter limit", which specifies the
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maximum allowed ratio of miter length to line width. For example, the
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PDF backend uses the default value of 10 specified by the PDF standard,
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while the SVG backend does not even specify the miter limit, resulting
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in a default value of 4 per the SVG specification. Matplotlib does not
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currently allow the user to adjust this parameter.
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A more detailed description of the effect of a miter limit can be found
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in the `Mozilla Developer Docs
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<https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute/stroke-miterlimit>`_
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.. plot::
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:alt: Demo of possible JoinStyle's
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from matplotlib._enums import JoinStyle
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JoinStyle.demo()
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"""
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miter = "miter"
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round = "round"
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bevel = "bevel"
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@staticmethod
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def demo():
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"""Demonstrate how each JoinStyle looks for various join angles."""
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import numpy as np
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import matplotlib.pyplot as plt
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def plot_angle(ax, x, y, angle, style):
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phi = np.radians(angle)
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xx = [x + .5, x, x + .5*np.cos(phi)]
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yy = [y, y, y + .5*np.sin(phi)]
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ax.plot(xx, yy, lw=12, color='tab:blue', solid_joinstyle=style)
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ax.plot(xx, yy, lw=1, color='black')
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ax.plot(xx[1], yy[1], 'o', color='tab:red', markersize=3)
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fig, ax = plt.subplots(figsize=(5, 4), constrained_layout=True)
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ax.set_title('Join style')
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for x, style in enumerate(['miter', 'round', 'bevel']):
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ax.text(x, 5, style)
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for y, angle in enumerate([20, 45, 60, 90, 120]):
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plot_angle(ax, x, y, angle, style)
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if x == 0:
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ax.text(-1.3, y, f'{angle} degrees')
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ax.set_xlim(-1.5, 2.75)
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ax.set_ylim(-.5, 5.5)
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ax.set_axis_off()
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fig.show()
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JoinStyle.input_description = "{" \
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+ ", ".join([f"'{js.name}'" for js in JoinStyle]) \
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+ "}"
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class CapStyle(str, Enum):
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r"""
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Define how the two endpoints (caps) of an unclosed line are drawn.
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How to draw the start and end points of lines that represent a closed curve
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(i.e. that end in a `~.path.Path.CLOSEPOLY`) is controlled by the line's
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`JoinStyle`. For all other lines, how the start and end points are drawn is
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controlled by the *CapStyle*.
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For a visual impression of each *CapStyle*, `view these docs online
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<CapStyle>` or run `CapStyle.demo`.
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By default, `~.backend_bases.GraphicsContextBase` draws a stroked line as
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squared off at its endpoints.
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**Supported values:**
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.. rst-class:: value-list
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'butt'
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the line is squared off at its endpoint.
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'projecting'
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the line is squared off as in *butt*, but the filled in area
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extends beyond the endpoint a distance of ``linewidth/2``.
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'round'
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like *butt*, but a semicircular cap is added to the end of the
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line, of radius ``linewidth/2``.
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.. plot::
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:alt: Demo of possible CapStyle's
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from matplotlib._enums import CapStyle
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CapStyle.demo()
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"""
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butt = "butt"
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projecting = "projecting"
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round = "round"
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@staticmethod
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def demo():
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"""Demonstrate how each CapStyle looks for a thick line segment."""
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import matplotlib.pyplot as plt
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fig = plt.figure(figsize=(4, 1.2))
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ax = fig.add_axes([0, 0, 1, 0.8])
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ax.set_title('Cap style')
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for x, style in enumerate(['butt', 'round', 'projecting']):
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ax.text(x+0.25, 0.85, style, ha='center')
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xx = [x, x+0.5]
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yy = [0, 0]
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ax.plot(xx, yy, lw=12, color='tab:blue', solid_capstyle=style)
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ax.plot(xx, yy, lw=1, color='black')
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ax.plot(xx, yy, 'o', color='tab:red', markersize=3)
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ax.set_ylim(-.5, 1.5)
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ax.set_axis_off()
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fig.show()
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CapStyle.input_description = "{" \
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+ ", ".join([f"'{cs.name}'" for cs in CapStyle]) \
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+ "}"
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_docstring.interpd.register(
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JoinStyle=JoinStyle.input_description,
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CapStyle=CapStyle.input_description,
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)
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