Add gallery example "Decorated lines" (style="~")

[yvonnefroehlich]

Description of proposed changes

This PR aims to add a gallery example showing how to generated "Decorated lines".

Upstream GMT documentation: https://docs.generic-mapping-tools.org/dev/plot.html#s

Related to:

• Gallery example Line fronts (style="f")
• PR Add gallery example "Quoted lines" (style="q") #2563

Preview: https://pygmt-dev--2564.org.readthedocs.build/en/2564/gallery/lines/decorated_lines.html

Reminders

• Run make format and make check to make sure the code follows the style guide.
• Add tests for new features or tests that would have caught the bug that you're fixing.
• Add new public functions/methods/classes to doc/api/index.rst.
• Write detailed docstrings for all functions/methods.
• If wrapping a new module, open a 'Wrap new GMT module' issue and submit reasonably-sized PRs.
• If adding new functionality, add an example to docstrings or tutorials.
• Use underscores (not hyphens) in names of Python files and directories.

Slash Commands

You can write slash commands (/command) in the first line of a comment to perform
specific operations. Supported slash commands are:

• /format: automatically format and lint the code
• /test-gmt-dev: run full tests on the latest GMT development version

[yvonnefroehlich]

/format

[yvonnefroehlich]

/format

[seisman]

Looks good.

[yvonnefroehlich]

Based on the upstream GMT documentation at https://docs.generic-mapping-tools.org/dev/plot.html#s it should be possible to rotate the symbol by appending +aangle:

+aangle
Force symbols at a fixed angle, +an for line-normal, or +ap for line-parallel [Default].

However, so far this does not work for me (for quoted lines it works to rotate the label by appending +aangle).

Code example:

import pygmt
import numpy as np


size = 5
x = np.array([-size, size])
y = np.array([3, 3])

fig = pygmt.Figure()

fig.basemap(
    region=[-size, size, -size, size],
    projection="X" + str(size*2) + "c",
    frame=True,
)

for i_line in [
        "~d2c:+ss1c",
        "~d2c:+ss1c+a20",
        "qd1c:+ltext",
        "qd1c:+ltext+a20",
        ]:
    fig.plot(
        x=x,
        y=y,
        style=i_line,
        pen="1.25p,black",
    )
    
    fig.text(
        x=0,
        y=y[0]+0.7,
        text=i_line,
        font="10p",
    )
    
    y = y - 2
    
fig.show()
# fig.savefig(fname="decorated_lines_rotated.png")

Output figure:

[seisman]

Based on the upstream GMT documentation at https://docs.generic-mapping-tools.org/dev/plot.html#s it should be possible to rotate the symbol by appending +aangle:

+aangle
Force symbols at a fixed angle, +an for line-normal, or +ap for line-parallel [Default].

However, so far this does not work for me (for quoted lines it works to rotate the label by appending +aangle).

Likely an upstream bug or a missing feature. Please report to the upstream GMT repository.

[yvonnefroehlich]

Based on the upstream GMT documentation at https://docs.generic-mapping-tools.org/dev/plot.html#s it should be possible to rotate the symbol by appending +aangle:

+aangle
Force symbols at a fixed angle, +an for line-normal, or +ap for line-parallel [Default].

However, so far this does not work for me (for quoted lines it works to rotate the label by appending +aangle).

Likely an upstream bug or a missing feature. Please report to the upstream GMT repository.

Please see issue GenericMappingTools/gmt#7591.