Textangle breaks when the figure size changes.

[CompRhys]

The following snippet should produce a figure where the annotation is parallel to the line, however if the figure size changes the rotation of the annotation doesn't change.

import plotly.graph_objects as go
import math

# Create a figure
fig = go.Figure()

# Add some sample data
fig.add_trace(go.Scatter(x=[1, 2, 3, 4, 5], y=[10, 12, 15, 17, 20], mode="lines", name="Data"))

# Define the start and end points of the diagonal line
x0, y0 = 1, 11  # Start point
x1, y1 = 5, 19  # End point

# Calculate the angle for the annotation text
angle = math.degrees(math.atan2((y1 - y0), (x1 - x0)))

# Add a diagonal line using add_shape
fig.add_shape(
    type="line",
    x0=x0,
    y0=y0,
    x1=x1,
    y1=y1,
    line=dict(color="Green", width=2, dash="dash"),
)

# Calculate the midpoint position
mid_x = (x0 + x1) / 2
mid_y = (y0 + y1) / 2

# Annotate the line with rotated text
fig.add_annotation(
    x=mid_x,  # Midpoint of the line for annotation position
    y=mid_y,
    text="Diagonal Line",
    showarrow=False,
    textangle=angle,  # Rotate text to match line angle
    font=dict(color="Green"),
    xshift=10,  # Optional: Adjust this to fine-tune horizontal alignment
    yshift=-10  # Optional: Adjust this to fine-tune vertical alignment
)

fig.update_layout(title="Diagonal Line with Parallel Annotation")
fig.show()

[gvwilson]

thanks for the bug report @CompRhys - I'll see if we can get it into an upcoming release.

[CompRhys]

It's not particularly obvious that this is a bug because it may simply be too involves to have the text angles rotate adaptively as the figure size is changed but would be great to have!