fix: correctly access axes ranges after coord flip in geom_path

[AlFontal]

Description

This PR fixes a bug where arrowheads in geom_path (and derivatives like geom_segment) were distorted when using coord_flip().

The issue was caused by geom_path using coord.range(panel_params) to calculate the data range for aspect ratio corrections. coord_flip.range() returns the ranges of the original data variables (where x is the mapped variable, which becomes vertical). However, geom_path expects the ranges to correspond to the physical visual axes (horizontal and vertical width).

The fix is to use panel_params.x.range and panel_params.y.range directly, as plotnine ensures panel_params.x always corresponds to the horizontal visual axis.

Changes

• Modified plotnine/geoms/geom_path.py: updated get_paths to access panel_params.x.range and panel_params.y.range directly.

Before:

import pandas as pd
import plotnine as p9
df = pd.DataFrame({
    "sample": ["A", "B", "C", "D", "E"],
    "value":  [0.1, 0.3, 0.6, 0.4, 0.8],
})

(p9.ggplot(df, p9.aes(x="sample", y="value"))
    + p9.geom_segment(
        p9.aes(xend="sample", y=0, yend="value"),
        arrow=p9.arrow(angle=30, length=0.2, ends="last", type="open"),
    )
    + p9.coord_flip()
)

Now:

(p9.ggplot(df, p9.aes(x="sample", y="value"))
    + p9.geom_segment(
        p9.aes(xend="sample", y=0, yend="value"),
        arrow=p9.arrow(angle=30, length=0.2, ends="last"),
    )
    + p9.coord_flip()
)

Related issue

Closes #1014.

[AlFontal]

I ran the test suite locally and it seems to pass. Wondering whether it might make sense to create an actual test_coord_flip test that compares the png's generated by manually flipping and coord flipping, but I worry that the implementation doesn't 100% work pixel-perfect as of right now...