FMU with many Inputs / Outputs

[Franzisdrak]

Problem:

uv run python -m fmpy.webapp

for a FMU with > 19 Inputs and Outputs, i get the following error:

Simulation failed. Vertical spacing cannot be greater than (1 / (rows - 1)) = 0.055556. 
The resulting plot would have 19 rows (rows=19).

Expected behaviour:

The FMU loads correctly and the simulation is run.

[Fstarnb]

I can reproduce this: create_plotly_figure always passes vertical_spacing=0.06 into plotly.subplots.make_subplots. Plotly requires

vertical_spacing <= 1 / (rows - 1)

so 19 rows fails (1/18 ≈ 0.0556 < 0.06), matching the error you saw.

A small fix in fmpy.util.create_plotly_figure:

n_rows = max(len(trajectories), 1)
if n_rows <= 1:
    vertical_spacing = 0.0
else:
    vertical_spacing = min(0.06, 1.0 / (n_rows - 1) * 0.9)

fig = make_subplots(
    rows=n_rows,
    cols=1,
    vertical_spacing=vertical_spacing,
    shared_xaxes=True,
)

Verified with unit tests for 1, 5, 18, 19, 25, and 40 signals (previously 19+ raised). Happy to open a PR if external contributions are accepted again.