Link to issue

#5552 - [FEATURE]: Access values calculated / derived by plotly.js as part of plotting

Closes #5552

Description of change

This PR introduces an initial implementation of get_computed_values() to expose values computed by Plotly.js in a structured and programmatic way.

The implementation supports retrieval of:

• axis_ranges: The final computed [min, max] range for each axis
• axis_types: The detected axis type (e.g., linear, log, date, category)

Key aspects of this implementation:

• Provides a filtered interface over full_figure_for_development() to return only requested computed values
• Uses a single-pass traversal of the layout to efficiently extract multiple computed properties
• Uses a simple and robust startswith approach to identify axis keys (e.g., xaxis, yaxis, xaxis2)
• Ensures JSON-serializable outputs by converting ranges to lists
• Includes validation for the include parameter and early return for empty input

Demo

import plotly.graph_objects as go

# Create a sample figure
fig = go.Figure(go.Scatter(x=[1, 2, 3], y=[10, 20, 30]))

# Retrieve axis ranges
fig.get_computed_values(include=["axis_ranges"])
# {'axis_ranges': {'xaxis': [...], 'yaxis': [...]}}

# Retrieve axis types
fig.get_computed_values(include=["axis_types"])
# {'axis_types': {'xaxis': 'linear', 'yaxis': 'linear'}}

# Retrieve both together
fig.get_computed_values(include=["axis_ranges", "axis_types"])
# {
 #   'axis_ranges': {'xaxis': [...], 'yaxis': [...]},
#  'axis_types': {'xaxis': 'linear', 'yaxis': 'linear'}
# }

Testing strategy

Added a comprehensive test suite in tests/test_core/test_update_objects/test_get_computed_values.py:

• Basic Extraction: Verified axis range extraction for standard plots
• Multi-Axis Support: Verified handling of multiple axes (e.g., xaxis2, yaxis2)
• Axis Types: Verified standalone extraction of axis types
• Combined Retrieval: Verified correct behavior when requesting multiple keys together
• Input Validation: Verified invalid inputs raise descriptive ValueError
• Serialization Safety: Verified tuple ranges are converted to lists
• Early Exit: Verified empty include skips rendering
• Efficiency: Verified single call to full_figure_for_development() when multiple keys are requested

Note: Tests use mocking for the Kaleido rendering engine to ensure environment-agnostic reliability during CI.

Additional information (optional)

This implementation establishes the API structure for accessing computed Plotly.js values and demonstrates its extensibility by supporting multiple properties (axis_ranges, axis_types) using a scalable single-pass design.

Future extensions could include:

• tick values and tick labels
• margins and layout-derived geometry
• box/violin plot statistics
• direct integration with FigureWidget to avoid reliance on Kaleido

Guidelines

• I have reviewed the pull request guidelines and the Code of Conduct and confirm that this PR follows them.
• I have added an entry to the changelog if needed (not required for documentation PRs).