_map_title crashes for orthographic maps with UnboundLocalError: xpt
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- Dominant language
- Python
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Description
This actually occurs for other plot types as well.
Version: cfplot 3.4.0; python 3.12
Observed behavior:
- Orthographic contour plot crashes when cf-plot tries to render the map title
- If the title is removed, the plot renders successfully
Expected behavior:
- Orthographic contour plots should render with a title
- At minimum, _map_title should not crash if a projection-specific title anchor has not been computed
Minimal failing scenario:
- Projection: ortho
- Default GUI-style settings:
- [lat_0 = 0.0]
- [lon_0 = 0.0
- Render a contour plot with a non-empty title
Probable root cause:
_map_title() appears to compute xpt, ypt only for some projections, then unconditionally uses them in the non-dims branch.
From the installed 3.4.0 source, the title-anchor coordinates are assigned for cases such as:
- npstere
- spstere
- lcc
but later the code does:
else:
halign = "center"
plotvars.mymap.text(
xpt,
ypt,
title,
...
)
For ortho, xpt/ypt do not appear to be initialized before this branch is reached.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by locating _map_title and reproduce the minimal ortho contour plot with a non-empty title using the stated default settings. Trace how xpt and ypt are assigned for each projection, then verify that orthographic plots render with titles without an UnboundLocalError.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- data-visualization
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Clearly specified
- Newbie friendliness
- 52/100