FIX: Toolbar savefig respects rcparams #615
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@martinRenou if you have time to look at this that would be amazing. |
ianhi
commented
Jan 14, 2026
Fixes matplotlib#138, matplotlib#234, matplotlib#339 The Download button now respects ALL matplotlib savefig.* rcParams instead of always saving as PNG with hardcoded settings. Implementation: - Override Toolbar.save_figure() to call canvas._send_save_buffer() - Add Canvas._send_save_buffer() that calls figure.savefig() without hardcoded parameters (respects all rcParams) - Send buffer + format metadata to frontend via ipywidgets comm - Update frontend handle_save() to accept buffers from backend - Support multiple formats with correct MIME types: PNG, PDF, SVG, EPS, JPEG, TIFF, PS, TIF - Set correct file extensions based on format - Maintain backward compatibility with canvas.toDataURL() fallback Respects these rcParams: - savefig.format (png, pdf, svg, jpg, eps, etc.) - savefig.dpi (resolution) - savefig.transparent (transparent backgrounds) - savefig.facecolor (custom background colors) - All other savefig.* parameters Co-Authored-By: Claude Sonnet 4.5 <[email protected]>
Manual test notebook (tests/manual_test_rcparams_save.ipynb): - Tests all savefig.* rcParams (format, transparent, facecolor, dpi) - Tests multiple formats: PNG, PDF, SVG, JPEG - Includes verification checklist - Documents expected behavior for each test case Python unit tests (tests/test_download.py): - Test _send_save_buffer respects savefig.format (PNG, PDF, SVG) - Test download() method calls _send_save_buffer - Test Toolbar.save_figure() calls _send_save_buffer - Test respects savefig.dpi and savefig.transparent rcParams - Test warns on unsupported format (e.g., webp) - Add 'tests' to pytest testpaths in pyproject.toml Addresses issues matplotlib#138, matplotlib#234, matplotlib#339 Co-Authored-By: Claude Sonnet 4.5 <[email protected]>
- Add public download() method to Canvas class
- Allows triggering downloads from Python code without clicking button
- Respects all savefig rcParams like the toolbar button
- Includes comprehensive docstring with examples
- Add test file demonstrating programmatic usage
Use cases:
- Batch downloading multiple figures
- Automated workflows
- Custom save logic in notebooks
Example:
fig, ax = plt.subplots()
ax.plot([1, 2, 3])
fig.canvas.download() # Triggers browser download
Co-Authored-By: Claude Sonnet 4.5 <[email protected]>
martinRenou
approved these changes
Jan 15, 2026
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Make the toolbar savefig button respect the matplotlib rcparams
Closes: #138
and thereby
Closes: #234
Closes: #339
Implementation
Let the backend handle the actual buffer generation, then just add the correct mimetype to the bundle for download. Much simpler than i expected.
Tests
The most important test is the manual_test notebook i added. I ran through this and it worked for me as expected. I will try it again with the PR binder link