feat(embed): exportPNG canvas compositor + postMessage export protocol#28
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handle.exportPNG({scale, includeWidgets}) composites the per-panel canvas
stack (gpu/plot/axes/colorbar/markers/scalebar/title, insets on top) onto
one offscreen canvas at DPR*scale and returns a PNG data URL. WebGPU
panels are force-redrawn and read back in the same synchronous task, so
callers need no settling delay. Standalone HTML gains a message listener
(anyplotlib_export_png -> anyplotlib_export_png_result) riding the same
channel as awi_state, for iframe hosts.
render() now returns its internal api ({panels, exportPNG, gpu disposers});
mount() captures it — this also fixes mount().dispose(), which previously
referenced closure-scoped state it could not reach and silently no-oped.
This was referenced Jul 12, 2026
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
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Summary
handle.exportPNG({scale, includeWidgets})composites the per-panel canvas stack (gpu/plot/axes/colorbar/markers/scalebar/title, insets on top) onto one offscreen canvas at DPR×scale and resolves to a PNG data URL.messagelistener (anyplotlib_export_png→anyplotlib_export_png_result) so iframe hosts (SpyDE report cells) can harvest WYSIWYG snapshots.render()now returns its internal api andmount()captures it —mount().dispose()previously referenced closure state it couldn't reach and silently no-oped.Branch is based on
release/v0.2.0(main hasn't caught up to the release-prep commits), so those two commits appear in the diff until main is fast-forwarded.Tests
tests/test_embed/test_export_png.py: 7 passed (basic pixel/LUT checks, multi-panel arrangement, iframe postMessage round-trip, WebGPU readback — skips cleanly without an adapter). Fulltest_embed/+test_plot2d/+test_layouts/regression: 439 passed, 6 pre-existing baseline skips.