Fix export to image not capturing current view position#1784
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ghostiee-11 wants to merge 2 commits into
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Fix export to image not capturing current view position#1784ghostiee-11 wants to merge 2 commits into
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When exporting VegaLite charts as PNG/JPEG/SVG/PDF, the exported image now matches the browser viewport instead of rendering at default bounds. Three improvements: - Capture zoom/pan bounds from the live panel selection state and inject them into the export spec (via selection value or scale.domain) - Scale export dimensions to at least 1600x800 to match typical browser container sizes, preventing geographic map projections from cropping - Set width/height directly on the Panel Vega pane before export so Panel Vega.export() uses the correct dimensions
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ghostiee-11
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March 22, 2026 07:07
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #1784 +/- ##
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+ Coverage 69.29% 69.30% +0.01%
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Files 171 171
Lines 29249 29263 +14
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+ Hits 20269 20282 +13
- Misses 8980 8981 +1 ☔ View full report in Codecov by Harness. 🚀 New features to boost your workflow:
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ahuang11
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Mar 24, 2026
ahuang11
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ahuang11
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I think the result is desired. However, I'm not sure this is the right implementation; seems overly complex.
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| panel = getattr(self.component, '_panel', None) | ||
| if panel is None or not hasattr(panel, 'selection') or panel.selection is None: | ||
| return None | ||
| bounds = {} | ||
| for param_name in panel.selection.param: | ||
| if param_name == 'name': | ||
| continue | ||
| value = getattr(panel.selection, param_name) |
Contributor
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Not a big fan of all the getattr and hasattr
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Yeah sure will fix it
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| @staticmethod | ||
| def _inject_encoding_domains(spec: dict, bounds: dict) -> None: | ||
| """Fallback: inject scale.domain on matching encoding channels. | ||
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| Modifies spec in place. Handles x, y, x2, y2 channels. | ||
| Does not handle longitude/latitude (they use projections, not scales). | ||
| """ | ||
| def inject_encoding(enc: dict) -> dict: | ||
| enc = dict(enc) | ||
| for channel in ('x', 'y', 'x2', 'y2'): | ||
| if channel not in enc: | ||
| continue | ||
| ch_spec = enc[channel] | ||
| field = ch_spec.get('field') | ||
| if field and field in bounds: | ||
| ch_spec = dict(ch_spec) | ||
| scale = dict(ch_spec.get('scale', {})) | ||
| scale['domain'] = list(bounds[field]) | ||
| ch_spec['scale'] = scale | ||
| enc[channel] = ch_spec | ||
| return enc | ||
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| if 'encoding' in spec: | ||
| spec['encoding'] = inject_encoding(spec['encoding']) | ||
| if 'layer' in spec: | ||
| spec['layer'] = [ | ||
| dict(layer, encoding=inject_encoding(layer['encoding'])) | ||
| if 'encoding' in layer else layer | ||
| for layer in spec['layer'] | ||
| ] | ||
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| @staticmethod | ||
| def _apply_bounds_to_spec(spec: dict, bounds: dict) -> dict: | ||
| """Inject zoom/pan bounds into a Vega-Lite spec. | ||
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| Uses two strategies for standard x/y charts: | ||
| 1. Primary: Set the value of an interval selection with bind="scales". | ||
| 2. Fallback: Inject scale.domain on encoding channels directly. | ||
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| For geographic maps with projections, zoom/pan state is preserved | ||
| by matching the export dimensions to the live panel dimensions | ||
| (handled in export(), not here). | ||
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| Parameters | ||
| ---------- | ||
| spec : dict | ||
| The Vega-Lite specification. | ||
| bounds : dict | ||
| Field-name-to-[min, max] mapping from the live selection. | ||
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| Returns | ||
| ------- | ||
| dict | ||
| Modified spec with current view bounds applied. | ||
| """ | ||
| spec = dict(spec) | ||
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| # Strategy 1: Set selection parameter value (universal approach) | ||
| if VegaLiteEditor._set_selection_value(spec, bounds): | ||
| return spec | ||
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| # Also check inside layers for selection params | ||
| if 'layer' in spec: | ||
| for i, layer in enumerate(spec['layer']): | ||
| if not isinstance(layer, dict): | ||
| continue | ||
| layer = dict(layer) | ||
| if VegaLiteEditor._set_selection_value(layer, bounds): | ||
| layers = list(spec['layer']) | ||
| layers[i] = layer | ||
| spec['layer'] = layers | ||
| return spec | ||
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| # Strategy 2: Fallback to scale.domain injection on encodings | ||
| VegaLiteEditor._inject_encoding_domains(spec, bounds) | ||
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| # Recurse into concatenated specs | ||
| for key in ('hconcat', 'vconcat', 'concat'): | ||
| if key in spec: | ||
| spec[key] = [ | ||
| VegaLiteEditor._apply_bounds_to_spec(sub, bounds) | ||
| for sub in spec[key] | ||
| ] | ||
| return spec |
Contributor
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Is there a way to simplify?
Comment on lines
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| # uses them instead of its own defaults | ||
| if hasattr(panel, 'width'): | ||
| panel.width = export_width | ||
| if hasattr(panel, 'height'): | ||
| panel.height = export_height |
Contributor
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I think all panels should have width.
ahuang11
marked this pull request as draft
March 24, 2026 01:56
Collaborator
Author
|
Thanks for the review! You're right that the implementation is more complex than it needs to be. The core fix for #1773 is really about export dimensions not matching the browser viewport. I'll simplify by:
I'll push a simplified version shortly. |
Strip overengineered bounds-capture logic per review feedback. The core issue was container-sized specs exporting at 800x400. Fix uses 1600x800 viewport defaults instead. Removes all getattr/hasattr guards, bounds injection, and recursion helpers.
ghostiee-11
marked this pull request as ready for review
March 24, 2026 16:12
Contributor
|
The simplification doesn't exactly capture current view; only makes it bigger? |
ahuang11
marked this pull request as draft
March 24, 2026 17:23
Collaborator
Author
|
Yup.. lemme look and refactor this according to this issue |
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Fixes #1773
The fix captures the current view bounds from the live panel before the export recreates the component, and ensures the export dimensions match the browser viewport instead of the spec's smaller defaults.
After fix:
How it was tested
Uploaded a fireball dataset in Lumen AI, generated a world map with
projection: equalEarth, and exported as PNG. Before the fix, the export showed only North America. After the fix, the full world map is visible matching the browser view. Also added 21 unit tests.