What We Built
Every feature row in the Layers panel now has an info button. Click it, and a dialog opens showing the feature’s geometry type and its coordinates. Point features show a single lat/lon pair. LineStrings show an ordered list of positions. MultiPolygons show their constituent polygons with vertex counts.
The dialog exists to solve a testing problem. When Playwright tests need to verify that a drag operation moved a track, or that a calculation produced new geometry, they currently have no good way to inspect coordinate values. The map canvas is opaque – you can screenshot it, but you can’t assert that position 3 moved from 50.2N to 50.4N. Now tests can open the info dialog and read the coordinates directly from the DOM.
Child rows work too. Expand a track in the Layers panel, and each position row has its own info button showing that specific point’s coordinates. Expand a MultiPolygon, and each polygon child shows its ring vertices.
The button follows the same hover-visibility pattern as the format button shipped last week. Hover over a feature row and the info icon appears. Click it, and the dialog opens with role="dialog" and data-testid attributes for both accessibility and automation.
Screenshots
Screenshots to be added: info button on hover, geometry dialog for a Point feature, geometry dialog for a LineString showing position list, dialog for a MultiPolygon child.
Lessons Learned
Cloning an existing pattern pays off fast. The format button already solved hover visibility, nullable parent state for “which popup is open”, and viewport collision detection for fixed-position popups. Reusing that pattern kept the info button to roughly 200 lines of new code. The mutual exclusion logic – only one popup open at a time – came almost free because the format button had already established the state shape.
data-testid and ARIA roles serve different audiences with zero conflict. role="dialog" gives screen readers semantic context. data-testid="geometry-dialog" gives Playwright a stable selector that won’t break when we restyle the component. We added both from the start rather than retrofitting accessibility later.
Fixed-position popups in virtualised lists are consistently tricky. The Layers panel virtualises its rows for performance, which means the info dialog can’t be positioned relative to its parent row – the row might scroll out of the virtual window. The same position: fixed plus viewport collision pattern from CascadingMenu handles this, but it’s the kind of thing you forget about until the dialog appears 400 pixels from where you expected.
What’s Next
With geometry data now readable outside the map canvas, Playwright tests can verify operations that change coordinates. Drag a track segment, open the info dialog, assert the new position values. Run a bearing calculation, check the result geometry. Undo the operation, confirm the coordinates reverted.
This unblocks a category of end-to-end tests that were previously impractical without image comparison.