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fix(umap): render landmark triangles with scattergl to fix touch-pan desync #295

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Merged
lstein merged 1 commit into from
Jun 4, 2026
Merged

fix(umap): render landmark triangles with scattergl to fix touch-pan desync #295

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11 changes: 9 additions & 2 deletions photomap/frontend/static/javascript/umap.js
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Original file line number Diff line number Diff line change
Expand Up @@ -1210,12 +1210,19 @@ function updateLandmarkTrace() {
const y = clustersInView.map((c) => c.center.y + verticalOffset);
const markerColors = clustersInView.map((c) => c.color);

// Triangle-down markers at bottom of thumbnails
// Triangle-down markers at bottom of thumbnails.
// Rendered with scattergl (WebGL) to match the main point traces. The main
// points use scattergl, so an SVG `scatter` trace here was the only visible
// element on the SVG layer. During a touch pan, Plotly translates the SVG
// layer immediately but only repaints the WebGL scene once the gesture
// settles, so on tablets a touch-and-immediately-drag made the triangles
// slide alone while the dots stayed frozen. Keeping the triangles in the
// same WebGL pipeline makes them freeze-and-snap together with the points.
const landmarkTrace = {
x,
y,
mode: "markers",
type: "scatter",
type: "scattergl",
marker: {
size: triangleSize,
color: markerColors,
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