Vector layer flashes white on every pan frame

• While dragging, the whole vector layer vanishes for roughly 100 ms and reappears on release.
• The performance panel shows VectorLayer.renderFrame taking more than 30 ms per frame.
• The flash duration grows as feature density increases.

1. Set updateWhileInteracting to false and confirm the flash disappears.
2. Time the style function across all features to measure per-frame cost.
3. Check whether declutter is on, since it re-lays out every label each frame.
4. Count source.getFeatures().length.

Keep interaction redraw only for the dynamic layer, share one style object, set declutter: false and updateWhileAnimating: false, or move the dense point layer to ol.layer.WebGLPoints.

console.log('要素数', source.getFeatures().length);
var t0 = performance.now();
source.getFeatures().forEach(function (f) { layer.getStyleFunction()(f, 1); });
console.log('样式耗时 ms', performance.now() - t0);

var layer = new ol.layer.Vector({
  source: source,
  style: sharedStyle,
  updateWhileInteracting: true,
  updateWhileAnimating: false,
  declutter: false
});

• Turning off updateWhileInteracting on a layer that must track the cursor makes features visibly trail the basemap.
• Filtering the source to reduce the feature count changes the data rather than the render cost.