visibility hook for capital cities marks

client/src/hooks/map/useCapitals.ts

@@ -0,0 +1,20 @@
+import { useEffect } from "react";
+import type VectorLayer from "ol/layer/Vector";
+import type VectorSource from "ol/source/Vector";
+
+/**
+ * Hook that controls the opacity of the capitals layer depending on the selected district.
+ * 
+ * @param capitalsLayer - The OpenLayers VectorLayer instance for capitals.
+ * @param value - Value to observe, boolean.
+ */
+export function useCapitals(
+    capitalsLayer: VectorLayer<VectorSource<any>> | null,
+    value: boolean
+) {
+    useEffect(() => {
+        if (!capitalsLayer) return;
+
+        capitalsLayer.setOpacity(value ? 0 : 1);
+    }, [capitalsLayer, value]);
+}