Lot's of small improvements

Logic/StrayClickHandler.ts

@@ -0,0 +1,49 @@
+import {Basemap} from "./Basemap";
+import L from "leaflet";
+import {UIEventSource} from "../UI/UIEventSource";
+import {UIElement} from "../UI/UIElement";
+
+/**
+ * The stray-click-hanlders adds a marker to the map if no feature was clicked.
+ * Shows the given uiToShow-element in the messagebox
+ */
+export class StrayClickHandler {
+    private _basemap: Basemap;
+    private _lastMarker;
+    private _leftMessage: UIEventSource<() => UIElement>;
+    private _uiToShow: (() => UIElement);
+
+    constructor(
+        basemap: Basemap,
+        selectElement: UIEventSource<any>,
+        leftMessage: UIEventSource<() => UIElement>, 
+        uiToShow: (() => UIElement)) {
+        this._basemap = basemap;
+        this._leftMessage = leftMessage;
+        this._uiToShow = uiToShow;
+        const self = this;
+        const map = basemap.map;
+        basemap.LastClickLocation.addCallback(function (lastClick) {
+
+            if (self._lastMarker !== undefined) {
+                map.removeLayer(self._lastMarker);
+            }
+
+            self._lastMarker = L.marker([lastClick.lat, lastClick.lon]);
+            self._lastMarker.addTo(map);
+
+            leftMessage.setData(self._uiToShow);
+
+        });
+
+        selectElement.addCallback(() => {
+            if (self._lastMarker !== undefined) {
+                map.removeLayer(self._lastMarker);
+                this._lastMarker = undefined;
+            }
+        })
+
+    }
+
+
+}