Let a tap name a Ziel and download the view in front of you.

The same queue fetches that view at every prepared scale when Download-Knopf is on.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/adapters/marks-db.ts

@@ -1,4 +1,4 @@
-import type { MarksPort } from "../karte/types";
+import type { MarksPort, RememberedMarks } from "../karte/types";
 
 const DB_NAME = "karte";
 const STORE = "marks";
@@ -21,16 +21,23 @@ function stringsFrom(value: unknown): string[] {
   return value.filter((item): item is string => typeof item === "string");
 }
 
-function rememberedFrom(value: unknown): { heruntergeladen: string[]; ziele: string[] } {
-  if (Array.isArray(value)) return { heruntergeladen: stringsFrom(value), ziele: [] };
+function rememberedFrom(value: unknown): RememberedMarks {
+  if (Array.isArray(value)) {
+    return { heruntergeladen: stringsFrom(value), ziele: [], downloadKnopf: false };
+  }
   if (value && typeof value === "object") {
-    const record = value as { heruntergeladen?: unknown; ziele?: unknown };
+    const record = value as {
+      heruntergeladen?: unknown;
+      ziele?: unknown;
+      downloadKnopf?: unknown;
+    };
     return {
       heruntergeladen: stringsFrom(record.heruntergeladen),
       ziele: stringsFrom(record.ziele),
+      downloadKnopf: record.downloadKnopf === true,
     };
   }
-  return { heruntergeladen: [], ziele: [] };
+  return { heruntergeladen: [], ziele: [], downloadKnopf: false };
 }
 
 function settle(tx: IDBTransaction, value: () => unknown): Promise<unknown> {
@@ -60,7 +67,11 @@ export function createMarksDb(): MarksPort {
       try {
         const tx = db.transaction(STORE, "readwrite");
         tx.objectStore(STORE).put(
-          { heruntergeladen: state.heruntergeladen, ziele: state.ziele },
+          {
+            heruntergeladen: state.heruntergeladen,
+            ziele: state.ziele,
+            downloadKnopf: state.downloadKnopf,
+          },
           KEY,
         );
         await settle(tx, () => undefined);

src/karte/fakes.ts

@@ -18,13 +18,15 @@ export function createMemoryCache(initial: string[] = []): CachePort {
 export function createMemoryMarks(initial: string[] = []): MarksPort {
   let heruntergeladen = [...initial];
   let ziele: string[] = [];
+  let downloadKnopf = false;
   return {
     async read() {
-      return { heruntergeladen: [...heruntergeladen], ziele: [...ziele] };
+      return { heruntergeladen: [...heruntergeladen], ziele: [...ziele], downloadKnopf };
     },
     async write(state) {
       heruntergeladen = [...state.heruntergeladen];
       ziele = [...state.ziele];
+      downloadKnopf = state.downloadKnopf;
     },
   };
 }

src/karte/koordinate.ts

@@ -1,6 +1,6 @@
-import { toPoint } from "mgrs";
+import { forward, toPoint } from "mgrs";
 import proj4 from "proj4";
-import type { Point } from "./types";
+import type { KoordinateText, Point } from "./types";
 
 proj4.defs(
   "EPSG:25832",
@@ -10,10 +10,31 @@ proj4.defs(
 const DIGITS = "Rechtswert und Hochwert müssen genau fünf Ziffern haben.";
 const GITTER_NOTICE = "Dieses Gitter ist keine gültige Koordinate.";
 const BLATT = "Kein Blatt deckt diese Koordinate.";
+const MGRS_1M = /^(\d{1,2}[C-HJ-NP-X])([A-HJ-NP-Z]{2})(\d{5})(\d{5})$/;
 
 /** Zone, latitude band, and 100 km square. I and O are not MGRS letters. */
 const GITTER_PATTERN = /^(\d{1,2})([C-HJ-NP-X])([A-HJ-NP-Z]{2})$/;
 
+/** Nearest metre inside the 100 km square, written as Gitter, Rechtswert, and Hochwert. */
+export function writeKoordinate(point: Point): KoordinateText | null {
+  const easting = Math.round(point.easting);
+  const northing = Math.round(point.northing);
+  const geographic = proj4("EPSG:25832", "EPSG:4326", [easting, northing]);
+  let mgrsText: string;
+  try {
+    mgrsText = forward([geographic[0], geographic[1]], 5);
+  } catch {
+    return null;
+  }
+  const match = MGRS_1M.exec(mgrsText);
+  if (!match) return null;
+  return {
+    gitter: `${match[1]} ${match[2]}`,
+    rechtswert: match[3],
+    hochwert: match[4],
+  };
+}
+
 export function parseKoordinate(
   input: { gitter: string; rechtswert: string; hochwert: string },
   blattCovers: (point: Point) => boolean,

src/karte/session.test.ts

@@ -48,6 +48,7 @@ async function openSheet(options?: {
   clock?: ReturnType<typeof createFetchClock>;
   uebersicht?: Uebersicht;
   maxSpanMeters?: number;
+  minResolutionMeters?: number;
 }) {
   const cache = options?.cache ?? createMemoryCache();
   const marks = options?.marks ?? createMemoryMarks();
@@ -57,7 +58,11 @@ async function openSheet(options?: {
     cache,
     marks,
     kacheln: clock,
-    config: { ...shippedConfig, maxSpanMeters: options?.maxSpanMeters ?? shippedConfig.maxSpanMeters },
+    config: {
+      ...shippedConfig,
+      maxSpanMeters: options?.maxSpanMeters ?? shippedConfig.maxSpanMeters,
+      minResolutionMeters: options?.minResolutionMeters ?? shippedConfig.minResolutionMeters,
+    },
     viewport: options?.viewport ?? phone,
     standort: options?.standort,
     online: options?.online ?? false,
@@ -431,6 +436,202 @@ describe("naming a Ziel", () => {
   });
 });
 
+describe("tapping the Karte", () => {
+  test("a tap within 44 px deletes the nearest Ziel and leaves the view", async () => {
+    const { karte } = await openSheet({ uebersicht: withHole, online: true });
+    karte.enterKoordinate(sample);
+    karte.enterKoordinate({ gitter: "32U MA", rechtswert: "67100", hochwert: "78109" });
+    karte.panTo({ easting: 465_000, northing: 5_580_000 });
+    karte.zoomTo(7);
+    const older = karte.snapshot().ziele[1].point;
+    karte.tap({ easting: older.easting, northing: older.northing - 10 });
+    const snapshot = karte.snapshot();
+    expect(snapshot.ziele.map((ziel) => ziel.koordinate)).toEqual(["32U MA 67100 78109"]);
+    expect(snapshot.center).toEqual({ easting: 465_000, northing: 5_580_000 });
+    expect(snapshot.resolution).toBe(7);
+  });
+
+  test("a tie within 44 px deletes the newer Ziel", async () => {
+    const { karte } = await openSheet({ uebersicht: withHole, online: true });
+    karte.enterKoordinate(sample);
+    karte.enterKoordinate({ gitter: "32U MA", rechtswert: "67100", hochwert: "78109" });
+    const [newer, older] = karte.snapshot().ziele;
+    karte.panTo({ easting: 465_000, northing: 5_580_000 });
+    karte.zoomTo(1.25);
+    karte.tap({
+      easting: (newer.point.easting + older.point.easting) / 2,
+      northing: (newer.point.northing + older.point.northing) / 2,
+    });
+    const snapshot = karte.snapshot();
+    expect(snapshot.ziele.map((ziel) => ziel.koordinate)).toEqual(["32U MA 67030 78109"]);
+    expect(snapshot.center).toEqual({ easting: 465_000, northing: 5_580_000 });
+    expect(snapshot.resolution).toBe(1.25);
+  });
+
+  test("a tap farther than 44 px adds that metre and leaves the view and the typed fields", async () => {
+    const { karte } = await openSheet({ uebersicht: withHole, online: true });
+    karte.enterKoordinate({ gitter: "32u ma", rechtswert: "67030", hochwert: "78109" });
+    karte.panTo({ easting: 465_000, northing: 5_580_000 });
+    karte.zoomTo(10);
+    const typed = karte.snapshot().koordinate;
+    karte.tap({ easting: 481_000, northing: 5_578_109 });
+    const snapshot = karte.snapshot();
+    expect(snapshot.ziele.map((ziel) => ziel.koordinate)).toEqual([
+      "32U MA 81000 78109",
+      "32U MA 67030 78109",
+    ]);
+    expect(Math.abs(snapshot.ziele[0].point.easting - 481_000)).toBeLessThan(1);
+    expect(Math.abs(snapshot.ziele[0].point.northing - 5_578_109)).toBeLessThan(1);
+    expect(snapshot.center).toEqual({ easting: 465_000, northing: 5_580_000 });
+    expect(snapshot.resolution).toBe(10);
+    expect(snapshot.koordinate).toEqual(typed);
+    expect(snapshot.notice).toBeNull();
+  });
+
+  test("a repeated Koordinate from a tap is refused and changes nothing else", async () => {
+    const { karte } = await openSheet({
+      uebersicht: wideSquare,
+      online: true,
+      minResolutionMeters: 0.001,
+    });
+    karte.enterKoordinate({ gitter: "32u ma", rechtswert: "67030", hochwert: "78109" });
+    const ziel = karte.snapshot().ziele[0];
+    karte.panTo({ easting: 420_000, northing: 5_520_000 });
+    karte.zoomTo(0.001);
+    const kept = karte.snapshot();
+    // 0.2 m west stays in this metre, and at 0.001 m/px it is outside 44 px.
+    karte.tap({ easting: ziel.point.easting - 0.2, northing: ziel.point.northing });
+    const snapshot = karte.snapshot();
+    expect(snapshot.notice).toBe("Diese Koordinate ist schon ein Ziel.");
+    expect(snapshot.ziele).toEqual(kept.ziele);
+    expect(snapshot.center).toEqual(kept.center);
+    expect(snapshot.resolution).toBe(0.001);
+    expect(snapshot.koordinate).toEqual(kept.koordinate);
+  });
+
+  test("the 44 px radius is inclusive, and one metre farther names that metre", async () => {
+    const { karte } = await openSheet({ uebersicht: wideSquare, online: true });
+    karte.enterKoordinate(sample);
+    const onTheEdge = karte.snapshot().ziele[0].point;
+    karte.panTo({ easting: 420_000, northing: 5_520_000 });
+    karte.zoomTo(10);
+    const typed = karte.snapshot().koordinate;
+    karte.tap({ easting: onTheEdge.easting, northing: onTheEdge.northing + 440 });
+    expect(karte.snapshot().ziele).toEqual([]);
+    expect(karte.snapshot().center).toEqual({ easting: 420_000, northing: 5_520_000 });
+    expect(karte.snapshot().resolution).toBe(10);
+    expect(karte.snapshot().koordinate).toEqual(typed);
+
+    karte.enterKoordinate(sample);
+    const again = karte.snapshot().ziele[0].point;
+    karte.panTo({ easting: 420_000, northing: 5_520_000 });
+    karte.zoomTo(10);
+    karte.tap({ easting: again.easting, northing: again.northing + 441 });
+    const snapshot = karte.snapshot();
+    expect(snapshot.ziele.map((ziel) => ziel.koordinate)).toEqual([
+      "32U MA 67030 78550",
+      "32U MA 67030 78109",
+    ]);
+    expect(snapshot.center).toEqual({ easting: 420_000, northing: 5_520_000 });
+    expect(snapshot.resolution).toBe(10);
+    expect(snapshot.koordinate).toEqual(typed);
+  });
+
+  test("a tap 100 m away deletes at 7 m per pixel and adds at 1.25 m per pixel", async () => {
+    const { karte } = await openSheet({ uebersicht: wideSquare, online: true });
+    karte.enterKoordinate(sample);
+    const ziel = karte.snapshot().ziele[0].point;
+    karte.panTo({ easting: 420_000, northing: 5_520_000 });
+    karte.zoomTo(1.25);
+    karte.tap({ easting: ziel.easting, northing: ziel.northing + 100 });
+    expect(karte.snapshot().ziele.map((item) => item.koordinate)).toEqual([
+      "32U MA 67030 78209",
+      "32U MA 67030 78109",
+    ]);
+    expect(karte.snapshot().center).toEqual({ easting: 420_000, northing: 5_520_000 });
+    expect(karte.snapshot().resolution).toBe(1.25);
+
+    karte.zoomTo(7);
+    karte.tap({ easting: ziel.easting, northing: ziel.northing + 100 });
+    expect(karte.snapshot().ziele.map((item) => item.koordinate)).toEqual(["32U MA 67030 78109"]);
+    karte.tap({ easting: ziel.easting, northing: ziel.northing + 100 });
+    expect(karte.snapshot().ziele).toEqual([]);
+    expect(karte.snapshot().center).toEqual({ easting: 420_000, northing: 5_520_000 });
+    expect(karte.snapshot().resolution).toBe(7);
+  });
+
+  test("a tap on the Standort adds a Ziel there when no Ziel is within 44 px", async () => {
+    const standort = { easting: 467_030, northing: 5_578_109 };
+    const { karte } = await openSheet({ uebersicht: wideSquare, online: true, standort });
+    const before = karte.snapshot();
+    karte.tap(standort);
+    const snapshot = karte.snapshot();
+    expect(snapshot.ziele.map((ziel) => ziel.koordinate)).toEqual(["32U MA 67030 78109"]);
+    expect(Math.abs(snapshot.ziele[0].point.easting - standort.easting)).toBeLessThan(1);
+    expect(Math.abs(snapshot.ziele[0].point.northing - standort.northing)).toBeLessThan(1);
+    expect(snapshot.standort).toEqual(standort);
+    expect(snapshot.center).toEqual(before.center);
+    expect(snapshot.resolution).toBe(before.resolution);
+    expect(snapshot.koordinate).toEqual(before.koordinate);
+  });
+
+  test("a tap on the Standort deletes a Ziel within 44 px and leaves the Standort", async () => {
+    const { karte } = await openSheet({ uebersicht: wideSquare, online: true });
+    karte.enterKoordinate(sample);
+    const ziel = karte.snapshot().ziele[0].point;
+    const center = karte.snapshot().center;
+    karte.reportStandort(ziel);
+    karte.tap(ziel);
+    expect(karte.snapshot().ziele).toEqual([]);
+    expect(karte.snapshot().standort).toEqual(ziel);
+    expect(karte.snapshot().center).toEqual(center);
+  });
+
+  test("a tap no Blatt covers leaves the list, the notice, and the view", async () => {
+    const { karte } = await openSheet({ uebersicht: withHole, online: true });
+    karte.enterKoordinate(sample);
+    karte.enterKoordinate({ gitter: "32U MA", rechtswert: "6703", hochwert: "78109" });
+    karte.panTo({ easting: 465_000, northing: 5_580_000 });
+    karte.zoomTo(10);
+    const kept = karte.snapshot();
+    expect(kept.notice).toBe("Rechtswert und Hochwert müssen genau fünf Ziffern haben.");
+    karte.tap({ easting: 475_000, northing: 5_578_109 });
+    const snapshot = karte.snapshot();
+    expect(snapshot.notice).toBe(kept.notice);
+    expect(snapshot.ziele).toEqual(kept.ziele);
+    expect(snapshot.center).toEqual(kept.center);
+    expect(snapshot.resolution).toBe(kept.resolution);
+    expect(snapshot.koordinate).toEqual(kept.koordinate);
+  });
+
+  test("a Ziel added by a tap keeps a later first Standort from moving the view", async () => {
+    const { karte } = await openSheet({ uebersicht: wideSquare, online: true });
+    const opening = karte.snapshot().center;
+    karte.tap({ easting: 481_000, northing: 5_578_109 });
+    karte.reportStandort({ easting: 420_000, northing: 5_520_000 });
+    expect(karte.snapshot().center).toEqual(opening);
+    expect(karte.snapshot().standort).toEqual({ easting: 420_000, northing: 5_520_000 });
+    expect(karte.snapshot().ziele.map((ziel) => ziel.koordinate)).toEqual(["32U MA 81000 78109"]);
+  });
+
+  test("leaving the page keeps a Ziel added by a tap and drops one removed by a tap", async () => {
+    const cache = createMemoryCache();
+    const marks = createMemoryMarks();
+    const first = await openSheet({ uebersicht: withHole, cache, marks, online: true });
+    first.karte.enterKoordinate(sample);
+    first.karte.tap({ easting: 481_000, northing: 5_578_109 });
+    first.karte.tap(first.karte.snapshot().ziele[1].point);
+    expect(first.karte.snapshot().ziele.map((ziel) => ziel.koordinate)).toEqual([
+      "32U MA 81000 78109",
+    ]);
+
+    const kept = await openSheet({ uebersicht: withHole, cache, marks, online: true });
+    expect(kept.karte.snapshot().ziele.map((ziel) => ziel.koordinate)).toEqual([
+      "32U MA 81000 78109",
+    ]);
+  });
+});
+
 describe("Standort and Entfernung", () => {
   test("a late first Standort centers the view once", async () => {
     const { karte } = await openSheet();
@@ -779,3 +980,264 @@ describe("downloading Hessen", () => {
     expect(appearance(karte, TILE_A)).toBe("blank-not-on-device");
   });
 });
+
+describe("downloading the current view", () => {
+  test("the Download-Knopf starts off, is remembered, and deleteCache leaves it", async () => {
+    const marks = createMemoryMarks(["Hessen"]);
+    const first = await openSheet({ marks, uebersicht: wideSquare });
+    expect(first.karte.snapshot().downloadKnopf).toBe(false);
+    expect(first.karte.snapshot().ziele).toEqual([]);
+
+    first.karte.setDownloadKnopf(true);
+    expect(first.karte.snapshot().downloadKnopf).toBe(true);
+    first.karte.enterKoordinate(sample);
+    first.karte.deleteCache();
+    expect(first.karte.snapshot().downloadKnopf).toBe(true);
+    expect(first.karte.snapshot().ziele.map((ziel) => ziel.koordinate)).toEqual([
+      "32U MA 67030 78109",
+    ]);
+
+    const second = await openSheet({ marks, uebersicht: wideSquare });
+    expect(second.karte.snapshot().downloadKnopf).toBe(true);
+    expect(second.karte.snapshot().ziele.map((ziel) => ziel.koordinate)).toEqual([
+      "32U MA 67030 78109",
+    ]);
+
+    second.karte.setDownloadKnopf(false);
+    const third = await openSheet({ marks, uebersicht: wideSquare });
+    expect(third.karte.snapshot().downloadKnopf).toBe(false);
+    expect(third.karte.snapshot().ziele).toHaveLength(1);
+  });
+
+  test("downloadView fetches the finer Kacheln inside a view that covers a Blatt, current scale first", async () => {
+    const opened = await openSheet({
+      viewport: oneTile,
+      uebersicht: {
+        tileSizePx: 10,
+        resolutions: [10, 20],
+        blaetter: [{ minE: 0, minN: 0, maxE: 200, maxN: 200 }],
+        gebiete: [{ name: "Hessen", covers: "all" }],
+      },
+    });
+    opened.karte.zoomTo(20);
+    opened.karte.panTo({ easting: 100, northing: 100 });
+    opened.karte.downloadView();
+    expect(opened.karte.snapshot().visit).toEqual({ arrived: 0, total: 5 });
+
+    opened.karte.setOnline(true);
+    await opened.clock.tick();
+    opened.karte.setOnline(false);
+    expect(appearance(opened.karte, "1/0/0")).toBe("drawn");
+    opened.karte.zoomTo(10);
+    opened.karte.panTo({ easting: 50, northing: 50 });
+    expect(appearance(opened.karte, "0/0/0")).toBe("blank-not-on-device");
+    opened.karte.panTo({ easting: 150, northing: 150 });
+    expect(appearance(opened.karte, "0/1/1")).toBe("blank-not-on-device");
+  });
+
+  test("a later pan does not add Kacheln to the view fill", async () => {
+    const { karte, clock } = await openSheet({ viewport: oneTile });
+    karte.zoomTo(10);
+    karte.panTo({ easting: 50, northing: 50 });
+    karte.downloadView();
+    expect(karte.snapshot().visit).toEqual({ arrived: 0, total: 1 });
+
+    karte.panTo({ easting: 250, northing: 50 });
+    karte.zoomTo(30);
+    expect(karte.snapshot().visit).toEqual({ arrived: 0, total: 1 });
+    karte.zoomTo(10);
+
+    karte.setOnline(true);
+    await clock.tick();
+    expect(karte.snapshot().visit).toEqual({ arrived: 0, total: 1 });
+    await clock.tick();
+    expect(karte.snapshot().visit).toBeNull();
+    karte.setOnline(false);
+    karte.panTo({ easting: 50, northing: 50 });
+    expect(appearance(karte, TILE_A)).toBe("drawn");
+    karte.panTo({ easting: 150, northing: 50 });
+    expect(appearance(karte, TILE_B)).toBe("blank-not-on-device");
+  });
+
+  test("downloadView skips Kacheln already in the Cache", async () => {
+    const { karte, clock } = await openSheet({
+      viewport: threeTiles,
+      cache: createMemoryCache([TILE_A]),
+    });
+    karte.zoomTo(10);
+    karte.panTo({ easting: 150, northing: 50 });
+    karte.downloadView();
+    expect(appearance(karte, TILE_A)).toBe("drawn");
+    expect(karte.snapshot().visit).toEqual({ arrived: 0, total: 2 });
+    karte.setOnline(true);
+    await clock.tick();
+    await clock.tick();
+    expect(karte.snapshot().visit).toBeNull();
+    expect(appearance(karte, TILE_B)).toBe("drawn");
+    expect(appearance(karte, TILE_C)).toBe("drawn");
+  });
+
+  test("downloadView fetches nothing when the view is already in the Cache", async () => {
+    const { karte, clock } = await openSheet({
+      viewport: oneTile,
+      cache: createMemoryCache([TILE_A]),
+    });
+    karte.zoomTo(10);
+    karte.panTo({ easting: 50, northing: 50 });
+    karte.setOnline(true);
+    karte.downloadView();
+    expect(karte.snapshot().visit).toBeNull();
+    expect(appearance(karte, TILE_A)).toBe("drawn");
+    await clock.tick();
+    await clock.tick();
+    karte.setOnline(false);
+    karte.panTo({ easting: 150, northing: 50 });
+    expect(appearance(karte, TILE_B)).toBe("blank-not-on-device");
+    expect(karte.snapshot().visit).toBeNull();
+  });
+
+  test("a second downloadView while that fill is unfinished adds nothing", async () => {
+    const { karte, clock } = await openSheet({ viewport: threeTiles });
+    karte.zoomTo(10);
+    karte.panTo({ easting: 150, northing: 50 });
+    karte.downloadView();
+    expect(karte.snapshot().visit).toEqual({ arrived: 0, total: 3 });
+    karte.setOnline(true);
+    await clock.tick();
+    expect(karte.snapshot().visit).toEqual({ arrived: 1, total: 3 });
+    karte.panTo({ easting: 50, northing: 50 });
+    karte.downloadView();
+    expect(karte.snapshot().visit).toEqual({ arrived: 1, total: 3 });
+    await clock.tick();
+    await clock.tick();
+    expect(karte.snapshot().visit).toBeNull();
+    karte.setOnline(false);
+    karte.zoomTo(10);
+    karte.panTo({ easting: 250, northing: 50 });
+    expect(appearance(karte, TILE_C)).toBe("drawn");
+  });
+
+  test("startHessen while a view fill runs still fetches the missing Hessen Kacheln", async () => {
+    const opened = await openSheet({
+      viewport: oneTile,
+      uebersicht: {
+        tileSizePx: 10,
+        resolutions: [10],
+        blaetter: [{ minE: 0, minN: 0, maxE: 300, maxN: 100 }],
+        gebiete: [{ name: "Hessen", covers: [{ minE: 0, minN: 0, maxE: 200, maxN: 100 }] }],
+      },
+    });
+    opened.karte.zoomTo(10);
+    opened.karte.panTo({ easting: 250, northing: 50 });
+    opened.karte.downloadView();
+    expect(opened.karte.snapshot().visit).toEqual({ arrived: 0, total: 1 });
+    expect(opened.karte.snapshot().hessen).toEqual({ arrived: 0, total: 2 });
+    opened.karte.startHessen();
+    expect(opened.karte.snapshot().visit).toEqual({ arrived: 0, total: 3 });
+    opened.karte.setOnline(true);
+    await opened.clock.tick();
+    await opened.clock.tick();
+    await opened.clock.tick();
+    expect(opened.karte.snapshot().visit).toBeNull();
+    expect(opened.karte.snapshot().hessen).toEqual({ arrived: 2, total: 2 });
+    opened.karte.setOnline(false);
+    opened.karte.panTo({ easting: 50, northing: 50 });
+    expect(appearance(opened.karte, TILE_A)).toBe("drawn");
+  });
+
+  test("the view fill and the Hessen fill share one visit count, current view first", async () => {
+    const { karte, clock } = await openSheet({ viewport: oneTile });
+    karte.zoomTo(10);
+    karte.panTo({ easting: 50, northing: 50 });
+    karte.downloadView();
+    karte.startHessen();
+    expect(karte.snapshot().visit).toEqual({ arrived: 0, total: 3 });
+    karte.setOnline(true);
+    await clock.tick();
+    expect(karte.snapshot().visit).toEqual({ arrived: 1, total: 3 });
+    karte.setOnline(false);
+    expect(appearance(karte, TILE_A)).toBe("drawn");
+    karte.panTo({ easting: 150, northing: 50 });
+    expect(appearance(karte, TILE_B)).toBe("blank-not-on-device");
+    karte.setOnline(true);
+    await clock.tick();
+    await clock.tick();
+    expect(karte.snapshot().visit).toBeNull();
+    expect(karte.snapshot().hessen).toEqual({ arrived: 3, total: 3 });
+  });
+
+  test("closing drops the view fill, and downloadView again fetches what is still missing", async () => {
+    const opened = await openSheet({
+      viewport: oneTile,
+      uebersicht: {
+        tileSizePx: 10,
+        resolutions: [10, 20],
+        blaetter: [{ minE: 0, minN: 0, maxE: 200, maxN: 200 }],
+        gebiete: [{ name: "Hessen", covers: "all" }],
+      },
+    });
+    opened.karte.zoomTo(20);
+    opened.karte.panTo({ easting: 100, northing: 100 });
+    opened.karte.downloadView();
+    expect(opened.karte.snapshot().visit).toEqual({ arrived: 0, total: 5 });
+    opened.karte.setOnline(true);
+    await opened.clock.tick();
+    opened.karte.setAppOpen(false);
+    expect(opened.karte.snapshot().visit).toBeNull();
+    await opened.clock.tick();
+
+    opened.karte.setAppOpen(true);
+    expect(opened.karte.snapshot().visit).toBeNull();
+    await opened.clock.tick();
+    await opened.clock.tick();
+    opened.karte.setOnline(false);
+    opened.karte.zoomTo(10);
+    opened.karte.panTo({ easting: 50, northing: 50 });
+    expect(appearance(opened.karte, "0/0/0")).toBe("blank-not-on-device");
+
+    opened.karte.zoomTo(20);
+    opened.karte.panTo({ easting: 100, northing: 100 });
+    opened.karte.setOnline(true);
+    opened.karte.downloadView();
+    expect(opened.karte.snapshot().visit).toEqual({ arrived: 0, total: 4 });
+  });
+
+  test("deleteCache drops an unfinished view fill and does not start a fetch", async () => {
+    const { karte, clock } = await openSheet({ viewport: threeTiles });
+    karte.zoomTo(10);
+    karte.panTo({ easting: 150, northing: 50 });
+    karte.setOnline(true);
+    karte.downloadView();
+    karte.startHessen();
+    await clock.tick();
+    expect(karte.snapshot().visit).toEqual({ arrived: 1, total: 3 });
+    karte.deleteCache();
+    expect(karte.snapshot().visit).toBeNull();
+    expect(appearance(karte, TILE_A)).toBe("blank-not-on-device");
+    expect(appearance(karte, TILE_B)).toBe("blank-not-on-device");
+    await clock.tick();
+    expect(appearance(karte, TILE_B)).toBe("blank-not-on-device");
+    expect(karte.snapshot().visit).toBeNull();
+    expect(karte.snapshot().hessen).toEqual({ arrived: 0, total: 3 });
+  });
+
+  test("losing the network pauses the view fill and regaining it continues", async () => {
+    const { karte, clock } = await openSheet({ viewport: threeTiles });
+    karte.zoomTo(10);
+    karte.panTo({ easting: 150, northing: 50 });
+    karte.downloadView();
+    karte.setOnline(true);
+    await clock.tick();
+    karte.setOnline(false);
+    expect(karte.snapshot().visit).toEqual({ arrived: 1, total: 3 });
+    karte.panTo({ easting: 50, northing: 50 });
+    await clock.tick();
+    expect(appearance(karte, TILE_B)).toBe("blank-not-on-device");
+    expect(karte.snapshot().visit).toEqual({ arrived: 1, total: 3 });
+    karte.setOnline(true);
+    await clock.tick();
+    expect(karte.snapshot().visit).toEqual({ arrived: 2, total: 3 });
+    await clock.tick();
+    expect(karte.snapshot().visit).toBeNull();
+  });
+});

src/karte/session.ts

@@ -1,5 +1,5 @@
 import { maxResolutionMeters } from "../config";
-import { parseKoordinate } from "./koordinate";
+import { parseKoordinate, writeKoordinate } from "./koordinate";
 import type {
   KachelView,
   KarteOptions,
@@ -168,10 +168,12 @@ export async function openKarte(options: KarteOptions): Promise<KarteSession> {
   let personMovedView = false;
   let personEnteredZiel = false;
   let ziele = restoreZiele(markState.ziele);
+  let downloadKnopf = markState.downloadKnopf === true;
   let koordinateNotice: string | null = null;
   let koordinate = { gitter: "32U MA", rechtswert: "", hochwert: "" };
   let queue: string[] = [];
   let hessenFill: string[] | null = null;
+  let viewFill: string[] | null = null;
   let fetchesHeld = false;
   const inFlight = new Map<string, AbortController>();
   const failed = new Set<string>();
@@ -208,8 +210,12 @@ export async function openKarte(options: KarteOptions): Promise<KarteSession> {
     for (const listener of listeners) listener();
   }
 
-  function persistZiele(): void {
-    void marks.write({ heruntergeladen: [], ziele: ziele.map((item) => item.koordinate) });
+  function persistMarks(): void {
+    void marks.write({
+      heruntergeladen: [],
+      ziele: ziele.map((item) => item.koordinate),
+      downloadKnopf,
+    });
   }
 
   function restoreZiele(canonical: string[]): { koordinate: string; point: Point }[] {
@@ -282,6 +288,9 @@ export async function openKarte(options: KarteOptions): Promise<KarteSession> {
     if (hessenFill) {
       for (const id of hessenFill) push(id);
     }
+    if (viewFill) {
+      for (const id of viewFill) push(id);
+    }
     queue = ordered;
     pump();
   }
@@ -305,6 +314,7 @@ export async function openKarte(options: KarteOptions): Promise<KarteSession> {
       stored.add(id);
       await cache.put(id, bytes);
       if (hessenFill?.every((tile) => cached.has(tile))) hessenFill = null;
+      if (viewFill?.every((tile) => cached.has(tile))) viewFill = null;
     } catch (error) {
       if (!isAbort(error)) failed.add(id);
     } finally {
@@ -339,17 +349,48 @@ export async function openKarte(options: KarteOptions): Promise<KarteSession> {
       standort: standort ? { ...standort } : null,
       notice,
       koordinate: { ...koordinate },
+      downloadKnopf,
       hessen: { arrived: hessenArrived(), total: hessenIds.length },
       visit: visitOf(),
       kacheln: views,
     };
   }
 
+  function visitIds(): string[] {
+    const ids: string[] = [];
+    const seen = new Set<string>();
+    for (const id of hessenFill ?? []) {
+      if (seen.has(id)) continue;
+      seen.add(id);
+      ids.push(id);
+    }
+    for (const id of viewFill ?? []) {
+      if (seen.has(id)) continue;
+      seen.add(id);
+      ids.push(id);
+    }
+    return ids;
+  }
+
   function visitOf(): { arrived: number; total: number } | null {
-    if (!hessenFill) return null;
+    const ids = visitIds();
+    if (ids.length === 0) return null;
     let arrived = 0;
-    for (const id of hessenFill) if (cached.has(id)) arrived += 1;
-    return { arrived, total: hessenFill.length };
+    for (const id of ids) if (cached.has(id)) arrived += 1;
+    return { arrived, total: ids.length };
+  }
+
+  function idsCovering(rect: Rect): string[] {
+    const ids: string[] = [];
+    const seen = new Set<string>();
+    for (let zi = 0; zi < uebersicht.resolutions.length; zi += 1) {
+      for (const cell of cellsInView(zi, rect, uebersicht.resolutions, uebersicht.tileSizePx)) {
+        if (seen.has(cell.id) || !catalog.has(cell.id)) continue;
+        seen.add(cell.id);
+        ids.push(cell.id);
+      }
+    }
+    return ids;
   }
 
   const session: KarteSession = {
@@ -399,6 +440,7 @@ export async function openKarte(options: KarteOptions): Promise<KarteSession> {
       appOpen = open;
       if (!open) {
         hessenFill = null;
+        viewFill = null;
         abortInFlight(() => true);
       } else {
         releaseFetches();
@@ -417,6 +459,43 @@ export async function openKarte(options: KarteOptions): Promise<KarteSession> {
       }
       publish();
     },
+    tap(point) {
+      const radius = 44 * resolution;
+      let nearest = -1;
+      let nearestDistance = Infinity;
+      for (let index = 0; index < ziele.length; index += 1) {
+        const distance = Math.hypot(
+          point.easting - ziele[index].point.easting,
+          point.northing - ziele[index].point.northing,
+        );
+        if (distance <= radius && distance < nearestDistance) {
+          nearest = index;
+          nearestDistance = distance;
+        }
+      }
+      if (nearest >= 0) {
+        ziele = ziele.filter((_, index) => index !== nearest);
+        persistMarks();
+        publish();
+        return;
+      }
+      const written = writeKoordinate(point);
+      if (!written) return;
+      const parsed = parseKoordinate(written, (candidate) =>
+        uebersicht.blaetter.some((blatt) => coversPoint(blatt, candidate)),
+      );
+      if (!parsed.ok) return;
+      if (ziele.some((item) => item.koordinate === parsed.koordinate)) {
+        koordinateNotice = "Diese Koordinate ist schon ein Ziel.";
+        publish();
+        return;
+      }
+      koordinateNotice = null;
+      ziele = [{ koordinate: parsed.koordinate, point: parsed.point }, ...ziele];
+      personEnteredZiel = true;
+      persistMarks();
+      publish();
+    },
     enterKoordinate(input) {
       const parsed = parseKoordinate(input, (point) =>
         uebersicht.blaetter.some((blatt) => coversPoint(blatt, point)),
@@ -442,7 +521,7 @@ export async function openKarte(options: KarteOptions): Promise<KarteSession> {
       releaseFetches();
       center = { ...parsed.point };
       resolution = clamp(config.openResolutionMeters);
-      persistZiele();
+      persistMarks();
       rebuild();
       publish();
     },
@@ -450,7 +529,12 @@ export async function openKarte(options: KarteOptions): Promise<KarteSession> {
       const next = ziele.filter((item) => item.koordinate !== koordinate);
       if (next.length === ziele.length) return;
       ziele = next;
-      persistZiele();
+      persistMarks();
+      publish();
+    },
+    setDownloadKnopf(on) {
+      downloadKnopf = on;
+      persistMarks();
       publish();
     },
     centerOnStandort() {
@@ -481,9 +565,21 @@ export async function openKarte(options: KarteOptions): Promise<KarteSession> {
       rebuild();
       publish();
     },
+    downloadView() {
+      if (viewFill) return;
+      const missing = idsCovering(viewRect(center, resolution, viewport)).filter(
+        (id) => !cached.has(id),
+      );
+      if (missing.length === 0) return;
+      releaseFetches();
+      viewFill = missing;
+      rebuild();
+      publish();
+    },
     deleteCache() {
       fetchesHeld = true;
       hessenFill = null;
+      viewFill = null;
       abortInFlight(() => true);
       const ids = [...stored];
       cached.clear();

src/karte/types.ts

@@ -58,6 +58,7 @@ export type KarteSnapshot = {
   standort: Point | null;
   notice: string | null;
   koordinate: KoordinateText;
+  downloadKnopf: boolean;
   hessen: { arrived: number; total: number };
   visit: { arrived: number; total: number } | null;
   kacheln: KachelView[];
@@ -69,9 +70,16 @@ export interface CachePort {
   delete(ids: string[]): Promise<void>;
 }
 
+/** Device memory for Ziele and the Download-Knopf. `heruntergeladen` is only how an older value is read. */
+export type RememberedMarks = {
+  heruntergeladen: string[];
+  ziele: string[];
+  downloadKnopf: boolean;
+};
+
 export interface MarksPort {
-  read(): Promise<{ heruntergeladen: string[]; ziele: string[] }>;
-  write(state: { heruntergeladen: string[]; ziele: string[] }): Promise<void>;
+  read(): Promise<RememberedMarks>;
+  write(state: RememberedMarks): Promise<void>;
 }
 
 /** Fetches Kachel bytes. The session decides when, and stores them in the Cache. */
@@ -102,9 +110,12 @@ export type KarteSession = {
   setAppOpen(open: boolean): void;
   setOnline(online: boolean): void;
   enterKoordinate(input: KoordinateText): void;
+  tap(point: Point): void;
   deleteZiel(koordinate: string): void;
   centerOnStandort(): void;
   centerOnZiel(koordinate: string): void;
   startHessen(): void;
+  setDownloadKnopf(on: boolean): void;
+  downloadView(): void;
   deleteCache(): void;
 };

src/style.css

@@ -43,6 +43,14 @@ input {
   background: #e7e1d4;
 }
 
+.map-download {
+  position: absolute;
+  z-index: 2;
+  right: max(12px, env(safe-area-inset-right));
+  bottom: max(12px, env(safe-area-inset-bottom));
+  max-width: calc(100% - 24px);
+}
+
 .map .ol-viewport {
   background: #e7e1d4;
 }
@@ -123,6 +131,23 @@ label {
   font-weight: 600;
 }
 
+.download-knopf {
+  flex-direction: row;
+  align-items: center;
+  gap: 10px;
+  min-height: 44px;
+}
+
+.download-knopf input {
+  width: 1.25rem;
+  height: 1.25rem;
+  min-height: 0;
+  margin: 0;
+  padding: 0;
+  flex: 0 0 auto;
+  accent-color: #1e3328;
+}
+
 input {
   width: 100%;
   min-height: 44px;

src/ui/map.ts

@@ -217,6 +217,10 @@ export function createFieldMap(
     pushView();
   };
 
+  map.on("singleclick", (event) => {
+    const [easting, northing] = event.coordinate;
+    session.tap({ easting, northing });
+  });
   map.on("pointerdrag", rememberGesture);
   map.getViewport()?.addEventListener("wheel", rememberGesture, { passive: true });
   map.on("moveend", () => {

src/ui/screen.ts

@@ -36,6 +36,7 @@ export function mountScreen(
       </div>
     </div>
     <div id="einstellungen" class="fold" hidden>
+      <label class="download-knopf"><input type="checkbox" /> Download-Knopf</label>
       <div class="gebiet">
         <p hidden></p>
         <button type="button" class="hessen-download">Hessen herunterladen</button>
@@ -67,6 +68,7 @@ export function mountScreen(
   const hochwert = panel.querySelector<HTMLInputElement>('input[name="hochwert"]');
   const zielList = panel.querySelector<HTMLElement>(".ziel-list");
   const standortButton = panel.querySelector<HTMLButtonElement>(".actions button");
+  const downloadKnopf = panel.querySelector<HTMLInputElement>(".download-knopf input");
   const gebietBlock = panel.querySelector<HTMLElement>(".gebiet");
   const gebietText = panel.querySelector<HTMLElement>(".gebiet p");
   const gebietButton = panel.querySelector<HTMLButtonElement>(".gebiet button");
@@ -88,6 +90,7 @@ export function mountScreen(
     !hochwert ||
     !zielList ||
     !standortButton ||
+    !downloadKnopf ||
     !gebietBlock ||
     !gebietText ||
     !gebietButton ||
@@ -107,6 +110,11 @@ export function mountScreen(
   hochwert.value = opening.koordinate.hochwert;
 
   const fieldMap = createFieldMap(mapElement, uebersicht, session);
+  const viewDownload = document.createElement("button");
+  viewDownload.type = "button";
+  viewDownload.className = "map-download";
+  viewDownload.textContent = "Diese Ansicht herunterladen";
+  viewDownload.addEventListener("click", () => session.downloadView());
   let pendingWipe = false;
   let kachelKey = kachelnOf(session.snapshot());
 
@@ -133,6 +141,9 @@ export function mountScreen(
   });
 
   standortButton.addEventListener("click", () => session.centerOnStandort());
+  downloadKnopf.addEventListener("change", () => {
+    session.setDownloadKnopf(downloadKnopf.checked);
+  });
   gebietButton.addEventListener("click", () => {
     if (gebietButton.disabled) return;
     session.startHessen();
@@ -192,6 +203,10 @@ export function mountScreen(
       notice.textContent = "";
     }
 
+    downloadKnopf.checked = snapshot.downloadKnopf;
+    if (snapshot.downloadKnopf) mapElement.append(viewDownload);
+    else viewDownload.remove();
+
     const missing = snapshot.hessen.arrived < snapshot.hessen.total;
     gebietBlock.hidden = false;
     gebietButton.textContent = "Hessen herunterladen";