From 16442bab080dd591d53a0ebdd3f807fa2117c27e Mon Sep 17 00:00:00 2001
From: l5y <220195275+l5yth@users.noreply.github.com>
Date: Wed, 12 Nov 2025 20:49:03 +0100
Subject: [PATCH] Tighten map auto-fit behaviour (#435)

---
 .../__tests__/map-auto-fit-settings.test.js   | 47 ++++++++++++++++
 web/public/assets/js/app/main.js              | 12 ++---
 .../assets/js/app/map-auto-fit-settings.js    | 54 +++++++++++++++++++
 3 files changed, 107 insertions(+), 6 deletions(-)
 create mode 100644 web/public/assets/js/app/__tests__/map-auto-fit-settings.test.js
 create mode 100644 web/public/assets/js/app/map-auto-fit-settings.js

diff --git a/web/public/assets/js/app/__tests__/map-auto-fit-settings.test.js b/web/public/assets/js/app/__tests__/map-auto-fit-settings.test.js
new file mode 100644
index 0000000..cd86174
--- /dev/null
+++ b/web/public/assets/js/app/__tests__/map-auto-fit-settings.test.js
@@ -0,0 +1,47 @@
+/*
+ * Copyright © 2025-26 l5yth & contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import test from 'node:test';
+import assert from 'node:assert/strict';
+
+import { resolveAutoFitBoundsConfig, __testUtils } from '../map-auto-fit-settings.js';
+
+const { MINIMUM_AUTO_FIT_RANGE_KM, AUTO_FIT_PADDING_FRACTION } = __testUtils;
+
+test('resolveAutoFitBoundsConfig returns defaults without a distance limit', () => {
+  const config = resolveAutoFitBoundsConfig({ hasDistanceLimit: false, maxDistanceKm: null });
+  assert.equal(config.paddingFraction, AUTO_FIT_PADDING_FRACTION);
+  assert.equal(config.minimumRangeKm, MINIMUM_AUTO_FIT_RANGE_KM);
+});
+
+test('resolveAutoFitBoundsConfig constrains minimum range by the limit radius', () => {
+  const config = resolveAutoFitBoundsConfig({ hasDistanceLimit: true, maxDistanceKm: 2 });
+  assert.equal(config.paddingFraction, AUTO_FIT_PADDING_FRACTION);
+  assert.ok(config.minimumRangeKm >= MINIMUM_AUTO_FIT_RANGE_KM);
+  assert.ok(config.minimumRangeKm <= 2);
+});
+
+test('resolveAutoFitBoundsConfig respects small distance limits', () => {
+  const config = resolveAutoFitBoundsConfig({ hasDistanceLimit: true, maxDistanceKm: 0.1 });
+  assert.equal(config.paddingFraction, AUTO_FIT_PADDING_FRACTION);
+  assert.equal(config.minimumRangeKm, 0.1);
+});
+
+test('resolveAutoFitBoundsConfig tolerates invalid input', () => {
+  const config = resolveAutoFitBoundsConfig({ hasDistanceLimit: true, maxDistanceKm: -5 });
+  assert.equal(config.paddingFraction, AUTO_FIT_PADDING_FRACTION);
+  assert.equal(config.minimumRangeKm, MINIMUM_AUTO_FIT_RANGE_KM);
+});
diff --git a/web/public/assets/js/app/main.js b/web/public/assets/js/app/main.js
index d9db049..ce682d8 100644
--- a/web/public/assets/js/app/main.js
+++ b/web/public/assets/js/app/main.js
@@ -16,6 +16,7 @@
 
 import { computeBoundingBox, computeBoundsForPoints, haversineDistanceKm } from './map-bounds.js';
 import { createMapAutoFitController } from './map-auto-fit-controller.js';
+import { resolveAutoFitBoundsConfig } from './map-auto-fit-settings.js';
 import { attachNodeInfoRefreshToMarker, overlayToPopupNode } from './map-marker-node-info.js';
 import { createShortInfoOverlayStack } from './short-info-overlay-manager.js';
 import { refreshNodeInformation } from './node-details.js';
@@ -394,6 +395,10 @@ let messagesById = new Map();
     ? config.maxDistanceKm
     : null;
   const LIMIT_DISTANCE = Number.isFinite(MAX_DISTANCE_KM);
+  const autoFitBoundsConfig = resolveAutoFitBoundsConfig({
+    hasDistanceLimit: LIMIT_DISTANCE,
+    maxDistanceKm: MAX_DISTANCE_KM
+  });
   const INITIAL_VIEW_PADDING_PX = 12;
   const AUTO_FIT_PADDING_PX = 12;
   const MAX_INITIAL_ZOOM = 13;
@@ -3587,12 +3592,7 @@ let messagesById = new Map();
       });
     }
     if (pts.length && fitBoundsEl && fitBoundsEl.checked) {
-      const bounds = computeBoundsForPoints(pts, {
-        paddingFraction: 0.2,
-        minimumRangeKm: LIMIT_DISTANCE
-          ? Math.min(Math.max(MAX_DISTANCE_KM * 0.1, 1), MAX_DISTANCE_KM)
-          : 1
-      });
+      const bounds = computeBoundsForPoints(pts, { ...autoFitBoundsConfig });
       fitMapToBounds(bounds, { animate: false, paddingPx: AUTO_FIT_PADDING_PX });
     }
     overlayStack.cleanupOrphans();
diff --git a/web/public/assets/js/app/map-auto-fit-settings.js b/web/public/assets/js/app/map-auto-fit-settings.js
new file mode 100644
index 0000000..1568b11
--- /dev/null
+++ b/web/public/assets/js/app/map-auto-fit-settings.js
@@ -0,0 +1,54 @@
+/*
+ * Copyright © 2025-26 l5yth & contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const MINIMUM_AUTO_FIT_RANGE_KM = 0.25;
+const AUTO_FIT_PADDING_FRACTION = 0.02;
+
+/**
+ * Resolve auto-fit bounds configuration for the active map constraints.
+ *
+ * @param {{ hasDistanceLimit: boolean, maxDistanceKm: number | null }} options
+ *   - ``hasDistanceLimit`` indicates whether a maximum display radius is enforced.
+ *   - ``maxDistanceKm`` provides the configured maximum distance in kilometres.
+ * @returns {{ paddingFraction: number, minimumRangeKm: number }}
+ *   Bounds options suitable for ``computeBoundsForPoints``.
+ */
+export function resolveAutoFitBoundsConfig({ hasDistanceLimit, maxDistanceKm } = {}) {
+  const effectiveMaxDistance = Number.isFinite(maxDistanceKm) && maxDistanceKm > 0
+    ? maxDistanceKm
+    : null;
+
+  if (!hasDistanceLimit || !effectiveMaxDistance) {
+    return {
+      paddingFraction: AUTO_FIT_PADDING_FRACTION,
+      minimumRangeKm: MINIMUM_AUTO_FIT_RANGE_KM
+    };
+  }
+
+  const minimumRange = Math.min(MINIMUM_AUTO_FIT_RANGE_KM, effectiveMaxDistance);
+  const resolvedMinimumRange = Number.isFinite(minimumRange) && minimumRange > 0
+    ? minimumRange
+    : MINIMUM_AUTO_FIT_RANGE_KM;
+  return {
+    paddingFraction: AUTO_FIT_PADDING_FRACTION,
+    minimumRangeKm: resolvedMinimumRange
+  };
+}
+
+export const __testUtils = {
+  MINIMUM_AUTO_FIT_RANGE_KM,
+  AUTO_FIT_PADDING_FRACTION
+};