From 18bc70d4fa7453c1191fc446327d1e24d5defe6d Mon Sep 17 00:00:00 2001
From: Iván Ávalos <avalos@disroot.org>
Date: Sun, 16 Jan 2022 02:31:26 -0600
Subject: Set zoom limits of mapControl by converting zoom levels to Mapnik
 scale denominators

---
 .../TrackerMap/android/map/MapFragment.kt          | 46 ++++++++++++++++++----
 .../mx/trackermap/TrackerMap/utils/MapCalculus.kt  | 31 +++++++++++++++
 2 files changed, 69 insertions(+), 8 deletions(-)
 create mode 100644 shared/src/commonMain/kotlin/mx/trackermap/TrackerMap/utils/MapCalculus.kt

diff --git a/androidApp/src/main/java/mx/trackermap/TrackerMap/android/map/MapFragment.kt b/androidApp/src/main/java/mx/trackermap/TrackerMap/android/map/MapFragment.kt
index 4a63e65..9fa37c9 100644
--- a/androidApp/src/main/java/mx/trackermap/TrackerMap/android/map/MapFragment.kt
+++ b/androidApp/src/main/java/mx/trackermap/TrackerMap/android/map/MapFragment.kt
@@ -18,6 +18,7 @@ import mil.nga.sf.wkt.GeometryReader
 import java.io.File
 import mx.trackermap.TrackerMap.android.R
 import mx.trackermap.TrackerMap.client.models.Geofence
+import mx.trackermap.TrackerMap.utils.MapCalculus
 import mx.trackermap.TrackerMap.utils.MarkerType
 
 typealias MarkerCallback = (Int?) -> Unit
@@ -60,7 +61,10 @@ class MapFragment : GlobeMapFragment() {
         if (tileInfo == null) {
             val layer = resources.getStringArray(R.array.maps_streets_tile_url)
             val tmpInfo = RemoteTileInfoNew(layer[0], layer[1].toInt(), layer[2].toInt())
-            tileInfo = makeTileInfo(layer[0], tmpInfo)
+            tileInfo = tileInfoSetCacheDir(layer[0], tmpInfo)
+            tileInfo?.let {
+                setZoomLimits(it.minZoom, it.maxZoom)
+            }
         }
 
         val params = SamplingParams()
@@ -77,7 +81,16 @@ class MapFragment : GlobeMapFragment() {
 
         val latitude = 23.191
         val longitude = -100.36
-        focusOn(latitude, longitude, zoom = 0.4, animated = false)
+        focusOn(latitude, longitude, height = 0.4, animated = false)
+    }
+
+    override fun mapDidStopMoving(
+        mapControl: MapController?,
+        corners: Array<out Point3d>?,
+        userMotion: Boolean
+    ) {
+        super.mapDidStopMoving(mapControl, corners, userMotion)
+        Log.d("MapFragment", "Height: ${mapControl?.height}")
     }
 
     override fun userDidSelect(
@@ -221,7 +234,8 @@ class MapFragment : GlobeMapFragment() {
             mbr.expandByFraction(0.1)
 
             mapControl.addPostSurfaceRunnable {
-                val zoom = mapControl.findHeightToViewBounds(mbr, mbr.middle())
+                val zoom = mapControl.zoomLimitMax.coerceAtLeast(
+                    mapControl.findHeightToViewBounds(mbr, mbr.middle()))
                 mapControl.setPositionGeo(mbr.middle(), zoom)
             }
         }
@@ -301,17 +315,19 @@ class MapFragment : GlobeMapFragment() {
         ))
     }
 
-    fun focusOn(latitude: Double, longitude: Double, zoom: Double = 0.00009, animated: Boolean = true) {
+    fun focusOn(latitude: Double, longitude: Double, height: Double = 0.00009, animated: Boolean = true) {
         val lat = latitude * Math.PI / 180
         val lon = longitude * Math.PI / 180
+        // Ensure height is equal or higher than bottom limit
+        val z = mapControl.zoomLimitMin.coerceAtLeast(height)
         if (animated) {
-            mapControl.animatePositionGeo(lon, lat, zoom, 0.2)
+            mapControl.animatePositionGeo(lon, lat, z, 0.2)
         } else {
-            mapControl.setPositionGeo(lon, lat, zoom)
+            mapControl.setPositionGeo(lon, lat, z)
         }
     }
 
-    private fun makeTileInfo(url: String, tileInfo: TileInfoNew): TileInfoNew? {
+    private fun tileInfoSetCacheDir(url: String, tileInfo: TileInfoNew): TileInfoNew? {
         return context?.let {
             val cacheDirName = url.toByteArray(Charsets.UTF_8).md5().hex
             val cacheDirMap = File(it.cacheDir, cacheDirName)
@@ -323,11 +339,25 @@ class MapFragment : GlobeMapFragment() {
         }
     }
 
+    private fun setZoomLimits(minZoom: Int, maxZoom: Int) {
+        mapControl?.setZoomLimits(
+            mapControl.heightForMapScale(
+                MapCalculus.zoomLevelToScale(maxZoom)
+                    ?: MapCalculus.zoomLevelToScale(20)!!
+            ),
+            mapControl.heightForMapScale(
+                MapCalculus.zoomLevelToScale(minZoom)
+                    ?: MapCalculus.zoomLevelToScale(1)!!
+            )
+        )
+    }
+
     fun updateTileInfo(url: String, tileInfo: TileInfoNew) {
         context?.let {
-            this.tileInfo = makeTileInfo(url, tileInfo)
+            this.tileInfo = tileInfoSetCacheDir(url, tileInfo)
             this.tileInfo?.let {
                 loader?.changeTileInfo(it)
+                setZoomLimits(tileInfo.minZoom, tileInfo.maxZoom)
             }
         }
     }
diff --git a/shared/src/commonMain/kotlin/mx/trackermap/TrackerMap/utils/MapCalculus.kt b/shared/src/commonMain/kotlin/mx/trackermap/TrackerMap/utils/MapCalculus.kt
new file mode 100644
index 0000000..8c58179
--- /dev/null
+++ b/shared/src/commonMain/kotlin/mx/trackermap/TrackerMap/utils/MapCalculus.kt
@@ -0,0 +1,31 @@
+package mx.trackermap.TrackerMap.utils
+
+class MapCalculus {
+    companion object {
+        // Source: https://github.com/openstreetmap/mapnik-stylesheets/blob/master/zoom-to-scale.txt
+        fun zoomLevelToScale(zoom: Int): Double? =
+            when (zoom) {
+                1 -> 279541132.014
+                2 -> 139770566.007
+                3 -> 69885283.0036
+                4 -> 34942641.5018
+                5 -> 17471320.7509
+                6 -> 8735660.37545
+                7 -> 4367830.18772
+                8 -> 2183915.09386
+                9 -> 1091957.54693
+                10 -> 545978.773466
+                11 -> 272989.386733
+                12 -> 136494.693366
+                13 -> 68247.3466832
+                14 -> 34123.6733416
+                15 -> 17061.8366708
+                16 -> 8530.9183354
+                17 -> 4265.4591677
+                18 -> 2132.72958385
+                19 -> 1000.0 // made up
+                20 -> 500.0 // made up
+                else -> null
+        }
+    }
+}
\ No newline at end of file
-- 
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