Initial commit

.gitignore

@@ -0,0 +1,5 @@
+build/
+.gradle/
+.idea/
+
+*.iml

build.gradle.kts

@@ -0,0 +1,58 @@
+import org.jetbrains.compose.compose
+import org.jetbrains.compose.desktop.application.dsl.TargetFormat
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+
+plugins {
+    kotlin("multiplatform")
+    id("org.jetbrains.compose")
+}
+
+group = "center.sciptog"
+version = "1.0-SNAPSHOT"
+
+repositories {
+    google()
+    mavenCentral()
+    maven("https://maven.pkg.jetbrains.space/public/p/compose/dev")
+}
+
+val ktorVersion by extra("2.0.3")
+
+kotlin {
+    jvm {
+        compilations.all {
+            kotlinOptions.jvmTarget = "11"
+        }
+        withJava()
+    }
+    sourceSets {
+        commonMain{
+            dependencies{
+                api(compose.runtime)
+                api(compose.foundation)
+                api(compose.material)
+                implementation("io.ktor:ktor-client-core:$ktorVersion")
+                implementation("io.ktor:ktor-client-cio:$ktorVersion")
+                implementation("io.github.microutils:kotlin-logging:2.1.23")
+                implementation("ch.qos.logback:logback-classic:1.2.11")
+            }
+        }
+        val jvmMain by getting {
+            dependencies {
+                implementation(compose.desktop.currentOs)
+            }
+        }
+        val jvmTest by getting
+    }
+}
+
+compose.desktop {
+    application {
+        mainClass = "MainKt"
+        nativeDistributions {
+            targetFormats(TargetFormat.Dmg, TargetFormat.Msi, TargetFormat.Deb)
+            packageName = "maps-kt-compose"
+            packageVersion = "1.0.0"
+        }
+    }
+}

gradle.properties

@@ -0,0 +1,4 @@
+kotlin.code.style=official
+kotlin.version=1.6.10
+agp.version=4.2.2
+compose.version=1.1.0

gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,5 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.3.3-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

gradlew

@@ -0,0 +1,234 @@
+#!/bin/sh
+
+#
+# Copyright © 2015-2021 the original authors.
+#
+# 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
+#
+#      https://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.
+#
+
+##############################################################################
+#
+#   Gradle start up script for POSIX generated by Gradle.
+#
+#   Important for running:
+#
+#   (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
+#       noncompliant, but you have some other compliant shell such as ksh or
+#       bash, then to run this script, type that shell name before the whole
+#       command line, like:
+#
+#           ksh Gradle
+#
+#       Busybox and similar reduced shells will NOT work, because this script
+#       requires all of these POSIX shell features:
+#         * functions;
+#         * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
+#           «${var#prefix}», «${var%suffix}», and «$( cmd )»;
+#         * compound commands having a testable exit status, especially «case»;
+#         * various built-in commands including «command», «set», and «ulimit».
+#
+#   Important for patching:
+#
+#   (2) This script targets any POSIX shell, so it avoids extensions provided
+#       by Bash, Ksh, etc; in particular arrays are avoided.
+#
+#       The "traditional" practice of packing multiple parameters into a
+#       space-separated string is a well documented source of bugs and security
+#       problems, so this is (mostly) avoided, by progressively accumulating
+#       options in "$@", and eventually passing that to Java.
+#
+#       Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
+#       and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
+#       see the in-line comments for details.
+#
+#       There are tweaks for specific operating systems such as AIX, CygWin,
+#       Darwin, MinGW, and NonStop.
+#
+#   (3) This script is generated from the Groovy template
+#       https://github.com/gradle/gradle/blob/master/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       within the Gradle project.
+#
+#       You can find Gradle at https://github.com/gradle/gradle/.
+#
+##############################################################################
+
+# Attempt to set APP_HOME
+
+# Resolve links: $0 may be a link
+app_path=$0
+
+# Need this for daisy-chained symlinks.
+while
+    APP_HOME=${app_path%"${app_path##*/}"}  # leaves a trailing /; empty if no leading path
+    [ -h "$app_path" ]
+do
+    ls=$( ls -ld "$app_path" )
+    link=${ls#*' -> '}
+    case $link in             #(
+      /*)   app_path=$link ;; #(
+      *)    app_path=$APP_HOME$link ;;
+    esac
+done
+
+APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit
+
+APP_NAME="Gradle"
+APP_BASE_NAME=${0##*/}
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD=maximum
+
+warn () {
+    echo "$*"
+} >&2
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+} >&2
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "$( uname )" in                #(
+  CYGWIN* )         cygwin=true  ;; #(
+  Darwin* )         darwin=true  ;; #(
+  MSYS* | MINGW* )  msys=true    ;; #(
+  NONSTOP* )        nonstop=true ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD=$JAVA_HOME/jre/sh/java
+    else
+        JAVACMD=$JAVA_HOME/bin/java
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD=java
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+    case $MAX_FD in #(
+      max*)
+        MAX_FD=$( ulimit -H -n ) ||
+            warn "Could not query maximum file descriptor limit"
+    esac
+    case $MAX_FD in  #(
+      '' | soft) :;; #(
+      *)
+        ulimit -n "$MAX_FD" ||
+            warn "Could not set maximum file descriptor limit to $MAX_FD"
+    esac
+fi
+
+# Collect all arguments for the java command, stacking in reverse order:
+#   * args from the command line
+#   * the main class name
+#   * -classpath
+#   * -D...appname settings
+#   * --module-path (only if needed)
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
+
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if "$cygwin" || "$msys" ; then
+    APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
+    CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
+
+    JAVACMD=$( cygpath --unix "$JAVACMD" )
+
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    for arg do
+        if
+            case $arg in                                #(
+              -*)   false ;;                            # don't mess with options #(
+              /?*)  t=${arg#/} t=/${t%%/*}              # looks like a POSIX filepath
+                    [ -e "$t" ] ;;                      #(
+              *)    false ;;
+            esac
+        then
+            arg=$( cygpath --path --ignore --mixed "$arg" )
+        fi
+        # Roll the args list around exactly as many times as the number of
+        # args, so each arg winds up back in the position where it started, but
+        # possibly modified.
+        #
+        # NB: a `for` loop captures its iteration list before it begins, so
+        # changing the positional parameters here affects neither the number of
+        # iterations, nor the values presented in `arg`.
+        shift                   # remove old arg
+        set -- "$@" "$arg"      # push replacement arg
+    done
+fi
+
+# Collect all arguments for the java command;
+#   * $DEFAULT_JVM_OPTS, $JAVA_OPTS, and $GRADLE_OPTS can contain fragments of
+#     shell script including quotes and variable substitutions, so put them in
+#     double quotes to make sure that they get re-expanded; and
+#   * put everything else in single quotes, so that it's not re-expanded.
+
+set -- \
+        "-Dorg.gradle.appname=$APP_BASE_NAME" \
+        -classpath "$CLASSPATH" \
+        org.gradle.wrapper.GradleWrapperMain \
+        "$@"
+
+# Use "xargs" to parse quoted args.
+#
+# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
+#
+# In Bash we could simply go:
+#
+#   readarray ARGS < <( xargs -n1 <<<"$var" ) &&
+#   set -- "${ARGS[@]}" "$@"
+#
+# but POSIX shell has neither arrays nor command substitution, so instead we
+# post-process each arg (as a line of input to sed) to backslash-escape any
+# character that might be a shell metacharacter, then use eval to reverse
+# that process (while maintaining the separation between arguments), and wrap
+# the whole thing up as a single "set" statement.
+#
+# This will of course break if any of these variables contains a newline or
+# an unmatched quote.
+#
+
+eval "set -- $(
+        printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
+        xargs -n1 |
+        sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
+        tr '\n' ' '
+    )" '"$@"'
+
+exec "$JAVACMD" "$@"

gradlew.bat

@@ -0,0 +1,89 @@
+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      https://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+
+@if "%DEBUG%" == "" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%" == "" set DIRNAME=.
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if "%ERRORLEVEL%" == "0" goto execute
+
+echo.
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto execute
+
+echo.
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
+
+:end
+@rem End local scope for the variables with windows NT shell
+if "%ERRORLEVEL%"=="0" goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
+exit /b 1
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega

settings.gradle.kts

@@ -0,0 +1,17 @@
+// Copyright 2000-2022 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+pluginManagement {
+    repositories {
+        google()
+        gradlePluginPortal()
+        mavenCentral()
+        maven("https://maven.pkg.jetbrains.space/public/p/compose/dev")
+    }
+
+    plugins {
+        kotlin("multiplatform").version(extra["kotlin.version"] as String)
+        id("org.jetbrains.compose").version(extra["compose.version"] as String)
+    }
+}
+
+rootProject.name = "maps-kt-compose"
+

src/jvmMain/kotlin/Main.kt

@@ -0,0 +1,31 @@
+// Copyright 2000-2021 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+import androidx.compose.desktop.ui.tooling.preview.Preview
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.material.Button
+import androidx.compose.material.MaterialTheme
+import androidx.compose.material.Text
+import androidx.compose.runtime.*
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.window.Window
+import androidx.compose.ui.window.application
+import centre.sciprog.maps.compose.GeodeticMapCoordinates
+import centre.sciprog.maps.compose.MapRectangle
+import centre.sciprog.maps.compose.MapView
+
+@Composable
+@Preview
+fun App() {
+    MaterialTheme {
+        val map = MapRectangle(
+            GeodeticMapCoordinates.ofDegrees(66.513260, 0.0),
+            GeodeticMapCoordinates.ofDegrees(40.979897, 44.999999),
+        )
+        MapView(map, modifier = Modifier.fillMaxSize())
+    }
+}
+
+fun main() = application {
+    Window(onCloseRequest = ::exitApplication) {
+        App()
+    }
+}

src/jvmMain/kotlin/centre/sciprog/maps/compose/MapView.kt

@@ -0,0 +1,179 @@
+package centre.sciprog.maps.compose
+
+import androidx.compose.foundation.Canvas
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.material.Text
+import androidx.compose.runtime.*
+import androidx.compose.ui.ExperimentalComposeUiApi
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.geometry.Offset
+import androidx.compose.ui.geometry.Size
+import androidx.compose.ui.graphics.ImageBitmap
+import androidx.compose.ui.graphics.toComposeImageBitmap
+import androidx.compose.ui.input.pointer.PointerEventType
+import androidx.compose.ui.input.pointer.onPointerEvent
+import io.ktor.client.HttpClient
+import io.ktor.client.engine.cio.CIO
+import io.ktor.client.request.get
+import io.ktor.client.statement.readBytes
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Deferred
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.async
+import mu.KotlinLogging
+import org.jetbrains.skia.Image
+import java.net.URL
+import kotlin.math.*
+
+
+private const val TILE_SIZE = 256
+
+
+private data class OsMapTileId(
+    val zoom: Int,
+    val i: Int,
+    val j: Int,
+)
+
+private fun OsMapTileId.osmUrl() = URL("https://tile.openstreetmap.org/${zoom.toInt()}/${i}/${j}.png")
+
+private data class OsMapTile(
+    val id: OsMapTileId,
+    val image: ImageBitmap,
+)
+
+private class OsMapCache(val scope: CoroutineScope, val client: HttpClient) {
+    private val cache = HashMap<OsMapTileId, Deferred<ImageBitmap>>()
+
+    public suspend fun loadTile(id: OsMapTileId): OsMapTile {
+        val image = cache.getOrPut(id) {
+            scope.async(Dispatchers.IO) {
+                val url = id.osmUrl()
+                val byteArray = client.get(url).readBytes()
+
+                logger.debug { "Finished downloading map tile with id $id from $url" }
+
+                Image.makeFromEncoded(byteArray).toComposeImageBitmap()
+            }
+        }.await()
+
+        return OsMapTile(id, image)
+    }
+}
+
+
+private val logger = KotlinLogging.logger("MapView")
+
+@OptIn(ExperimentalComposeUiApi::class)
+@Composable
+fun MapView(
+    initialRectangle: MapRectangle,
+    modifier: Modifier,
+    client: HttpClient = remember { HttpClient(CIO) },
+    initialZoom: Double? = null,
+) {
+    val mapRectangle by remember { mutableStateOf(initialRectangle) }
+
+    val scope = rememberCoroutineScope()
+    val mapCache = remember { OsMapCache(scope, client) }
+
+    val mapTiles = mutableStateListOf<OsMapTile>()
+
+    var canvasSize by remember { mutableStateOf(Size(512f,512f)) }
+
+    //TODO provide override for tiling
+    val numTilesHorizontal by derivedStateOf {
+        ceil(canvasSize.width / TILE_SIZE).toInt()
+
+    }
+    val numTilesVertical by derivedStateOf {
+        ceil(canvasSize.height / TILE_SIZE).toInt()
+    }
+
+    val zoom by derivedStateOf {
+        val xOffsetUnscaled = mapRectangle.bottomRight.longitude - mapRectangle.topLeft.longitude
+        val yOffsetUnscaled = ln(
+            tan(PI / 4 + mapRectangle.topLeft.latitude / 2) / tan(PI / 4 + mapRectangle.bottomRight.latitude / 2)
+        )
+
+        initialZoom ?: ceil(
+            log2(
+                PI / max(
+                    abs(xOffsetUnscaled / numTilesHorizontal),
+                    abs(yOffsetUnscaled / numTilesVertical)
+                )
+            )
+        )
+    }
+
+    //val scaleFactor = WebMercatorProjection.scaleFactor(computedZoom)
+
+    val topLeft by derivedStateOf { with(WebMercatorProjection) { mapRectangle.topLeft.toMercator(zoom) } }
+
+    LaunchedEffect(canvasSize, zoom) {
+
+        val startIndexHorizontal = (topLeft.x / TILE_SIZE).toInt()
+        val startIndexVertical = (topLeft.y / TILE_SIZE).toInt()
+
+        mapTiles.clear()
+
+        for (j in 0 until numTilesVertical) {
+            for (i in 0 until numTilesHorizontal) {
+                val tileId = OsMapTileId(zoom.toInt(), startIndexHorizontal + i, startIndexVertical + j)
+                val tile = mapCache.loadTile(tileId)
+                mapTiles.add(tile)
+            }
+        }
+
+    }
+
+    var coordinates by remember { mutableStateOf<GeodeticMapCoordinates?>(null) }
+
+    val canvasModifier = modifier.onPointerEvent(PointerEventType.Move) {
+        val position = it.changes.first().position
+        val screenCoordinates = TileWebMercatorCoordinates(
+            zoom,
+            position.x.toDouble() + topLeft.x,
+            position.y.toDouble() + topLeft.y
+        )
+        coordinates = with(WebMercatorProjection) {
+            screenCoordinates.toGeodetic()
+        }
+    }.onPointerEvent(PointerEventType.Press) {
+        println(coordinates)
+    }.fillMaxSize()
+//        .pointerInput(Unit) {
+//        forEachGesture {
+//            awaitPointerEventScope {
+//                val down = awaitFirstDown()
+//                drag(down.id) {
+//                    println(currentEvent.mouseEvent?.button)
+//                }
+//            }
+//        }
+//    }
+
+    Column {
+        //Text(coordinates.toString())
+        Canvas(canvasModifier) {
+            if(canvasSize!= size) {
+                canvasSize = size
+                logger.debug { "Redraw canvas. Size: $size" }
+            }
+
+            mapTiles.forEach { (id, image) ->
+                //converting back from tile index to screen offset
+                logger.debug { "Drawing tile $id" }
+                val offset = Offset(
+                    id.i.toFloat() * TILE_SIZE - topLeft.x.toFloat(),
+                    id.j.toFloat() * TILE_SIZE - topLeft.y.toFloat()
+                )
+                drawImage(
+                    image = image,
+                    topLeft = offset
+                )
+            }
+        }
+    }
+}

src/jvmMain/kotlin/centre/sciprog/maps/compose/MercatorProjection.kt

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2018-2021 KMath contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package centre.sciprog.maps.compose
+
+import kotlin.math.*
+
+public data class MercatorCoordinates(val x: Double, val y: Double)
+
+/**
+ * @param baseLongitude the longitude offset in radians
+ * @param radius the average radius of the Earth
+ * @param correctedRadius optional radius correction to account for ellipsoid model
+ */
+public open class MercatorProjection(
+    public val baseLongitude: Double = 0.0,
+    protected val radius: Double = DEFAULT_EARTH_RADIUS,
+    private val correctedRadius: ((GeodeticMapCoordinates) -> Double)? = null,
+) {
+
+    public fun MercatorCoordinates.toGeodetic(): GeodeticMapCoordinates {
+        val res = GeodeticMapCoordinates.ofRadians(
+            atan(sinh(y / radius)),
+            baseLongitude + x / radius,
+        )
+        return if (correctedRadius != null) {
+            val r = correctedRadius.invoke(res)
+            GeodeticMapCoordinates.ofRadians(
+                atan(sinh(y / r)),
+                baseLongitude + x / r,
+            )
+        } else {
+            res
+        }
+    }
+
+    /**
+     * https://en.wikipedia.org/wiki/Web_Mercator_projection#Formulas
+     */
+    public fun GeodeticMapCoordinates.toMercator(): MercatorCoordinates {
+        require(abs(latitude) <= MAXIMUM_LATITUDE) { "Latitude exceeds the maximum latitude for mercator coordinates" }
+        val r = correctedRadius?.invoke(this) ?: radius
+        return MercatorCoordinates(
+            x = r * (longitude - baseLongitude),
+            y = r * ln(tan(PI / 4 + latitude / 2))
+        )
+    }
+
+    public companion object : MercatorProjection(0.0, 6378137.0) {
+        public const val MAXIMUM_LATITUDE: Double = 85.05113
+        public val DEFAULT_EARTH_RADIUS: Double = radius
+    }
+}

src/jvmMain/kotlin/centre/sciprog/maps/compose/WebMercatorProjection.kt

@@ -0,0 +1,62 @@
+/*
+ * Copyright 2018-2021 KMath contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package centre.sciprog.maps.compose
+
+import kotlin.math.*
+
+public data class TileWebMercatorCoordinates(val zoom: Double, val x: Double, val y: Double)
+
+public object WebMercatorProjection  {
+
+    /**
+     * Compute radians to projection coordinates ratio for given [zoom] factor
+     */
+    public fun scaleFactor(zoom: Double) = 256.0 / 2 / PI * 2.0.pow(zoom)
+
+    public fun TileWebMercatorCoordinates.toGeodetic(): GeodeticMapCoordinates {
+        val scaleFactor = scaleFactor(zoom)
+        val longitude = x / scaleFactor - PI
+        val latitude = (atan(exp(PI - y / scaleFactor)) - PI / 4) * 2
+        return GeodeticMapCoordinates.ofRadians(latitude, longitude)
+    }
+
+    /**
+     * https://en.wikipedia.org/wiki/Web_Mercator_projection#Formulas
+     */
+    public fun GeodeticMapCoordinates.toMercator(zoom: Double): TileWebMercatorCoordinates {
+        require(abs(latitude) <= MercatorProjection.MAXIMUM_LATITUDE) { "Latitude exceeds the maximum latitude for mercator coordinates" }
+
+        val scaleFactor = scaleFactor(zoom)
+        return TileWebMercatorCoordinates(
+            zoom = zoom,
+            x = scaleFactor * (longitude + PI),
+            y = scaleFactor * (PI - ln(tan(PI / 4 + latitude / 2)))
+        )
+    }
+
+    /**
+     * Compute and offset of [target] coordinate relative to [base] coordinate. If [zoom] is null, then optimal zoom
+     * will be computed to put the resulting x and y coordinates between -127.0 and 128.0
+     */
+    public fun computeOffset(
+        base: GeodeticMapCoordinates,
+        target: GeodeticMapCoordinates,
+        zoom: Double? = null,
+    ): TileWebMercatorCoordinates {
+        val xOffsetUnscaled = target.longitude - base.longitude
+        val yOffsetUnscaled = ln(
+            tan(PI / 4 + target.latitude / 2) / tan(PI / 4 + base.latitude / 2)
+        )
+
+        val computedZoom = zoom ?: ceil(log2(PI / max(abs(xOffsetUnscaled), abs(yOffsetUnscaled))))
+        val scaleFactor = scaleFactor(computedZoom)
+        return TileWebMercatorCoordinates(
+            computedZoom,
+            x = scaleFactor * xOffsetUnscaled,
+            y = scaleFactor * yOffsetUnscaled
+        )
+    }
+}

src/jvmMain/kotlin/centre/sciprog/maps/compose/coordinates.kt

@@ -0,0 +1,60 @@
+package centre.sciprog.maps.compose
+
+import kotlinx.coroutines.flow.Flow
+import kotlin.math.PI
+
+/**
+ * Geodetic coordinated
+ */
+public class GeodeticMapCoordinates private constructor(public val latitude: Double, public val longitude: Double) {
+
+    override fun equals(other: Any?): Boolean {
+        if (this === other) return true
+        if (other == null || this::class != other::class) return false
+
+        other as GeodeticMapCoordinates
+
+        if (latitude != other.latitude) return false
+        if (longitude != other.longitude) return false
+
+        return true
+    }
+
+    override fun hashCode(): Int {
+        var result = latitude.hashCode()
+        result = 31 * result + longitude.hashCode()
+        return result
+    }
+
+    override fun toString(): String {
+        return "GeodeticCoordinates(latitude=${latitude / PI * 180}, longitude=${longitude / PI * 180})"
+    }
+
+
+    public companion object {
+        public fun ofRadians(latitude: Double, longitude: Double): GeodeticMapCoordinates {
+            require(longitude in (-PI)..(PI)) { "Longitude $longitude is not in (-PI)..(PI)" }
+            return GeodeticMapCoordinates(latitude, longitude.rem(PI / 2))
+        }
+
+        public fun ofDegrees(latitude: Double, longitude: Double): GeodeticMapCoordinates {
+            require(latitude in (-90.0)..(90.0)) { "Latitude $latitude is not in -90..90" }
+            return GeodeticMapCoordinates(latitude * PI / 180, (longitude.rem(180) * PI / 180))
+        }
+    }
+}
+
+public interface GeoToScreenConversion {
+    public fun getScreenX(gmc: GeodeticMapCoordinates): Double
+    public fun getScreenY(gmc: GeodeticMapCoordinates): Double
+
+    public fun invalidationFlow(): Flow<Unit>
+}
+
+public interface ScreenMapCoordinates {
+    public val gmc: GeodeticMapCoordinates
+    public val converter: GeoToScreenConversion
+
+    public val x: Double get() = converter.getScreenX(gmc)
+    public val y: Double get() = converter.getScreenX(gmc)
+}

src/jvmMain/kotlin/centre/sciprog/maps/compose/model.kt

@@ -0,0 +1,26 @@
+package centre.sciprog.maps.compose
+
+import kotlin.math.abs
+
+class MapRectangle(
+    var topLeft: GeodeticMapCoordinates,
+    var bottomRight: GeodeticMapCoordinates,
+) {
+    init {
+        require(topLeft.latitude >= bottomRight.latitude)
+        require(topLeft.longitude <= bottomRight.longitude)
+    }
+    val topRight: GeodeticMapCoordinates = GeodeticMapCoordinates.ofRadians(topLeft.latitude, bottomRight.longitude)
+    val bottomLeft: GeodeticMapCoordinates = GeodeticMapCoordinates.ofRadians(bottomRight.latitude, topLeft.longitude)
+}
+
+sealed interface MapFeature
+
+class MapLine(
+    val from: GeodeticMapCoordinates,
+    val to: GeodeticMapCoordinates,
+) : MapFeature
+
+class MapCircle(
+    val center: GeodeticMapCoordinates,
+)