Main menu cancels background map creation when obsolete (#9072)

core/src/com/unciv/logic/map/mapgenerator/MapGenerator.kt

@@ -21,6 +21,8 @@ import com.unciv.ui.screens.mapeditorscreen.MapGeneratorSteps
 import com.unciv.ui.screens.mapeditorscreen.TileInfoNormalizer
 import com.unciv.utils.Log
 import com.unciv.utils.debug
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.isActive
 import kotlin.math.abs
 import kotlin.math.max
 import kotlin.math.pow
@@ -31,7 +33,8 @@ import kotlin.math.ulp
 import kotlin.random.Random
 
 
-class MapGenerator(val ruleset: Ruleset) {
+class MapGenerator(val ruleset: Ruleset, private val coroutineScope: CoroutineScope? = null) {
+
     companion object {
         private const val consoleTimings = false
     }
@@ -202,6 +205,7 @@ class MapGenerator(val ruleset: Ruleset) {
 
 
     private fun runAndMeasure(text: String, action: ()->Unit) {
+        if (coroutineScope?.isActive == false) return
         if (!consoleTimings) return action()
         val startNanos = System.nanoTime()
         action()

core/src/com/unciv/ui/screens/mainmenuscreen/MainMenuScreen.kt

@@ -52,7 +52,8 @@ import com.unciv.ui.screens.worldscreen.WorldScreen
 import com.unciv.ui.screens.worldscreen.mainmenu.WorldScreenMenuPopup
 import com.unciv.utils.concurrency.Concurrency
 import com.unciv.utils.concurrency.launchOnGLThread
-import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.isActive
 import kotlin.math.min
 
 
@@ -63,6 +64,8 @@ class MainMenuScreen: BaseScreen(), RecreateOnResize {
     private val singleColumn = isCrampedPortrait()
     private var easterEggRuleset: Ruleset? = null  // Cache it so the next 'egg' can be found in Civilopedia
 
+    private var backgroundMapGenerationJob: Job? = null
+
     /** Create one **Main Menu Button** including onClick/key binding
      *  @param text      The text to display on the button
      *  @param icon      The path of the icon to display on the button
@@ -86,7 +89,10 @@ class MainMenuScreen: BaseScreen(), RecreateOnResize {
         table.add(text.toLabel(fontSize = 30, alignment = Align.left)).expand().left().minWidth(200f)
 
         table.touchable = Touchable.enabled
-        table.onActivation(function)
+        table.onActivation {
+            stopBackgroundMapGeneration()
+            function()
+        }
 
         if (key != null) {
             if (!keyVisualOnly)
@@ -110,9 +116,7 @@ class MainMenuScreen: BaseScreen(), RecreateOnResize {
         // guard in UncivGame.create, simply omit the background so the user can at least get to options
         // (let him crash when loading a game but avoid locking him out entirely)
         if (game.settings.tileSet in TileSetCache)
-            Concurrency.run("ShowMapBackground") {
+            startBackgroundMapGeneration()
-                showMapBackground()
-            }
 
         val column1 = Table().apply { defaults().pad(10f).fillX() }
         val column2 = if (singleColumn) column1 else Table().apply { defaults().pad(10f).fillX() }
@@ -185,7 +189,9 @@ class MainMenuScreen: BaseScreen(), RecreateOnResize {
         stage.addActor(helpButton)
     }
 
-    private fun CoroutineScope.showMapBackground() {
+    private fun startBackgroundMapGeneration() {
+        stopBackgroundMapGeneration()  // shouldn't be necessary as resize re-instantiates this class
+        backgroundMapGenerationJob = Concurrency.run("ShowMapBackground") {
             var scale = 1f
             var mapWidth = stage.width / TileGroupMap.groupHorizontalAdvance
             var mapHeight = stage.height / TileGroupMap.groupSize
@@ -202,12 +208,12 @@ class MainMenuScreen: BaseScreen(), RecreateOnResize {
             }
             val mapRuleset = if (game.settings.enableEasterEggs) easterEggRuleset ?: baseRuleset else baseRuleset
 
-        val newMap = MapGenerator(mapRuleset)
+            val newMap = MapGenerator(mapRuleset, this)
                 .generateMap(MapParameters().apply {
                     shape = MapShape.rectangular
                     mapSize = MapSizeNew(MapSize.Small)
                     type = MapType.pangaea
-                temperatureExtremeness = 0.7f
+                    temperatureExtremeness = .7f
                     waterThreshold = -0.1f // mainly land, gets about 30% water
                     modifyForEasterEgg()
                 })
@@ -219,15 +225,31 @@ class MainMenuScreen: BaseScreen(), RecreateOnResize {
                     newMap
                 ) {}
                 mapHolder.setScale(scale)
+
                 backgroundTable.addAction(Actions.sequence(
                     Actions.fadeOut(0f),
                     Actions.run {
+                        backgroundTable.clearChildren()
                         backgroundTable.addActor(mapHolder)
                         mapHolder.center(backgroundTable)
                     },
                     Actions.fadeIn(0.3f)
                 ))
             }
+        }.apply {
+            invokeOnCompletion {
+                backgroundMapGenerationJob = null
+            }
+        }
+    }
+
+    private fun stopBackgroundMapGeneration() {
+        val currentJob = backgroundMapGenerationJob
+            ?: return
+        backgroundMapGenerationJob = null
+        if (currentJob.isCancelled) return
+        currentJob.cancel()
+        backgroundTable.clearActions()
     }
 
     private fun resumeGame() {
@@ -293,6 +315,7 @@ class MainMenuScreen: BaseScreen(), RecreateOnResize {
     }
 
     private fun openCivilopedia() {
+        stopBackgroundMapGeneration()
         val rulesetParameters = game.settings.lastGameSetup?.gameParameters
         val ruleset = easterEggRuleset ?:
             if (rulesetParameters == null)
@@ -304,5 +327,8 @@ class MainMenuScreen: BaseScreen(), RecreateOnResize {
         game.pushScreen(CivilopediaScreen(ruleset))
     }
 
-    override fun recreate(): BaseScreen = MainMenuScreen()
+    override fun recreate(): BaseScreen {
+        stopBackgroundMapGeneration()
+        return MainMenuScreen()
+    }
 }